// available on the target, and it performs a variety of other optimizations
// related to loop induction variables.
//
+// Terminology note: this code has a lot of handling for "post-increment" or
+// "post-inc" users. This is not talking about post-increment addressing modes;
+// it is instead talking about code like this:
+//
+// %i = phi [ 0, %entry ], [ %i.next, %latch ]
+// ...
+// %i.next = add %i, 1
+// %c = icmp eq %i.next, %n
+//
+// The SCEV for %i is {0,+,1}<%L>. The SCEV for %i.next is {1,+,1}<%L>, however
+// it's useful to think about these as the same register, with some uses using
+// the value of the register before the add and some using // it after. In this
+// example, the icmp is a post-increment user, since it uses %i.next, which is
+// the value of the induction variable after the increment. The other common
+// case of post-increment users is users outside the loop.
+//
+// TODO: More sophistication in the way Formulae are generated and filtered.
+//
+// TODO: Handle multiple loops at a time.
+//
+// TODO: Should TargetLowering::AddrMode::BaseGV be changed to a ConstantExpr
+// instead of a GlobalValue?
+//
+// TODO: When truncation is free, truncate ICmp users' operands to make it a
+// smaller encoding (on x86 at least).
+//
+// TODO: When a negated register is used by an add (such as in a list of
+// multiple base registers, or as the increment expression in an addrec),
+// we may not actually need both reg and (-1 * reg) in registers; the
+// negation can be implemented by using a sub instead of an add. The
+// lack of support for taking this into consideration when making
+// register pressure decisions is partly worked around by the "Special"
+// use kind.
+//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "loop-reduce"
#include "llvm/IntrinsicInst.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Analysis/IVUsers.h"
+#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/LoopPass.h"
#include "llvm/Analysis/ScalarEvolutionExpander.h"
-#include "llvm/Transforms/Utils/AddrModeMatcher.h"
+#include "llvm/Assembly/Writer.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
-#include "llvm/ADT/Statistic.h"
+#include "llvm/ADT/SmallBitVector.h"
+#include "llvm/ADT/SetVector.h"
+#include "llvm/ADT/DenseSet.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/ValueHandle.h"
#include <algorithm>
using namespace llvm;
-STATISTIC(NumReduced , "Number of IV uses strength reduced");
-STATISTIC(NumInserted, "Number of PHIs inserted");
-STATISTIC(NumVariable, "Number of PHIs with variable strides");
-STATISTIC(NumEliminated, "Number of strides eliminated");
-STATISTIC(NumShadow, "Number of Shadow IVs optimized");
-STATISTIC(NumImmSunk, "Number of common expr immediates sunk into uses");
-STATISTIC(NumLoopCond, "Number of loop terminating conds optimized");
-STATISTIC(NumCountZero, "Number of count iv optimized to count toward zero");
+/// MaxIVUsers is an arbitrary threshold that provides an early opportunitiy for
+/// bail out. This threshold is far beyond the number of users that LSR can
+/// conceivably solve, so it should not affect generated code, but catches the
+/// worst cases before LSR burns too much compile time and stack space.
+static const unsigned MaxIVUsers = 200;
+
+// Temporary flag to cleanup congruent phis after LSR phi expansion.
+// It's currently disabled until we can determine whether it's truly useful or
+// not. The flag should be removed after the v3.0 release.
+// This is now needed for ivchains.
+static cl::opt<bool> EnablePhiElim(
+ "enable-lsr-phielim", cl::Hidden, cl::init(true),
+ cl::desc("Enable LSR phi elimination"));
+
+#ifndef NDEBUG
+// Stress test IV chain generation.
+static cl::opt<bool> StressIVChain(
+ "stress-ivchain", cl::Hidden, cl::init(false),
+ cl::desc("Stress test LSR IV chains"));
+#else
+static bool StressIVChain = false;
+#endif
+
+namespace {
+
+/// RegSortData - This class holds data which is used to order reuse candidates.
+class RegSortData {
+public:
+ /// UsedByIndices - This represents the set of LSRUse indices which reference
+ /// a particular register.
+ SmallBitVector UsedByIndices;
+
+ RegSortData() {}
+
+ void print(raw_ostream &OS) const;
+ void dump() const;
+};
+
+}
+
+void RegSortData::print(raw_ostream &OS) const {
+ OS << "[NumUses=" << UsedByIndices.count() << ']';
+}
-static cl::opt<bool> EnableFullLSRMode("enable-full-lsr",
- cl::init(false),
- cl::Hidden);
+void RegSortData::dump() const {
+ print(errs()); errs() << '\n';
+}
namespace {
- struct BasedUser;
+/// RegUseTracker - Map register candidates to information about how they are
+/// used.
+class RegUseTracker {
+ typedef DenseMap<const SCEV *, RegSortData> RegUsesTy;
- /// IVInfo - This structure keeps track of one IV expression inserted during
- /// StrengthReduceStridedIVUsers. It contains the stride, the common base, as
- /// well as the PHI node and increment value created for rewrite.
- struct IVExpr {
- const SCEV *Stride;
- const SCEV *Base;
- PHINode *PHI;
+ RegUsesTy RegUsesMap;
+ SmallVector<const SCEV *, 16> RegSequence;
- IVExpr(const SCEV *const stride, const SCEV *const base, PHINode *phi)
- : Stride(stride), Base(base), PHI(phi) {}
- };
+public:
+ void CountRegister(const SCEV *Reg, size_t LUIdx);
+ void DropRegister(const SCEV *Reg, size_t LUIdx);
+ void SwapAndDropUse(size_t LUIdx, size_t LastLUIdx);
+
+ bool isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const;
+
+ const SmallBitVector &getUsedByIndices(const SCEV *Reg) const;
+
+ void clear();
+
+ typedef SmallVectorImpl<const SCEV *>::iterator iterator;
+ typedef SmallVectorImpl<const SCEV *>::const_iterator const_iterator;
+ iterator begin() { return RegSequence.begin(); }
+ iterator end() { return RegSequence.end(); }
+ const_iterator begin() const { return RegSequence.begin(); }
+ const_iterator end() const { return RegSequence.end(); }
+};
+
+}
+
+void
+RegUseTracker::CountRegister(const SCEV *Reg, size_t LUIdx) {
+ std::pair<RegUsesTy::iterator, bool> Pair =
+ RegUsesMap.insert(std::make_pair(Reg, RegSortData()));
+ RegSortData &RSD = Pair.first->second;
+ if (Pair.second)
+ RegSequence.push_back(Reg);
+ RSD.UsedByIndices.resize(std::max(RSD.UsedByIndices.size(), LUIdx + 1));
+ RSD.UsedByIndices.set(LUIdx);
+}
+
+void
+RegUseTracker::DropRegister(const SCEV *Reg, size_t LUIdx) {
+ RegUsesTy::iterator It = RegUsesMap.find(Reg);
+ assert(It != RegUsesMap.end());
+ RegSortData &RSD = It->second;
+ assert(RSD.UsedByIndices.size() > LUIdx);
+ RSD.UsedByIndices.reset(LUIdx);
+}
+
+void
+RegUseTracker::SwapAndDropUse(size_t LUIdx, size_t LastLUIdx) {
+ assert(LUIdx <= LastLUIdx);
+
+ // Update RegUses. The data structure is not optimized for this purpose;
+ // we must iterate through it and update each of the bit vectors.
+ for (RegUsesTy::iterator I = RegUsesMap.begin(), E = RegUsesMap.end();
+ I != E; ++I) {
+ SmallBitVector &UsedByIndices = I->second.UsedByIndices;
+ if (LUIdx < UsedByIndices.size())
+ UsedByIndices[LUIdx] =
+ LastLUIdx < UsedByIndices.size() ? UsedByIndices[LastLUIdx] : 0;
+ UsedByIndices.resize(std::min(UsedByIndices.size(), LastLUIdx));
+ }
+}
+
+bool
+RegUseTracker::isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const {
+ RegUsesTy::const_iterator I = RegUsesMap.find(Reg);
+ if (I == RegUsesMap.end())
+ return false;
+ const SmallBitVector &UsedByIndices = I->second.UsedByIndices;
+ int i = UsedByIndices.find_first();
+ if (i == -1) return false;
+ if ((size_t)i != LUIdx) return true;
+ return UsedByIndices.find_next(i) != -1;
+}
+
+const SmallBitVector &RegUseTracker::getUsedByIndices(const SCEV *Reg) const {
+ RegUsesTy::const_iterator I = RegUsesMap.find(Reg);
+ assert(I != RegUsesMap.end() && "Unknown register!");
+ return I->second.UsedByIndices;
+}
+
+void RegUseTracker::clear() {
+ RegUsesMap.clear();
+ RegSequence.clear();
+}
+
+namespace {
+
+/// Formula - This class holds information that describes a formula for
+/// computing satisfying a use. It may include broken-out immediates and scaled
+/// registers.
+struct Formula {
+ /// AM - This is used to represent complex addressing, as well as other kinds
+ /// of interesting uses.
+ TargetLowering::AddrMode AM;
+
+ /// BaseRegs - The list of "base" registers for this use. When this is
+ /// non-empty, AM.HasBaseReg should be set to true.
+ SmallVector<const SCEV *, 2> BaseRegs;
+
+ /// ScaledReg - The 'scaled' register for this use. This should be non-null
+ /// when AM.Scale is not zero.
+ const SCEV *ScaledReg;
+
+ /// UnfoldedOffset - An additional constant offset which added near the
+ /// use. This requires a temporary register, but the offset itself can
+ /// live in an add immediate field rather than a register.
+ int64_t UnfoldedOffset;
- /// IVsOfOneStride - This structure keeps track of all IV expression inserted
- /// during StrengthReduceStridedIVUsers for a particular stride of the IV.
- struct IVsOfOneStride {
- std::vector<IVExpr> IVs;
+ Formula() : ScaledReg(0), UnfoldedOffset(0) {}
- void addIV(const SCEV *const Stride, const SCEV *const Base, PHINode *PHI) {
- IVs.push_back(IVExpr(Stride, Base, PHI));
+ void InitialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE);
+
+ unsigned getNumRegs() const;
+ Type *getType() const;
+
+ void DeleteBaseReg(const SCEV *&S);
+
+ bool referencesReg(const SCEV *S) const;
+ bool hasRegsUsedByUsesOtherThan(size_t LUIdx,
+ const RegUseTracker &RegUses) const;
+
+ void print(raw_ostream &OS) const;
+ void dump() const;
+};
+
+}
+
+/// DoInitialMatch - Recursion helper for InitialMatch.
+static void DoInitialMatch(const SCEV *S, Loop *L,
+ SmallVectorImpl<const SCEV *> &Good,
+ SmallVectorImpl<const SCEV *> &Bad,
+ ScalarEvolution &SE) {
+ // Collect expressions which properly dominate the loop header.
+ if (SE.properlyDominates(S, L->getHeader())) {
+ Good.push_back(S);
+ return;
+ }
+
+ // Look at add operands.
+ if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
+ for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
+ I != E; ++I)
+ DoInitialMatch(*I, L, Good, Bad, SE);
+ return;
+ }
+
+ // Look at addrec operands.
+ if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S))
+ if (!AR->getStart()->isZero()) {
+ DoInitialMatch(AR->getStart(), L, Good, Bad, SE);
+ DoInitialMatch(SE.getAddRecExpr(SE.getConstant(AR->getType(), 0),
+ AR->getStepRecurrence(SE),
+ // FIXME: AR->getNoWrapFlags()
+ AR->getLoop(), SCEV::FlagAnyWrap),
+ L, Good, Bad, SE);
+ return;
+ }
+
+ // Handle a multiplication by -1 (negation) if it didn't fold.
+ if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S))
+ if (Mul->getOperand(0)->isAllOnesValue()) {
+ SmallVector<const SCEV *, 4> Ops(Mul->op_begin()+1, Mul->op_end());
+ const SCEV *NewMul = SE.getMulExpr(Ops);
+
+ SmallVector<const SCEV *, 4> MyGood;
+ SmallVector<const SCEV *, 4> MyBad;
+ DoInitialMatch(NewMul, L, MyGood, MyBad, SE);
+ const SCEV *NegOne = SE.getSCEV(ConstantInt::getAllOnesValue(
+ SE.getEffectiveSCEVType(NewMul->getType())));
+ for (SmallVectorImpl<const SCEV *>::const_iterator I = MyGood.begin(),
+ E = MyGood.end(); I != E; ++I)
+ Good.push_back(SE.getMulExpr(NegOne, *I));
+ for (SmallVectorImpl<const SCEV *>::const_iterator I = MyBad.begin(),
+ E = MyBad.end(); I != E; ++I)
+ Bad.push_back(SE.getMulExpr(NegOne, *I));
+ return;
}
- };
- class LoopStrengthReduce : public LoopPass {
- IVUsers *IU;
- ScalarEvolution *SE;
- bool Changed;
+ // Ok, we can't do anything interesting. Just stuff the whole thing into a
+ // register and hope for the best.
+ Bad.push_back(S);
+}
- /// IVsByStride - Keep track of all IVs that have been inserted for a
- /// particular stride.
- std::map<const SCEV *, IVsOfOneStride> IVsByStride;
+/// InitialMatch - Incorporate loop-variant parts of S into this Formula,
+/// attempting to keep all loop-invariant and loop-computable values in a
+/// single base register.
+void Formula::InitialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE) {
+ SmallVector<const SCEV *, 4> Good;
+ SmallVector<const SCEV *, 4> Bad;
+ DoInitialMatch(S, L, Good, Bad, SE);
+ if (!Good.empty()) {
+ const SCEV *Sum = SE.getAddExpr(Good);
+ if (!Sum->isZero())
+ BaseRegs.push_back(Sum);
+ AM.HasBaseReg = true;
+ }
+ if (!Bad.empty()) {
+ const SCEV *Sum = SE.getAddExpr(Bad);
+ if (!Sum->isZero())
+ BaseRegs.push_back(Sum);
+ AM.HasBaseReg = true;
+ }
+}
- /// DeadInsts - Keep track of instructions we may have made dead, so that
- /// we can remove them after we are done working.
- SmallVector<WeakVH, 16> DeadInsts;
+/// getNumRegs - Return the total number of register operands used by this
+/// formula. This does not include register uses implied by non-constant
+/// addrec strides.
+unsigned Formula::getNumRegs() const {
+ return !!ScaledReg + BaseRegs.size();
+}
- /// TLI - Keep a pointer of a TargetLowering to consult for determining
- /// transformation profitability.
- const TargetLowering *TLI;
-
- public:
- static char ID; // Pass ID, replacement for typeid
- explicit LoopStrengthReduce(const TargetLowering *tli = NULL) :
- LoopPass(&ID), TLI(tli) {}
-
- bool runOnLoop(Loop *L, LPPassManager &LPM);
-
- virtual void getAnalysisUsage(AnalysisUsage &AU) const {
- // We split critical edges, so we change the CFG. However, we do update
- // many analyses if they are around.
- AU.addPreservedID(LoopSimplifyID);
- AU.addPreserved("loops");
- AU.addPreserved("domfrontier");
- AU.addPreserved("domtree");
-
- AU.addRequiredID(LoopSimplifyID);
- AU.addRequired<ScalarEvolution>();
- AU.addPreserved<ScalarEvolution>();
- AU.addRequired<IVUsers>();
- AU.addPreserved<IVUsers>();
- }
-
- private:
- void OptimizeIndvars(Loop *L);
-
- /// OptimizeLoopTermCond - Change loop terminating condition to use the
- /// postinc iv when possible.
- void OptimizeLoopTermCond(Loop *L);
-
- /// OptimizeShadowIV - If IV is used in a int-to-float cast
- /// inside the loop then try to eliminate the cast opeation.
- void OptimizeShadowIV(Loop *L);
-
- /// OptimizeMax - Rewrite the loop's terminating condition
- /// if it uses a max computation.
- ICmpInst *OptimizeMax(Loop *L, ICmpInst *Cond,
- IVStrideUse* &CondUse);
-
- /// OptimizeLoopCountIV - If, after all sharing of IVs, the IV used for
- /// deciding when to exit the loop is used only for that purpose, try to
- /// rearrange things so it counts down to a test against zero.
- bool OptimizeLoopCountIV(Loop *L);
- bool OptimizeLoopCountIVOfStride(const SCEV* &Stride,
- IVStrideUse* &CondUse, Loop *L);
-
- /// StrengthReduceIVUsersOfStride - Strength reduce all of the users of a
- /// single stride of IV. All of the users may have different starting
- /// values, and this may not be the only stride.
- void StrengthReduceIVUsersOfStride(const SCEV *Stride,
- IVUsersOfOneStride &Uses,
- Loop *L);
- void StrengthReduceIVUsers(Loop *L);
-
- ICmpInst *ChangeCompareStride(Loop *L, ICmpInst *Cond,
- IVStrideUse* &CondUse,
- const SCEV* &CondStride,
- bool PostPass = false);
-
- bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse,
- const SCEV* &CondStride);
- bool RequiresTypeConversion(const Type *Ty, const Type *NewTy);
- const SCEV *CheckForIVReuse(bool, bool, bool, const SCEV *,
- IVExpr&, const Type*,
- const std::vector<BasedUser>& UsersToProcess);
- bool ValidScale(bool, int64_t,
- const std::vector<BasedUser>& UsersToProcess);
- bool ValidOffset(bool, int64_t, int64_t,
- const std::vector<BasedUser>& UsersToProcess);
- const SCEV *CollectIVUsers(const SCEV *Stride,
- IVUsersOfOneStride &Uses,
- Loop *L,
- bool &AllUsesAreAddresses,
- bool &AllUsesAreOutsideLoop,
- std::vector<BasedUser> &UsersToProcess);
- bool StrideMightBeShared(const SCEV *Stride, Loop *L, bool CheckPreInc);
- bool ShouldUseFullStrengthReductionMode(
- const std::vector<BasedUser> &UsersToProcess,
- const Loop *L,
- bool AllUsesAreAddresses,
- const SCEV *Stride);
- void PrepareToStrengthReduceFully(
- std::vector<BasedUser> &UsersToProcess,
- const SCEV *Stride,
- const SCEV *CommonExprs,
- const Loop *L,
- SCEVExpander &PreheaderRewriter);
- void PrepareToStrengthReduceFromSmallerStride(
- std::vector<BasedUser> &UsersToProcess,
- Value *CommonBaseV,
- const IVExpr &ReuseIV,
- Instruction *PreInsertPt);
- void PrepareToStrengthReduceWithNewPhi(
- std::vector<BasedUser> &UsersToProcess,
- const SCEV *Stride,
- const SCEV *CommonExprs,
- Value *CommonBaseV,
- Instruction *IVIncInsertPt,
- const Loop *L,
- SCEVExpander &PreheaderRewriter);
-
- void DeleteTriviallyDeadInstructions();
- };
+/// getType - Return the type of this formula, if it has one, or null
+/// otherwise. This type is meaningless except for the bit size.
+Type *Formula::getType() const {
+ return !BaseRegs.empty() ? BaseRegs.front()->getType() :
+ ScaledReg ? ScaledReg->getType() :
+ AM.BaseGV ? AM.BaseGV->getType() :
+ 0;
}
-char LoopStrengthReduce::ID = 0;
-static RegisterPass<LoopStrengthReduce>
-X("loop-reduce", "Loop Strength Reduction");
+/// DeleteBaseReg - Delete the given base reg from the BaseRegs list.
+void Formula::DeleteBaseReg(const SCEV *&S) {
+ if (&S != &BaseRegs.back())
+ std::swap(S, BaseRegs.back());
+ BaseRegs.pop_back();
+}
-Pass *llvm::createLoopStrengthReducePass(const TargetLowering *TLI) {
- return new LoopStrengthReduce(TLI);
+/// referencesReg - Test if this formula references the given register.
+bool Formula::referencesReg(const SCEV *S) const {
+ return S == ScaledReg ||
+ std::find(BaseRegs.begin(), BaseRegs.end(), S) != BaseRegs.end();
}
-/// DeleteTriviallyDeadInstructions - If any of the instructions is the
-/// specified set are trivially dead, delete them and see if this makes any of
-/// their operands subsequently dead.
-void LoopStrengthReduce::DeleteTriviallyDeadInstructions() {
- while (!DeadInsts.empty()) {
- Instruction *I = dyn_cast_or_null<Instruction>(DeadInsts.pop_back_val());
+/// hasRegsUsedByUsesOtherThan - Test whether this formula uses registers
+/// which are used by uses other than the use with the given index.
+bool Formula::hasRegsUsedByUsesOtherThan(size_t LUIdx,
+ const RegUseTracker &RegUses) const {
+ if (ScaledReg)
+ if (RegUses.isRegUsedByUsesOtherThan(ScaledReg, LUIdx))
+ return true;
+ for (SmallVectorImpl<const SCEV *>::const_iterator I = BaseRegs.begin(),
+ E = BaseRegs.end(); I != E; ++I)
+ if (RegUses.isRegUsedByUsesOtherThan(*I, LUIdx))
+ return true;
+ return false;
+}
- if (I == 0 || !isInstructionTriviallyDead(I))
- continue;
+void Formula::print(raw_ostream &OS) const {
+ bool First = true;
+ if (AM.BaseGV) {
+ if (!First) OS << " + "; else First = false;
+ WriteAsOperand(OS, AM.BaseGV, /*PrintType=*/false);
+ }
+ if (AM.BaseOffs != 0) {
+ if (!First) OS << " + "; else First = false;
+ OS << AM.BaseOffs;
+ }
+ for (SmallVectorImpl<const SCEV *>::const_iterator I = BaseRegs.begin(),
+ E = BaseRegs.end(); I != E; ++I) {
+ if (!First) OS << " + "; else First = false;
+ OS << "reg(" << **I << ')';
+ }
+ if (AM.HasBaseReg && BaseRegs.empty()) {
+ if (!First) OS << " + "; else First = false;
+ OS << "**error: HasBaseReg**";
+ } else if (!AM.HasBaseReg && !BaseRegs.empty()) {
+ if (!First) OS << " + "; else First = false;
+ OS << "**error: !HasBaseReg**";
+ }
+ if (AM.Scale != 0) {
+ if (!First) OS << " + "; else First = false;
+ OS << AM.Scale << "*reg(";
+ if (ScaledReg)
+ OS << *ScaledReg;
+ else
+ OS << "<unknown>";
+ OS << ')';
+ }
+ if (UnfoldedOffset != 0) {
+ if (!First) OS << " + "; else First = false;
+ OS << "imm(" << UnfoldedOffset << ')';
+ }
+}
- for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
- if (Instruction *U = dyn_cast<Instruction>(*OI)) {
- *OI = 0;
- if (U->use_empty())
- DeadInsts.push_back(U);
+void Formula::dump() const {
+ print(errs()); errs() << '\n';
+}
+
+/// isAddRecSExtable - Return true if the given addrec can be sign-extended
+/// without changing its value.
+static bool isAddRecSExtable(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
+ Type *WideTy =
+ IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(AR->getType()) + 1);
+ return isa<SCEVAddRecExpr>(SE.getSignExtendExpr(AR, WideTy));
+}
+
+/// isAddSExtable - Return true if the given add can be sign-extended
+/// without changing its value.
+static bool isAddSExtable(const SCEVAddExpr *A, ScalarEvolution &SE) {
+ Type *WideTy =
+ IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(A->getType()) + 1);
+ return isa<SCEVAddExpr>(SE.getSignExtendExpr(A, WideTy));
+}
+
+/// isMulSExtable - Return true if the given mul can be sign-extended
+/// without changing its value.
+static bool isMulSExtable(const SCEVMulExpr *M, ScalarEvolution &SE) {
+ Type *WideTy =
+ IntegerType::get(SE.getContext(),
+ SE.getTypeSizeInBits(M->getType()) * M->getNumOperands());
+ return isa<SCEVMulExpr>(SE.getSignExtendExpr(M, WideTy));
+}
+
+/// getExactSDiv - Return an expression for LHS /s RHS, if it can be determined
+/// and if the remainder is known to be zero, or null otherwise. If
+/// IgnoreSignificantBits is true, expressions like (X * Y) /s Y are simplified
+/// to Y, ignoring that the multiplication may overflow, which is useful when
+/// the result will be used in a context where the most significant bits are
+/// ignored.
+static const SCEV *getExactSDiv(const SCEV *LHS, const SCEV *RHS,
+ ScalarEvolution &SE,
+ bool IgnoreSignificantBits = false) {
+ // Handle the trivial case, which works for any SCEV type.
+ if (LHS == RHS)
+ return SE.getConstant(LHS->getType(), 1);
+
+ // Handle a few RHS special cases.
+ const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS);
+ if (RC) {
+ const APInt &RA = RC->getValue()->getValue();
+ // Handle x /s -1 as x * -1, to give ScalarEvolution a chance to do
+ // some folding.
+ if (RA.isAllOnesValue())
+ return SE.getMulExpr(LHS, RC);
+ // Handle x /s 1 as x.
+ if (RA == 1)
+ return LHS;
+ }
+
+ // Check for a division of a constant by a constant.
+ if (const SCEVConstant *C = dyn_cast<SCEVConstant>(LHS)) {
+ if (!RC)
+ return 0;
+ const APInt &LA = C->getValue()->getValue();
+ const APInt &RA = RC->getValue()->getValue();
+ if (LA.srem(RA) != 0)
+ return 0;
+ return SE.getConstant(LA.sdiv(RA));
+ }
+
+ // Distribute the sdiv over addrec operands, if the addrec doesn't overflow.
+ if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS)) {
+ if (IgnoreSignificantBits || isAddRecSExtable(AR, SE)) {
+ const SCEV *Step = getExactSDiv(AR->getStepRecurrence(SE), RHS, SE,
+ IgnoreSignificantBits);
+ if (!Step) return 0;
+ const SCEV *Start = getExactSDiv(AR->getStart(), RHS, SE,
+ IgnoreSignificantBits);
+ if (!Start) return 0;
+ // FlagNW is independent of the start value, step direction, and is
+ // preserved with smaller magnitude steps.
+ // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
+ return SE.getAddRecExpr(Start, Step, AR->getLoop(), SCEV::FlagAnyWrap);
+ }
+ return 0;
+ }
+
+ // Distribute the sdiv over add operands, if the add doesn't overflow.
+ if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(LHS)) {
+ if (IgnoreSignificantBits || isAddSExtable(Add, SE)) {
+ SmallVector<const SCEV *, 8> Ops;
+ for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
+ I != E; ++I) {
+ const SCEV *Op = getExactSDiv(*I, RHS, SE,
+ IgnoreSignificantBits);
+ if (!Op) return 0;
+ Ops.push_back(Op);
}
+ return SE.getAddExpr(Ops);
+ }
+ return 0;
+ }
- I->eraseFromParent();
- Changed = true;
+ // Check for a multiply operand that we can pull RHS out of.
+ if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS)) {
+ if (IgnoreSignificantBits || isMulSExtable(Mul, SE)) {
+ SmallVector<const SCEV *, 4> Ops;
+ bool Found = false;
+ for (SCEVMulExpr::op_iterator I = Mul->op_begin(), E = Mul->op_end();
+ I != E; ++I) {
+ const SCEV *S = *I;
+ if (!Found)
+ if (const SCEV *Q = getExactSDiv(S, RHS, SE,
+ IgnoreSignificantBits)) {
+ S = Q;
+ Found = true;
+ }
+ Ops.push_back(S);
+ }
+ return Found ? SE.getMulExpr(Ops) : 0;
+ }
+ return 0;
+ }
+
+ // Otherwise we don't know.
+ return 0;
+}
+
+/// ExtractImmediate - If S involves the addition of a constant integer value,
+/// return that integer value, and mutate S to point to a new SCEV with that
+/// value excluded.
+static int64_t ExtractImmediate(const SCEV *&S, ScalarEvolution &SE) {
+ if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
+ if (C->getValue()->getValue().getMinSignedBits() <= 64) {
+ S = SE.getConstant(C->getType(), 0);
+ return C->getValue()->getSExtValue();
+ }
+ } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
+ SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
+ int64_t Result = ExtractImmediate(NewOps.front(), SE);
+ if (Result != 0)
+ S = SE.getAddExpr(NewOps);
+ return Result;
+ } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
+ SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
+ int64_t Result = ExtractImmediate(NewOps.front(), SE);
+ if (Result != 0)
+ S = SE.getAddRecExpr(NewOps, AR->getLoop(),
+ // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
+ SCEV::FlagAnyWrap);
+ return Result;
+ }
+ return 0;
+}
+
+/// ExtractSymbol - If S involves the addition of a GlobalValue address,
+/// return that symbol, and mutate S to point to a new SCEV with that
+/// value excluded.
+static GlobalValue *ExtractSymbol(const SCEV *&S, ScalarEvolution &SE) {
+ if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
+ if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue())) {
+ S = SE.getConstant(GV->getType(), 0);
+ return GV;
+ }
+ } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
+ SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
+ GlobalValue *Result = ExtractSymbol(NewOps.back(), SE);
+ if (Result)
+ S = SE.getAddExpr(NewOps);
+ return Result;
+ } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
+ SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
+ GlobalValue *Result = ExtractSymbol(NewOps.front(), SE);
+ if (Result)
+ S = SE.getAddRecExpr(NewOps, AR->getLoop(),
+ // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
+ SCEV::FlagAnyWrap);
+ return Result;
}
+ return 0;
}
/// isAddressUse - Returns true if the specified instruction is using the
switch (II->getIntrinsicID()) {
default: break;
case Intrinsic::prefetch:
- case Intrinsic::x86_sse2_loadu_dq:
- case Intrinsic::x86_sse2_loadu_pd:
- case Intrinsic::x86_sse_loadu_ps:
case Intrinsic::x86_sse_storeu_ps:
case Intrinsic::x86_sse2_storeu_pd:
case Intrinsic::x86_sse2_storeu_dq:
case Intrinsic::x86_sse2_storel_dq:
- if (II->getOperand(1) == OperandVal)
+ if (II->getArgOperand(0) == OperandVal)
isAddress = true;
break;
}
}
/// getAccessType - Return the type of the memory being accessed.
-static const Type *getAccessType(const Instruction *Inst) {
- const Type *AccessTy = Inst->getType();
+static Type *getAccessType(const Instruction *Inst) {
+ Type *AccessTy = Inst->getType();
if (const StoreInst *SI = dyn_cast<StoreInst>(Inst))
AccessTy = SI->getOperand(0)->getType();
else if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
case Intrinsic::x86_sse2_storeu_pd:
case Intrinsic::x86_sse2_storeu_dq:
case Intrinsic::x86_sse2_storel_dq:
- AccessTy = II->getOperand(1)->getType();
+ AccessTy = II->getArgOperand(0)->getType();
break;
}
}
- return AccessTy;
-}
-namespace {
- /// BasedUser - For a particular base value, keep information about how we've
- /// partitioned the expression so far.
- struct BasedUser {
- /// Base - The Base value for the PHI node that needs to be inserted for
- /// this use. As the use is processed, information gets moved from this
- /// field to the Imm field (below). BasedUser values are sorted by this
- /// field.
- const SCEV *Base;
-
- /// Inst - The instruction using the induction variable.
- Instruction *Inst;
-
- /// OperandValToReplace - The operand value of Inst to replace with the
- /// EmittedBase.
- Value *OperandValToReplace;
-
- /// Imm - The immediate value that should be added to the base immediately
- /// before Inst, because it will be folded into the imm field of the
- /// instruction. This is also sometimes used for loop-variant values that
- /// must be added inside the loop.
- const SCEV *Imm;
-
- /// Phi - The induction variable that performs the striding that
- /// should be used for this user.
- PHINode *Phi;
-
- // isUseOfPostIncrementedValue - True if this should use the
- // post-incremented version of this IV, not the preincremented version.
- // This can only be set in special cases, such as the terminating setcc
- // instruction for a loop and uses outside the loop that are dominated by
- // the loop.
- bool isUseOfPostIncrementedValue;
-
- BasedUser(IVStrideUse &IVSU, ScalarEvolution *se)
- : Base(IVSU.getOffset()), Inst(IVSU.getUser()),
- OperandValToReplace(IVSU.getOperandValToReplace()),
- Imm(se->getIntegerSCEV(0, Base->getType())),
- isUseOfPostIncrementedValue(IVSU.isUseOfPostIncrementedValue()) {}
-
- // Once we rewrite the code to insert the new IVs we want, update the
- // operands of Inst to use the new expression 'NewBase', with 'Imm' added
- // to it.
- void RewriteInstructionToUseNewBase(const SCEV *NewBase,
- Instruction *InsertPt,
- SCEVExpander &Rewriter, Loop *L, Pass *P,
- SmallVectorImpl<WeakVH> &DeadInsts,
- ScalarEvolution *SE);
-
- Value *InsertCodeForBaseAtPosition(const SCEV *NewBase,
- const Type *Ty,
- SCEVExpander &Rewriter,
- Instruction *IP,
- ScalarEvolution *SE);
- void dump() const;
- };
-}
+ // All pointers have the same requirements, so canonicalize them to an
+ // arbitrary pointer type to minimize variation.
+ if (PointerType *PTy = dyn_cast<PointerType>(AccessTy))
+ AccessTy = PointerType::get(IntegerType::get(PTy->getContext(), 1),
+ PTy->getAddressSpace());
-void BasedUser::dump() const {
- dbgs() << " Base=" << *Base;
- dbgs() << " Imm=" << *Imm;
- dbgs() << " Inst: " << *Inst;
+ return AccessTy;
}
-Value *BasedUser::InsertCodeForBaseAtPosition(const SCEV *NewBase,
- const Type *Ty,
- SCEVExpander &Rewriter,
- Instruction *IP,
- ScalarEvolution *SE) {
- Value *Base = Rewriter.expandCodeFor(NewBase, 0, IP);
-
- // Wrap the base in a SCEVUnknown so that ScalarEvolution doesn't try to
- // re-analyze it.
- const SCEV *NewValSCEV = SE->getUnknown(Base);
-
- // Always emit the immediate into the same block as the user.
- NewValSCEV = SE->getAddExpr(NewValSCEV, Imm);
-
- return Rewriter.expandCodeFor(NewValSCEV, Ty, IP);
+/// isExistingPhi - Return true if this AddRec is already a phi in its loop.
+static bool isExistingPhi(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
+ for (BasicBlock::iterator I = AR->getLoop()->getHeader()->begin();
+ PHINode *PN = dyn_cast<PHINode>(I); ++I) {
+ if (SE.isSCEVable(PN->getType()) &&
+ (SE.getEffectiveSCEVType(PN->getType()) ==
+ SE.getEffectiveSCEVType(AR->getType())) &&
+ SE.getSCEV(PN) == AR)
+ return true;
+ }
+ return false;
}
+/// Check if expanding this expression is likely to incur significant cost. This
+/// is tricky because SCEV doesn't track which expressions are actually computed
+/// by the current IR.
+///
+/// We currently allow expansion of IV increments that involve adds,
+/// multiplication by constants, and AddRecs from existing phis.
+///
+/// TODO: Allow UDivExpr if we can find an existing IV increment that is an
+/// obvious multiple of the UDivExpr.
+static bool isHighCostExpansion(const SCEV *S,
+ SmallPtrSet<const SCEV*, 8> &Processed,
+ ScalarEvolution &SE) {
+ // Zero/One operand expressions
+ switch (S->getSCEVType()) {
+ case scUnknown:
+ case scConstant:
+ return false;
+ case scTruncate:
+ return isHighCostExpansion(cast<SCEVTruncateExpr>(S)->getOperand(),
+ Processed, SE);
+ case scZeroExtend:
+ return isHighCostExpansion(cast<SCEVZeroExtendExpr>(S)->getOperand(),
+ Processed, SE);
+ case scSignExtend:
+ return isHighCostExpansion(cast<SCEVSignExtendExpr>(S)->getOperand(),
+ Processed, SE);
+ }
+
+ if (!Processed.insert(S))
+ return false;
-// Once we rewrite the code to insert the new IVs we want, update the
-// operands of Inst to use the new expression 'NewBase', with 'Imm' added
-// to it. NewBasePt is the last instruction which contributes to the
-// value of NewBase in the case that it's a diffferent instruction from
-// the PHI that NewBase is computed from, or null otherwise.
-//
-void BasedUser::RewriteInstructionToUseNewBase(const SCEV *NewBase,
- Instruction *NewBasePt,
- SCEVExpander &Rewriter, Loop *L, Pass *P,
- SmallVectorImpl<WeakVH> &DeadInsts,
- ScalarEvolution *SE) {
- if (!isa<PHINode>(Inst)) {
- // By default, insert code at the user instruction.
- BasicBlock::iterator InsertPt = Inst;
-
- // However, if the Operand is itself an instruction, the (potentially
- // complex) inserted code may be shared by many users. Because of this, we
- // want to emit code for the computation of the operand right before its old
- // computation. This is usually safe, because we obviously used to use the
- // computation when it was computed in its current block. However, in some
- // cases (e.g. use of a post-incremented induction variable) the NewBase
- // value will be pinned to live somewhere after the original computation.
- // In this case, we have to back off.
- //
- // If this is a use outside the loop (which means after, since it is based
- // on a loop indvar) we use the post-incremented value, so that we don't
- // artificially make the preinc value live out the bottom of the loop.
- if (!isUseOfPostIncrementedValue && L->contains(Inst)) {
- if (NewBasePt && isa<PHINode>(OperandValToReplace)) {
- InsertPt = NewBasePt;
- ++InsertPt;
- } else if (Instruction *OpInst
- = dyn_cast<Instruction>(OperandValToReplace)) {
- InsertPt = OpInst;
- while (isa<PHINode>(InsertPt)) ++InsertPt;
- }
+ if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
+ for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
+ I != E; ++I) {
+ if (isHighCostExpansion(*I, Processed, SE))
+ return true;
}
- Value *NewVal = InsertCodeForBaseAtPosition(NewBase,
- OperandValToReplace->getType(),
- Rewriter, InsertPt, SE);
- // Replace the use of the operand Value with the new Phi we just created.
- Inst->replaceUsesOfWith(OperandValToReplace, NewVal);
-
- DEBUG(dbgs() << " Replacing with ");
- DEBUG(WriteAsOperand(dbgs(), NewVal, /*PrintType=*/false));
- DEBUG(dbgs() << ", which has value " << *NewBase << " plus IMM "
- << *Imm << "\n");
- return;
+ return false;
}
- // PHI nodes are more complex. We have to insert one copy of the NewBase+Imm
- // expression into each operand block that uses it. Note that PHI nodes can
- // have multiple entries for the same predecessor. We use a map to make sure
- // that a PHI node only has a single Value* for each predecessor (which also
- // prevents us from inserting duplicate code in some blocks).
- DenseMap<BasicBlock*, Value*> InsertedCode;
- PHINode *PN = cast<PHINode>(Inst);
- for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
- if (PN->getIncomingValue(i) == OperandValToReplace) {
- // If the original expression is outside the loop, put the replacement
- // code in the same place as the original expression,
- // which need not be an immediate predecessor of this PHI. This way we
- // need only one copy of it even if it is referenced multiple times in
- // the PHI. We don't do this when the original expression is inside the
- // loop because multiple copies sometimes do useful sinking of code in
- // that case(?).
- Instruction *OldLoc = dyn_cast<Instruction>(OperandValToReplace);
- BasicBlock *PHIPred = PN->getIncomingBlock(i);
- if (L->contains(OldLoc)) {
- // If this is a critical edge, split the edge so that we do not insert
- // the code on all predecessor/successor paths. We do this unless this
- // is the canonical backedge for this loop, as this can make some
- // inserted code be in an illegal position.
- if (e != 1 && PHIPred->getTerminator()->getNumSuccessors() > 1 &&
- !isa<IndirectBrInst>(PHIPred->getTerminator()) &&
- (PN->getParent() != L->getHeader() || !L->contains(PHIPred))) {
-
- // First step, split the critical edge.
- BasicBlock *NewBB = SplitCriticalEdge(PHIPred, PN->getParent(),
- P, false);
-
- // Next step: move the basic block. In particular, if the PHI node
- // is outside of the loop, and PredTI is in the loop, we want to
- // move the block to be immediately before the PHI block, not
- // immediately after PredTI.
- if (L->contains(PHIPred) && !L->contains(PN))
- NewBB->moveBefore(PN->getParent());
-
- // Splitting the edge can reduce the number of PHI entries we have.
- e = PN->getNumIncomingValues();
- PHIPred = NewBB;
- i = PN->getBasicBlockIndex(PHIPred);
+ if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
+ if (Mul->getNumOperands() == 2) {
+ // Multiplication by a constant is ok
+ if (isa<SCEVConstant>(Mul->getOperand(0)))
+ return isHighCostExpansion(Mul->getOperand(1), Processed, SE);
+
+ // If we have the value of one operand, check if an existing
+ // multiplication already generates this expression.
+ if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Mul->getOperand(1))) {
+ Value *UVal = U->getValue();
+ for (Value::use_iterator UI = UVal->use_begin(), UE = UVal->use_end();
+ UI != UE; ++UI) {
+ // If U is a constant, it may be used by a ConstantExpr.
+ Instruction *User = dyn_cast<Instruction>(*UI);
+ if (User && User->getOpcode() == Instruction::Mul
+ && SE.isSCEVable(User->getType())) {
+ return SE.getSCEV(User) == Mul;
+ }
}
}
- Value *&Code = InsertedCode[PHIPred];
- if (!Code) {
- // Insert the code into the end of the predecessor block.
- Instruction *InsertPt = (L->contains(OldLoc)) ?
- PHIPred->getTerminator() :
- OldLoc->getParent()->getTerminator();
- Code = InsertCodeForBaseAtPosition(NewBase, PN->getType(),
- Rewriter, InsertPt, SE);
-
- DEBUG(dbgs() << " Changing PHI use to ");
- DEBUG(WriteAsOperand(dbgs(), Code, /*PrintType=*/false));
- DEBUG(dbgs() << ", which has value " << *NewBase << " plus IMM "
- << *Imm << "\n");
- }
-
- // Replace the use of the operand Value with the new Phi we just created.
- PN->setIncomingValue(i, Code);
- Rewriter.clear();
}
}
- // PHI node might have become a constant value after SplitCriticalEdge.
- DeadInsts.push_back(Inst);
-}
-
-
-/// fitsInAddressMode - Return true if V can be subsumed within an addressing
-/// mode, and does not need to be put in a register first.
-static bool fitsInAddressMode(const SCEV *V, const Type *AccessTy,
- const TargetLowering *TLI, bool HasBaseReg) {
- if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(V)) {
- int64_t VC = SC->getValue()->getSExtValue();
- if (TLI) {
- TargetLowering::AddrMode AM;
- AM.BaseOffs = VC;
- AM.HasBaseReg = HasBaseReg;
- return TLI->isLegalAddressingMode(AM, AccessTy);
- } else {
- // Defaults to PPC. PPC allows a sign-extended 16-bit immediate field.
- return (VC > -(1 << 16) && VC < (1 << 16)-1);
- }
+ if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
+ if (isExistingPhi(AR, SE))
+ return false;
}
- if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(V))
- if (GlobalValue *GV = dyn_cast<GlobalValue>(SU->getValue())) {
- if (TLI) {
- TargetLowering::AddrMode AM;
- AM.BaseGV = GV;
- AM.HasBaseReg = HasBaseReg;
- return TLI->isLegalAddressingMode(AM, AccessTy);
- } else {
- // Default: assume global addresses are not legal.
- }
- }
-
- return false;
+ // Fow now, consider any other type of expression (div/mul/min/max) high cost.
+ return true;
}
-/// MoveLoopVariantsToImmediateField - Move any subexpressions from Val that are
-/// loop varying to the Imm operand.
-static void MoveLoopVariantsToImmediateField(const SCEV *&Val, const SCEV *&Imm,
- Loop *L, ScalarEvolution *SE) {
- if (Val->isLoopInvariant(L)) return; // Nothing to do.
+/// DeleteTriviallyDeadInstructions - If any of the instructions is the
+/// specified set are trivially dead, delete them and see if this makes any of
+/// their operands subsequently dead.
+static bool
+DeleteTriviallyDeadInstructions(SmallVectorImpl<WeakVH> &DeadInsts) {
+ bool Changed = false;
- if (const SCEVAddExpr *SAE = dyn_cast<SCEVAddExpr>(Val)) {
- SmallVector<const SCEV *, 4> NewOps;
- NewOps.reserve(SAE->getNumOperands());
+ while (!DeadInsts.empty()) {
+ Instruction *I = dyn_cast_or_null<Instruction>(&*DeadInsts.pop_back_val());
- for (unsigned i = 0; i != SAE->getNumOperands(); ++i)
- if (!SAE->getOperand(i)->isLoopInvariant(L)) {
- // If this is a loop-variant expression, it must stay in the immediate
- // field of the expression.
- Imm = SE->getAddExpr(Imm, SAE->getOperand(i));
- } else {
- NewOps.push_back(SAE->getOperand(i));
+ if (I == 0 || !isInstructionTriviallyDead(I))
+ continue;
+
+ for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
+ if (Instruction *U = dyn_cast<Instruction>(*OI)) {
+ *OI = 0;
+ if (U->use_empty())
+ DeadInsts.push_back(U);
}
- if (NewOps.empty())
- Val = SE->getIntegerSCEV(0, Val->getType());
- else
- Val = SE->getAddExpr(NewOps);
- } else if (const SCEVAddRecExpr *SARE = dyn_cast<SCEVAddRecExpr>(Val)) {
- // Try to pull immediates out of the start value of nested addrec's.
- const SCEV *Start = SARE->getStart();
- MoveLoopVariantsToImmediateField(Start, Imm, L, SE);
-
- SmallVector<const SCEV *, 4> Ops(SARE->op_begin(), SARE->op_end());
- Ops[0] = Start;
- Val = SE->getAddRecExpr(Ops, SARE->getLoop());
- } else {
- // Otherwise, all of Val is variant, move the whole thing over.
- Imm = SE->getAddExpr(Imm, Val);
- Val = SE->getIntegerSCEV(0, Val->getType());
+ I->eraseFromParent();
+ Changed = true;
}
+
+ return Changed;
}
+namespace {
-/// MoveImmediateValues - Look at Val, and pull out any additions of constants
-/// that can fit into the immediate field of instructions in the target.
-/// Accumulate these immediate values into the Imm value.
-static void MoveImmediateValues(const TargetLowering *TLI,
- const Type *AccessTy,
- const SCEV *&Val, const SCEV *&Imm,
- bool isAddress, Loop *L,
- ScalarEvolution *SE) {
- if (const SCEVAddExpr *SAE = dyn_cast<SCEVAddExpr>(Val)) {
- SmallVector<const SCEV *, 4> NewOps;
- NewOps.reserve(SAE->getNumOperands());
+/// Cost - This class is used to measure and compare candidate formulae.
+class Cost {
+ /// TODO: Some of these could be merged. Also, a lexical ordering
+ /// isn't always optimal.
+ unsigned NumRegs;
+ unsigned AddRecCost;
+ unsigned NumIVMuls;
+ unsigned NumBaseAdds;
+ unsigned ImmCost;
+ unsigned SetupCost;
+
+public:
+ Cost()
+ : NumRegs(0), AddRecCost(0), NumIVMuls(0), NumBaseAdds(0), ImmCost(0),
+ SetupCost(0) {}
+
+ bool operator<(const Cost &Other) const;
+
+ void Loose();
+
+#ifndef NDEBUG
+ // Once any of the metrics loses, they must all remain losers.
+ bool isValid() {
+ return ((NumRegs | AddRecCost | NumIVMuls | NumBaseAdds
+ | ImmCost | SetupCost) != ~0u)
+ || ((NumRegs & AddRecCost & NumIVMuls & NumBaseAdds
+ & ImmCost & SetupCost) == ~0u);
+ }
+#endif
- for (unsigned i = 0; i != SAE->getNumOperands(); ++i) {
- const SCEV *NewOp = SAE->getOperand(i);
- MoveImmediateValues(TLI, AccessTy, NewOp, Imm, isAddress, L, SE);
+ bool isLoser() {
+ assert(isValid() && "invalid cost");
+ return NumRegs == ~0u;
+ }
- if (!NewOp->isLoopInvariant(L)) {
- // If this is a loop-variant expression, it must stay in the immediate
- // field of the expression.
- Imm = SE->getAddExpr(Imm, NewOp);
- } else {
- NewOps.push_back(NewOp);
- }
- }
+ void RateFormula(const Formula &F,
+ SmallPtrSet<const SCEV *, 16> &Regs,
+ const DenseSet<const SCEV *> &VisitedRegs,
+ const Loop *L,
+ const SmallVectorImpl<int64_t> &Offsets,
+ ScalarEvolution &SE, DominatorTree &DT,
+ SmallPtrSet<const SCEV *, 16> *LoserRegs = 0);
+
+ void print(raw_ostream &OS) const;
+ void dump() const;
+
+private:
+ void RateRegister(const SCEV *Reg,
+ SmallPtrSet<const SCEV *, 16> &Regs,
+ const Loop *L,
+ ScalarEvolution &SE, DominatorTree &DT);
+ void RatePrimaryRegister(const SCEV *Reg,
+ SmallPtrSet<const SCEV *, 16> &Regs,
+ const Loop *L,
+ ScalarEvolution &SE, DominatorTree &DT,
+ SmallPtrSet<const SCEV *, 16> *LoserRegs);
+};
- if (NewOps.empty())
- Val = SE->getIntegerSCEV(0, Val->getType());
- else
- Val = SE->getAddExpr(NewOps);
- return;
- } else if (const SCEVAddRecExpr *SARE = dyn_cast<SCEVAddRecExpr>(Val)) {
- // Try to pull immediates out of the start value of nested addrec's.
- const SCEV *Start = SARE->getStart();
- MoveImmediateValues(TLI, AccessTy, Start, Imm, isAddress, L, SE);
+}
- if (Start != SARE->getStart()) {
- SmallVector<const SCEV *, 4> Ops(SARE->op_begin(), SARE->op_end());
- Ops[0] = Start;
- Val = SE->getAddRecExpr(Ops, SARE->getLoop());
+/// RateRegister - Tally up interesting quantities from the given register.
+void Cost::RateRegister(const SCEV *Reg,
+ SmallPtrSet<const SCEV *, 16> &Regs,
+ const Loop *L,
+ ScalarEvolution &SE, DominatorTree &DT) {
+ if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg)) {
+ // If this is an addrec for another loop, don't second-guess its addrec phi
+ // nodes. LSR isn't currently smart enough to reason about more than one
+ // loop at a time. LSR has already run on inner loops, will not run on outer
+ // loops, and cannot be expected to change sibling loops.
+ if (AR->getLoop() != L) {
+ // If the AddRec exists, consider it's register free and leave it alone.
+ if (isExistingPhi(AR, SE))
+ return;
+
+ // Otherwise, do not consider this formula at all.
+ Loose();
+ return;
}
- return;
- } else if (const SCEVMulExpr *SME = dyn_cast<SCEVMulExpr>(Val)) {
- // Transform "8 * (4 + v)" -> "32 + 8*V" if "32" fits in the immed field.
- if (isAddress &&
- fitsInAddressMode(SME->getOperand(0), AccessTy, TLI, false) &&
- SME->getNumOperands() == 2 && SME->isLoopInvariant(L)) {
-
- const SCEV *SubImm = SE->getIntegerSCEV(0, Val->getType());
- const SCEV *NewOp = SME->getOperand(1);
- MoveImmediateValues(TLI, AccessTy, NewOp, SubImm, isAddress, L, SE);
-
- // If we extracted something out of the subexpressions, see if we can
- // simplify this!
- if (NewOp != SME->getOperand(1)) {
- // Scale SubImm up by "8". If the result is a target constant, we are
- // good.
- SubImm = SE->getMulExpr(SubImm, SME->getOperand(0));
- if (fitsInAddressMode(SubImm, AccessTy, TLI, false)) {
- // Accumulate the immediate.
- Imm = SE->getAddExpr(Imm, SubImm);
-
- // Update what is left of 'Val'.
- Val = SE->getMulExpr(SME->getOperand(0), NewOp);
+ AddRecCost += 1; /// TODO: This should be a function of the stride.
+
+ // Add the step value register, if it needs one.
+ // TODO: The non-affine case isn't precisely modeled here.
+ if (!AR->isAffine() || !isa<SCEVConstant>(AR->getOperand(1))) {
+ if (!Regs.count(AR->getOperand(1))) {
+ RateRegister(AR->getOperand(1), Regs, L, SE, DT);
+ if (isLoser())
return;
- }
}
}
}
+ ++NumRegs;
+
+ // Rough heuristic; favor registers which don't require extra setup
+ // instructions in the preheader.
+ if (!isa<SCEVUnknown>(Reg) &&
+ !isa<SCEVConstant>(Reg) &&
+ !(isa<SCEVAddRecExpr>(Reg) &&
+ (isa<SCEVUnknown>(cast<SCEVAddRecExpr>(Reg)->getStart()) ||
+ isa<SCEVConstant>(cast<SCEVAddRecExpr>(Reg)->getStart()))))
+ ++SetupCost;
+
+ NumIVMuls += isa<SCEVMulExpr>(Reg) &&
+ SE.hasComputableLoopEvolution(Reg, L);
+}
- // Loop-variant expressions must stay in the immediate field of the
- // expression.
- if ((isAddress && fitsInAddressMode(Val, AccessTy, TLI, false)) ||
- !Val->isLoopInvariant(L)) {
- Imm = SE->getAddExpr(Imm, Val);
- Val = SE->getIntegerSCEV(0, Val->getType());
+/// RatePrimaryRegister - Record this register in the set. If we haven't seen it
+/// before, rate it. Optional LoserRegs provides a way to declare any formula
+/// that refers to one of those regs an instant loser.
+void Cost::RatePrimaryRegister(const SCEV *Reg,
+ SmallPtrSet<const SCEV *, 16> &Regs,
+ const Loop *L,
+ ScalarEvolution &SE, DominatorTree &DT,
+ SmallPtrSet<const SCEV *, 16> *LoserRegs) {
+ if (LoserRegs && LoserRegs->count(Reg)) {
+ Loose();
return;
}
+ if (Regs.insert(Reg)) {
+ RateRegister(Reg, Regs, L, SE, DT);
+ if (isLoser())
+ LoserRegs->insert(Reg);
+ }
+}
+
+void Cost::RateFormula(const Formula &F,
+ SmallPtrSet<const SCEV *, 16> &Regs,
+ const DenseSet<const SCEV *> &VisitedRegs,
+ const Loop *L,
+ const SmallVectorImpl<int64_t> &Offsets,
+ ScalarEvolution &SE, DominatorTree &DT,
+ SmallPtrSet<const SCEV *, 16> *LoserRegs) {
+ // Tally up the registers.
+ if (const SCEV *ScaledReg = F.ScaledReg) {
+ if (VisitedRegs.count(ScaledReg)) {
+ Loose();
+ return;
+ }
+ RatePrimaryRegister(ScaledReg, Regs, L, SE, DT, LoserRegs);
+ if (isLoser())
+ return;
+ }
+ for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
+ E = F.BaseRegs.end(); I != E; ++I) {
+ const SCEV *BaseReg = *I;
+ if (VisitedRegs.count(BaseReg)) {
+ Loose();
+ return;
+ }
+ RatePrimaryRegister(BaseReg, Regs, L, SE, DT, LoserRegs);
+ if (isLoser())
+ return;
+ }
- // Otherwise, no immediates to move.
+ // Determine how many (unfolded) adds we'll need inside the loop.
+ size_t NumBaseParts = F.BaseRegs.size() + (F.UnfoldedOffset != 0);
+ if (NumBaseParts > 1)
+ NumBaseAdds += NumBaseParts - 1;
+
+ // Tally up the non-zero immediates.
+ for (SmallVectorImpl<int64_t>::const_iterator I = Offsets.begin(),
+ E = Offsets.end(); I != E; ++I) {
+ int64_t Offset = (uint64_t)*I + F.AM.BaseOffs;
+ if (F.AM.BaseGV)
+ ImmCost += 64; // Handle symbolic values conservatively.
+ // TODO: This should probably be the pointer size.
+ else if (Offset != 0)
+ ImmCost += APInt(64, Offset, true).getMinSignedBits();
+ }
+ assert(isValid() && "invalid cost");
}
-static void MoveImmediateValues(const TargetLowering *TLI,
- Instruction *User,
- const SCEV *&Val, const SCEV *&Imm,
- bool isAddress, Loop *L,
- ScalarEvolution *SE) {
- const Type *AccessTy = getAccessType(User);
- MoveImmediateValues(TLI, AccessTy, Val, Imm, isAddress, L, SE);
+/// Loose - Set this cost to a losing value.
+void Cost::Loose() {
+ NumRegs = ~0u;
+ AddRecCost = ~0u;
+ NumIVMuls = ~0u;
+ NumBaseAdds = ~0u;
+ ImmCost = ~0u;
+ SetupCost = ~0u;
}
-/// SeparateSubExprs - Decompose Expr into all of the subexpressions that are
-/// added together. This is used to reassociate common addition subexprs
-/// together for maximal sharing when rewriting bases.
-static void SeparateSubExprs(SmallVector<const SCEV *, 16> &SubExprs,
- const SCEV *Expr,
- ScalarEvolution *SE) {
- if (const SCEVAddExpr *AE = dyn_cast<SCEVAddExpr>(Expr)) {
- for (unsigned j = 0, e = AE->getNumOperands(); j != e; ++j)
- SeparateSubExprs(SubExprs, AE->getOperand(j), SE);
- } else if (const SCEVAddRecExpr *SARE = dyn_cast<SCEVAddRecExpr>(Expr)) {
- const SCEV *Zero = SE->getIntegerSCEV(0, Expr->getType());
- if (SARE->getOperand(0) == Zero) {
- SubExprs.push_back(Expr);
- } else {
- // Compute the addrec with zero as its base.
- SmallVector<const SCEV *, 4> Ops(SARE->op_begin(), SARE->op_end());
- Ops[0] = Zero; // Start with zero base.
- SubExprs.push_back(SE->getAddRecExpr(Ops, SARE->getLoop()));
-
-
- SeparateSubExprs(SubExprs, SARE->getOperand(0), SE);
- }
- } else if (!Expr->isZero()) {
- // Do not add zero.
- SubExprs.push_back(Expr);
- }
-}
-
-// This is logically local to the following function, but C++ says we have
-// to make it file scope.
-struct SubExprUseData { unsigned Count; bool notAllUsesAreFree; };
-
-/// RemoveCommonExpressionsFromUseBases - Look through all of the Bases of all
-/// the Uses, removing any common subexpressions, except that if all such
-/// subexpressions can be folded into an addressing mode for all uses inside
-/// the loop (this case is referred to as "free" in comments herein) we do
-/// not remove anything. This looks for things like (a+b+c) and
-/// (a+c+d) and computes the common (a+c) subexpression. The common expression
-/// is *removed* from the Bases and returned.
-static const SCEV *
-RemoveCommonExpressionsFromUseBases(std::vector<BasedUser> &Uses,
- ScalarEvolution *SE, Loop *L,
- const TargetLowering *TLI) {
- unsigned NumUses = Uses.size();
-
- // Only one use? This is a very common case, so we handle it specially and
- // cheaply.
- const SCEV *Zero = SE->getIntegerSCEV(0, Uses[0].Base->getType());
- const SCEV *Result = Zero;
- const SCEV *FreeResult = Zero;
- if (NumUses == 1) {
- // If the use is inside the loop, use its base, regardless of what it is:
- // it is clearly shared across all the IV's. If the use is outside the loop
- // (which means after it) we don't want to factor anything *into* the loop,
- // so just use 0 as the base.
- if (L->contains(Uses[0].Inst))
- std::swap(Result, Uses[0].Base);
- return Result;
- }
+/// operator< - Choose the lower cost.
+bool Cost::operator<(const Cost &Other) const {
+ if (NumRegs != Other.NumRegs)
+ return NumRegs < Other.NumRegs;
+ if (AddRecCost != Other.AddRecCost)
+ return AddRecCost < Other.AddRecCost;
+ if (NumIVMuls != Other.NumIVMuls)
+ return NumIVMuls < Other.NumIVMuls;
+ if (NumBaseAdds != Other.NumBaseAdds)
+ return NumBaseAdds < Other.NumBaseAdds;
+ if (ImmCost != Other.ImmCost)
+ return ImmCost < Other.ImmCost;
+ if (SetupCost != Other.SetupCost)
+ return SetupCost < Other.SetupCost;
+ return false;
+}
- // To find common subexpressions, count how many of Uses use each expression.
- // If any subexpressions are used Uses.size() times, they are common.
- // Also track whether all uses of each expression can be moved into an
- // an addressing mode "for free"; such expressions are left within the loop.
- // struct SubExprUseData { unsigned Count; bool notAllUsesAreFree; };
- std::map<const SCEV *, SubExprUseData> SubExpressionUseData;
-
- // UniqueSubExprs - Keep track of all of the subexpressions we see in the
- // order we see them.
- SmallVector<const SCEV *, 16> UniqueSubExprs;
-
- SmallVector<const SCEV *, 16> SubExprs;
- unsigned NumUsesInsideLoop = 0;
- for (unsigned i = 0; i != NumUses; ++i) {
- // If the user is outside the loop, just ignore it for base computation.
- // Since the user is outside the loop, it must be *after* the loop (if it
- // were before, it could not be based on the loop IV). We don't want users
- // after the loop to affect base computation of values *inside* the loop,
- // because we can always add their offsets to the result IV after the loop
- // is done, ensuring we get good code inside the loop.
- if (!L->contains(Uses[i].Inst))
- continue;
- NumUsesInsideLoop++;
-
- // If the base is zero (which is common), return zero now, there are no
- // CSEs we can find.
- if (Uses[i].Base == Zero) return Zero;
-
- // If this use is as an address we may be able to put CSEs in the addressing
- // mode rather than hoisting them.
- bool isAddrUse = isAddressUse(Uses[i].Inst, Uses[i].OperandValToReplace);
- // We may need the AccessTy below, but only when isAddrUse, so compute it
- // only in that case.
- const Type *AccessTy = 0;
- if (isAddrUse)
- AccessTy = getAccessType(Uses[i].Inst);
-
- // Split the expression into subexprs.
- SeparateSubExprs(SubExprs, Uses[i].Base, SE);
- // Add one to SubExpressionUseData.Count for each subexpr present, and
- // if the subexpr is not a valid immediate within an addressing mode use,
- // set SubExpressionUseData.notAllUsesAreFree. We definitely want to
- // hoist these out of the loop (if they are common to all uses).
- for (unsigned j = 0, e = SubExprs.size(); j != e; ++j) {
- if (++SubExpressionUseData[SubExprs[j]].Count == 1)
- UniqueSubExprs.push_back(SubExprs[j]);
- if (!isAddrUse || !fitsInAddressMode(SubExprs[j], AccessTy, TLI, false))
- SubExpressionUseData[SubExprs[j]].notAllUsesAreFree = true;
- }
- SubExprs.clear();
- }
-
- // Now that we know how many times each is used, build Result. Iterate over
- // UniqueSubexprs so that we have a stable ordering.
- for (unsigned i = 0, e = UniqueSubExprs.size(); i != e; ++i) {
- std::map<const SCEV *, SubExprUseData>::iterator I =
- SubExpressionUseData.find(UniqueSubExprs[i]);
- assert(I != SubExpressionUseData.end() && "Entry not found?");
- if (I->second.Count == NumUsesInsideLoop) { // Found CSE!
- if (I->second.notAllUsesAreFree)
- Result = SE->getAddExpr(Result, I->first);
- else
- FreeResult = SE->getAddExpr(FreeResult, I->first);
- } else
- // Remove non-cse's from SubExpressionUseData.
- SubExpressionUseData.erase(I);
- }
-
- if (FreeResult != Zero) {
- // We have some subexpressions that can be subsumed into addressing
- // modes in every use inside the loop. However, it's possible that
- // there are so many of them that the combined FreeResult cannot
- // be subsumed, or that the target cannot handle both a FreeResult
- // and a Result in the same instruction (for example because it would
- // require too many registers). Check this.
- for (unsigned i=0; i<NumUses; ++i) {
- if (!L->contains(Uses[i].Inst))
- continue;
- // We know this is an addressing mode use; if there are any uses that
- // are not, FreeResult would be Zero.
- const Type *AccessTy = getAccessType(Uses[i].Inst);
- if (!fitsInAddressMode(FreeResult, AccessTy, TLI, Result!=Zero)) {
- // FIXME: could split up FreeResult into pieces here, some hoisted
- // and some not. There is no obvious advantage to this.
- Result = SE->getAddExpr(Result, FreeResult);
- FreeResult = Zero;
- break;
- }
- }
- }
+void Cost::print(raw_ostream &OS) const {
+ OS << NumRegs << " reg" << (NumRegs == 1 ? "" : "s");
+ if (AddRecCost != 0)
+ OS << ", with addrec cost " << AddRecCost;
+ if (NumIVMuls != 0)
+ OS << ", plus " << NumIVMuls << " IV mul" << (NumIVMuls == 1 ? "" : "s");
+ if (NumBaseAdds != 0)
+ OS << ", plus " << NumBaseAdds << " base add"
+ << (NumBaseAdds == 1 ? "" : "s");
+ if (ImmCost != 0)
+ OS << ", plus " << ImmCost << " imm cost";
+ if (SetupCost != 0)
+ OS << ", plus " << SetupCost << " setup cost";
+}
- // If we found no CSE's, return now.
- if (Result == Zero) return Result;
+void Cost::dump() const {
+ print(errs()); errs() << '\n';
+}
- // If we still have a FreeResult, remove its subexpressions from
- // SubExpressionUseData. This means they will remain in the use Bases.
- if (FreeResult != Zero) {
- SeparateSubExprs(SubExprs, FreeResult, SE);
- for (unsigned j = 0, e = SubExprs.size(); j != e; ++j) {
- std::map<const SCEV *, SubExprUseData>::iterator I =
- SubExpressionUseData.find(SubExprs[j]);
- SubExpressionUseData.erase(I);
- }
- SubExprs.clear();
- }
+namespace {
- // Otherwise, remove all of the CSE's we found from each of the base values.
- for (unsigned i = 0; i != NumUses; ++i) {
- // Uses outside the loop don't necessarily include the common base, but
- // the final IV value coming into those uses does. Instead of trying to
- // remove the pieces of the common base, which might not be there,
- // subtract off the base to compensate for this.
- if (!L->contains(Uses[i].Inst)) {
- Uses[i].Base = SE->getMinusSCEV(Uses[i].Base, Result);
- continue;
- }
+/// LSRFixup - An operand value in an instruction which is to be replaced
+/// with some equivalent, possibly strength-reduced, replacement.
+struct LSRFixup {
+ /// UserInst - The instruction which will be updated.
+ Instruction *UserInst;
- // Split the expression into subexprs.
- SeparateSubExprs(SubExprs, Uses[i].Base, SE);
+ /// OperandValToReplace - The operand of the instruction which will
+ /// be replaced. The operand may be used more than once; every instance
+ /// will be replaced.
+ Value *OperandValToReplace;
- // Remove any common subexpressions.
- for (unsigned j = 0, e = SubExprs.size(); j != e; ++j)
- if (SubExpressionUseData.count(SubExprs[j])) {
- SubExprs.erase(SubExprs.begin()+j);
- --j; --e;
- }
+ /// PostIncLoops - If this user is to use the post-incremented value of an
+ /// induction variable, this variable is non-null and holds the loop
+ /// associated with the induction variable.
+ PostIncLoopSet PostIncLoops;
- // Finally, add the non-shared expressions together.
- if (SubExprs.empty())
- Uses[i].Base = Zero;
- else
- Uses[i].Base = SE->getAddExpr(SubExprs);
- SubExprs.clear();
- }
+ /// LUIdx - The index of the LSRUse describing the expression which
+ /// this fixup needs, minus an offset (below).
+ size_t LUIdx;
- return Result;
-}
+ /// Offset - A constant offset to be added to the LSRUse expression.
+ /// This allows multiple fixups to share the same LSRUse with different
+ /// offsets, for example in an unrolled loop.
+ int64_t Offset;
-/// ValidScale - Check whether the given Scale is valid for all loads and
-/// stores in UsersToProcess.
-///
-bool LoopStrengthReduce::ValidScale(bool HasBaseReg, int64_t Scale,
- const std::vector<BasedUser>& UsersToProcess) {
- if (!TLI)
- return true;
+ bool isUseFullyOutsideLoop(const Loop *L) const;
- for (unsigned i = 0, e = UsersToProcess.size(); i!=e; ++i) {
- // If this is a load or other access, pass the type of the access in.
- const Type *AccessTy =
- Type::getVoidTy(UsersToProcess[i].Inst->getContext());
- if (isAddressUse(UsersToProcess[i].Inst,
- UsersToProcess[i].OperandValToReplace))
- AccessTy = getAccessType(UsersToProcess[i].Inst);
- else if (isa<PHINode>(UsersToProcess[i].Inst))
- continue;
+ LSRFixup();
- TargetLowering::AddrMode AM;
- if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(UsersToProcess[i].Imm))
- AM.BaseOffs = SC->getValue()->getSExtValue();
- AM.HasBaseReg = HasBaseReg || !UsersToProcess[i].Base->isZero();
- AM.Scale = Scale;
+ void print(raw_ostream &OS) const;
+ void dump() const;
+};
- // If load[imm+r*scale] is illegal, bail out.
- if (!TLI->isLegalAddressingMode(AM, AccessTy))
- return false;
- }
- return true;
}
-/// ValidOffset - Check whether the given Offset is valid for all loads and
-/// stores in UsersToProcess.
-///
-bool LoopStrengthReduce::ValidOffset(bool HasBaseReg,
- int64_t Offset,
- int64_t Scale,
- const std::vector<BasedUser>& UsersToProcess) {
- if (!TLI)
+LSRFixup::LSRFixup()
+ : UserInst(0), OperandValToReplace(0), LUIdx(~size_t(0)), Offset(0) {}
+
+/// isUseFullyOutsideLoop - Test whether this fixup always uses its
+/// value outside of the given loop.
+bool LSRFixup::isUseFullyOutsideLoop(const Loop *L) const {
+ // PHI nodes use their value in their incoming blocks.
+ if (const PHINode *PN = dyn_cast<PHINode>(UserInst)) {
+ for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
+ if (PN->getIncomingValue(i) == OperandValToReplace &&
+ L->contains(PN->getIncomingBlock(i)))
+ return false;
return true;
+ }
- for (unsigned i=0, e = UsersToProcess.size(); i!=e; ++i) {
- // If this is a load or other access, pass the type of the access in.
- const Type *AccessTy =
- Type::getVoidTy(UsersToProcess[i].Inst->getContext());
- if (isAddressUse(UsersToProcess[i].Inst,
- UsersToProcess[i].OperandValToReplace))
- AccessTy = getAccessType(UsersToProcess[i].Inst);
- else if (isa<PHINode>(UsersToProcess[i].Inst))
- continue;
-
- TargetLowering::AddrMode AM;
- if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(UsersToProcess[i].Imm))
- AM.BaseOffs = SC->getValue()->getSExtValue();
- AM.BaseOffs = (uint64_t)AM.BaseOffs + (uint64_t)Offset;
- AM.HasBaseReg = HasBaseReg || !UsersToProcess[i].Base->isZero();
- AM.Scale = Scale;
+ return !L->contains(UserInst);
+}
- // If load[imm+r*scale] is illegal, bail out.
- if (!TLI->isLegalAddressingMode(AM, AccessTy))
- return false;
+void LSRFixup::print(raw_ostream &OS) const {
+ OS << "UserInst=";
+ // Store is common and interesting enough to be worth special-casing.
+ if (StoreInst *Store = dyn_cast<StoreInst>(UserInst)) {
+ OS << "store ";
+ WriteAsOperand(OS, Store->getOperand(0), /*PrintType=*/false);
+ } else if (UserInst->getType()->isVoidTy())
+ OS << UserInst->getOpcodeName();
+ else
+ WriteAsOperand(OS, UserInst, /*PrintType=*/false);
+
+ OS << ", OperandValToReplace=";
+ WriteAsOperand(OS, OperandValToReplace, /*PrintType=*/false);
+
+ for (PostIncLoopSet::const_iterator I = PostIncLoops.begin(),
+ E = PostIncLoops.end(); I != E; ++I) {
+ OS << ", PostIncLoop=";
+ WriteAsOperand(OS, (*I)->getHeader(), /*PrintType=*/false);
}
- return true;
+
+ if (LUIdx != ~size_t(0))
+ OS << ", LUIdx=" << LUIdx;
+
+ if (Offset != 0)
+ OS << ", Offset=" << Offset;
}
-/// RequiresTypeConversion - Returns true if converting Ty1 to Ty2 is not
-/// a nop.
-bool LoopStrengthReduce::RequiresTypeConversion(const Type *Ty1,
- const Type *Ty2) {
- if (Ty1 == Ty2)
- return false;
- Ty1 = SE->getEffectiveSCEVType(Ty1);
- Ty2 = SE->getEffectiveSCEVType(Ty2);
- if (Ty1 == Ty2)
- return false;
- if (Ty1->canLosslesslyBitCastTo(Ty2))
- return false;
- if (TLI && TLI->isTruncateFree(Ty1, Ty2))
- return false;
- return true;
+void LSRFixup::dump() const {
+ print(errs()); errs() << '\n';
}
-/// CheckForIVReuse - Returns the multiple if the stride is the multiple
-/// of a previous stride and it is a legal value for the target addressing
-/// mode scale component and optional base reg. This allows the users of
-/// this stride to be rewritten as prev iv * factor. It returns 0 if no
-/// reuse is possible. Factors can be negative on same targets, e.g. ARM.
-///
-/// If all uses are outside the loop, we don't require that all multiplies
-/// be folded into the addressing mode, nor even that the factor be constant;
-/// a multiply (executed once) outside the loop is better than another IV
-/// within. Well, usually.
-const SCEV *LoopStrengthReduce::CheckForIVReuse(bool HasBaseReg,
- bool AllUsesAreAddresses,
- bool AllUsesAreOutsideLoop,
- const SCEV *Stride,
- IVExpr &IV, const Type *Ty,
- const std::vector<BasedUser>& UsersToProcess) {
- if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Stride)) {
- int64_t SInt = SC->getValue()->getSExtValue();
- for (unsigned NewStride = 0, e = IU->StrideOrder.size();
- NewStride != e; ++NewStride) {
- std::map<const SCEV *, IVsOfOneStride>::iterator SI =
- IVsByStride.find(IU->StrideOrder[NewStride]);
- if (SI == IVsByStride.end() || !isa<SCEVConstant>(SI->first))
- continue;
- // The other stride has no uses, don't reuse it.
- std::map<const SCEV *, IVUsersOfOneStride *>::iterator UI =
- IU->IVUsesByStride.find(IU->StrideOrder[NewStride]);
- if (UI->second->Users.empty())
- continue;
- int64_t SSInt = cast<SCEVConstant>(SI->first)->getValue()->getSExtValue();
- if (SI->first != Stride &&
- (unsigned(abs64(SInt)) < SSInt || (SInt % SSInt) != 0))
- continue;
- int64_t Scale = SInt / SSInt;
- // Check that this stride is valid for all the types used for loads and
- // stores; if it can be used for some and not others, we might as well use
- // the original stride everywhere, since we have to create the IV for it
- // anyway. If the scale is 1, then we don't need to worry about folding
- // multiplications.
- if (Scale == 1 ||
- (AllUsesAreAddresses &&
- ValidScale(HasBaseReg, Scale, UsersToProcess))) {
- // Prefer to reuse an IV with a base of zero.
- for (std::vector<IVExpr>::iterator II = SI->second.IVs.begin(),
- IE = SI->second.IVs.end(); II != IE; ++II)
- // Only reuse previous IV if it would not require a type conversion
- // and if the base difference can be folded.
- if (II->Base->isZero() &&
- !RequiresTypeConversion(II->Base->getType(), Ty)) {
- IV = *II;
- return SE->getIntegerSCEV(Scale, Stride->getType());
- }
- // Otherwise, settle for an IV with a foldable base.
- if (AllUsesAreAddresses)
- for (std::vector<IVExpr>::iterator II = SI->second.IVs.begin(),
- IE = SI->second.IVs.end(); II != IE; ++II)
- // Only reuse previous IV if it would not require a type conversion
- // and if the base difference can be folded.
- if (SE->getEffectiveSCEVType(II->Base->getType()) ==
- SE->getEffectiveSCEVType(Ty) &&
- isa<SCEVConstant>(II->Base)) {
- int64_t Base =
- cast<SCEVConstant>(II->Base)->getValue()->getSExtValue();
- if (Base > INT32_MIN && Base <= INT32_MAX &&
- ValidOffset(HasBaseReg, -Base * Scale,
- Scale, UsersToProcess)) {
- IV = *II;
- return SE->getIntegerSCEV(Scale, Stride->getType());
- }
- }
- }
- }
- } else if (AllUsesAreOutsideLoop) {
- // Accept nonconstant strides here; it is really really right to substitute
- // an existing IV if we can.
- for (unsigned NewStride = 0, e = IU->StrideOrder.size();
- NewStride != e; ++NewStride) {
- std::map<const SCEV *, IVsOfOneStride>::iterator SI =
- IVsByStride.find(IU->StrideOrder[NewStride]);
- if (SI == IVsByStride.end() || !isa<SCEVConstant>(SI->first))
- continue;
- int64_t SSInt = cast<SCEVConstant>(SI->first)->getValue()->getSExtValue();
- if (SI->first != Stride && SSInt != 1)
- continue;
- for (std::vector<IVExpr>::iterator II = SI->second.IVs.begin(),
- IE = SI->second.IVs.end(); II != IE; ++II)
- // Accept nonzero base here.
- // Only reuse previous IV if it would not require a type conversion.
- if (!RequiresTypeConversion(II->Base->getType(), Ty)) {
- IV = *II;
- return Stride;
- }
- }
- // Special case, old IV is -1*x and this one is x. Can treat this one as
- // -1*old.
- for (unsigned NewStride = 0, e = IU->StrideOrder.size();
- NewStride != e; ++NewStride) {
- std::map<const SCEV *, IVsOfOneStride>::iterator SI =
- IVsByStride.find(IU->StrideOrder[NewStride]);
- if (SI == IVsByStride.end())
- continue;
- if (const SCEVMulExpr *ME = dyn_cast<SCEVMulExpr>(SI->first))
- if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(ME->getOperand(0)))
- if (Stride == ME->getOperand(1) &&
- SC->getValue()->getSExtValue() == -1LL)
- for (std::vector<IVExpr>::iterator II = SI->second.IVs.begin(),
- IE = SI->second.IVs.end(); II != IE; ++II)
- // Accept nonzero base here.
- // Only reuse previous IV if it would not require type conversion.
- if (!RequiresTypeConversion(II->Base->getType(), Ty)) {
- IV = *II;
- return SE->getIntegerSCEV(-1LL, Stride->getType());
- }
- }
+namespace {
+
+/// UniquifierDenseMapInfo - A DenseMapInfo implementation for holding
+/// DenseMaps and DenseSets of sorted SmallVectors of const SCEV*.
+struct UniquifierDenseMapInfo {
+ static SmallVector<const SCEV *, 2> getEmptyKey() {
+ SmallVector<const SCEV *, 2> V;
+ V.push_back(reinterpret_cast<const SCEV *>(-1));
+ return V;
}
- return SE->getIntegerSCEV(0, Stride->getType());
-}
-
-/// PartitionByIsUseOfPostIncrementedValue - Simple boolean predicate that
-/// returns true if Val's isUseOfPostIncrementedValue is true.
-static bool PartitionByIsUseOfPostIncrementedValue(const BasedUser &Val) {
- return Val.isUseOfPostIncrementedValue;
-}
-
-/// isNonConstantNegative - Return true if the specified scev is negated, but
-/// not a constant.
-static bool isNonConstantNegative(const SCEV *Expr) {
- const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Expr);
- if (!Mul) return false;
-
- // If there is a constant factor, it will be first.
- const SCEVConstant *SC = dyn_cast<SCEVConstant>(Mul->getOperand(0));
- if (!SC) return false;
-
- // Return true if the value is negative, this matches things like (-42 * V).
- return SC->getValue()->getValue().isNegative();
-}
-
-/// CollectIVUsers - Transform our list of users and offsets to a bit more
-/// complex table. In this new vector, each 'BasedUser' contains 'Base', the
-/// base of the strided accesses, as well as the old information from Uses. We
-/// progressively move information from the Base field to the Imm field, until
-/// we eventually have the full access expression to rewrite the use.
-const SCEV *LoopStrengthReduce::CollectIVUsers(const SCEV *Stride,
- IVUsersOfOneStride &Uses,
- Loop *L,
- bool &AllUsesAreAddresses,
- bool &AllUsesAreOutsideLoop,
- std::vector<BasedUser> &UsersToProcess) {
- // FIXME: Generalize to non-affine IV's.
- if (!Stride->isLoopInvariant(L))
- return SE->getIntegerSCEV(0, Stride->getType());
-
- UsersToProcess.reserve(Uses.Users.size());
- for (ilist<IVStrideUse>::iterator I = Uses.Users.begin(),
- E = Uses.Users.end(); I != E; ++I) {
- UsersToProcess.push_back(BasedUser(*I, SE));
-
- // Move any loop variant operands from the offset field to the immediate
- // field of the use, so that we don't try to use something before it is
- // computed.
- MoveLoopVariantsToImmediateField(UsersToProcess.back().Base,
- UsersToProcess.back().Imm, L, SE);
- assert(UsersToProcess.back().Base->isLoopInvariant(L) &&
- "Base value is not loop invariant!");
- }
-
- // We now have a whole bunch of uses of like-strided induction variables, but
- // they might all have different bases. We want to emit one PHI node for this
- // stride which we fold as many common expressions (between the IVs) into as
- // possible. Start by identifying the common expressions in the base values
- // for the strides (e.g. if we have "A+C+B" and "A+B+D" as our bases, find
- // "A+B"), emit it to the preheader, then remove the expression from the
- // UsersToProcess base values.
- const SCEV *CommonExprs =
- RemoveCommonExpressionsFromUseBases(UsersToProcess, SE, L, TLI);
-
- // Next, figure out what we can represent in the immediate fields of
- // instructions. If we can represent anything there, move it to the imm
- // fields of the BasedUsers. We do this so that it increases the commonality
- // of the remaining uses.
- unsigned NumPHI = 0;
- bool HasAddress = false;
- for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i) {
- // If the user is not in the current loop, this means it is using the exit
- // value of the IV. Do not put anything in the base, make sure it's all in
- // the immediate field to allow as much factoring as possible.
- if (!L->contains(UsersToProcess[i].Inst)) {
- UsersToProcess[i].Imm = SE->getAddExpr(UsersToProcess[i].Imm,
- UsersToProcess[i].Base);
- UsersToProcess[i].Base =
- SE->getIntegerSCEV(0, UsersToProcess[i].Base->getType());
- } else {
- // Not all uses are outside the loop.
- AllUsesAreOutsideLoop = false;
-
- // Addressing modes can be folded into loads and stores. Be careful that
- // the store is through the expression, not of the expression though.
- bool isPHI = false;
- bool isAddress = isAddressUse(UsersToProcess[i].Inst,
- UsersToProcess[i].OperandValToReplace);
- if (isa<PHINode>(UsersToProcess[i].Inst)) {
- isPHI = true;
- ++NumPHI;
- }
- if (isAddress)
- HasAddress = true;
+ static SmallVector<const SCEV *, 2> getTombstoneKey() {
+ SmallVector<const SCEV *, 2> V;
+ V.push_back(reinterpret_cast<const SCEV *>(-2));
+ return V;
+ }
- // If this use isn't an address, then not all uses are addresses.
- if (!isAddress && !isPHI)
- AllUsesAreAddresses = false;
+ static unsigned getHashValue(const SmallVector<const SCEV *, 2> &V) {
+ unsigned Result = 0;
+ for (SmallVectorImpl<const SCEV *>::const_iterator I = V.begin(),
+ E = V.end(); I != E; ++I)
+ Result ^= DenseMapInfo<const SCEV *>::getHashValue(*I);
+ return Result;
+ }
- MoveImmediateValues(TLI, UsersToProcess[i].Inst, UsersToProcess[i].Base,
- UsersToProcess[i].Imm, isAddress, L, SE);
- }
+ static bool isEqual(const SmallVector<const SCEV *, 2> &LHS,
+ const SmallVector<const SCEV *, 2> &RHS) {
+ return LHS == RHS;
}
+};
+
+/// LSRUse - This class holds the state that LSR keeps for each use in
+/// IVUsers, as well as uses invented by LSR itself. It includes information
+/// about what kinds of things can be folded into the user, information about
+/// the user itself, and information about how the use may be satisfied.
+/// TODO: Represent multiple users of the same expression in common?
+class LSRUse {
+ DenseSet<SmallVector<const SCEV *, 2>, UniquifierDenseMapInfo> Uniquifier;
+
+public:
+ /// KindType - An enum for a kind of use, indicating what types of
+ /// scaled and immediate operands it might support.
+ enum KindType {
+ Basic, ///< A normal use, with no folding.
+ Special, ///< A special case of basic, allowing -1 scales.
+ Address, ///< An address use; folding according to TargetLowering
+ ICmpZero ///< An equality icmp with both operands folded into one.
+ // TODO: Add a generic icmp too?
+ };
- // If one of the use is a PHI node and all other uses are addresses, still
- // allow iv reuse. Essentially we are trading one constant multiplication
- // for one fewer iv.
- if (NumPHI > 1)
- AllUsesAreAddresses = false;
+ KindType Kind;
+ Type *AccessTy;
- // There are no in-loop address uses.
- if (AllUsesAreAddresses && (!HasAddress && !AllUsesAreOutsideLoop))
- AllUsesAreAddresses = false;
+ SmallVector<int64_t, 8> Offsets;
+ int64_t MinOffset;
+ int64_t MaxOffset;
- return CommonExprs;
-}
+ /// AllFixupsOutsideLoop - This records whether all of the fixups using this
+ /// LSRUse are outside of the loop, in which case some special-case heuristics
+ /// may be used.
+ bool AllFixupsOutsideLoop;
-/// ShouldUseFullStrengthReductionMode - Test whether full strength-reduction
-/// is valid and profitable for the given set of users of a stride. In
-/// full strength-reduction mode, all addresses at the current stride are
-/// strength-reduced all the way down to pointer arithmetic.
-///
-bool LoopStrengthReduce::ShouldUseFullStrengthReductionMode(
- const std::vector<BasedUser> &UsersToProcess,
- const Loop *L,
- bool AllUsesAreAddresses,
- const SCEV *Stride) {
- if (!EnableFullLSRMode)
- return false;
+ /// WidestFixupType - This records the widest use type for any fixup using
+ /// this LSRUse. FindUseWithSimilarFormula can't consider uses with different
+ /// max fixup widths to be equivalent, because the narrower one may be relying
+ /// on the implicit truncation to truncate away bogus bits.
+ Type *WidestFixupType;
- // The heuristics below aim to avoid increasing register pressure, but
- // fully strength-reducing all the addresses increases the number of
- // add instructions, so don't do this when optimizing for size.
- // TODO: If the loop is large, the savings due to simpler addresses
- // may oughtweight the costs of the extra increment instructions.
- if (L->getHeader()->getParent()->hasFnAttr(Attribute::OptimizeForSize))
- return false;
+ /// Formulae - A list of ways to build a value that can satisfy this user.
+ /// After the list is populated, one of these is selected heuristically and
+ /// used to formulate a replacement for OperandValToReplace in UserInst.
+ SmallVector<Formula, 12> Formulae;
- // TODO: For now, don't do full strength reduction if there could
- // potentially be greater-stride multiples of the current stride
- // which could reuse the current stride IV.
- if (IU->StrideOrder.back() != Stride)
- return false;
+ /// Regs - The set of register candidates used by all formulae in this LSRUse.
+ SmallPtrSet<const SCEV *, 4> Regs;
- // Iterate through the uses to find conditions that automatically rule out
- // full-lsr mode.
- for (unsigned i = 0, e = UsersToProcess.size(); i != e; ) {
- const SCEV *Base = UsersToProcess[i].Base;
- const SCEV *Imm = UsersToProcess[i].Imm;
- // If any users have a loop-variant component, they can't be fully
- // strength-reduced.
- if (Imm && !Imm->isLoopInvariant(L))
- return false;
- // If there are to users with the same base and the difference between
- // the two Imm values can't be folded into the address, full
- // strength reduction would increase register pressure.
- do {
- const SCEV *CurImm = UsersToProcess[i].Imm;
- if ((CurImm || Imm) && CurImm != Imm) {
- if (!CurImm) CurImm = SE->getIntegerSCEV(0, Stride->getType());
- if (!Imm) Imm = SE->getIntegerSCEV(0, Stride->getType());
- const Instruction *Inst = UsersToProcess[i].Inst;
- const Type *AccessTy = getAccessType(Inst);
- const SCEV *Diff = SE->getMinusSCEV(UsersToProcess[i].Imm, Imm);
- if (!Diff->isZero() &&
- (!AllUsesAreAddresses ||
- !fitsInAddressMode(Diff, AccessTy, TLI, /*HasBaseReg=*/true)))
- return false;
- }
- } while (++i != e && Base == UsersToProcess[i].Base);
- }
+ LSRUse(KindType K, Type *T) : Kind(K), AccessTy(T),
+ MinOffset(INT64_MAX),
+ MaxOffset(INT64_MIN),
+ AllFixupsOutsideLoop(true),
+ WidestFixupType(0) {}
- // If there's exactly one user in this stride, fully strength-reducing it
- // won't increase register pressure. If it's starting from a non-zero base,
- // it'll be simpler this way.
- if (UsersToProcess.size() == 1 && !UsersToProcess[0].Base->isZero())
- return true;
+ bool HasFormulaWithSameRegs(const Formula &F) const;
+ bool InsertFormula(const Formula &F);
+ void DeleteFormula(Formula &F);
+ void RecomputeRegs(size_t LUIdx, RegUseTracker &Reguses);
- // Otherwise, if there are any users in this stride that don't require
- // a register for their base, full strength-reduction will increase
- // register pressure.
- for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i)
- if (UsersToProcess[i].Base->isZero())
- return false;
+ void print(raw_ostream &OS) const;
+ void dump() const;
+};
- // Otherwise, go for it.
- return true;
}
-/// InsertAffinePhi Create and insert a PHI node for an induction variable
-/// with the specified start and step values in the specified loop.
-///
-/// If NegateStride is true, the stride should be negated by using a
-/// subtract instead of an add.
-///
-/// Return the created phi node.
-///
-static PHINode *InsertAffinePhi(const SCEV *Start, const SCEV *Step,
- Instruction *IVIncInsertPt,
- const Loop *L,
- SCEVExpander &Rewriter) {
- assert(Start->isLoopInvariant(L) && "New PHI start is not loop invariant!");
- assert(Step->isLoopInvariant(L) && "New PHI stride is not loop invariant!");
-
- BasicBlock *Header = L->getHeader();
- BasicBlock *Preheader = L->getLoopPreheader();
- BasicBlock *LatchBlock = L->getLoopLatch();
- const Type *Ty = Start->getType();
- Ty = Rewriter.SE.getEffectiveSCEVType(Ty);
-
- PHINode *PN = PHINode::Create(Ty, "lsr.iv", Header->begin());
- PN->addIncoming(Rewriter.expandCodeFor(Start, Ty, Preheader->getTerminator()),
- Preheader);
+/// HasFormula - Test whether this use as a formula which has the same
+/// registers as the given formula.
+bool LSRUse::HasFormulaWithSameRegs(const Formula &F) const {
+ SmallVector<const SCEV *, 2> Key = F.BaseRegs;
+ if (F.ScaledReg) Key.push_back(F.ScaledReg);
+ // Unstable sort by host order ok, because this is only used for uniquifying.
+ std::sort(Key.begin(), Key.end());
+ return Uniquifier.count(Key);
+}
- // If the stride is negative, insert a sub instead of an add for the
- // increment.
- bool isNegative = isNonConstantNegative(Step);
- const SCEV *IncAmount = Step;
- if (isNegative)
- IncAmount = Rewriter.SE.getNegativeSCEV(Step);
-
- // Insert an add instruction right before the terminator corresponding
- // to the back-edge or just before the only use. The location is determined
- // by the caller and passed in as IVIncInsertPt.
- Value *StepV = Rewriter.expandCodeFor(IncAmount, Ty,
- Preheader->getTerminator());
- Instruction *IncV;
- if (isNegative) {
- IncV = BinaryOperator::CreateSub(PN, StepV, "lsr.iv.next",
- IVIncInsertPt);
- } else {
- IncV = BinaryOperator::CreateAdd(PN, StepV, "lsr.iv.next",
- IVIncInsertPt);
- }
- if (!isa<ConstantInt>(StepV)) ++NumVariable;
+/// InsertFormula - If the given formula has not yet been inserted, add it to
+/// the list, and return true. Return false otherwise.
+bool LSRUse::InsertFormula(const Formula &F) {
+ SmallVector<const SCEV *, 2> Key = F.BaseRegs;
+ if (F.ScaledReg) Key.push_back(F.ScaledReg);
+ // Unstable sort by host order ok, because this is only used for uniquifying.
+ std::sort(Key.begin(), Key.end());
- PN->addIncoming(IncV, LatchBlock);
+ if (!Uniquifier.insert(Key).second)
+ return false;
- ++NumInserted;
- return PN;
-}
+ // Using a register to hold the value of 0 is not profitable.
+ assert((!F.ScaledReg || !F.ScaledReg->isZero()) &&
+ "Zero allocated in a scaled register!");
+#ifndef NDEBUG
+ for (SmallVectorImpl<const SCEV *>::const_iterator I =
+ F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I)
+ assert(!(*I)->isZero() && "Zero allocated in a base register!");
+#endif
-static void SortUsersToProcess(std::vector<BasedUser> &UsersToProcess) {
- // We want to emit code for users inside the loop first. To do this, we
- // rearrange BasedUser so that the entries at the end have
- // isUseOfPostIncrementedValue = false, because we pop off the end of the
- // vector (so we handle them first).
- std::partition(UsersToProcess.begin(), UsersToProcess.end(),
- PartitionByIsUseOfPostIncrementedValue);
+ // Add the formula to the list.
+ Formulae.push_back(F);
- // Sort this by base, so that things with the same base are handled
- // together. By partitioning first and stable-sorting later, we are
- // guaranteed that within each base we will pop off users from within the
- // loop before users outside of the loop with a particular base.
- //
- // We would like to use stable_sort here, but we can't. The problem is that
- // const SCEV *'s don't have a deterministic ordering w.r.t to each other, so
- // we don't have anything to do a '<' comparison on. Because we think the
- // number of uses is small, do a horrible bubble sort which just relies on
- // ==.
- for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i) {
- // Get a base value.
- const SCEV *Base = UsersToProcess[i].Base;
-
- // Compact everything with this base to be consecutive with this one.
- for (unsigned j = i+1; j != e; ++j) {
- if (UsersToProcess[j].Base == Base) {
- std::swap(UsersToProcess[i+1], UsersToProcess[j]);
- ++i;
- }
- }
- }
-}
+ // Record registers now being used by this use.
+ Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
-/// PrepareToStrengthReduceFully - Prepare to fully strength-reduce
-/// UsersToProcess, meaning lowering addresses all the way down to direct
-/// pointer arithmetic.
-///
-void
-LoopStrengthReduce::PrepareToStrengthReduceFully(
- std::vector<BasedUser> &UsersToProcess,
- const SCEV *Stride,
- const SCEV *CommonExprs,
- const Loop *L,
- SCEVExpander &PreheaderRewriter) {
- DEBUG(dbgs() << " Fully reducing all users\n");
-
- // Rewrite the UsersToProcess records, creating a separate PHI for each
- // unique Base value.
- Instruction *IVIncInsertPt = L->getLoopLatch()->getTerminator();
- for (unsigned i = 0, e = UsersToProcess.size(); i != e; ) {
- // TODO: The uses are grouped by base, but not sorted. We arbitrarily
- // pick the first Imm value here to start with, and adjust it for the
- // other uses.
- const SCEV *Imm = UsersToProcess[i].Imm;
- const SCEV *Base = UsersToProcess[i].Base;
- const SCEV *Start = SE->getAddExpr(CommonExprs, Base, Imm);
- PHINode *Phi = InsertAffinePhi(Start, Stride, IVIncInsertPt, L,
- PreheaderRewriter);
- // Loop over all the users with the same base.
- do {
- UsersToProcess[i].Base = SE->getIntegerSCEV(0, Stride->getType());
- UsersToProcess[i].Imm = SE->getMinusSCEV(UsersToProcess[i].Imm, Imm);
- UsersToProcess[i].Phi = Phi;
- assert(UsersToProcess[i].Imm->isLoopInvariant(L) &&
- "ShouldUseFullStrengthReductionMode should reject this!");
- } while (++i != e && Base == UsersToProcess[i].Base);
- }
+ return true;
}
-/// FindIVIncInsertPt - Return the location to insert the increment instruction.
-/// If the only use if a use of postinc value, (must be the loop termination
-/// condition), then insert it just before the use.
-static Instruction *FindIVIncInsertPt(std::vector<BasedUser> &UsersToProcess,
- const Loop *L) {
- if (UsersToProcess.size() == 1 &&
- UsersToProcess[0].isUseOfPostIncrementedValue &&
- L->contains(UsersToProcess[0].Inst))
- return UsersToProcess[0].Inst;
- return L->getLoopLatch()->getTerminator();
+/// DeleteFormula - Remove the given formula from this use's list.
+void LSRUse::DeleteFormula(Formula &F) {
+ if (&F != &Formulae.back())
+ std::swap(F, Formulae.back());
+ Formulae.pop_back();
}
-/// PrepareToStrengthReduceWithNewPhi - Insert a new induction variable for the
-/// given users to share.
-///
-void
-LoopStrengthReduce::PrepareToStrengthReduceWithNewPhi(
- std::vector<BasedUser> &UsersToProcess,
- const SCEV *Stride,
- const SCEV *CommonExprs,
- Value *CommonBaseV,
- Instruction *IVIncInsertPt,
- const Loop *L,
- SCEVExpander &PreheaderRewriter) {
- DEBUG(dbgs() << " Inserting new PHI:\n");
-
- PHINode *Phi = InsertAffinePhi(SE->getUnknown(CommonBaseV),
- Stride, IVIncInsertPt, L,
- PreheaderRewriter);
-
- // Remember this in case a later stride is multiple of this.
- IVsByStride[Stride].addIV(Stride, CommonExprs, Phi);
-
- // All the users will share this new IV.
- for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i)
- UsersToProcess[i].Phi = Phi;
-
- DEBUG(dbgs() << " IV=");
- DEBUG(WriteAsOperand(dbgs(), Phi, /*PrintType=*/false));
- DEBUG(dbgs() << "\n");
-}
-
-/// PrepareToStrengthReduceFromSmallerStride - Prepare for the given users to
-/// reuse an induction variable with a stride that is a factor of the current
-/// induction variable.
-///
-void
-LoopStrengthReduce::PrepareToStrengthReduceFromSmallerStride(
- std::vector<BasedUser> &UsersToProcess,
- Value *CommonBaseV,
- const IVExpr &ReuseIV,
- Instruction *PreInsertPt) {
- DEBUG(dbgs() << " Rewriting in terms of existing IV of STRIDE "
- << *ReuseIV.Stride << " and BASE " << *ReuseIV.Base << "\n");
-
- // All the users will share the reused IV.
- for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i)
- UsersToProcess[i].Phi = ReuseIV.PHI;
-
- Constant *C = dyn_cast<Constant>(CommonBaseV);
- if (C &&
- (!C->isNullValue() &&
- !fitsInAddressMode(SE->getUnknown(CommonBaseV), CommonBaseV->getType(),
- TLI, false)))
- // We want the common base emitted into the preheader! This is just
- // using cast as a copy so BitCast (no-op cast) is appropriate
- CommonBaseV = new BitCastInst(CommonBaseV, CommonBaseV->getType(),
- "commonbase", PreInsertPt);
-}
-
-static bool IsImmFoldedIntoAddrMode(GlobalValue *GV, int64_t Offset,
- const Type *AccessTy,
- std::vector<BasedUser> &UsersToProcess,
- const TargetLowering *TLI) {
- SmallVector<Instruction*, 16> AddrModeInsts;
- for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i) {
- if (UsersToProcess[i].isUseOfPostIncrementedValue)
- continue;
- ExtAddrMode AddrMode =
- AddressingModeMatcher::Match(UsersToProcess[i].OperandValToReplace,
- AccessTy, UsersToProcess[i].Inst,
- AddrModeInsts, *TLI);
- if (GV && GV != AddrMode.BaseGV)
- return false;
- if (Offset && !AddrMode.BaseOffs)
- // FIXME: How to accurate check it's immediate offset is folded.
- return false;
- AddrModeInsts.clear();
+/// RecomputeRegs - Recompute the Regs field, and update RegUses.
+void LSRUse::RecomputeRegs(size_t LUIdx, RegUseTracker &RegUses) {
+ // Now that we've filtered out some formulae, recompute the Regs set.
+ SmallPtrSet<const SCEV *, 4> OldRegs = Regs;
+ Regs.clear();
+ for (SmallVectorImpl<Formula>::const_iterator I = Formulae.begin(),
+ E = Formulae.end(); I != E; ++I) {
+ const Formula &F = *I;
+ if (F.ScaledReg) Regs.insert(F.ScaledReg);
+ Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
}
- return true;
+
+ // Update the RegTracker.
+ for (SmallPtrSet<const SCEV *, 4>::iterator I = OldRegs.begin(),
+ E = OldRegs.end(); I != E; ++I)
+ if (!Regs.count(*I))
+ RegUses.DropRegister(*I, LUIdx);
}
-/// StrengthReduceIVUsersOfStride - Strength reduce all of the users of a single
-/// stride of IV. All of the users may have different starting values, and this
-/// may not be the only stride.
-void
-LoopStrengthReduce::StrengthReduceIVUsersOfStride(const SCEV *Stride,
- IVUsersOfOneStride &Uses,
- Loop *L) {
- // If all the users are moved to another stride, then there is nothing to do.
- if (Uses.Users.empty())
- return;
+void LSRUse::print(raw_ostream &OS) const {
+ OS << "LSR Use: Kind=";
+ switch (Kind) {
+ case Basic: OS << "Basic"; break;
+ case Special: OS << "Special"; break;
+ case ICmpZero: OS << "ICmpZero"; break;
+ case Address:
+ OS << "Address of ";
+ if (AccessTy->isPointerTy())
+ OS << "pointer"; // the full pointer type could be really verbose
+ else
+ OS << *AccessTy;
+ }
- // Keep track if every use in UsersToProcess is an address. If they all are,
- // we may be able to rewrite the entire collection of them in terms of a
- // smaller-stride IV.
- bool AllUsesAreAddresses = true;
-
- // Keep track if every use of a single stride is outside the loop. If so,
- // we want to be more aggressive about reusing a smaller-stride IV; a
- // multiply outside the loop is better than another IV inside. Well, usually.
- bool AllUsesAreOutsideLoop = true;
-
- // Transform our list of users and offsets to a bit more complex table. In
- // this new vector, each 'BasedUser' contains 'Base' the base of the
- // strided accessas well as the old information from Uses. We progressively
- // move information from the Base field to the Imm field, until we eventually
- // have the full access expression to rewrite the use.
- std::vector<BasedUser> UsersToProcess;
- const SCEV *CommonExprs = CollectIVUsers(Stride, Uses, L, AllUsesAreAddresses,
- AllUsesAreOutsideLoop,
- UsersToProcess);
-
- // Sort the UsersToProcess array so that users with common bases are
- // next to each other.
- SortUsersToProcess(UsersToProcess);
-
- // If we managed to find some expressions in common, we'll need to carry
- // their value in a register and add it in for each use. This will take up
- // a register operand, which potentially restricts what stride values are
- // valid.
- bool HaveCommonExprs = !CommonExprs->isZero();
- const Type *ReplacedTy = CommonExprs->getType();
-
- // If all uses are addresses, consider sinking the immediate part of the
- // common expression back into uses if they can fit in the immediate fields.
- if (TLI && HaveCommonExprs && AllUsesAreAddresses) {
- const SCEV *NewCommon = CommonExprs;
- const SCEV *Imm = SE->getIntegerSCEV(0, ReplacedTy);
- MoveImmediateValues(TLI, Type::getVoidTy(
- L->getLoopPreheader()->getContext()),
- NewCommon, Imm, true, L, SE);
- if (!Imm->isZero()) {
- bool DoSink = true;
-
- // If the immediate part of the common expression is a GV, check if it's
- // possible to fold it into the target addressing mode.
- GlobalValue *GV = 0;
- if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(Imm))
- GV = dyn_cast<GlobalValue>(SU->getValue());
- int64_t Offset = 0;
- if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Imm))
- Offset = SC->getValue()->getSExtValue();
- if (GV || Offset)
- // Pass VoidTy as the AccessTy to be conservative, because
- // there could be multiple access types among all the uses.
- DoSink = IsImmFoldedIntoAddrMode(GV, Offset,
- Type::getVoidTy(L->getLoopPreheader()->getContext()),
- UsersToProcess, TLI);
-
- if (DoSink) {
- DEBUG(dbgs() << " Sinking " << *Imm << " back down into uses\n");
- for (unsigned i = 0, e = UsersToProcess.size(); i != e; ++i)
- UsersToProcess[i].Imm = SE->getAddExpr(UsersToProcess[i].Imm, Imm);
- CommonExprs = NewCommon;
- HaveCommonExprs = !CommonExprs->isZero();
- ++NumImmSunk;
- }
- }
+ OS << ", Offsets={";
+ for (SmallVectorImpl<int64_t>::const_iterator I = Offsets.begin(),
+ E = Offsets.end(); I != E; ++I) {
+ OS << *I;
+ if (llvm::next(I) != E)
+ OS << ',';
}
+ OS << '}';
- // Now that we know what we need to do, insert the PHI node itself.
- //
- DEBUG(dbgs() << "LSR: Examining IVs of TYPE " << *ReplacedTy << " of STRIDE "
- << *Stride << ":\n"
- << " Common base: " << *CommonExprs << "\n");
+ if (AllFixupsOutsideLoop)
+ OS << ", all-fixups-outside-loop";
- SCEVExpander Rewriter(*SE);
- SCEVExpander PreheaderRewriter(*SE);
+ if (WidestFixupType)
+ OS << ", widest fixup type: " << *WidestFixupType;
+}
- BasicBlock *Preheader = L->getLoopPreheader();
- Instruction *PreInsertPt = Preheader->getTerminator();
- BasicBlock *LatchBlock = L->getLoopLatch();
- Instruction *IVIncInsertPt = LatchBlock->getTerminator();
-
- Value *CommonBaseV = Constant::getNullValue(ReplacedTy);
-
- const SCEV *RewriteFactor = SE->getIntegerSCEV(0, ReplacedTy);
- IVExpr ReuseIV(SE->getIntegerSCEV(0,
- Type::getInt32Ty(Preheader->getContext())),
- SE->getIntegerSCEV(0,
- Type::getInt32Ty(Preheader->getContext())),
- 0);
-
- // Choose a strength-reduction strategy and prepare for it by creating
- // the necessary PHIs and adjusting the bookkeeping.
- if (ShouldUseFullStrengthReductionMode(UsersToProcess, L,
- AllUsesAreAddresses, Stride)) {
- PrepareToStrengthReduceFully(UsersToProcess, Stride, CommonExprs, L,
- PreheaderRewriter);
- } else {
- // Emit the initial base value into the loop preheader.
- CommonBaseV = PreheaderRewriter.expandCodeFor(CommonExprs, ReplacedTy,
- PreInsertPt);
-
- // If all uses are addresses, check if it is possible to reuse an IV. The
- // new IV must have a stride that is a multiple of the old stride; the
- // multiple must be a number that can be encoded in the scale field of the
- // target addressing mode; and we must have a valid instruction after this
- // substitution, including the immediate field, if any.
- RewriteFactor = CheckForIVReuse(HaveCommonExprs, AllUsesAreAddresses,
- AllUsesAreOutsideLoop,
- Stride, ReuseIV, ReplacedTy,
- UsersToProcess);
- if (!RewriteFactor->isZero())
- PrepareToStrengthReduceFromSmallerStride(UsersToProcess, CommonBaseV,
- ReuseIV, PreInsertPt);
- else {
- IVIncInsertPt = FindIVIncInsertPt(UsersToProcess, L);
- PrepareToStrengthReduceWithNewPhi(UsersToProcess, Stride, CommonExprs,
- CommonBaseV, IVIncInsertPt,
- L, PreheaderRewriter);
- }
- }
-
- // Process all the users now, replacing their strided uses with
- // strength-reduced forms. This outer loop handles all bases, the inner
- // loop handles all users of a particular base.
- while (!UsersToProcess.empty()) {
- const SCEV *Base = UsersToProcess.back().Base;
- Instruction *Inst = UsersToProcess.back().Inst;
-
- // Emit the code for Base into the preheader.
- Value *BaseV = 0;
- if (!Base->isZero()) {
- BaseV = PreheaderRewriter.expandCodeFor(Base, 0, PreInsertPt);
-
- DEBUG(dbgs() << " INSERTING code for BASE = " << *Base << ":");
- if (BaseV->hasName())
- DEBUG(dbgs() << " Result value name = %" << BaseV->getName());
- DEBUG(dbgs() << "\n");
-
- // If BaseV is a non-zero constant, make sure that it gets inserted into
- // the preheader, instead of being forward substituted into the uses. We
- // do this by forcing a BitCast (noop cast) to be inserted into the
- // preheader in this case.
- if (!fitsInAddressMode(Base, getAccessType(Inst), TLI, false) &&
- isa<Constant>(BaseV)) {
- // We want this constant emitted into the preheader! This is just
- // using cast as a copy so BitCast (no-op cast) is appropriate
- BaseV = new BitCastInst(BaseV, BaseV->getType(), "preheaderinsert",
- PreInsertPt);
- }
- }
+void LSRUse::dump() const {
+ print(errs()); errs() << '\n';
+}
- // Emit the code to add the immediate offset to the Phi value, just before
- // the instructions that we identified as using this stride and base.
- do {
- // FIXME: Use emitted users to emit other users.
- BasedUser &User = UsersToProcess.back();
+/// isLegalUse - Test whether the use described by AM is "legal", meaning it can
+/// be completely folded into the user instruction at isel time. This includes
+/// address-mode folding and special icmp tricks.
+static bool isLegalUse(const TargetLowering::AddrMode &AM,
+ LSRUse::KindType Kind, Type *AccessTy,
+ const TargetLowering *TLI) {
+ switch (Kind) {
+ case LSRUse::Address:
+ // If we have low-level target information, ask the target if it can
+ // completely fold this address.
+ if (TLI) return TLI->isLegalAddressingMode(AM, AccessTy);
+
+ // Otherwise, just guess that reg+reg addressing is legal.
+ return !AM.BaseGV && AM.BaseOffs == 0 && AM.Scale <= 1;
+
+ case LSRUse::ICmpZero:
+ // There's not even a target hook for querying whether it would be legal to
+ // fold a GV into an ICmp.
+ if (AM.BaseGV)
+ return false;
- DEBUG(dbgs() << " Examining ");
- if (User.isUseOfPostIncrementedValue)
- DEBUG(dbgs() << "postinc");
- else
- DEBUG(dbgs() << "preinc");
- DEBUG(dbgs() << " use ");
- DEBUG(WriteAsOperand(dbgs(), UsersToProcess.back().OperandValToReplace,
- /*PrintType=*/false));
- DEBUG(dbgs() << " in Inst: " << *User.Inst);
-
- // If this instruction wants to use the post-incremented value, move it
- // after the post-inc and use its value instead of the PHI.
- Value *RewriteOp = User.Phi;
- if (User.isUseOfPostIncrementedValue) {
- RewriteOp = User.Phi->getIncomingValueForBlock(LatchBlock);
- // If this user is in the loop, make sure it is the last thing in the
- // loop to ensure it is dominated by the increment. In case it's the
- // only use of the iv, the increment instruction is already before the
- // use.
- if (L->contains(User.Inst) && User.Inst != IVIncInsertPt)
- User.Inst->moveBefore(IVIncInsertPt);
- }
+ // ICmp only has two operands; don't allow more than two non-trivial parts.
+ if (AM.Scale != 0 && AM.HasBaseReg && AM.BaseOffs != 0)
+ return false;
- const SCEV *RewriteExpr = SE->getUnknown(RewriteOp);
+ // ICmp only supports no scale or a -1 scale, as we can "fold" a -1 scale by
+ // putting the scaled register in the other operand of the icmp.
+ if (AM.Scale != 0 && AM.Scale != -1)
+ return false;
- if (SE->getEffectiveSCEVType(RewriteOp->getType()) !=
- SE->getEffectiveSCEVType(ReplacedTy)) {
- assert(SE->getTypeSizeInBits(RewriteOp->getType()) >
- SE->getTypeSizeInBits(ReplacedTy) &&
- "Unexpected widening cast!");
- RewriteExpr = SE->getTruncateExpr(RewriteExpr, ReplacedTy);
- }
+ // If we have low-level target information, ask the target if it can fold an
+ // integer immediate on an icmp.
+ if (AM.BaseOffs != 0) {
+ if (!TLI)
+ return false;
+ // We have one of:
+ // ICmpZero BaseReg + Offset => ICmp BaseReg, -Offset
+ // ICmpZero -1*ScaleReg + Offset => ICmp ScaleReg, Offset
+ // Offs is the ICmp immediate.
+ int64_t Offs = AM.BaseOffs;
+ if (AM.Scale == 0)
+ Offs = -(uint64_t)Offs; // The cast does the right thing with INT64_MIN.
+ return TLI->isLegalICmpImmediate(Offs);
+ }
- // If we had to insert new instructions for RewriteOp, we have to
- // consider that they may not have been able to end up immediately
- // next to RewriteOp, because non-PHI instructions may never precede
- // PHI instructions in a block. In this case, remember where the last
- // instruction was inserted so that if we're replacing a different
- // PHI node, we can use the later point to expand the final
- // RewriteExpr.
- Instruction *NewBasePt = dyn_cast<Instruction>(RewriteOp);
- if (RewriteOp == User.Phi) NewBasePt = 0;
-
- // Clear the SCEVExpander's expression map so that we are guaranteed
- // to have the code emitted where we expect it.
- Rewriter.clear();
-
- // If we are reusing the iv, then it must be multiplied by a constant
- // factor to take advantage of the addressing mode scale component.
- if (!RewriteFactor->isZero()) {
- // If we're reusing an IV with a nonzero base (currently this happens
- // only when all reuses are outside the loop) subtract that base here.
- // The base has been used to initialize the PHI node but we don't want
- // it here.
- if (!ReuseIV.Base->isZero()) {
- const SCEV *typedBase = ReuseIV.Base;
- if (SE->getEffectiveSCEVType(RewriteExpr->getType()) !=
- SE->getEffectiveSCEVType(ReuseIV.Base->getType())) {
- // It's possible the original IV is a larger type than the new IV,
- // in which case we have to truncate the Base. We checked in
- // RequiresTypeConversion that this is valid.
- assert(SE->getTypeSizeInBits(RewriteExpr->getType()) <
- SE->getTypeSizeInBits(ReuseIV.Base->getType()) &&
- "Unexpected lengthening conversion!");
- typedBase = SE->getTruncateExpr(ReuseIV.Base,
- RewriteExpr->getType());
- }
- RewriteExpr = SE->getMinusSCEV(RewriteExpr, typedBase);
- }
+ // ICmpZero BaseReg + -1*ScaleReg => ICmp BaseReg, ScaleReg
+ return true;
- // Multiply old variable, with base removed, by new scale factor.
- RewriteExpr = SE->getMulExpr(RewriteFactor,
- RewriteExpr);
-
- // The common base is emitted in the loop preheader. But since we
- // are reusing an IV, it has not been used to initialize the PHI node.
- // Add it to the expression used to rewrite the uses.
- // When this use is outside the loop, we earlier subtracted the
- // common base, and are adding it back here. Use the same expression
- // as before, rather than CommonBaseV, so DAGCombiner will zap it.
- if (!CommonExprs->isZero()) {
- if (L->contains(User.Inst))
- RewriteExpr = SE->getAddExpr(RewriteExpr,
- SE->getUnknown(CommonBaseV));
- else
- RewriteExpr = SE->getAddExpr(RewriteExpr, CommonExprs);
- }
- }
+ case LSRUse::Basic:
+ // Only handle single-register values.
+ return !AM.BaseGV && AM.Scale == 0 && AM.BaseOffs == 0;
- // Now that we know what we need to do, insert code before User for the
- // immediate and any loop-variant expressions.
- if (BaseV)
- // Add BaseV to the PHI value if needed.
- RewriteExpr = SE->getAddExpr(RewriteExpr, SE->getUnknown(BaseV));
-
- User.RewriteInstructionToUseNewBase(RewriteExpr, NewBasePt,
- Rewriter, L, this,
- DeadInsts, SE);
-
- // Mark old value we replaced as possibly dead, so that it is eliminated
- // if we just replaced the last use of that value.
- DeadInsts.push_back(User.OperandValToReplace);
-
- UsersToProcess.pop_back();
- ++NumReduced;
-
- // If there are any more users to process with the same base, process them
- // now. We sorted by base above, so we just have to check the last elt.
- } while (!UsersToProcess.empty() && UsersToProcess.back().Base == Base);
- // TODO: Next, find out which base index is the most common, pull it out.
- }
-
- // IMPORTANT TODO: Figure out how to partition the IV's with this stride, but
- // different starting values, into different PHIs.
-}
-
-void LoopStrengthReduce::StrengthReduceIVUsers(Loop *L) {
- // Note: this processes each stride/type pair individually. All users
- // passed into StrengthReduceIVUsersOfStride have the same type AND stride.
- // Also, note that we iterate over IVUsesByStride indirectly by using
- // StrideOrder. This extra layer of indirection makes the ordering of
- // strides deterministic - not dependent on map order.
- for (unsigned Stride = 0, e = IU->StrideOrder.size(); Stride != e; ++Stride) {
- std::map<const SCEV *, IVUsersOfOneStride *>::iterator SI =
- IU->IVUsesByStride.find(IU->StrideOrder[Stride]);
- assert(SI != IU->IVUsesByStride.end() && "Stride doesn't exist!");
- // FIXME: Generalize to non-affine IV's.
- if (!SI->first->isLoopInvariant(L))
- continue;
- StrengthReduceIVUsersOfStride(SI->first, *SI->second, L);
+ case LSRUse::Special:
+ // Only handle -1 scales, or no scale.
+ return AM.Scale == 0 || AM.Scale == -1;
}
+
+ llvm_unreachable("Invalid LSRUse Kind!");
}
-/// FindIVUserForCond - If Cond has an operand that is an expression of an IV,
-/// set the IV user and stride information and return true, otherwise return
-/// false.
-bool LoopStrengthReduce::FindIVUserForCond(ICmpInst *Cond,
- IVStrideUse *&CondUse,
- const SCEV* &CondStride) {
- for (unsigned Stride = 0, e = IU->StrideOrder.size();
- Stride != e && !CondUse; ++Stride) {
- std::map<const SCEV *, IVUsersOfOneStride *>::iterator SI =
- IU->IVUsesByStride.find(IU->StrideOrder[Stride]);
- assert(SI != IU->IVUsesByStride.end() && "Stride doesn't exist!");
-
- for (ilist<IVStrideUse>::iterator UI = SI->second->Users.begin(),
- E = SI->second->Users.end(); UI != E; ++UI)
- if (UI->getUser() == Cond) {
- // NOTE: we could handle setcc instructions with multiple uses here, but
- // InstCombine does it as well for simple uses, it's not clear that it
- // occurs enough in real life to handle.
- CondUse = UI;
- CondStride = SI->first;
- return true;
- }
+static bool isLegalUse(TargetLowering::AddrMode AM,
+ int64_t MinOffset, int64_t MaxOffset,
+ LSRUse::KindType Kind, Type *AccessTy,
+ const TargetLowering *TLI) {
+ // Check for overflow.
+ if (((int64_t)((uint64_t)AM.BaseOffs + MinOffset) > AM.BaseOffs) !=
+ (MinOffset > 0))
+ return false;
+ AM.BaseOffs = (uint64_t)AM.BaseOffs + MinOffset;
+ if (isLegalUse(AM, Kind, AccessTy, TLI)) {
+ AM.BaseOffs = (uint64_t)AM.BaseOffs - MinOffset;
+ // Check for overflow.
+ if (((int64_t)((uint64_t)AM.BaseOffs + MaxOffset) > AM.BaseOffs) !=
+ (MaxOffset > 0))
+ return false;
+ AM.BaseOffs = (uint64_t)AM.BaseOffs + MaxOffset;
+ return isLegalUse(AM, Kind, AccessTy, TLI);
}
return false;
}
-namespace {
- // Constant strides come first which in turns are sorted by their absolute
- // values. If absolute values are the same, then positive strides comes first.
- // e.g.
- // 4, -1, X, 1, 2 ==> 1, -1, 2, 4, X
- struct StrideCompare {
- const ScalarEvolution *SE;
- explicit StrideCompare(const ScalarEvolution *se) : SE(se) {}
-
- bool operator()(const SCEV *LHS, const SCEV *RHS) {
- const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS);
- const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS);
- if (LHSC && RHSC) {
- int64_t LV = LHSC->getValue()->getSExtValue();
- int64_t RV = RHSC->getValue()->getSExtValue();
- uint64_t ALV = (LV < 0) ? -LV : LV;
- uint64_t ARV = (RV < 0) ? -RV : RV;
- if (ALV == ARV) {
- if (LV != RV)
- return LV > RV;
- } else {
- return ALV < ARV;
- }
+static bool isAlwaysFoldable(int64_t BaseOffs,
+ GlobalValue *BaseGV,
+ bool HasBaseReg,
+ LSRUse::KindType Kind, Type *AccessTy,
+ const TargetLowering *TLI) {
+ // Fast-path: zero is always foldable.
+ if (BaseOffs == 0 && !BaseGV) return true;
+
+ // Conservatively, create an address with an immediate and a
+ // base and a scale.
+ TargetLowering::AddrMode AM;
+ AM.BaseOffs = BaseOffs;
+ AM.BaseGV = BaseGV;
+ AM.HasBaseReg = HasBaseReg;
+ AM.Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
+
+ // Canonicalize a scale of 1 to a base register if the formula doesn't
+ // already have a base register.
+ if (!AM.HasBaseReg && AM.Scale == 1) {
+ AM.Scale = 0;
+ AM.HasBaseReg = true;
+ }
- // If it's the same value but different type, sort by bit width so
- // that we emit larger induction variables before smaller
- // ones, letting the smaller be re-written in terms of larger ones.
- return SE->getTypeSizeInBits(RHS->getType()) <
- SE->getTypeSizeInBits(LHS->getType());
- }
- return LHSC && !RHSC;
- }
- };
+ return isLegalUse(AM, Kind, AccessTy, TLI);
}
-/// ChangeCompareStride - If a loop termination compare instruction is the
-/// only use of its stride, and the compaison is against a constant value,
-/// try eliminate the stride by moving the compare instruction to another
-/// stride and change its constant operand accordingly. e.g.
-///
-/// loop:
-/// ...
-/// v1 = v1 + 3
-/// v2 = v2 + 1
-/// if (v2 < 10) goto loop
-/// =>
-/// loop:
-/// ...
-/// v1 = v1 + 3
-/// if (v1 < 30) goto loop
-ICmpInst *LoopStrengthReduce::ChangeCompareStride(Loop *L, ICmpInst *Cond,
- IVStrideUse* &CondUse,
- const SCEV* &CondStride,
- bool PostPass) {
- // If there's only one stride in the loop, there's nothing to do here.
- if (IU->StrideOrder.size() < 2)
- return Cond;
- // If there are other users of the condition's stride, don't bother
- // trying to change the condition because the stride will still
- // remain.
- std::map<const SCEV *, IVUsersOfOneStride *>::iterator I =
- IU->IVUsesByStride.find(CondStride);
- if (I == IU->IVUsesByStride.end())
- return Cond;
- if (I->second->Users.size() > 1) {
- for (ilist<IVStrideUse>::iterator II = I->second->Users.begin(),
- EE = I->second->Users.end(); II != EE; ++II) {
- if (II->getUser() == Cond)
- continue;
- if (!isInstructionTriviallyDead(II->getUser()))
- return Cond;
- }
- }
- // Only handle constant strides for now.
- const SCEVConstant *SC = dyn_cast<SCEVConstant>(CondStride);
- if (!SC) return Cond;
-
- ICmpInst::Predicate Predicate = Cond->getPredicate();
- int64_t CmpSSInt = SC->getValue()->getSExtValue();
- unsigned BitWidth = SE->getTypeSizeInBits(CondStride->getType());
- uint64_t SignBit = 1ULL << (BitWidth-1);
- const Type *CmpTy = Cond->getOperand(0)->getType();
- const Type *NewCmpTy = NULL;
- unsigned TyBits = SE->getTypeSizeInBits(CmpTy);
- unsigned NewTyBits = 0;
- const SCEV *NewStride = NULL;
- Value *NewCmpLHS = NULL;
- Value *NewCmpRHS = NULL;
- int64_t Scale = 1;
- const SCEV *NewOffset = SE->getIntegerSCEV(0, CmpTy);
-
- if (ConstantInt *C = dyn_cast<ConstantInt>(Cond->getOperand(1))) {
- int64_t CmpVal = C->getValue().getSExtValue();
-
- // Check the relevant induction variable for conformance to
- // the pattern.
- const SCEV *IV = SE->getSCEV(Cond->getOperand(0));
- const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV);
- if (!AR || !AR->isAffine())
- return Cond;
+static bool isAlwaysFoldable(const SCEV *S,
+ int64_t MinOffset, int64_t MaxOffset,
+ bool HasBaseReg,
+ LSRUse::KindType Kind, Type *AccessTy,
+ const TargetLowering *TLI,
+ ScalarEvolution &SE) {
+ // Fast-path: zero is always foldable.
+ if (S->isZero()) return true;
+
+ // Conservatively, create an address with an immediate and a
+ // base and a scale.
+ int64_t BaseOffs = ExtractImmediate(S, SE);
+ GlobalValue *BaseGV = ExtractSymbol(S, SE);
+
+ // If there's anything else involved, it's not foldable.
+ if (!S->isZero()) return false;
+
+ // Fast-path: zero is always foldable.
+ if (BaseOffs == 0 && !BaseGV) return true;
+
+ // Conservatively, create an address with an immediate and a
+ // base and a scale.
+ TargetLowering::AddrMode AM;
+ AM.BaseOffs = BaseOffs;
+ AM.BaseGV = BaseGV;
+ AM.HasBaseReg = HasBaseReg;
+ AM.Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
+
+ return isLegalUse(AM, MinOffset, MaxOffset, Kind, AccessTy, TLI);
+}
- const SCEVConstant *StartC = dyn_cast<SCEVConstant>(AR->getStart());
- // Check stride constant and the comparision constant signs to detect
- // overflow.
- if (StartC) {
- if ((StartC->getValue()->getSExtValue() < CmpVal && CmpSSInt < 0) ||
- (StartC->getValue()->getSExtValue() > CmpVal && CmpSSInt > 0))
- return Cond;
- } else {
- // More restrictive check for the other cases.
- if ((CmpVal & SignBit) != (CmpSSInt & SignBit))
- return Cond;
- }
+namespace {
- // Look for a suitable stride / iv as replacement.
- for (unsigned i = 0, e = IU->StrideOrder.size(); i != e; ++i) {
- std::map<const SCEV *, IVUsersOfOneStride *>::iterator SI =
- IU->IVUsesByStride.find(IU->StrideOrder[i]);
- if (!isa<SCEVConstant>(SI->first) || SI->second->Users.empty())
- continue;
- int64_t SSInt = cast<SCEVConstant>(SI->first)->getValue()->getSExtValue();
- if (SSInt == CmpSSInt ||
- abs64(SSInt) < abs64(CmpSSInt) ||
- (SSInt % CmpSSInt) != 0)
- continue;
+/// UseMapDenseMapInfo - A DenseMapInfo implementation for holding
+/// DenseMaps and DenseSets of pairs of const SCEV* and LSRUse::Kind.
+struct UseMapDenseMapInfo {
+ static std::pair<const SCEV *, LSRUse::KindType> getEmptyKey() {
+ return std::make_pair(reinterpret_cast<const SCEV *>(-1), LSRUse::Basic);
+ }
- Scale = SSInt / CmpSSInt;
- int64_t NewCmpVal = CmpVal * Scale;
+ static std::pair<const SCEV *, LSRUse::KindType> getTombstoneKey() {
+ return std::make_pair(reinterpret_cast<const SCEV *>(-2), LSRUse::Basic);
+ }
- // If old icmp value fits in icmp immediate field, but the new one doesn't
- // try something else.
- if (TLI &&
- TLI->isLegalICmpImmediate(CmpVal) &&
- !TLI->isLegalICmpImmediate(NewCmpVal))
- continue;
+ static unsigned
+ getHashValue(const std::pair<const SCEV *, LSRUse::KindType> &V) {
+ unsigned Result = DenseMapInfo<const SCEV *>::getHashValue(V.first);
+ Result ^= DenseMapInfo<unsigned>::getHashValue(unsigned(V.second));
+ return Result;
+ }
- APInt Mul = APInt(BitWidth*2, CmpVal, true);
- Mul = Mul * APInt(BitWidth*2, Scale, true);
- // Check for overflow.
- if (!Mul.isSignedIntN(BitWidth))
- continue;
- // Check for overflow in the stride's type too.
- if (!Mul.isSignedIntN(SE->getTypeSizeInBits(SI->first->getType())))
- continue;
+ static bool isEqual(const std::pair<const SCEV *, LSRUse::KindType> &LHS,
+ const std::pair<const SCEV *, LSRUse::KindType> &RHS) {
+ return LHS == RHS;
+ }
+};
- // Watch out for overflow.
- if (ICmpInst::isSigned(Predicate) &&
- (CmpVal & SignBit) != (NewCmpVal & SignBit))
- continue;
+/// IVInc - An individual increment in a Chain of IV increments.
+/// Relate an IV user to an expression that computes the IV it uses from the IV
+/// used by the previous link in the Chain.
+///
+/// For the head of a chain, IncExpr holds the absolute SCEV expression for the
+/// original IVOperand. The head of the chain's IVOperand is only valid during
+/// chain collection, before LSR replaces IV users. During chain generation,
+/// IncExpr can be used to find the new IVOperand that computes the same
+/// expression.
+struct IVInc {
+ Instruction *UserInst;
+ Value* IVOperand;
+ const SCEV *IncExpr;
+
+ IVInc(Instruction *U, Value *O, const SCEV *E):
+ UserInst(U), IVOperand(O), IncExpr(E) {}
+};
+
+// IVChain - The list of IV increments in program order.
+// We typically add the head of a chain without finding subsequent links.
+struct IVChain {
+ SmallVector<IVInc,1> Incs;
+ const SCEV *ExprBase;
+
+ IVChain() : ExprBase(0) {}
+
+ IVChain(const IVInc &Head, const SCEV *Base)
+ : Incs(1, Head), ExprBase(Base) {}
+
+ typedef SmallVectorImpl<IVInc>::const_iterator const_iterator;
+
+ // begin - return the first increment in the chain.
+ const_iterator begin() const {
+ assert(!Incs.empty());
+ return llvm::next(Incs.begin());
+ }
+ const_iterator end() const {
+ return Incs.end();
+ }
- // Pick the best iv to use trying to avoid a cast.
- NewCmpLHS = NULL;
- for (ilist<IVStrideUse>::iterator UI = SI->second->Users.begin(),
- E = SI->second->Users.end(); UI != E; ++UI) {
- Value *Op = UI->getOperandValToReplace();
-
- // If the IVStrideUse implies a cast, check for an actual cast which
- // can be used to find the original IV expression.
- if (SE->getEffectiveSCEVType(Op->getType()) !=
- SE->getEffectiveSCEVType(SI->first->getType())) {
- CastInst *CI = dyn_cast<CastInst>(Op);
- // If it's not a simple cast, it's complicated.
- if (!CI)
- continue;
- // If it's a cast from a type other than the stride type,
- // it's complicated.
- if (CI->getOperand(0)->getType() != SI->first->getType())
- continue;
- // Ok, we found the IV expression in the stride's type.
- Op = CI->getOperand(0);
- }
+ // hasIncs - Returns true if this chain contains any increments.
+ bool hasIncs() const { return Incs.size() >= 2; }
+
+ // add - Add an IVInc to the end of this chain.
+ void add(const IVInc &X) { Incs.push_back(X); }
+
+ // tailUserInst - Returns the last UserInst in the chain.
+ Instruction *tailUserInst() const { return Incs.back().UserInst; }
+
+ // isProfitableIncrement - Returns true if IncExpr can be profitably added to
+ // this chain.
+ bool isProfitableIncrement(const SCEV *OperExpr,
+ const SCEV *IncExpr,
+ ScalarEvolution&);
+};
+
+/// ChainUsers - Helper for CollectChains to track multiple IV increment uses.
+/// Distinguish between FarUsers that definitely cross IV increments and
+/// NearUsers that may be used between IV increments.
+struct ChainUsers {
+ SmallPtrSet<Instruction*, 4> FarUsers;
+ SmallPtrSet<Instruction*, 4> NearUsers;
+};
+
+/// LSRInstance - This class holds state for the main loop strength reduction
+/// logic.
+class LSRInstance {
+ IVUsers &IU;
+ ScalarEvolution &SE;
+ DominatorTree &DT;
+ LoopInfo &LI;
+ const TargetLowering *const TLI;
+ Loop *const L;
+ bool Changed;
+
+ /// IVIncInsertPos - This is the insert position that the current loop's
+ /// induction variable increment should be placed. In simple loops, this is
+ /// the latch block's terminator. But in more complicated cases, this is a
+ /// position which will dominate all the in-loop post-increment users.
+ Instruction *IVIncInsertPos;
+
+ /// Factors - Interesting factors between use strides.
+ SmallSetVector<int64_t, 8> Factors;
+
+ /// Types - Interesting use types, to facilitate truncation reuse.
+ SmallSetVector<Type *, 4> Types;
+
+ /// Fixups - The list of operands which are to be replaced.
+ SmallVector<LSRFixup, 16> Fixups;
+
+ /// Uses - The list of interesting uses.
+ SmallVector<LSRUse, 16> Uses;
+
+ /// RegUses - Track which uses use which register candidates.
+ RegUseTracker RegUses;
+
+ // Limit the number of chains to avoid quadratic behavior. We don't expect to
+ // have more than a few IV increment chains in a loop. Missing a Chain falls
+ // back to normal LSR behavior for those uses.
+ static const unsigned MaxChains = 8;
+
+ /// IVChainVec - IV users can form a chain of IV increments.
+ SmallVector<IVChain, MaxChains> IVChainVec;
+
+ /// IVIncSet - IV users that belong to profitable IVChains.
+ SmallPtrSet<Use*, MaxChains> IVIncSet;
+
+ void OptimizeShadowIV();
+ bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse);
+ ICmpInst *OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse);
+ void OptimizeLoopTermCond();
+
+ void ChainInstruction(Instruction *UserInst, Instruction *IVOper,
+ SmallVectorImpl<ChainUsers> &ChainUsersVec);
+ void FinalizeChain(IVChain &Chain);
+ void CollectChains();
+ void GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter,
+ SmallVectorImpl<WeakVH> &DeadInsts);
+
+ void CollectInterestingTypesAndFactors();
+ void CollectFixupsAndInitialFormulae();
+
+ LSRFixup &getNewFixup() {
+ Fixups.push_back(LSRFixup());
+ return Fixups.back();
+ }
- NewCmpLHS = Op;
- if (NewCmpLHS->getType() == CmpTy)
- break;
- }
- if (!NewCmpLHS)
- continue;
+ // Support for sharing of LSRUses between LSRFixups.
+ typedef DenseMap<std::pair<const SCEV *, LSRUse::KindType>,
+ size_t,
+ UseMapDenseMapInfo> UseMapTy;
+ UseMapTy UseMap;
+
+ bool reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg,
+ LSRUse::KindType Kind, Type *AccessTy);
+
+ std::pair<size_t, int64_t> getUse(const SCEV *&Expr,
+ LSRUse::KindType Kind,
+ Type *AccessTy);
+
+ void DeleteUse(LSRUse &LU, size_t LUIdx);
+
+ LSRUse *FindUseWithSimilarFormula(const Formula &F, const LSRUse &OrigLU);
+
+ void InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
+ void InsertSupplementalFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
+ void CountRegisters(const Formula &F, size_t LUIdx);
+ bool InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F);
+
+ void CollectLoopInvariantFixupsAndFormulae();
+
+ void GenerateReassociations(LSRUse &LU, unsigned LUIdx, Formula Base,
+ unsigned Depth = 0);
+ void GenerateCombinations(LSRUse &LU, unsigned LUIdx, Formula Base);
+ void GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
+ void GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
+ void GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx, Formula Base);
+ void GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base);
+ void GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base);
+ void GenerateCrossUseConstantOffsets();
+ void GenerateAllReuseFormulae();
+
+ void FilterOutUndesirableDedicatedRegisters();
+
+ size_t EstimateSearchSpaceComplexity() const;
+ void NarrowSearchSpaceByDetectingSupersets();
+ void NarrowSearchSpaceByCollapsingUnrolledCode();
+ void NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
+ void NarrowSearchSpaceByPickingWinnerRegs();
+ void NarrowSearchSpaceUsingHeuristics();
+
+ void SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
+ Cost &SolutionCost,
+ SmallVectorImpl<const Formula *> &Workspace,
+ const Cost &CurCost,
+ const SmallPtrSet<const SCEV *, 16> &CurRegs,
+ DenseSet<const SCEV *> &VisitedRegs) const;
+ void Solve(SmallVectorImpl<const Formula *> &Solution) const;
+
+ BasicBlock::iterator
+ HoistInsertPosition(BasicBlock::iterator IP,
+ const SmallVectorImpl<Instruction *> &Inputs) const;
+ BasicBlock::iterator
+ AdjustInsertPositionForExpand(BasicBlock::iterator IP,
+ const LSRFixup &LF,
+ const LSRUse &LU,
+ SCEVExpander &Rewriter) const;
+
+ Value *Expand(const LSRFixup &LF,
+ const Formula &F,
+ BasicBlock::iterator IP,
+ SCEVExpander &Rewriter,
+ SmallVectorImpl<WeakVH> &DeadInsts) const;
+ void RewriteForPHI(PHINode *PN, const LSRFixup &LF,
+ const Formula &F,
+ SCEVExpander &Rewriter,
+ SmallVectorImpl<WeakVH> &DeadInsts,
+ Pass *P) const;
+ void Rewrite(const LSRFixup &LF,
+ const Formula &F,
+ SCEVExpander &Rewriter,
+ SmallVectorImpl<WeakVH> &DeadInsts,
+ Pass *P) const;
+ void ImplementSolution(const SmallVectorImpl<const Formula *> &Solution,
+ Pass *P);
+
+public:
+ LSRInstance(const TargetLowering *tli, Loop *l, Pass *P);
+
+ bool getChanged() const { return Changed; }
+
+ void print_factors_and_types(raw_ostream &OS) const;
+ void print_fixups(raw_ostream &OS) const;
+ void print_uses(raw_ostream &OS) const;
+ void print(raw_ostream &OS) const;
+ void dump() const;
+};
- NewCmpTy = NewCmpLHS->getType();
- NewTyBits = SE->getTypeSizeInBits(NewCmpTy);
- const Type *NewCmpIntTy = IntegerType::get(Cond->getContext(), NewTyBits);
- if (RequiresTypeConversion(NewCmpTy, CmpTy)) {
- // Check if it is possible to rewrite it using
- // an iv / stride of a smaller integer type.
- unsigned Bits = NewTyBits;
- if (ICmpInst::isSigned(Predicate))
- --Bits;
- uint64_t Mask = (1ULL << Bits) - 1;
- if (((uint64_t)NewCmpVal & Mask) != (uint64_t)NewCmpVal)
- continue;
- }
+}
- // Don't rewrite if use offset is non-constant and the new type is
- // of a different type.
- // FIXME: too conservative?
- if (NewTyBits != TyBits && !isa<SCEVConstant>(CondUse->getOffset()))
- continue;
+/// OptimizeShadowIV - If IV is used in a int-to-float cast
+/// inside the loop then try to eliminate the cast operation.
+void LSRInstance::OptimizeShadowIV() {
+ const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
+ if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
+ return;
- if (!PostPass) {
- bool AllUsesAreAddresses = true;
- bool AllUsesAreOutsideLoop = true;
- std::vector<BasedUser> UsersToProcess;
- const SCEV *CommonExprs = CollectIVUsers(SI->first, *SI->second, L,
- AllUsesAreAddresses,
- AllUsesAreOutsideLoop,
- UsersToProcess);
- // Avoid rewriting the compare instruction with an iv of new stride
- // if it's likely the new stride uses will be rewritten using the
- // stride of the compare instruction.
- if (AllUsesAreAddresses &&
- ValidScale(!CommonExprs->isZero(), Scale, UsersToProcess))
- continue;
- }
+ for (IVUsers::const_iterator UI = IU.begin(), E = IU.end();
+ UI != E; /* empty */) {
+ IVUsers::const_iterator CandidateUI = UI;
+ ++UI;
+ Instruction *ShadowUse = CandidateUI->getUser();
+ Type *DestTy = NULL;
+ bool IsSigned = false;
+
+ /* If shadow use is a int->float cast then insert a second IV
+ to eliminate this cast.
+
+ for (unsigned i = 0; i < n; ++i)
+ foo((double)i);
+
+ is transformed into
+
+ double d = 0.0;
+ for (unsigned i = 0; i < n; ++i, ++d)
+ foo(d);
+ */
+ if (UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->getUser())) {
+ IsSigned = false;
+ DestTy = UCast->getDestTy();
+ }
+ else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->getUser())) {
+ IsSigned = true;
+ DestTy = SCast->getDestTy();
+ }
+ if (!DestTy) continue;
- // Avoid rewriting the compare instruction with an iv which has
- // implicit extension or truncation built into it.
- // TODO: This is over-conservative.
- if (SE->getTypeSizeInBits(CondUse->getOffset()->getType()) != TyBits)
- continue;
+ if (TLI) {
+ // If target does not support DestTy natively then do not apply
+ // this transformation.
+ EVT DVT = TLI->getValueType(DestTy);
+ if (!TLI->isTypeLegal(DVT)) continue;
+ }
- // If scale is negative, use swapped predicate unless it's testing
- // for equality.
- if (Scale < 0 && !Cond->isEquality())
- Predicate = ICmpInst::getSwappedPredicate(Predicate);
+ PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0));
+ if (!PH) continue;
+ if (PH->getNumIncomingValues() != 2) continue;
- NewStride = IU->StrideOrder[i];
- if (!isa<PointerType>(NewCmpTy))
- NewCmpRHS = ConstantInt::get(NewCmpTy, NewCmpVal);
- else {
- Constant *CI = ConstantInt::get(NewCmpIntTy, NewCmpVal);
- NewCmpRHS = ConstantExpr::getIntToPtr(CI, NewCmpTy);
- }
- NewOffset = TyBits == NewTyBits
- ? SE->getMulExpr(CondUse->getOffset(),
- SE->getConstant(CmpTy, Scale))
- : SE->getConstant(NewCmpIntTy,
- cast<SCEVConstant>(CondUse->getOffset())->getValue()
- ->getSExtValue()*Scale);
- break;
+ Type *SrcTy = PH->getType();
+ int Mantissa = DestTy->getFPMantissaWidth();
+ if (Mantissa == -1) continue;
+ if ((int)SE.getTypeSizeInBits(SrcTy) > Mantissa)
+ continue;
+
+ unsigned Entry, Latch;
+ if (PH->getIncomingBlock(0) == L->getLoopPreheader()) {
+ Entry = 0;
+ Latch = 1;
+ } else {
+ Entry = 1;
+ Latch = 0;
}
- }
- // Forgo this transformation if it the increment happens to be
- // unfortunately positioned after the condition, and the condition
- // has multiple uses which prevent it from being moved immediately
- // before the branch. See
- // test/Transforms/LoopStrengthReduce/change-compare-stride-trickiness-*.ll
- // for an example of this situation.
- if (!Cond->hasOneUse()) {
- for (BasicBlock::iterator I = Cond, E = Cond->getParent()->end();
- I != E; ++I)
- if (I == NewCmpLHS)
- return Cond;
- }
+ ConstantInt *Init = dyn_cast<ConstantInt>(PH->getIncomingValue(Entry));
+ if (!Init) continue;
+ Constant *NewInit = ConstantFP::get(DestTy, IsSigned ?
+ (double)Init->getSExtValue() :
+ (double)Init->getZExtValue());
+
+ BinaryOperator *Incr =
+ dyn_cast<BinaryOperator>(PH->getIncomingValue(Latch));
+ if (!Incr) continue;
+ if (Incr->getOpcode() != Instruction::Add
+ && Incr->getOpcode() != Instruction::Sub)
+ continue;
+
+ /* Initialize new IV, double d = 0.0 in above example. */
+ ConstantInt *C = NULL;
+ if (Incr->getOperand(0) == PH)
+ C = dyn_cast<ConstantInt>(Incr->getOperand(1));
+ else if (Incr->getOperand(1) == PH)
+ C = dyn_cast<ConstantInt>(Incr->getOperand(0));
+ else
+ continue;
- if (NewCmpRHS) {
- // Create a new compare instruction using new stride / iv.
- ICmpInst *OldCond = Cond;
- // Insert new compare instruction.
- Cond = new ICmpInst(OldCond, Predicate, NewCmpLHS, NewCmpRHS,
- L->getHeader()->getName() + ".termcond");
+ if (!C) continue;
- DEBUG(dbgs() << " Change compare stride in Inst " << *OldCond);
- DEBUG(dbgs() << " to " << *Cond << '\n');
+ // Ignore negative constants, as the code below doesn't handle them
+ // correctly. TODO: Remove this restriction.
+ if (!C->getValue().isStrictlyPositive()) continue;
- // Remove the old compare instruction. The old indvar is probably dead too.
- DeadInsts.push_back(CondUse->getOperandValToReplace());
- OldCond->replaceAllUsesWith(Cond);
- OldCond->eraseFromParent();
+ /* Add new PHINode. */
+ PHINode *NewPH = PHINode::Create(DestTy, 2, "IV.S.", PH);
- IU->IVUsesByStride[NewStride]->addUser(NewOffset, Cond, NewCmpLHS);
- CondUse = &IU->IVUsesByStride[NewStride]->Users.back();
- CondStride = NewStride;
- ++NumEliminated;
+ /* create new increment. '++d' in above example. */
+ Constant *CFP = ConstantFP::get(DestTy, C->getZExtValue());
+ BinaryOperator *NewIncr =
+ BinaryOperator::Create(Incr->getOpcode() == Instruction::Add ?
+ Instruction::FAdd : Instruction::FSub,
+ NewPH, CFP, "IV.S.next.", Incr);
+
+ NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry));
+ NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch));
+
+ /* Remove cast operation */
+ ShadowUse->replaceAllUsesWith(NewPH);
+ ShadowUse->eraseFromParent();
Changed = true;
+ break;
}
+}
- return Cond;
+/// FindIVUserForCond - If Cond has an operand that is an expression of an IV,
+/// set the IV user and stride information and return true, otherwise return
+/// false.
+bool LSRInstance::FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse) {
+ for (IVUsers::iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI)
+ if (UI->getUser() == Cond) {
+ // NOTE: we could handle setcc instructions with multiple uses here, but
+ // InstCombine does it as well for simple uses, it's not clear that it
+ // occurs enough in real life to handle.
+ CondUse = UI;
+ return true;
+ }
+ return false;
}
/// OptimizeMax - Rewrite the loop's terminating condition if it uses
/// are designed around them. The most obvious example of this is the
/// LoopInfo analysis, which doesn't remember trip count values. It
/// expects to be able to rediscover the trip count each time it is
-/// needed, and it does this using a simple analyis that only succeeds if
+/// needed, and it does this using a simple analysis that only succeeds if
/// the loop has a canonical induction variable.
///
/// However, when it comes time to generate code, the maximum operation
/// rewriting their conditions from ICMP_NE back to ICMP_SLT, and deleting
/// the instructions for the maximum computation.
///
-ICmpInst *LoopStrengthReduce::OptimizeMax(Loop *L, ICmpInst *Cond,
- IVStrideUse* &CondUse) {
+ICmpInst *LSRInstance::OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse) {
// Check that the loop matches the pattern we're looking for.
if (Cond->getPredicate() != CmpInst::ICMP_EQ &&
Cond->getPredicate() != CmpInst::ICMP_NE)
SelectInst *Sel = dyn_cast<SelectInst>(Cond->getOperand(1));
if (!Sel || !Sel->hasOneUse()) return Cond;
- const SCEV *BackedgeTakenCount = SE->getBackedgeTakenCount(L);
+ const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
return Cond;
- const SCEV *One = SE->getIntegerSCEV(1, BackedgeTakenCount->getType());
+ const SCEV *One = SE.getConstant(BackedgeTakenCount->getType(), 1);
// Add one to the backedge-taken count to get the trip count.
- const SCEV *IterationCount = SE->getAddExpr(BackedgeTakenCount, One);
-
- // Check for a max calculation that matches the pattern.
- if (!isa<SCEVSMaxExpr>(IterationCount) && !isa<SCEVUMaxExpr>(IterationCount))
+ const SCEV *IterationCount = SE.getAddExpr(One, BackedgeTakenCount);
+ if (IterationCount != SE.getSCEV(Sel)) return Cond;
+
+ // Check for a max calculation that matches the pattern. There's no check
+ // for ICMP_ULE here because the comparison would be with zero, which
+ // isn't interesting.
+ CmpInst::Predicate Pred = ICmpInst::BAD_ICMP_PREDICATE;
+ const SCEVNAryExpr *Max = 0;
+ if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(BackedgeTakenCount)) {
+ Pred = ICmpInst::ICMP_SLE;
+ Max = S;
+ } else if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(IterationCount)) {
+ Pred = ICmpInst::ICMP_SLT;
+ Max = S;
+ } else if (const SCEVUMaxExpr *U = dyn_cast<SCEVUMaxExpr>(IterationCount)) {
+ Pred = ICmpInst::ICMP_ULT;
+ Max = U;
+ } else {
+ // No match; bail.
return Cond;
- const SCEVNAryExpr *Max = cast<SCEVNAryExpr>(IterationCount);
- if (Max != SE->getSCEV(Sel)) return Cond;
+ }
// To handle a max with more than two operands, this optimization would
// require additional checking and setup.
const SCEV *MaxLHS = Max->getOperand(0);
const SCEV *MaxRHS = Max->getOperand(1);
- if (!MaxLHS || MaxLHS != One) return Cond;
+
+ // ScalarEvolution canonicalizes constants to the left. For < and >, look
+ // for a comparison with 1. For <= and >=, a comparison with zero.
+ if (!MaxLHS ||
+ (ICmpInst::isTrueWhenEqual(Pred) ? !MaxLHS->isZero() : (MaxLHS != One)))
+ return Cond;
// Check the relevant induction variable for conformance to
// the pattern.
- const SCEV *IV = SE->getSCEV(Cond->getOperand(0));
+ const SCEV *IV = SE.getSCEV(Cond->getOperand(0));
const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV);
if (!AR || !AR->isAffine() ||
AR->getStart() != One ||
- AR->getStepRecurrence(*SE) != One)
+ AR->getStepRecurrence(SE) != One)
return Cond;
assert(AR->getLoop() == L &&
// Check the right operand of the select, and remember it, as it will
// be used in the new comparison instruction.
Value *NewRHS = 0;
- if (SE->getSCEV(Sel->getOperand(1)) == MaxRHS)
+ if (ICmpInst::isTrueWhenEqual(Pred)) {
+ // Look for n+1, and grab n.
+ if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(1)))
+ if (isa<ConstantInt>(BO->getOperand(1)) &&
+ cast<ConstantInt>(BO->getOperand(1))->isOne() &&
+ SE.getSCEV(BO->getOperand(0)) == MaxRHS)
+ NewRHS = BO->getOperand(0);
+ if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(2)))
+ if (isa<ConstantInt>(BO->getOperand(1)) &&
+ cast<ConstantInt>(BO->getOperand(1))->isOne() &&
+ SE.getSCEV(BO->getOperand(0)) == MaxRHS)
+ NewRHS = BO->getOperand(0);
+ if (!NewRHS)
+ return Cond;
+ } else if (SE.getSCEV(Sel->getOperand(1)) == MaxRHS)
NewRHS = Sel->getOperand(1);
- else if (SE->getSCEV(Sel->getOperand(2)) == MaxRHS)
+ else if (SE.getSCEV(Sel->getOperand(2)) == MaxRHS)
NewRHS = Sel->getOperand(2);
- if (!NewRHS) return Cond;
+ else if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(MaxRHS))
+ NewRHS = SU->getValue();
+ else
+ // Max doesn't match expected pattern.
+ return Cond;
// Determine the new comparison opcode. It may be signed or unsigned,
// and the original comparison may be either equality or inequality.
- CmpInst::Predicate Pred =
- isa<SCEVSMaxExpr>(Max) ? CmpInst::ICMP_SLT : CmpInst::ICMP_ULT;
if (Cond->getPredicate() == CmpInst::ICMP_EQ)
Pred = CmpInst::getInversePredicate(Pred);
return NewCond;
}
-/// OptimizeShadowIV - If IV is used in a int-to-float cast
-/// inside the loop then try to eliminate the cast opeation.
-void LoopStrengthReduce::OptimizeShadowIV(Loop *L) {
+/// OptimizeLoopTermCond - Change loop terminating condition to use the
+/// postinc iv when possible.
+void
+LSRInstance::OptimizeLoopTermCond() {
+ SmallPtrSet<Instruction *, 4> PostIncs;
- const SCEV *BackedgeTakenCount = SE->getBackedgeTakenCount(L);
- if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
- return;
+ BasicBlock *LatchBlock = L->getLoopLatch();
+ SmallVector<BasicBlock*, 8> ExitingBlocks;
+ L->getExitingBlocks(ExitingBlocks);
- for (unsigned Stride = 0, e = IU->StrideOrder.size(); Stride != e;
- ++Stride) {
- std::map<const SCEV *, IVUsersOfOneStride *>::iterator SI =
- IU->IVUsesByStride.find(IU->StrideOrder[Stride]);
- assert(SI != IU->IVUsesByStride.end() && "Stride doesn't exist!");
- if (!isa<SCEVConstant>(SI->first))
+ for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
+ BasicBlock *ExitingBlock = ExitingBlocks[i];
+
+ // Get the terminating condition for the loop if possible. If we
+ // can, we want to change it to use a post-incremented version of its
+ // induction variable, to allow coalescing the live ranges for the IV into
+ // one register value.
+
+ BranchInst *TermBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
+ if (!TermBr)
+ continue;
+ // FIXME: Overly conservative, termination condition could be an 'or' etc..
+ if (TermBr->isUnconditional() || !isa<ICmpInst>(TermBr->getCondition()))
continue;
- for (ilist<IVStrideUse>::iterator UI = SI->second->Users.begin(),
- E = SI->second->Users.end(); UI != E; /* empty */) {
- ilist<IVStrideUse>::iterator CandidateUI = UI;
- ++UI;
- Instruction *ShadowUse = CandidateUI->getUser();
- const Type *DestTy = NULL;
-
- /* If shadow use is a int->float cast then insert a second IV
- to eliminate this cast.
-
- for (unsigned i = 0; i < n; ++i)
- foo((double)i);
-
- is transformed into
-
- double d = 0.0;
- for (unsigned i = 0; i < n; ++i, ++d)
- foo(d);
- */
- if (UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->getUser()))
- DestTy = UCast->getDestTy();
- else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->getUser()))
- DestTy = SCast->getDestTy();
- if (!DestTy) continue;
-
- if (TLI) {
- // If target does not support DestTy natively then do not apply
- // this transformation.
- EVT DVT = TLI->getValueType(DestTy);
- if (!TLI->isTypeLegal(DVT)) continue;
- }
+ // Search IVUsesByStride to find Cond's IVUse if there is one.
+ IVStrideUse *CondUse = 0;
+ ICmpInst *Cond = cast<ICmpInst>(TermBr->getCondition());
+ if (!FindIVUserForCond(Cond, CondUse))
+ continue;
- PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0));
- if (!PH) continue;
- if (PH->getNumIncomingValues() != 2) continue;
+ // If the trip count is computed in terms of a max (due to ScalarEvolution
+ // being unable to find a sufficient guard, for example), change the loop
+ // comparison to use SLT or ULT instead of NE.
+ // One consequence of doing this now is that it disrupts the count-down
+ // optimization. That's not always a bad thing though, because in such
+ // cases it may still be worthwhile to avoid a max.
+ Cond = OptimizeMax(Cond, CondUse);
+
+ // If this exiting block dominates the latch block, it may also use
+ // the post-inc value if it won't be shared with other uses.
+ // Check for dominance.
+ if (!DT.dominates(ExitingBlock, LatchBlock))
+ continue;
- const Type *SrcTy = PH->getType();
- int Mantissa = DestTy->getFPMantissaWidth();
- if (Mantissa == -1) continue;
- if ((int)SE->getTypeSizeInBits(SrcTy) > Mantissa)
- continue;
+ // Conservatively avoid trying to use the post-inc value in non-latch
+ // exits if there may be pre-inc users in intervening blocks.
+ if (LatchBlock != ExitingBlock)
+ for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI)
+ // Test if the use is reachable from the exiting block. This dominator
+ // query is a conservative approximation of reachability.
+ if (&*UI != CondUse &&
+ !DT.properlyDominates(UI->getUser()->getParent(), ExitingBlock)) {
+ // Conservatively assume there may be reuse if the quotient of their
+ // strides could be a legal scale.
+ const SCEV *A = IU.getStride(*CondUse, L);
+ const SCEV *B = IU.getStride(*UI, L);
+ if (!A || !B) continue;
+ if (SE.getTypeSizeInBits(A->getType()) !=
+ SE.getTypeSizeInBits(B->getType())) {
+ if (SE.getTypeSizeInBits(A->getType()) >
+ SE.getTypeSizeInBits(B->getType()))
+ B = SE.getSignExtendExpr(B, A->getType());
+ else
+ A = SE.getSignExtendExpr(A, B->getType());
+ }
+ if (const SCEVConstant *D =
+ dyn_cast_or_null<SCEVConstant>(getExactSDiv(B, A, SE))) {
+ const ConstantInt *C = D->getValue();
+ // Stride of one or negative one can have reuse with non-addresses.
+ if (C->isOne() || C->isAllOnesValue())
+ goto decline_post_inc;
+ // Avoid weird situations.
+ if (C->getValue().getMinSignedBits() >= 64 ||
+ C->getValue().isMinSignedValue())
+ goto decline_post_inc;
+ // Without TLI, assume that any stride might be valid, and so any
+ // use might be shared.
+ if (!TLI)
+ goto decline_post_inc;
+ // Check for possible scaled-address reuse.
+ Type *AccessTy = getAccessType(UI->getUser());
+ TargetLowering::AddrMode AM;
+ AM.Scale = C->getSExtValue();
+ if (TLI->isLegalAddressingMode(AM, AccessTy))
+ goto decline_post_inc;
+ AM.Scale = -AM.Scale;
+ if (TLI->isLegalAddressingMode(AM, AccessTy))
+ goto decline_post_inc;
+ }
+ }
+
+ DEBUG(dbgs() << " Change loop exiting icmp to use postinc iv: "
+ << *Cond << '\n');
- unsigned Entry, Latch;
- if (PH->getIncomingBlock(0) == L->getLoopPreheader()) {
- Entry = 0;
- Latch = 1;
+ // It's possible for the setcc instruction to be anywhere in the loop, and
+ // possible for it to have multiple users. If it is not immediately before
+ // the exiting block branch, move it.
+ if (&*++BasicBlock::iterator(Cond) != TermBr) {
+ if (Cond->hasOneUse()) {
+ Cond->moveBefore(TermBr);
} else {
- Entry = 1;
- Latch = 0;
+ // Clone the terminating condition and insert into the loopend.
+ ICmpInst *OldCond = Cond;
+ Cond = cast<ICmpInst>(Cond->clone());
+ Cond->setName(L->getHeader()->getName() + ".termcond");
+ ExitingBlock->getInstList().insert(TermBr, Cond);
+
+ // Clone the IVUse, as the old use still exists!
+ CondUse = &IU.AddUser(Cond, CondUse->getOperandValToReplace());
+ TermBr->replaceUsesOfWith(OldCond, Cond);
}
+ }
- ConstantInt *Init = dyn_cast<ConstantInt>(PH->getIncomingValue(Entry));
- if (!Init) continue;
- Constant *NewInit = ConstantFP::get(DestTy, Init->getZExtValue());
+ // If we get to here, we know that we can transform the setcc instruction to
+ // use the post-incremented version of the IV, allowing us to coalesce the
+ // live ranges for the IV correctly.
+ CondUse->transformToPostInc(L);
+ Changed = true;
- BinaryOperator *Incr =
- dyn_cast<BinaryOperator>(PH->getIncomingValue(Latch));
- if (!Incr) continue;
- if (Incr->getOpcode() != Instruction::Add
- && Incr->getOpcode() != Instruction::Sub)
- continue;
+ PostIncs.insert(Cond);
+ decline_post_inc:;
+ }
- /* Initialize new IV, double d = 0.0 in above example. */
- ConstantInt *C = NULL;
- if (Incr->getOperand(0) == PH)
- C = dyn_cast<ConstantInt>(Incr->getOperand(1));
- else if (Incr->getOperand(1) == PH)
- C = dyn_cast<ConstantInt>(Incr->getOperand(0));
- else
- continue;
+ // Determine an insertion point for the loop induction variable increment. It
+ // must dominate all the post-inc comparisons we just set up, and it must
+ // dominate the loop latch edge.
+ IVIncInsertPos = L->getLoopLatch()->getTerminator();
+ for (SmallPtrSet<Instruction *, 4>::const_iterator I = PostIncs.begin(),
+ E = PostIncs.end(); I != E; ++I) {
+ BasicBlock *BB =
+ DT.findNearestCommonDominator(IVIncInsertPos->getParent(),
+ (*I)->getParent());
+ if (BB == (*I)->getParent())
+ IVIncInsertPos = *I;
+ else if (BB != IVIncInsertPos->getParent())
+ IVIncInsertPos = BB->getTerminator();
+ }
+}
- if (!C) continue;
+/// reconcileNewOffset - Determine if the given use can accommodate a fixup
+/// at the given offset and other details. If so, update the use and
+/// return true.
+bool
+LSRInstance::reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg,
+ LSRUse::KindType Kind, Type *AccessTy) {
+ int64_t NewMinOffset = LU.MinOffset;
+ int64_t NewMaxOffset = LU.MaxOffset;
+ Type *NewAccessTy = AccessTy;
+
+ // Check for a mismatched kind. It's tempting to collapse mismatched kinds to
+ // something conservative, however this can pessimize in the case that one of
+ // the uses will have all its uses outside the loop, for example.
+ if (LU.Kind != Kind)
+ return false;
+ // Conservatively assume HasBaseReg is true for now.
+ if (NewOffset < LU.MinOffset) {
+ if (!isAlwaysFoldable(LU.MaxOffset - NewOffset, 0, HasBaseReg,
+ Kind, AccessTy, TLI))
+ return false;
+ NewMinOffset = NewOffset;
+ } else if (NewOffset > LU.MaxOffset) {
+ if (!isAlwaysFoldable(NewOffset - LU.MinOffset, 0, HasBaseReg,
+ Kind, AccessTy, TLI))
+ return false;
+ NewMaxOffset = NewOffset;
+ }
+ // Check for a mismatched access type, and fall back conservatively as needed.
+ // TODO: Be less conservative when the type is similar and can use the same
+ // addressing modes.
+ if (Kind == LSRUse::Address && AccessTy != LU.AccessTy)
+ NewAccessTy = Type::getVoidTy(AccessTy->getContext());
+
+ // Update the use.
+ LU.MinOffset = NewMinOffset;
+ LU.MaxOffset = NewMaxOffset;
+ LU.AccessTy = NewAccessTy;
+ if (NewOffset != LU.Offsets.back())
+ LU.Offsets.push_back(NewOffset);
+ return true;
+}
- // Ignore negative constants, as the code below doesn't handle them
- // correctly. TODO: Remove this restriction.
- if (!C->getValue().isStrictlyPositive()) continue;
+/// getUse - Return an LSRUse index and an offset value for a fixup which
+/// needs the given expression, with the given kind and optional access type.
+/// Either reuse an existing use or create a new one, as needed.
+std::pair<size_t, int64_t>
+LSRInstance::getUse(const SCEV *&Expr,
+ LSRUse::KindType Kind, Type *AccessTy) {
+ const SCEV *Copy = Expr;
+ int64_t Offset = ExtractImmediate(Expr, SE);
+
+ // Basic uses can't accept any offset, for example.
+ if (!isAlwaysFoldable(Offset, 0, /*HasBaseReg=*/true, Kind, AccessTy, TLI)) {
+ Expr = Copy;
+ Offset = 0;
+ }
- /* Add new PHINode. */
- PHINode *NewPH = PHINode::Create(DestTy, "IV.S.", PH);
+ std::pair<UseMapTy::iterator, bool> P =
+ UseMap.insert(std::make_pair(std::make_pair(Expr, Kind), 0));
+ if (!P.second) {
+ // A use already existed with this base.
+ size_t LUIdx = P.first->second;
+ LSRUse &LU = Uses[LUIdx];
+ if (reconcileNewOffset(LU, Offset, /*HasBaseReg=*/true, Kind, AccessTy))
+ // Reuse this use.
+ return std::make_pair(LUIdx, Offset);
+ }
- /* create new increment. '++d' in above example. */
- Constant *CFP = ConstantFP::get(DestTy, C->getZExtValue());
- BinaryOperator *NewIncr =
- BinaryOperator::Create(Incr->getOpcode() == Instruction::Add ?
- Instruction::FAdd : Instruction::FSub,
- NewPH, CFP, "IV.S.next.", Incr);
+ // Create a new use.
+ size_t LUIdx = Uses.size();
+ P.first->second = LUIdx;
+ Uses.push_back(LSRUse(Kind, AccessTy));
+ LSRUse &LU = Uses[LUIdx];
- NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry));
- NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch));
+ // We don't need to track redundant offsets, but we don't need to go out
+ // of our way here to avoid them.
+ if (LU.Offsets.empty() || Offset != LU.Offsets.back())
+ LU.Offsets.push_back(Offset);
- /* Remove cast operation */
- ShadowUse->replaceAllUsesWith(NewPH);
- ShadowUse->eraseFromParent();
- NumShadow++;
- break;
- }
- }
+ LU.MinOffset = Offset;
+ LU.MaxOffset = Offset;
+ return std::make_pair(LUIdx, Offset);
}
-/// OptimizeIndvars - Now that IVUsesByStride is set up with all of the indvar
-/// uses in the loop, look to see if we can eliminate some, in favor of using
-/// common indvars for the different uses.
-void LoopStrengthReduce::OptimizeIndvars(Loop *L) {
- // TODO: implement optzns here.
+/// DeleteUse - Delete the given use from the Uses list.
+void LSRInstance::DeleteUse(LSRUse &LU, size_t LUIdx) {
+ if (&LU != &Uses.back())
+ std::swap(LU, Uses.back());
+ Uses.pop_back();
- OptimizeShadowIV(L);
+ // Update RegUses.
+ RegUses.SwapAndDropUse(LUIdx, Uses.size());
}
-bool LoopStrengthReduce::StrideMightBeShared(const SCEV* Stride, Loop *L,
- bool CheckPreInc) {
- int64_t SInt = cast<SCEVConstant>(Stride)->getValue()->getSExtValue();
- for (unsigned i = 0, e = IU->StrideOrder.size(); i != e; ++i) {
- std::map<const SCEV *, IVUsersOfOneStride *>::iterator SI =
- IU->IVUsesByStride.find(IU->StrideOrder[i]);
- const SCEV *Share = SI->first;
- if (!isa<SCEVConstant>(SI->first) || Share == Stride)
- continue;
- int64_t SSInt = cast<SCEVConstant>(Share)->getValue()->getSExtValue();
- if (SSInt == SInt)
- return true; // This can definitely be reused.
- if (unsigned(abs64(SSInt)) < SInt || (SSInt % SInt) != 0)
- continue;
- int64_t Scale = SSInt / SInt;
- bool AllUsesAreAddresses = true;
- bool AllUsesAreOutsideLoop = true;
- std::vector<BasedUser> UsersToProcess;
- const SCEV *CommonExprs = CollectIVUsers(SI->first, *SI->second, L,
- AllUsesAreAddresses,
- AllUsesAreOutsideLoop,
- UsersToProcess);
- if (AllUsesAreAddresses &&
- ValidScale(!CommonExprs->isZero(), Scale, UsersToProcess)) {
- if (!CheckPreInc)
- return true;
- // Any pre-inc iv use?
- IVUsersOfOneStride &StrideUses = *IU->IVUsesByStride[Share];
- for (ilist<IVStrideUse>::iterator I = StrideUses.Users.begin(),
- E = StrideUses.Users.end(); I != E; ++I) {
- if (!I->isUseOfPostIncrementedValue())
- return true;
+/// FindUseWithFormula - Look for a use distinct from OrigLU which is has
+/// a formula that has the same registers as the given formula.
+LSRUse *
+LSRInstance::FindUseWithSimilarFormula(const Formula &OrigF,
+ const LSRUse &OrigLU) {
+ // Search all uses for the formula. This could be more clever.
+ for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
+ LSRUse &LU = Uses[LUIdx];
+ // Check whether this use is close enough to OrigLU, to see whether it's
+ // worthwhile looking through its formulae.
+ // Ignore ICmpZero uses because they may contain formulae generated by
+ // GenerateICmpZeroScales, in which case adding fixup offsets may
+ // be invalid.
+ if (&LU != &OrigLU &&
+ LU.Kind != LSRUse::ICmpZero &&
+ LU.Kind == OrigLU.Kind && OrigLU.AccessTy == LU.AccessTy &&
+ LU.WidestFixupType == OrigLU.WidestFixupType &&
+ LU.HasFormulaWithSameRegs(OrigF)) {
+ // Scan through this use's formulae.
+ for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(),
+ E = LU.Formulae.end(); I != E; ++I) {
+ const Formula &F = *I;
+ // Check to see if this formula has the same registers and symbols
+ // as OrigF.
+ if (F.BaseRegs == OrigF.BaseRegs &&
+ F.ScaledReg == OrigF.ScaledReg &&
+ F.AM.BaseGV == OrigF.AM.BaseGV &&
+ F.AM.Scale == OrigF.AM.Scale &&
+ F.UnfoldedOffset == OrigF.UnfoldedOffset) {
+ if (F.AM.BaseOffs == 0)
+ return &LU;
+ // This is the formula where all the registers and symbols matched;
+ // there aren't going to be any others. Since we declined it, we
+ // can skip the rest of the formulae and proceed to the next LSRUse.
+ break;
+ }
}
}
}
- return false;
+
+ // Nothing looked good.
+ return 0;
}
-/// isUsedByExitBranch - Return true if icmp is used by a loop terminating
-/// conditional branch or it's and / or with other conditions before being used
-/// as the condition.
-static bool isUsedByExitBranch(ICmpInst *Cond, Loop *L) {
- BasicBlock *CondBB = Cond->getParent();
- if (!L->isLoopExiting(CondBB))
- return false;
- BranchInst *TermBr = dyn_cast<BranchInst>(CondBB->getTerminator());
- if (!TermBr || !TermBr->isConditional())
- return false;
+void LSRInstance::CollectInterestingTypesAndFactors() {
+ SmallSetVector<const SCEV *, 4> Strides;
- Value *User = *Cond->use_begin();
- Instruction *UserInst = dyn_cast<Instruction>(User);
- while (UserInst &&
- (UserInst->getOpcode() == Instruction::And ||
- UserInst->getOpcode() == Instruction::Or)) {
- if (!UserInst->hasOneUse() || UserInst->getParent() != CondBB)
- return false;
- User = *User->use_begin();
- UserInst = dyn_cast<Instruction>(User);
+ // Collect interesting types and strides.
+ SmallVector<const SCEV *, 4> Worklist;
+ for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) {
+ const SCEV *Expr = IU.getExpr(*UI);
+
+ // Collect interesting types.
+ Types.insert(SE.getEffectiveSCEVType(Expr->getType()));
+
+ // Add strides for mentioned loops.
+ Worklist.push_back(Expr);
+ do {
+ const SCEV *S = Worklist.pop_back_val();
+ if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
+ if (AR->getLoop() == L)
+ Strides.insert(AR->getStepRecurrence(SE));
+ Worklist.push_back(AR->getStart());
+ } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
+ Worklist.append(Add->op_begin(), Add->op_end());
+ }
+ } while (!Worklist.empty());
}
- return User == TermBr;
+
+ // Compute interesting factors from the set of interesting strides.
+ for (SmallSetVector<const SCEV *, 4>::const_iterator
+ I = Strides.begin(), E = Strides.end(); I != E; ++I)
+ for (SmallSetVector<const SCEV *, 4>::const_iterator NewStrideIter =
+ llvm::next(I); NewStrideIter != E; ++NewStrideIter) {
+ const SCEV *OldStride = *I;
+ const SCEV *NewStride = *NewStrideIter;
+
+ if (SE.getTypeSizeInBits(OldStride->getType()) !=
+ SE.getTypeSizeInBits(NewStride->getType())) {
+ if (SE.getTypeSizeInBits(OldStride->getType()) >
+ SE.getTypeSizeInBits(NewStride->getType()))
+ NewStride = SE.getSignExtendExpr(NewStride, OldStride->getType());
+ else
+ OldStride = SE.getSignExtendExpr(OldStride, NewStride->getType());
+ }
+ if (const SCEVConstant *Factor =
+ dyn_cast_or_null<SCEVConstant>(getExactSDiv(NewStride, OldStride,
+ SE, true))) {
+ if (Factor->getValue()->getValue().getMinSignedBits() <= 64)
+ Factors.insert(Factor->getValue()->getValue().getSExtValue());
+ } else if (const SCEVConstant *Factor =
+ dyn_cast_or_null<SCEVConstant>(getExactSDiv(OldStride,
+ NewStride,
+ SE, true))) {
+ if (Factor->getValue()->getValue().getMinSignedBits() <= 64)
+ Factors.insert(Factor->getValue()->getValue().getSExtValue());
+ }
+ }
+
+ // If all uses use the same type, don't bother looking for truncation-based
+ // reuse.
+ if (Types.size() == 1)
+ Types.clear();
+
+ DEBUG(print_factors_and_types(dbgs()));
}
-static bool ShouldCountToZero(ICmpInst *Cond, IVStrideUse* &CondUse,
- ScalarEvolution *SE, Loop *L,
- const TargetLowering *TLI = 0) {
- if (!L->contains(Cond))
- return false;
+/// findIVOperand - Helper for CollectChains that finds an IV operand (computed
+/// by an AddRec in this loop) within [OI,OE) or returns OE. If IVUsers mapped
+/// Instructions to IVStrideUses, we could partially skip this.
+static User::op_iterator
+findIVOperand(User::op_iterator OI, User::op_iterator OE,
+ Loop *L, ScalarEvolution &SE) {
+ for(; OI != OE; ++OI) {
+ if (Instruction *Oper = dyn_cast<Instruction>(*OI)) {
+ if (!SE.isSCEVable(Oper->getType()))
+ continue;
- if (!isa<SCEVConstant>(CondUse->getOffset()))
- return false;
+ if (const SCEVAddRecExpr *AR =
+ dyn_cast<SCEVAddRecExpr>(SE.getSCEV(Oper))) {
+ if (AR->getLoop() == L)
+ break;
+ }
+ }
+ }
+ return OI;
+}
- // Handle only tests for equality for the moment.
- if (!Cond->isEquality() || !Cond->hasOneUse())
- return false;
- if (!isUsedByExitBranch(Cond, L))
- return false;
+/// getWideOperand - IVChain logic must consistenctly peek base TruncInst
+/// operands, so wrap it in a convenient helper.
+static Value *getWideOperand(Value *Oper) {
+ if (TruncInst *Trunc = dyn_cast<TruncInst>(Oper))
+ return Trunc->getOperand(0);
+ return Oper;
+}
- Value *CondOp0 = Cond->getOperand(0);
- const SCEV *IV = SE->getSCEV(CondOp0);
- const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV);
- if (!AR || !AR->isAffine())
- return false;
+/// isCompatibleIVType - Return true if we allow an IV chain to include both
+/// types.
+static bool isCompatibleIVType(Value *LVal, Value *RVal) {
+ Type *LType = LVal->getType();
+ Type *RType = RVal->getType();
+ return (LType == RType) || (LType->isPointerTy() && RType->isPointerTy());
+}
- const SCEVConstant *SC = dyn_cast<SCEVConstant>(AR->getStepRecurrence(*SE));
- if (!SC || SC->getValue()->getSExtValue() < 0)
- // If it's already counting down, don't do anything.
- return false;
+/// getExprBase - Return an approximation of this SCEV expression's "base", or
+/// NULL for any constant. Returning the expression itself is
+/// conservative. Returning a deeper subexpression is more precise and valid as
+/// long as it isn't less complex than another subexpression. For expressions
+/// involving multiple unscaled values, we need to return the pointer-type
+/// SCEVUnknown. This avoids forming chains across objects, such as:
+/// PrevOper==a[i], IVOper==b[i], IVInc==b-a.
+///
+/// Since SCEVUnknown is the rightmost type, and pointers are the rightmost
+/// SCEVUnknown, we simply return the rightmost SCEV operand.
+static const SCEV *getExprBase(const SCEV *S) {
+ switch (S->getSCEVType()) {
+ default: // uncluding scUnknown.
+ return S;
+ case scConstant:
+ return 0;
+ case scTruncate:
+ return getExprBase(cast<SCEVTruncateExpr>(S)->getOperand());
+ case scZeroExtend:
+ return getExprBase(cast<SCEVZeroExtendExpr>(S)->getOperand());
+ case scSignExtend:
+ return getExprBase(cast<SCEVSignExtendExpr>(S)->getOperand());
+ case scAddExpr: {
+ // Skip over scaled operands (scMulExpr) to follow add operands as long as
+ // there's nothing more complex.
+ // FIXME: not sure if we want to recognize negation.
+ const SCEVAddExpr *Add = cast<SCEVAddExpr>(S);
+ for (std::reverse_iterator<SCEVAddExpr::op_iterator> I(Add->op_end()),
+ E(Add->op_begin()); I != E; ++I) {
+ const SCEV *SubExpr = *I;
+ if (SubExpr->getSCEVType() == scAddExpr)
+ return getExprBase(SubExpr);
+
+ if (SubExpr->getSCEVType() != scMulExpr)
+ return SubExpr;
+ }
+ return S; // all operands are scaled, be conservative.
+ }
+ case scAddRecExpr:
+ return getExprBase(cast<SCEVAddRecExpr>(S)->getStart());
+ }
+}
+
+/// Return true if the chain increment is profitable to expand into a loop
+/// invariant value, which may require its own register. A profitable chain
+/// increment will be an offset relative to the same base. We allow such offsets
+/// to potentially be used as chain increment as long as it's not obviously
+/// expensive to expand using real instructions.
+bool IVChain::isProfitableIncrement(const SCEV *OperExpr,
+ const SCEV *IncExpr,
+ ScalarEvolution &SE) {
+ // Aggressively form chains when -stress-ivchain.
+ if (StressIVChain)
+ return true;
+
+ // Do not replace a constant offset from IV head with a nonconstant IV
+ // increment.
+ if (!isa<SCEVConstant>(IncExpr)) {
+ const SCEV *HeadExpr = SE.getSCEV(getWideOperand(Incs[0].IVOperand));
+ if (isa<SCEVConstant>(SE.getMinusSCEV(OperExpr, HeadExpr)))
+ return 0;
+ }
+
+ SmallPtrSet<const SCEV*, 8> Processed;
+ return !isHighCostExpansion(IncExpr, Processed, SE);
+}
+
+/// Return true if the number of registers needed for the chain is estimated to
+/// be less than the number required for the individual IV users. First prohibit
+/// any IV users that keep the IV live across increments (the Users set should
+/// be empty). Next count the number and type of increments in the chain.
+///
+/// Chaining IVs can lead to considerable code bloat if ISEL doesn't
+/// effectively use postinc addressing modes. Only consider it profitable it the
+/// increments can be computed in fewer registers when chained.
+///
+/// TODO: Consider IVInc free if it's already used in another chains.
+static bool
+isProfitableChain(IVChain &Chain, SmallPtrSet<Instruction*, 4> &Users,
+ ScalarEvolution &SE, const TargetLowering *TLI) {
+ if (StressIVChain)
+ return true;
- // If the RHS of the comparison is not an loop invariant, the rewrite
- // cannot be done. Also bail out if it's already comparing against a zero.
- // If we are checking this before cmp stride optimization, check if it's
- // comparing against a already legal immediate.
- Value *RHS = Cond->getOperand(1);
- ConstantInt *RHSC = dyn_cast<ConstantInt>(RHS);
- if (!L->isLoopInvariant(RHS) ||
- (RHSC && RHSC->isZero()) ||
- (RHSC && TLI && TLI->isLegalICmpImmediate(RHSC->getSExtValue())))
+ if (!Chain.hasIncs())
return false;
- // Make sure the IV is only used for counting. Value may be preinc or
- // postinc; 2 uses in either case.
- if (!CondOp0->hasNUses(2))
+ if (!Users.empty()) {
+ DEBUG(dbgs() << "Chain: " << *Chain.Incs[0].UserInst << " users:\n";
+ for (SmallPtrSet<Instruction*, 4>::const_iterator I = Users.begin(),
+ E = Users.end(); I != E; ++I) {
+ dbgs() << " " << **I << "\n";
+ });
return false;
+ }
+ assert(!Chain.Incs.empty() && "empty IV chains are not allowed");
- return true;
-}
+ // The chain itself may require a register, so intialize cost to 1.
+ int cost = 1;
-/// OptimizeLoopTermCond - Change loop terminating condition to use the
-/// postinc iv when possible.
-void LoopStrengthReduce::OptimizeLoopTermCond(Loop *L) {
- BasicBlock *LatchBlock = L->getLoopLatch();
- bool LatchExit = L->isLoopExiting(LatchBlock);
- SmallVector<BasicBlock*, 8> ExitingBlocks;
- L->getExitingBlocks(ExitingBlocks);
+ // A complete chain likely eliminates the need for keeping the original IV in
+ // a register. LSR does not currently know how to form a complete chain unless
+ // the header phi already exists.
+ if (isa<PHINode>(Chain.tailUserInst())
+ && SE.getSCEV(Chain.tailUserInst()) == Chain.Incs[0].IncExpr) {
+ --cost;
+ }
+ const SCEV *LastIncExpr = 0;
+ unsigned NumConstIncrements = 0;
+ unsigned NumVarIncrements = 0;
+ unsigned NumReusedIncrements = 0;
+ for (IVChain::const_iterator I = Chain.begin(), E = Chain.end();
+ I != E; ++I) {
+
+ if (I->IncExpr->isZero())
+ continue;
- for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
- BasicBlock *ExitingBlock = ExitingBlocks[i];
+ // Incrementing by zero or some constant is neutral. We assume constants can
+ // be folded into an addressing mode or an add's immediate operand.
+ if (isa<SCEVConstant>(I->IncExpr)) {
+ ++NumConstIncrements;
+ continue;
+ }
- // Finally, get the terminating condition for the loop if possible. If we
- // can, we want to change it to use a post-incremented version of its
- // induction variable, to allow coalescing the live ranges for the IV into
- // one register value.
+ if (I->IncExpr == LastIncExpr)
+ ++NumReusedIncrements;
+ else
+ ++NumVarIncrements;
- BranchInst *TermBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
- if (!TermBr)
+ LastIncExpr = I->IncExpr;
+ }
+ // An IV chain with a single increment is handled by LSR's postinc
+ // uses. However, a chain with multiple increments requires keeping the IV's
+ // value live longer than it needs to be if chained.
+ if (NumConstIncrements > 1)
+ --cost;
+
+ // Materializing increment expressions in the preheader that didn't exist in
+ // the original code may cost a register. For example, sign-extended array
+ // indices can produce ridiculous increments like this:
+ // IV + ((sext i32 (2 * %s) to i64) + (-1 * (sext i32 %s to i64)))
+ cost += NumVarIncrements;
+
+ // Reusing variable increments likely saves a register to hold the multiple of
+ // the stride.
+ cost -= NumReusedIncrements;
+
+ DEBUG(dbgs() << "Chain: " << *Chain.Incs[0].UserInst << " Cost: " << cost
+ << "\n");
+
+ return cost < 0;
+}
+
+/// ChainInstruction - Add this IV user to an existing chain or make it the head
+/// of a new chain.
+void LSRInstance::ChainInstruction(Instruction *UserInst, Instruction *IVOper,
+ SmallVectorImpl<ChainUsers> &ChainUsersVec) {
+ // When IVs are used as types of varying widths, they are generally converted
+ // to a wider type with some uses remaining narrow under a (free) trunc.
+ Value *const NextIV = getWideOperand(IVOper);
+ const SCEV *const OperExpr = SE.getSCEV(NextIV);
+ const SCEV *const OperExprBase = getExprBase(OperExpr);
+
+ // Visit all existing chains. Check if its IVOper can be computed as a
+ // profitable loop invariant increment from the last link in the Chain.
+ unsigned ChainIdx = 0, NChains = IVChainVec.size();
+ const SCEV *LastIncExpr = 0;
+ for (; ChainIdx < NChains; ++ChainIdx) {
+ IVChain &Chain = IVChainVec[ChainIdx];
+
+ // Prune the solution space aggressively by checking that both IV operands
+ // are expressions that operate on the same unscaled SCEVUnknown. This
+ // "base" will be canceled by the subsequent getMinusSCEV call. Checking
+ // first avoids creating extra SCEV expressions.
+ if (!StressIVChain && Chain.ExprBase != OperExprBase)
continue;
- // FIXME: Overly conservative, termination condition could be an 'or' etc..
- if (TermBr->isUnconditional() || !isa<ICmpInst>(TermBr->getCondition()))
+
+ Value *PrevIV = getWideOperand(Chain.Incs.back().IVOperand);
+ if (!isCompatibleIVType(PrevIV, NextIV))
continue;
- // Search IVUsesByStride to find Cond's IVUse if there is one.
- IVStrideUse *CondUse = 0;
- const SCEV *CondStride = 0;
- ICmpInst *Cond = cast<ICmpInst>(TermBr->getCondition());
- if (!FindIVUserForCond(Cond, CondUse, CondStride))
+ // A phi node terminates a chain.
+ if (isa<PHINode>(UserInst) && isa<PHINode>(Chain.tailUserInst()))
continue;
- // If the latch block is exiting and it's not a single block loop, it's
- // not safe to use postinc iv in other exiting blocks. FIXME: overly
- // conservative? How about icmp stride optimization?
- bool UsePostInc = !(e > 1 && LatchExit && ExitingBlock != LatchBlock);
- if (UsePostInc && ExitingBlock != LatchBlock) {
- if (!Cond->hasOneUse())
- // See below, we don't want the condition to be cloned.
- UsePostInc = false;
- else {
- // If exiting block is the latch block, we know it's safe and profitable
- // to transform the icmp to use post-inc iv. Otherwise do so only if it
- // would not reuse another iv and its iv would be reused by other uses.
- // We are optimizing for the case where the icmp is the only use of the
- // iv.
- IVUsersOfOneStride &StrideUses = *IU->IVUsesByStride[CondStride];
- for (ilist<IVStrideUse>::iterator I = StrideUses.Users.begin(),
- E = StrideUses.Users.end(); I != E; ++I) {
- if (I->getUser() == Cond)
- continue;
- if (!I->isUseOfPostIncrementedValue()) {
- UsePostInc = false;
- break;
- }
- }
- }
+ // The increment must be loop-invariant so it can be kept in a register.
+ const SCEV *PrevExpr = SE.getSCEV(PrevIV);
+ const SCEV *IncExpr = SE.getMinusSCEV(OperExpr, PrevExpr);
+ if (!SE.isLoopInvariant(IncExpr, L))
+ continue;
- // If iv for the stride might be shared and any of the users use pre-inc
- // iv might be used, then it's not safe to use post-inc iv.
- if (UsePostInc &&
- isa<SCEVConstant>(CondStride) &&
- StrideMightBeShared(CondStride, L, true))
- UsePostInc = false;
+ if (Chain.isProfitableIncrement(OperExpr, IncExpr, SE)) {
+ LastIncExpr = IncExpr;
+ break;
+ }
+ }
+ // If we haven't found a chain, create a new one, unless we hit the max. Don't
+ // bother for phi nodes, because they must be last in the chain.
+ if (ChainIdx == NChains) {
+ if (isa<PHINode>(UserInst))
+ return;
+ if (NChains >= MaxChains && !StressIVChain) {
+ DEBUG(dbgs() << "IV Chain Limit\n");
+ return;
}
+ LastIncExpr = OperExpr;
+ // IVUsers may have skipped over sign/zero extensions. We don't currently
+ // attempt to form chains involving extensions unless they can be hoisted
+ // into this loop's AddRec.
+ if (!isa<SCEVAddRecExpr>(LastIncExpr))
+ return;
+ ++NChains;
+ IVChainVec.push_back(IVChain(IVInc(UserInst, IVOper, LastIncExpr),
+ OperExprBase));
+ ChainUsersVec.resize(NChains);
+ DEBUG(dbgs() << "IV Chain#" << ChainIdx << " Head: (" << *UserInst
+ << ") IV=" << *LastIncExpr << "\n");
+ } else {
+ DEBUG(dbgs() << "IV Chain#" << ChainIdx << " Inc: (" << *UserInst
+ << ") IV+" << *LastIncExpr << "\n");
+ // Add this IV user to the end of the chain.
+ IVChainVec[ChainIdx].add(IVInc(UserInst, IVOper, LastIncExpr));
+ }
- // If the trip count is computed in terms of a max (due to ScalarEvolution
- // being unable to find a sufficient guard, for example), change the loop
- // comparison to use SLT or ULT instead of NE.
- Cond = OptimizeMax(L, Cond, CondUse);
+ SmallPtrSet<Instruction*,4> &NearUsers = ChainUsersVec[ChainIdx].NearUsers;
+ // This chain's NearUsers become FarUsers.
+ if (!LastIncExpr->isZero()) {
+ ChainUsersVec[ChainIdx].FarUsers.insert(NearUsers.begin(),
+ NearUsers.end());
+ NearUsers.clear();
+ }
- // If possible, change stride and operands of the compare instruction to
- // eliminate one stride. However, avoid rewriting the compare instruction
- // with an iv of new stride if it's likely the new stride uses will be
- // rewritten using the stride of the compare instruction.
- if (ExitingBlock == LatchBlock && isa<SCEVConstant>(CondStride)) {
- // If the condition stride is a constant and it's the only use, we might
- // want to optimize it first by turning it to count toward zero.
- if (!StrideMightBeShared(CondStride, L, false) &&
- !ShouldCountToZero(Cond, CondUse, SE, L, TLI))
- Cond = ChangeCompareStride(L, Cond, CondUse, CondStride);
+ // All other uses of IVOperand become near uses of the chain.
+ // We currently ignore intermediate values within SCEV expressions, assuming
+ // they will eventually be used be the current chain, or can be computed
+ // from one of the chain increments. To be more precise we could
+ // transitively follow its user and only add leaf IV users to the set.
+ for (Value::use_iterator UseIter = IVOper->use_begin(),
+ UseEnd = IVOper->use_end(); UseIter != UseEnd; ++UseIter) {
+ Instruction *OtherUse = dyn_cast<Instruction>(*UseIter);
+ if (!OtherUse || OtherUse == UserInst)
+ continue;
+ if (SE.isSCEVable(OtherUse->getType())
+ && !isa<SCEVUnknown>(SE.getSCEV(OtherUse))
+ && IU.isIVUserOrOperand(OtherUse)) {
+ continue;
}
+ NearUsers.insert(OtherUse);
+ }
- if (!UsePostInc)
- continue;
+ // Since this user is part of the chain, it's no longer considered a use
+ // of the chain.
+ ChainUsersVec[ChainIdx].FarUsers.erase(UserInst);
+}
- DEBUG(dbgs() << " Change loop exiting icmp to use postinc iv: "
- << *Cond << '\n');
+/// CollectChains - Populate the vector of Chains.
+///
+/// This decreases ILP at the architecture level. Targets with ample registers,
+/// multiple memory ports, and no register renaming probably don't want
+/// this. However, such targets should probably disable LSR altogether.
+///
+/// The job of LSR is to make a reasonable choice of induction variables across
+/// the loop. Subsequent passes can easily "unchain" computation exposing more
+/// ILP *within the loop* if the target wants it.
+///
+/// Finding the best IV chain is potentially a scheduling problem. Since LSR
+/// will not reorder memory operations, it will recognize this as a chain, but
+/// will generate redundant IV increments. Ideally this would be corrected later
+/// by a smart scheduler:
+/// = A[i]
+/// = A[i+x]
+/// A[i] =
+/// A[i+x] =
+///
+/// TODO: Walk the entire domtree within this loop, not just the path to the
+/// loop latch. This will discover chains on side paths, but requires
+/// maintaining multiple copies of the Chains state.
+void LSRInstance::CollectChains() {
+ DEBUG(dbgs() << "Collecting IV Chains.\n");
+ SmallVector<ChainUsers, 8> ChainUsersVec;
+
+ SmallVector<BasicBlock *,8> LatchPath;
+ BasicBlock *LoopHeader = L->getHeader();
+ for (DomTreeNode *Rung = DT.getNode(L->getLoopLatch());
+ Rung->getBlock() != LoopHeader; Rung = Rung->getIDom()) {
+ LatchPath.push_back(Rung->getBlock());
+ }
+ LatchPath.push_back(LoopHeader);
+
+ // Walk the instruction stream from the loop header to the loop latch.
+ for (SmallVectorImpl<BasicBlock *>::reverse_iterator
+ BBIter = LatchPath.rbegin(), BBEnd = LatchPath.rend();
+ BBIter != BBEnd; ++BBIter) {
+ for (BasicBlock::iterator I = (*BBIter)->begin(), E = (*BBIter)->end();
+ I != E; ++I) {
+ // Skip instructions that weren't seen by IVUsers analysis.
+ if (isa<PHINode>(I) || !IU.isIVUserOrOperand(I))
+ continue;
- // It's possible for the setcc instruction to be anywhere in the loop, and
- // possible for it to have multiple users. If it is not immediately before
- // the exiting block branch, move it.
- if (&*++BasicBlock::iterator(Cond) != (Instruction*)TermBr) {
- if (Cond->hasOneUse()) { // Condition has a single use, just move it.
- Cond->moveBefore(TermBr);
- } else {
- // Otherwise, clone the terminating condition and insert into the
- // loopend.
- Cond = cast<ICmpInst>(Cond->clone());
- Cond->setName(L->getHeader()->getName() + ".termcond");
- ExitingBlock->getInstList().insert(TermBr, Cond);
+ // Ignore users that are part of a SCEV expression. This way we only
+ // consider leaf IV Users. This effectively rediscovers a portion of
+ // IVUsers analysis but in program order this time.
+ if (SE.isSCEVable(I->getType()) && !isa<SCEVUnknown>(SE.getSCEV(I)))
+ continue;
- // Clone the IVUse, as the old use still exists!
- IU->IVUsesByStride[CondStride]->addUser(CondUse->getOffset(), Cond,
- CondUse->getOperandValToReplace());
- CondUse = &IU->IVUsesByStride[CondStride]->Users.back();
+ // Remove this instruction from any NearUsers set it may be in.
+ for (unsigned ChainIdx = 0, NChains = IVChainVec.size();
+ ChainIdx < NChains; ++ChainIdx) {
+ ChainUsersVec[ChainIdx].NearUsers.erase(I);
}
- }
+ // Search for operands that can be chained.
+ SmallPtrSet<Instruction*, 4> UniqueOperands;
+ User::op_iterator IVOpEnd = I->op_end();
+ User::op_iterator IVOpIter = findIVOperand(I->op_begin(), IVOpEnd, L, SE);
+ while (IVOpIter != IVOpEnd) {
+ Instruction *IVOpInst = cast<Instruction>(*IVOpIter);
+ if (UniqueOperands.insert(IVOpInst))
+ ChainInstruction(I, IVOpInst, ChainUsersVec);
+ IVOpIter = findIVOperand(llvm::next(IVOpIter), IVOpEnd, L, SE);
+ }
+ } // Continue walking down the instructions.
+ } // Continue walking down the domtree.
+ // Visit phi backedges to determine if the chain can generate the IV postinc.
+ for (BasicBlock::iterator I = L->getHeader()->begin();
+ PHINode *PN = dyn_cast<PHINode>(I); ++I) {
+ if (!SE.isSCEVable(PN->getType()))
+ continue;
- // If we get to here, we know that we can transform the setcc instruction to
- // use the post-incremented version of the IV, allowing us to coalesce the
- // live ranges for the IV correctly.
- CondUse->setOffset(SE->getMinusSCEV(CondUse->getOffset(), CondStride));
- CondUse->setIsUseOfPostIncrementedValue(true);
- Changed = true;
+ Instruction *IncV =
+ dyn_cast<Instruction>(PN->getIncomingValueForBlock(L->getLoopLatch()));
+ if (IncV)
+ ChainInstruction(PN, IncV, ChainUsersVec);
+ }
+ // Remove any unprofitable chains.
+ unsigned ChainIdx = 0;
+ for (unsigned UsersIdx = 0, NChains = IVChainVec.size();
+ UsersIdx < NChains; ++UsersIdx) {
+ if (!isProfitableChain(IVChainVec[UsersIdx],
+ ChainUsersVec[UsersIdx].FarUsers, SE, TLI))
+ continue;
+ // Preserve the chain at UsesIdx.
+ if (ChainIdx != UsersIdx)
+ IVChainVec[ChainIdx] = IVChainVec[UsersIdx];
+ FinalizeChain(IVChainVec[ChainIdx]);
+ ++ChainIdx;
+ }
+ IVChainVec.resize(ChainIdx);
+}
- ++NumLoopCond;
+void LSRInstance::FinalizeChain(IVChain &Chain) {
+ assert(!Chain.Incs.empty() && "empty IV chains are not allowed");
+ DEBUG(dbgs() << "Final Chain: " << *Chain.Incs[0].UserInst << "\n");
+
+ for (IVChain::const_iterator I = Chain.begin(), E = Chain.end();
+ I != E; ++I) {
+ DEBUG(dbgs() << " Inc: " << *I->UserInst << "\n");
+ User::op_iterator UseI =
+ std::find(I->UserInst->op_begin(), I->UserInst->op_end(), I->IVOperand);
+ assert(UseI != I->UserInst->op_end() && "cannot find IV operand");
+ IVIncSet.insert(UseI);
}
}
-bool LoopStrengthReduce::OptimizeLoopCountIVOfStride(const SCEV* &Stride,
- IVStrideUse* &CondUse,
- Loop *L) {
- // If the only use is an icmp of a loop exiting conditional branch, then
- // attempt the optimization.
- BasedUser User = BasedUser(*CondUse, SE);
- assert(isa<ICmpInst>(User.Inst) && "Expecting an ICMPInst!");
- ICmpInst *Cond = cast<ICmpInst>(User.Inst);
+/// Return true if the IVInc can be folded into an addressing mode.
+static bool canFoldIVIncExpr(const SCEV *IncExpr, Instruction *UserInst,
+ Value *Operand, const TargetLowering *TLI) {
+ const SCEVConstant *IncConst = dyn_cast<SCEVConstant>(IncExpr);
+ if (!IncConst || !isAddressUse(UserInst, Operand))
+ return false;
- // Less strict check now that compare stride optimization is done.
- if (!ShouldCountToZero(Cond, CondUse, SE, L))
+ if (IncConst->getValue()->getValue().getMinSignedBits() > 64)
return false;
- Value *CondOp0 = Cond->getOperand(0);
- PHINode *PHIExpr = dyn_cast<PHINode>(CondOp0);
- Instruction *Incr;
- if (!PHIExpr) {
- // Value tested is postinc. Find the phi node.
- Incr = dyn_cast<BinaryOperator>(CondOp0);
- // FIXME: Just use User.OperandValToReplace here?
- if (!Incr || Incr->getOpcode() != Instruction::Add)
- return false;
+ int64_t IncOffset = IncConst->getValue()->getSExtValue();
+ if (!isAlwaysFoldable(IncOffset, /*BaseGV=*/0, /*HaseBaseReg=*/false,
+ LSRUse::Address, getAccessType(UserInst), TLI))
+ return false;
- PHIExpr = dyn_cast<PHINode>(Incr->getOperand(0));
- if (!PHIExpr)
- return false;
- // 1 use for preinc value, the increment.
- if (!PHIExpr->hasOneUse())
- return false;
- } else {
- assert(isa<PHINode>(CondOp0) &&
- "Unexpected loop exiting counting instruction sequence!");
- PHIExpr = cast<PHINode>(CondOp0);
- // Value tested is preinc. Find the increment.
- // A CmpInst is not a BinaryOperator; we depend on this.
- Instruction::use_iterator UI = PHIExpr->use_begin();
- Incr = dyn_cast<BinaryOperator>(UI);
- if (!Incr)
- Incr = dyn_cast<BinaryOperator>(++UI);
- // One use for postinc value, the phi. Unnecessarily conservative?
- if (!Incr || !Incr->hasOneUse() || Incr->getOpcode() != Instruction::Add)
- return false;
+ return true;
+}
+
+/// GenerateIVChains - Generate an add or subtract for each IVInc in a chain to
+/// materialize the IV user's operand from the previous IV user's operand.
+void LSRInstance::GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter,
+ SmallVectorImpl<WeakVH> &DeadInsts) {
+ // Find the new IVOperand for the head of the chain. It may have been replaced
+ // by LSR.
+ const IVInc &Head = Chain.Incs[0];
+ User::op_iterator IVOpEnd = Head.UserInst->op_end();
+ User::op_iterator IVOpIter = findIVOperand(Head.UserInst->op_begin(),
+ IVOpEnd, L, SE);
+ Value *IVSrc = 0;
+ while (IVOpIter != IVOpEnd) {
+ IVSrc = getWideOperand(*IVOpIter);
+
+ // If this operand computes the expression that the chain needs, we may use
+ // it. (Check this after setting IVSrc which is used below.)
+ //
+ // Note that if Head.IncExpr is wider than IVSrc, then this phi is too
+ // narrow for the chain, so we can no longer use it. We do allow using a
+ // wider phi, assuming the LSR checked for free truncation. In that case we
+ // should already have a truncate on this operand such that
+ // getSCEV(IVSrc) == IncExpr.
+ if (SE.getSCEV(*IVOpIter) == Head.IncExpr
+ || SE.getSCEV(IVSrc) == Head.IncExpr) {
+ break;
+ }
+ IVOpIter = findIVOperand(llvm::next(IVOpIter), IVOpEnd, L, SE);
+ }
+ if (IVOpIter == IVOpEnd) {
+ // Gracefully give up on this chain.
+ DEBUG(dbgs() << "Concealed chain head: " << *Head.UserInst << "\n");
+ return;
}
- // Replace the increment with a decrement.
- DEBUG(dbgs() << "LSR: Examining use ");
- DEBUG(WriteAsOperand(dbgs(), CondOp0, /*PrintType=*/false));
- DEBUG(dbgs() << " in Inst: " << *Cond << '\n');
- BinaryOperator *Decr = BinaryOperator::Create(Instruction::Sub,
- Incr->getOperand(0), Incr->getOperand(1), "tmp", Incr);
- Incr->replaceAllUsesWith(Decr);
- Incr->eraseFromParent();
-
- // Substitute endval-startval for the original startval, and 0 for the
- // original endval. Since we're only testing for equality this is OK even
- // if the computation wraps around.
- BasicBlock *Preheader = L->getLoopPreheader();
- Instruction *PreInsertPt = Preheader->getTerminator();
- unsigned InBlock = L->contains(PHIExpr->getIncomingBlock(0)) ? 1 : 0;
- Value *StartVal = PHIExpr->getIncomingValue(InBlock);
- Value *EndVal = Cond->getOperand(1);
- DEBUG(dbgs() << " Optimize loop counting iv to count down ["
- << *EndVal << " .. " << *StartVal << "]\n");
-
- // FIXME: check for case where both are constant.
- Constant* Zero = ConstantInt::get(Cond->getOperand(1)->getType(), 0);
- BinaryOperator *NewStartVal = BinaryOperator::Create(Instruction::Sub,
- EndVal, StartVal, "tmp", PreInsertPt);
- PHIExpr->setIncomingValue(InBlock, NewStartVal);
- Cond->setOperand(1, Zero);
- DEBUG(dbgs() << " New icmp: " << *Cond << "\n");
-
- int64_t SInt = cast<SCEVConstant>(Stride)->getValue()->getSExtValue();
- const SCEV *NewStride = 0;
- bool Found = false;
- for (unsigned i = 0, e = IU->StrideOrder.size(); i != e; ++i) {
- const SCEV *OldStride = IU->StrideOrder[i];
- if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(OldStride))
- if (SC->getValue()->getSExtValue() == -SInt) {
- Found = true;
- NewStride = OldStride;
- break;
+ DEBUG(dbgs() << "Generate chain at: " << *IVSrc << "\n");
+ Type *IVTy = IVSrc->getType();
+ Type *IntTy = SE.getEffectiveSCEVType(IVTy);
+ const SCEV *LeftOverExpr = 0;
+ for (IVChain::const_iterator IncI = Chain.begin(),
+ IncE = Chain.end(); IncI != IncE; ++IncI) {
+
+ Instruction *InsertPt = IncI->UserInst;
+ if (isa<PHINode>(InsertPt))
+ InsertPt = L->getLoopLatch()->getTerminator();
+
+ // IVOper will replace the current IV User's operand. IVSrc is the IV
+ // value currently held in a register.
+ Value *IVOper = IVSrc;
+ if (!IncI->IncExpr->isZero()) {
+ // IncExpr was the result of subtraction of two narrow values, so must
+ // be signed.
+ const SCEV *IncExpr = SE.getNoopOrSignExtend(IncI->IncExpr, IntTy);
+ LeftOverExpr = LeftOverExpr ?
+ SE.getAddExpr(LeftOverExpr, IncExpr) : IncExpr;
+ }
+ if (LeftOverExpr && !LeftOverExpr->isZero()) {
+ // Expand the IV increment.
+ Rewriter.clearPostInc();
+ Value *IncV = Rewriter.expandCodeFor(LeftOverExpr, IntTy, InsertPt);
+ const SCEV *IVOperExpr = SE.getAddExpr(SE.getUnknown(IVSrc),
+ SE.getUnknown(IncV));
+ IVOper = Rewriter.expandCodeFor(IVOperExpr, IVTy, InsertPt);
+
+ // If an IV increment can't be folded, use it as the next IV value.
+ if (!canFoldIVIncExpr(LeftOverExpr, IncI->UserInst, IncI->IVOperand,
+ TLI)) {
+ assert(IVTy == IVOper->getType() && "inconsistent IV increment type");
+ IVSrc = IVOper;
+ LeftOverExpr = 0;
+ }
+ }
+ Type *OperTy = IncI->IVOperand->getType();
+ if (IVTy != OperTy) {
+ assert(SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy) &&
+ "cannot extend a chained IV");
+ IRBuilder<> Builder(InsertPt);
+ IVOper = Builder.CreateTruncOrBitCast(IVOper, OperTy, "lsr.chain");
+ }
+ IncI->UserInst->replaceUsesOfWith(IncI->IVOperand, IVOper);
+ DeadInsts.push_back(IncI->IVOperand);
+ }
+ // If LSR created a new, wider phi, we may also replace its postinc. We only
+ // do this if we also found a wide value for the head of the chain.
+ if (isa<PHINode>(Chain.tailUserInst())) {
+ for (BasicBlock::iterator I = L->getHeader()->begin();
+ PHINode *Phi = dyn_cast<PHINode>(I); ++I) {
+ if (!isCompatibleIVType(Phi, IVSrc))
+ continue;
+ Instruction *PostIncV = dyn_cast<Instruction>(
+ Phi->getIncomingValueForBlock(L->getLoopLatch()));
+ if (!PostIncV || (SE.getSCEV(PostIncV) != SE.getSCEV(IVSrc)))
+ continue;
+ Value *IVOper = IVSrc;
+ Type *PostIncTy = PostIncV->getType();
+ if (IVTy != PostIncTy) {
+ assert(PostIncTy->isPointerTy() && "mixing int/ptr IV types");
+ IRBuilder<> Builder(L->getLoopLatch()->getTerminator());
+ Builder.SetCurrentDebugLocation(PostIncV->getDebugLoc());
+ IVOper = Builder.CreatePointerCast(IVSrc, PostIncTy, "lsr.chain");
+ }
+ Phi->replaceUsesOfWith(PostIncV, IVOper);
+ DeadInsts.push_back(PostIncV);
+ }
+ }
+}
+
+void LSRInstance::CollectFixupsAndInitialFormulae() {
+ for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) {
+ Instruction *UserInst = UI->getUser();
+ // Skip IV users that are part of profitable IV Chains.
+ User::op_iterator UseI = std::find(UserInst->op_begin(), UserInst->op_end(),
+ UI->getOperandValToReplace());
+ assert(UseI != UserInst->op_end() && "cannot find IV operand");
+ if (IVIncSet.count(UseI))
+ continue;
+
+ // Record the uses.
+ LSRFixup &LF = getNewFixup();
+ LF.UserInst = UserInst;
+ LF.OperandValToReplace = UI->getOperandValToReplace();
+ LF.PostIncLoops = UI->getPostIncLoops();
+
+ LSRUse::KindType Kind = LSRUse::Basic;
+ Type *AccessTy = 0;
+ if (isAddressUse(LF.UserInst, LF.OperandValToReplace)) {
+ Kind = LSRUse::Address;
+ AccessTy = getAccessType(LF.UserInst);
+ }
+
+ const SCEV *S = IU.getExpr(*UI);
+
+ // Equality (== and !=) ICmps are special. We can rewrite (i == N) as
+ // (N - i == 0), and this allows (N - i) to be the expression that we work
+ // with rather than just N or i, so we can consider the register
+ // requirements for both N and i at the same time. Limiting this code to
+ // equality icmps is not a problem because all interesting loops use
+ // equality icmps, thanks to IndVarSimplify.
+ if (ICmpInst *CI = dyn_cast<ICmpInst>(LF.UserInst))
+ if (CI->isEquality()) {
+ // Swap the operands if needed to put the OperandValToReplace on the
+ // left, for consistency.
+ Value *NV = CI->getOperand(1);
+ if (NV == LF.OperandValToReplace) {
+ CI->setOperand(1, CI->getOperand(0));
+ CI->setOperand(0, NV);
+ NV = CI->getOperand(1);
+ Changed = true;
+ }
+
+ // x == y --> x - y == 0
+ const SCEV *N = SE.getSCEV(NV);
+ if (SE.isLoopInvariant(N, L)) {
+ // S is normalized, so normalize N before folding it into S
+ // to keep the result normalized.
+ N = TransformForPostIncUse(Normalize, N, CI, 0,
+ LF.PostIncLoops, SE, DT);
+ Kind = LSRUse::ICmpZero;
+ S = SE.getMinusSCEV(N, S);
+ }
+
+ // -1 and the negations of all interesting strides (except the negation
+ // of -1) are now also interesting.
+ for (size_t i = 0, e = Factors.size(); i != e; ++i)
+ if (Factors[i] != -1)
+ Factors.insert(-(uint64_t)Factors[i]);
+ Factors.insert(-1);
}
+
+ // Set up the initial formula for this use.
+ std::pair<size_t, int64_t> P = getUse(S, Kind, AccessTy);
+ LF.LUIdx = P.first;
+ LF.Offset = P.second;
+ LSRUse &LU = Uses[LF.LUIdx];
+ LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
+ if (!LU.WidestFixupType ||
+ SE.getTypeSizeInBits(LU.WidestFixupType) <
+ SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
+ LU.WidestFixupType = LF.OperandValToReplace->getType();
+
+ // If this is the first use of this LSRUse, give it a formula.
+ if (LU.Formulae.empty()) {
+ InsertInitialFormula(S, LU, LF.LUIdx);
+ CountRegisters(LU.Formulae.back(), LF.LUIdx);
+ }
}
- if (!Found)
- NewStride = SE->getIntegerSCEV(-SInt, Stride->getType());
- IU->AddUser(NewStride, CondUse->getOffset(), Cond, Cond->getOperand(0));
- IU->IVUsesByStride[Stride]->removeUser(CondUse);
+ DEBUG(print_fixups(dbgs()));
+}
+
+/// InsertInitialFormula - Insert a formula for the given expression into
+/// the given use, separating out loop-variant portions from loop-invariant
+/// and loop-computable portions.
+void
+LSRInstance::InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx) {
+ Formula F;
+ F.InitialMatch(S, L, SE);
+ bool Inserted = InsertFormula(LU, LUIdx, F);
+ assert(Inserted && "Initial formula already exists!"); (void)Inserted;
+}
- CondUse = &IU->IVUsesByStride[NewStride]->Users.back();
- Stride = NewStride;
+/// InsertSupplementalFormula - Insert a simple single-register formula for
+/// the given expression into the given use.
+void
+LSRInstance::InsertSupplementalFormula(const SCEV *S,
+ LSRUse &LU, size_t LUIdx) {
+ Formula F;
+ F.BaseRegs.push_back(S);
+ F.AM.HasBaseReg = true;
+ bool Inserted = InsertFormula(LU, LUIdx, F);
+ assert(Inserted && "Supplemental formula already exists!"); (void)Inserted;
+}
+
+/// CountRegisters - Note which registers are used by the given formula,
+/// updating RegUses.
+void LSRInstance::CountRegisters(const Formula &F, size_t LUIdx) {
+ if (F.ScaledReg)
+ RegUses.CountRegister(F.ScaledReg, LUIdx);
+ for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
+ E = F.BaseRegs.end(); I != E; ++I)
+ RegUses.CountRegister(*I, LUIdx);
+}
- ++NumCountZero;
+/// InsertFormula - If the given formula has not yet been inserted, add it to
+/// the list, and return true. Return false otherwise.
+bool LSRInstance::InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F) {
+ if (!LU.InsertFormula(F))
+ return false;
+ CountRegisters(F, LUIdx);
return true;
}
-/// OptimizeLoopCountIV - If, after all sharing of IVs, the IV used for deciding
-/// when to exit the loop is used only for that purpose, try to rearrange things
-/// so it counts down to a test against zero.
-bool LoopStrengthReduce::OptimizeLoopCountIV(Loop *L) {
- bool ThisChanged = false;
- for (unsigned i = 0, e = IU->StrideOrder.size(); i != e; ++i) {
- const SCEV *Stride = IU->StrideOrder[i];
- std::map<const SCEV *, IVUsersOfOneStride *>::iterator SI =
- IU->IVUsesByStride.find(Stride);
- assert(SI != IU->IVUsesByStride.end() && "Stride doesn't exist!");
- // FIXME: Generalize to non-affine IV's.
- if (!SI->first->isLoopInvariant(L))
- continue;
- // If stride is a constant and it has an icmpinst use, check if we can
- // optimize the loop to count down.
- if (isa<SCEVConstant>(Stride) && SI->second->Users.size() == 1) {
- Instruction *User = SI->second->Users.begin()->getUser();
- if (!isa<ICmpInst>(User))
- continue;
- const SCEV *CondStride = Stride;
- IVStrideUse *Use = &*SI->second->Users.begin();
- if (!OptimizeLoopCountIVOfStride(CondStride, Use, L))
+/// CollectLoopInvariantFixupsAndFormulae - Check for other uses of
+/// loop-invariant values which we're tracking. These other uses will pin these
+/// values in registers, making them less profitable for elimination.
+/// TODO: This currently misses non-constant addrec step registers.
+/// TODO: Should this give more weight to users inside the loop?
+void
+LSRInstance::CollectLoopInvariantFixupsAndFormulae() {
+ SmallVector<const SCEV *, 8> Worklist(RegUses.begin(), RegUses.end());
+ SmallPtrSet<const SCEV *, 8> Inserted;
+
+ while (!Worklist.empty()) {
+ const SCEV *S = Worklist.pop_back_val();
+
+ if (const SCEVNAryExpr *N = dyn_cast<SCEVNAryExpr>(S))
+ Worklist.append(N->op_begin(), N->op_end());
+ else if (const SCEVCastExpr *C = dyn_cast<SCEVCastExpr>(S))
+ Worklist.push_back(C->getOperand());
+ else if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S)) {
+ Worklist.push_back(D->getLHS());
+ Worklist.push_back(D->getRHS());
+ } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
+ if (!Inserted.insert(U)) continue;
+ const Value *V = U->getValue();
+ if (const Instruction *Inst = dyn_cast<Instruction>(V)) {
+ // Look for instructions defined outside the loop.
+ if (L->contains(Inst)) continue;
+ } else if (isa<UndefValue>(V))
+ // Undef doesn't have a live range, so it doesn't matter.
continue;
- ThisChanged = true;
-
- // Now check if it's possible to reuse this iv for other stride uses.
- for (unsigned j = 0, ee = IU->StrideOrder.size(); j != ee; ++j) {
- const SCEV *SStride = IU->StrideOrder[j];
- if (SStride == CondStride)
+ for (Value::const_use_iterator UI = V->use_begin(), UE = V->use_end();
+ UI != UE; ++UI) {
+ const Instruction *UserInst = dyn_cast<Instruction>(*UI);
+ // Ignore non-instructions.
+ if (!UserInst)
+ continue;
+ // Ignore instructions in other functions (as can happen with
+ // Constants).
+ if (UserInst->getParent()->getParent() != L->getHeader()->getParent())
continue;
- std::map<const SCEV *, IVUsersOfOneStride *>::iterator SII =
- IU->IVUsesByStride.find(SStride);
- assert(SII != IU->IVUsesByStride.end() && "Stride doesn't exist!");
- // FIXME: Generalize to non-affine IV's.
- if (!SII->first->isLoopInvariant(L))
+ // Ignore instructions not dominated by the loop.
+ const BasicBlock *UseBB = !isa<PHINode>(UserInst) ?
+ UserInst->getParent() :
+ cast<PHINode>(UserInst)->getIncomingBlock(
+ PHINode::getIncomingValueNumForOperand(UI.getOperandNo()));
+ if (!DT.dominates(L->getHeader(), UseBB))
continue;
- // FIXME: Rewrite other stride using CondStride.
+ // Ignore uses which are part of other SCEV expressions, to avoid
+ // analyzing them multiple times.
+ if (SE.isSCEVable(UserInst->getType())) {
+ const SCEV *UserS = SE.getSCEV(const_cast<Instruction *>(UserInst));
+ // If the user is a no-op, look through to its uses.
+ if (!isa<SCEVUnknown>(UserS))
+ continue;
+ if (UserS == U) {
+ Worklist.push_back(
+ SE.getUnknown(const_cast<Instruction *>(UserInst)));
+ continue;
+ }
+ }
+ // Ignore icmp instructions which are already being analyzed.
+ if (const ICmpInst *ICI = dyn_cast<ICmpInst>(UserInst)) {
+ unsigned OtherIdx = !UI.getOperandNo();
+ Value *OtherOp = const_cast<Value *>(ICI->getOperand(OtherIdx));
+ if (SE.hasComputableLoopEvolution(SE.getSCEV(OtherOp), L))
+ continue;
+ }
+
+ LSRFixup &LF = getNewFixup();
+ LF.UserInst = const_cast<Instruction *>(UserInst);
+ LF.OperandValToReplace = UI.getUse();
+ std::pair<size_t, int64_t> P = getUse(S, LSRUse::Basic, 0);
+ LF.LUIdx = P.first;
+ LF.Offset = P.second;
+ LSRUse &LU = Uses[LF.LUIdx];
+ LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
+ if (!LU.WidestFixupType ||
+ SE.getTypeSizeInBits(LU.WidestFixupType) <
+ SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
+ LU.WidestFixupType = LF.OperandValToReplace->getType();
+ InsertSupplementalFormula(U, LU, LF.LUIdx);
+ CountRegisters(LU.Formulae.back(), Uses.size() - 1);
+ break;
}
}
}
+}
+
+/// CollectSubexprs - Split S into subexpressions which can be pulled out into
+/// separate registers. If C is non-null, multiply each subexpression by C.
+static void CollectSubexprs(const SCEV *S, const SCEVConstant *C,
+ SmallVectorImpl<const SCEV *> &Ops,
+ const Loop *L,
+ ScalarEvolution &SE) {
+ if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
+ // Break out add operands.
+ for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
+ I != E; ++I)
+ CollectSubexprs(*I, C, Ops, L, SE);
+ return;
+ } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
+ // Split a non-zero base out of an addrec.
+ if (!AR->getStart()->isZero()) {
+ CollectSubexprs(SE.getAddRecExpr(SE.getConstant(AR->getType(), 0),
+ AR->getStepRecurrence(SE),
+ AR->getLoop(),
+ //FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
+ SCEV::FlagAnyWrap),
+ C, Ops, L, SE);
+ CollectSubexprs(AR->getStart(), C, Ops, L, SE);
+ return;
+ }
+ } else if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
+ // Break (C * (a + b + c)) into C*a + C*b + C*c.
+ if (Mul->getNumOperands() == 2)
+ if (const SCEVConstant *Op0 =
+ dyn_cast<SCEVConstant>(Mul->getOperand(0))) {
+ CollectSubexprs(Mul->getOperand(1),
+ C ? cast<SCEVConstant>(SE.getMulExpr(C, Op0)) : Op0,
+ Ops, L, SE);
+ return;
+ }
+ }
- Changed |= ThisChanged;
- return ThisChanged;
+ // Otherwise use the value itself, optionally with a scale applied.
+ Ops.push_back(C ? SE.getMulExpr(C, S) : S);
}
-bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager &LPM) {
- IU = &getAnalysis<IVUsers>();
- SE = &getAnalysis<ScalarEvolution>();
- Changed = false;
+/// GenerateReassociations - Split out subexpressions from adds and the bases of
+/// addrecs.
+void LSRInstance::GenerateReassociations(LSRUse &LU, unsigned LUIdx,
+ Formula Base,
+ unsigned Depth) {
+ // Arbitrarily cap recursion to protect compile time.
+ if (Depth >= 3) return;
- // If LoopSimplify form is not available, stay out of trouble.
- if (!L->getLoopPreheader() || !L->getLoopLatch())
- return false;
+ for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
+ const SCEV *BaseReg = Base.BaseRegs[i];
+
+ SmallVector<const SCEV *, 8> AddOps;
+ CollectSubexprs(BaseReg, 0, AddOps, L, SE);
- if (!IU->IVUsesByStride.empty()) {
- DEBUG(dbgs() << "\nLSR on \"" << L->getHeader()->getParent()->getName()
- << "\" ";
- L->print(dbgs()));
+ if (AddOps.size() == 1) continue;
- // Sort the StrideOrder so we process larger strides first.
- std::stable_sort(IU->StrideOrder.begin(), IU->StrideOrder.end(),
- StrideCompare(SE));
+ for (SmallVectorImpl<const SCEV *>::const_iterator J = AddOps.begin(),
+ JE = AddOps.end(); J != JE; ++J) {
- // Optimize induction variables. Some indvar uses can be transformed to use
- // strides that will be needed for other purposes. A common example of this
- // is the exit test for the loop, which can often be rewritten to use the
- // computation of some other indvar to decide when to terminate the loop.
- OptimizeIndvars(L);
+ // Loop-variant "unknown" values are uninteresting; we won't be able to
+ // do anything meaningful with them.
+ if (isa<SCEVUnknown>(*J) && !SE.isLoopInvariant(*J, L))
+ continue;
+
+ // Don't pull a constant into a register if the constant could be folded
+ // into an immediate field.
+ if (isAlwaysFoldable(*J, LU.MinOffset, LU.MaxOffset,
+ Base.getNumRegs() > 1,
+ LU.Kind, LU.AccessTy, TLI, SE))
+ continue;
+
+ // Collect all operands except *J.
+ SmallVector<const SCEV *, 8> InnerAddOps
+ (((const SmallVector<const SCEV *, 8> &)AddOps).begin(), J);
+ InnerAddOps.append
+ (llvm::next(J), ((const SmallVector<const SCEV *, 8> &)AddOps).end());
+
+ // Don't leave just a constant behind in a register if the constant could
+ // be folded into an immediate field.
+ if (InnerAddOps.size() == 1 &&
+ isAlwaysFoldable(InnerAddOps[0], LU.MinOffset, LU.MaxOffset,
+ Base.getNumRegs() > 1,
+ LU.Kind, LU.AccessTy, TLI, SE))
+ continue;
+
+ const SCEV *InnerSum = SE.getAddExpr(InnerAddOps);
+ if (InnerSum->isZero())
+ continue;
+ Formula F = Base;
+
+ // Add the remaining pieces of the add back into the new formula.
+ const SCEVConstant *InnerSumSC = dyn_cast<SCEVConstant>(InnerSum);
+ if (TLI && InnerSumSC &&
+ SE.getTypeSizeInBits(InnerSumSC->getType()) <= 64 &&
+ TLI->isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
+ InnerSumSC->getValue()->getZExtValue())) {
+ F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset +
+ InnerSumSC->getValue()->getZExtValue();
+ F.BaseRegs.erase(F.BaseRegs.begin() + i);
+ } else
+ F.BaseRegs[i] = InnerSum;
+
+ // Add J as its own register, or an unfolded immediate.
+ const SCEVConstant *SC = dyn_cast<SCEVConstant>(*J);
+ if (TLI && SC && SE.getTypeSizeInBits(SC->getType()) <= 64 &&
+ TLI->isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
+ SC->getValue()->getZExtValue()))
+ F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset +
+ SC->getValue()->getZExtValue();
+ else
+ F.BaseRegs.push_back(*J);
+
+ if (InsertFormula(LU, LUIdx, F))
+ // If that formula hadn't been seen before, recurse to find more like
+ // it.
+ GenerateReassociations(LU, LUIdx, LU.Formulae.back(), Depth+1);
+ }
+ }
+}
+
+/// GenerateCombinations - Generate a formula consisting of all of the
+/// loop-dominating registers added into a single register.
+void LSRInstance::GenerateCombinations(LSRUse &LU, unsigned LUIdx,
+ Formula Base) {
+ // This method is only interesting on a plurality of registers.
+ if (Base.BaseRegs.size() <= 1) return;
+
+ Formula F = Base;
+ F.BaseRegs.clear();
+ SmallVector<const SCEV *, 4> Ops;
+ for (SmallVectorImpl<const SCEV *>::const_iterator
+ I = Base.BaseRegs.begin(), E = Base.BaseRegs.end(); I != E; ++I) {
+ const SCEV *BaseReg = *I;
+ if (SE.properlyDominates(BaseReg, L->getHeader()) &&
+ !SE.hasComputableLoopEvolution(BaseReg, L))
+ Ops.push_back(BaseReg);
+ else
+ F.BaseRegs.push_back(BaseReg);
+ }
+ if (Ops.size() > 1) {
+ const SCEV *Sum = SE.getAddExpr(Ops);
+ // TODO: If Sum is zero, it probably means ScalarEvolution missed an
+ // opportunity to fold something. For now, just ignore such cases
+ // rather than proceed with zero in a register.
+ if (!Sum->isZero()) {
+ F.BaseRegs.push_back(Sum);
+ (void)InsertFormula(LU, LUIdx, F);
+ }
+ }
+}
+
+/// GenerateSymbolicOffsets - Generate reuse formulae using symbolic offsets.
+void LSRInstance::GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx,
+ Formula Base) {
+ // We can't add a symbolic offset if the address already contains one.
+ if (Base.AM.BaseGV) return;
+
+ for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
+ const SCEV *G = Base.BaseRegs[i];
+ GlobalValue *GV = ExtractSymbol(G, SE);
+ if (G->isZero() || !GV)
+ continue;
+ Formula F = Base;
+ F.AM.BaseGV = GV;
+ if (!isLegalUse(F.AM, LU.MinOffset, LU.MaxOffset,
+ LU.Kind, LU.AccessTy, TLI))
+ continue;
+ F.BaseRegs[i] = G;
+ (void)InsertFormula(LU, LUIdx, F);
+ }
+}
+
+/// GenerateConstantOffsets - Generate reuse formulae using symbolic offsets.
+void LSRInstance::GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx,
+ Formula Base) {
+ // TODO: For now, just add the min and max offset, because it usually isn't
+ // worthwhile looking at everything inbetween.
+ SmallVector<int64_t, 2> Worklist;
+ Worklist.push_back(LU.MinOffset);
+ if (LU.MaxOffset != LU.MinOffset)
+ Worklist.push_back(LU.MaxOffset);
+
+ for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
+ const SCEV *G = Base.BaseRegs[i];
+
+ for (SmallVectorImpl<int64_t>::const_iterator I = Worklist.begin(),
+ E = Worklist.end(); I != E; ++I) {
+ Formula F = Base;
+ F.AM.BaseOffs = (uint64_t)Base.AM.BaseOffs - *I;
+ if (isLegalUse(F.AM, LU.MinOffset - *I, LU.MaxOffset - *I,
+ LU.Kind, LU.AccessTy, TLI)) {
+ // Add the offset to the base register.
+ const SCEV *NewG = SE.getAddExpr(SE.getConstant(G->getType(), *I), G);
+ // If it cancelled out, drop the base register, otherwise update it.
+ if (NewG->isZero()) {
+ std::swap(F.BaseRegs[i], F.BaseRegs.back());
+ F.BaseRegs.pop_back();
+ } else
+ F.BaseRegs[i] = NewG;
+
+ (void)InsertFormula(LU, LUIdx, F);
+ }
+ }
+
+ int64_t Imm = ExtractImmediate(G, SE);
+ if (G->isZero() || Imm == 0)
+ continue;
+ Formula F = Base;
+ F.AM.BaseOffs = (uint64_t)F.AM.BaseOffs + Imm;
+ if (!isLegalUse(F.AM, LU.MinOffset, LU.MaxOffset,
+ LU.Kind, LU.AccessTy, TLI))
+ continue;
+ F.BaseRegs[i] = G;
+ (void)InsertFormula(LU, LUIdx, F);
+ }
+}
- // Change loop terminating condition to use the postinc iv when possible
- // and optimize loop terminating compare. FIXME: Move this after
- // StrengthReduceIVUsersOfStride?
- OptimizeLoopTermCond(L);
+/// GenerateICmpZeroScales - For ICmpZero, check to see if we can scale up
+/// the comparison. For example, x == y -> x*c == y*c.
+void LSRInstance::GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx,
+ Formula Base) {
+ if (LU.Kind != LSRUse::ICmpZero) return;
- // FIXME: We can shrink overlarge IV's here. e.g. if the code has
- // computation in i64 values and the target doesn't support i64, demote
- // the computation to 32-bit if safe.
+ // Determine the integer type for the base formula.
+ Type *IntTy = Base.getType();
+ if (!IntTy) return;
+ if (SE.getTypeSizeInBits(IntTy) > 64) return;
- // FIXME: Attempt to reuse values across multiple IV's. In particular, we
- // could have something like "for(i) { foo(i*8); bar(i*16) }", which should
- // be codegened as "for (j = 0;; j+=8) { foo(j); bar(j+j); }" on X86/PPC.
- // Need to be careful that IV's are all the same type. Only works for
- // intptr_t indvars.
+ // Don't do this if there is more than one offset.
+ if (LU.MinOffset != LU.MaxOffset) return;
- // IVsByStride keeps IVs for one particular loop.
- assert(IVsByStride.empty() && "Stale entries in IVsByStride?");
+ assert(!Base.AM.BaseGV && "ICmpZero use is not legal!");
- StrengthReduceIVUsers(L);
+ // Check each interesting stride.
+ for (SmallSetVector<int64_t, 8>::const_iterator
+ I = Factors.begin(), E = Factors.end(); I != E; ++I) {
+ int64_t Factor = *I;
- // After all sharing is done, see if we can adjust the loop to test against
- // zero instead of counting up to a maximum. This is usually faster.
- OptimizeLoopCountIV(L);
+ // Check that the multiplication doesn't overflow.
+ if (Base.AM.BaseOffs == INT64_MIN && Factor == -1)
+ continue;
+ int64_t NewBaseOffs = (uint64_t)Base.AM.BaseOffs * Factor;
+ if (NewBaseOffs / Factor != Base.AM.BaseOffs)
+ continue;
+
+ // Check that multiplying with the use offset doesn't overflow.
+ int64_t Offset = LU.MinOffset;
+ if (Offset == INT64_MIN && Factor == -1)
+ continue;
+ Offset = (uint64_t)Offset * Factor;
+ if (Offset / Factor != LU.MinOffset)
+ continue;
+
+ Formula F = Base;
+ F.AM.BaseOffs = NewBaseOffs;
+
+ // Check that this scale is legal.
+ if (!isLegalUse(F.AM, Offset, Offset, LU.Kind, LU.AccessTy, TLI))
+ continue;
+
+ // Compensate for the use having MinOffset built into it.
+ F.AM.BaseOffs = (uint64_t)F.AM.BaseOffs + Offset - LU.MinOffset;
+
+ const SCEV *FactorS = SE.getConstant(IntTy, Factor);
+
+ // Check that multiplying with each base register doesn't overflow.
+ for (size_t i = 0, e = F.BaseRegs.size(); i != e; ++i) {
+ F.BaseRegs[i] = SE.getMulExpr(F.BaseRegs[i], FactorS);
+ if (getExactSDiv(F.BaseRegs[i], FactorS, SE) != Base.BaseRegs[i])
+ goto next;
+ }
+
+ // Check that multiplying with the scaled register doesn't overflow.
+ if (F.ScaledReg) {
+ F.ScaledReg = SE.getMulExpr(F.ScaledReg, FactorS);
+ if (getExactSDiv(F.ScaledReg, FactorS, SE) != Base.ScaledReg)
+ continue;
+ }
+
+ // Check that multiplying with the unfolded offset doesn't overflow.
+ if (F.UnfoldedOffset != 0) {
+ if (F.UnfoldedOffset == INT64_MIN && Factor == -1)
+ continue;
+ F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset * Factor;
+ if (F.UnfoldedOffset / Factor != Base.UnfoldedOffset)
+ continue;
+ }
- // We're done analyzing this loop; release all the state we built up for it.
- IVsByStride.clear();
+ // If we make it here and it's legal, add it.
+ (void)InsertFormula(LU, LUIdx, F);
+ next:;
+ }
+}
- // Clean up after ourselves
- DeleteTriviallyDeadInstructions();
+/// GenerateScales - Generate stride factor reuse formulae by making use of
+/// scaled-offset address modes, for example.
+void LSRInstance::GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base) {
+ // Determine the integer type for the base formula.
+ Type *IntTy = Base.getType();
+ if (!IntTy) return;
+
+ // If this Formula already has a scaled register, we can't add another one.
+ if (Base.AM.Scale != 0) return;
+
+ // Check each interesting stride.
+ for (SmallSetVector<int64_t, 8>::const_iterator
+ I = Factors.begin(), E = Factors.end(); I != E; ++I) {
+ int64_t Factor = *I;
+
+ Base.AM.Scale = Factor;
+ Base.AM.HasBaseReg = Base.BaseRegs.size() > 1;
+ // Check whether this scale is going to be legal.
+ if (!isLegalUse(Base.AM, LU.MinOffset, LU.MaxOffset,
+ LU.Kind, LU.AccessTy, TLI)) {
+ // As a special-case, handle special out-of-loop Basic users specially.
+ // TODO: Reconsider this special case.
+ if (LU.Kind == LSRUse::Basic &&
+ isLegalUse(Base.AM, LU.MinOffset, LU.MaxOffset,
+ LSRUse::Special, LU.AccessTy, TLI) &&
+ LU.AllFixupsOutsideLoop)
+ LU.Kind = LSRUse::Special;
+ else
+ continue;
+ }
+ // For an ICmpZero, negating a solitary base register won't lead to
+ // new solutions.
+ if (LU.Kind == LSRUse::ICmpZero &&
+ !Base.AM.HasBaseReg && Base.AM.BaseOffs == 0 && !Base.AM.BaseGV)
+ continue;
+ // For each addrec base reg, apply the scale, if possible.
+ for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
+ if (const SCEVAddRecExpr *AR =
+ dyn_cast<SCEVAddRecExpr>(Base.BaseRegs[i])) {
+ const SCEV *FactorS = SE.getConstant(IntTy, Factor);
+ if (FactorS->isZero())
+ continue;
+ // Divide out the factor, ignoring high bits, since we'll be
+ // scaling the value back up in the end.
+ if (const SCEV *Quotient = getExactSDiv(AR, FactorS, SE, true)) {
+ // TODO: This could be optimized to avoid all the copying.
+ Formula F = Base;
+ F.ScaledReg = Quotient;
+ F.DeleteBaseReg(F.BaseRegs[i]);
+ (void)InsertFormula(LU, LUIdx, F);
+ }
+ }
}
+}
- // At this point, it is worth checking to see if any recurrence PHIs are also
- // dead, so that we can remove them as well.
- DeleteDeadPHIs(L->getHeader());
+/// GenerateTruncates - Generate reuse formulae from different IV types.
+void LSRInstance::GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base) {
+ // This requires TargetLowering to tell us which truncates are free.
+ if (!TLI) return;
+
+ // Don't bother truncating symbolic values.
+ if (Base.AM.BaseGV) return;
+
+ // Determine the integer type for the base formula.
+ Type *DstTy = Base.getType();
+ if (!DstTy) return;
+ DstTy = SE.getEffectiveSCEVType(DstTy);
+
+ for (SmallSetVector<Type *, 4>::const_iterator
+ I = Types.begin(), E = Types.end(); I != E; ++I) {
+ Type *SrcTy = *I;
+ if (SrcTy != DstTy && TLI->isTruncateFree(SrcTy, DstTy)) {
+ Formula F = Base;
+
+ if (F.ScaledReg) F.ScaledReg = SE.getAnyExtendExpr(F.ScaledReg, *I);
+ for (SmallVectorImpl<const SCEV *>::iterator J = F.BaseRegs.begin(),
+ JE = F.BaseRegs.end(); J != JE; ++J)
+ *J = SE.getAnyExtendExpr(*J, SrcTy);
+
+ // TODO: This assumes we've done basic processing on all uses and
+ // have an idea what the register usage is.
+ if (!F.hasRegsUsedByUsesOtherThan(LUIdx, RegUses))
+ continue;
+ (void)InsertFormula(LU, LUIdx, F);
+ }
+ }
+}
+
+namespace {
+
+/// WorkItem - Helper class for GenerateCrossUseConstantOffsets. It's used to
+/// defer modifications so that the search phase doesn't have to worry about
+/// the data structures moving underneath it.
+struct WorkItem {
+ size_t LUIdx;
+ int64_t Imm;
+ const SCEV *OrigReg;
+
+ WorkItem(size_t LI, int64_t I, const SCEV *R)
+ : LUIdx(LI), Imm(I), OrigReg(R) {}
+
+ void print(raw_ostream &OS) const;
+ void dump() const;
+};
+
+}
+
+void WorkItem::print(raw_ostream &OS) const {
+ OS << "in formulae referencing " << *OrigReg << " in use " << LUIdx
+ << " , add offset " << Imm;
+}
+
+void WorkItem::dump() const {
+ print(errs()); errs() << '\n';
+}
+
+/// GenerateCrossUseConstantOffsets - Look for registers which are a constant
+/// distance apart and try to form reuse opportunities between them.
+void LSRInstance::GenerateCrossUseConstantOffsets() {
+ // Group the registers by their value without any added constant offset.
+ typedef std::map<int64_t, const SCEV *> ImmMapTy;
+ typedef DenseMap<const SCEV *, ImmMapTy> RegMapTy;
+ RegMapTy Map;
+ DenseMap<const SCEV *, SmallBitVector> UsedByIndicesMap;
+ SmallVector<const SCEV *, 8> Sequence;
+ for (RegUseTracker::const_iterator I = RegUses.begin(), E = RegUses.end();
+ I != E; ++I) {
+ const SCEV *Reg = *I;
+ int64_t Imm = ExtractImmediate(Reg, SE);
+ std::pair<RegMapTy::iterator, bool> Pair =
+ Map.insert(std::make_pair(Reg, ImmMapTy()));
+ if (Pair.second)
+ Sequence.push_back(Reg);
+ Pair.first->second.insert(std::make_pair(Imm, *I));
+ UsedByIndicesMap[Reg] |= RegUses.getUsedByIndices(*I);
+ }
+
+ // Now examine each set of registers with the same base value. Build up
+ // a list of work to do and do the work in a separate step so that we're
+ // not adding formulae and register counts while we're searching.
+ SmallVector<WorkItem, 32> WorkItems;
+ SmallSet<std::pair<size_t, int64_t>, 32> UniqueItems;
+ for (SmallVectorImpl<const SCEV *>::const_iterator I = Sequence.begin(),
+ E = Sequence.end(); I != E; ++I) {
+ const SCEV *Reg = *I;
+ const ImmMapTy &Imms = Map.find(Reg)->second;
+
+ // It's not worthwhile looking for reuse if there's only one offset.
+ if (Imms.size() == 1)
+ continue;
+
+ DEBUG(dbgs() << "Generating cross-use offsets for " << *Reg << ':';
+ for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end();
+ J != JE; ++J)
+ dbgs() << ' ' << J->first;
+ dbgs() << '\n');
+
+ // Examine each offset.
+ for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end();
+ J != JE; ++J) {
+ const SCEV *OrigReg = J->second;
+
+ int64_t JImm = J->first;
+ const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(OrigReg);
+
+ if (!isa<SCEVConstant>(OrigReg) &&
+ UsedByIndicesMap[Reg].count() == 1) {
+ DEBUG(dbgs() << "Skipping cross-use reuse for " << *OrigReg << '\n');
+ continue;
+ }
+
+ // Conservatively examine offsets between this orig reg a few selected
+ // other orig regs.
+ ImmMapTy::const_iterator OtherImms[] = {
+ Imms.begin(), prior(Imms.end()),
+ Imms.lower_bound((Imms.begin()->first + prior(Imms.end())->first) / 2)
+ };
+ for (size_t i = 0, e = array_lengthof(OtherImms); i != e; ++i) {
+ ImmMapTy::const_iterator M = OtherImms[i];
+ if (M == J || M == JE) continue;
+
+ // Compute the difference between the two.
+ int64_t Imm = (uint64_t)JImm - M->first;
+ for (int LUIdx = UsedByIndices.find_first(); LUIdx != -1;
+ LUIdx = UsedByIndices.find_next(LUIdx))
+ // Make a memo of this use, offset, and register tuple.
+ if (UniqueItems.insert(std::make_pair(LUIdx, Imm)))
+ WorkItems.push_back(WorkItem(LUIdx, Imm, OrigReg));
+ }
+ }
+ }
+
+ Map.clear();
+ Sequence.clear();
+ UsedByIndicesMap.clear();
+ UniqueItems.clear();
+
+ // Now iterate through the worklist and add new formulae.
+ for (SmallVectorImpl<WorkItem>::const_iterator I = WorkItems.begin(),
+ E = WorkItems.end(); I != E; ++I) {
+ const WorkItem &WI = *I;
+ size_t LUIdx = WI.LUIdx;
+ LSRUse &LU = Uses[LUIdx];
+ int64_t Imm = WI.Imm;
+ const SCEV *OrigReg = WI.OrigReg;
+
+ Type *IntTy = SE.getEffectiveSCEVType(OrigReg->getType());
+ const SCEV *NegImmS = SE.getSCEV(ConstantInt::get(IntTy, -(uint64_t)Imm));
+ unsigned BitWidth = SE.getTypeSizeInBits(IntTy);
+
+ // TODO: Use a more targeted data structure.
+ for (size_t L = 0, LE = LU.Formulae.size(); L != LE; ++L) {
+ const Formula &F = LU.Formulae[L];
+ // Use the immediate in the scaled register.
+ if (F.ScaledReg == OrigReg) {
+ int64_t Offs = (uint64_t)F.AM.BaseOffs +
+ Imm * (uint64_t)F.AM.Scale;
+ // Don't create 50 + reg(-50).
+ if (F.referencesReg(SE.getSCEV(
+ ConstantInt::get(IntTy, -(uint64_t)Offs))))
+ continue;
+ Formula NewF = F;
+ NewF.AM.BaseOffs = Offs;
+ if (!isLegalUse(NewF.AM, LU.MinOffset, LU.MaxOffset,
+ LU.Kind, LU.AccessTy, TLI))
+ continue;
+ NewF.ScaledReg = SE.getAddExpr(NegImmS, NewF.ScaledReg);
+
+ // If the new scale is a constant in a register, and adding the constant
+ // value to the immediate would produce a value closer to zero than the
+ // immediate itself, then the formula isn't worthwhile.
+ if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewF.ScaledReg))
+ if (C->getValue()->isNegative() !=
+ (NewF.AM.BaseOffs < 0) &&
+ (C->getValue()->getValue().abs() * APInt(BitWidth, F.AM.Scale))
+ .ule(abs64(NewF.AM.BaseOffs)))
+ continue;
+
+ // OK, looks good.
+ (void)InsertFormula(LU, LUIdx, NewF);
+ } else {
+ // Use the immediate in a base register.
+ for (size_t N = 0, NE = F.BaseRegs.size(); N != NE; ++N) {
+ const SCEV *BaseReg = F.BaseRegs[N];
+ if (BaseReg != OrigReg)
+ continue;
+ Formula NewF = F;
+ NewF.AM.BaseOffs = (uint64_t)NewF.AM.BaseOffs + Imm;
+ if (!isLegalUse(NewF.AM, LU.MinOffset, LU.MaxOffset,
+ LU.Kind, LU.AccessTy, TLI)) {
+ if (!TLI ||
+ !TLI->isLegalAddImmediate((uint64_t)NewF.UnfoldedOffset + Imm))
+ continue;
+ NewF = F;
+ NewF.UnfoldedOffset = (uint64_t)NewF.UnfoldedOffset + Imm;
+ }
+ NewF.BaseRegs[N] = SE.getAddExpr(NegImmS, BaseReg);
+
+ // If the new formula has a constant in a register, and adding the
+ // constant value to the immediate would produce a value closer to
+ // zero than the immediate itself, then the formula isn't worthwhile.
+ for (SmallVectorImpl<const SCEV *>::const_iterator
+ J = NewF.BaseRegs.begin(), JE = NewF.BaseRegs.end();
+ J != JE; ++J)
+ if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*J))
+ if ((C->getValue()->getValue() + NewF.AM.BaseOffs).abs().slt(
+ abs64(NewF.AM.BaseOffs)) &&
+ (C->getValue()->getValue() +
+ NewF.AM.BaseOffs).countTrailingZeros() >=
+ CountTrailingZeros_64(NewF.AM.BaseOffs))
+ goto skip_formula;
+
+ // Ok, looks good.
+ (void)InsertFormula(LU, LUIdx, NewF);
+ break;
+ skip_formula:;
+ }
+ }
+ }
+ }
+}
+
+/// GenerateAllReuseFormulae - Generate formulae for each use.
+void
+LSRInstance::GenerateAllReuseFormulae() {
+ // This is split into multiple loops so that hasRegsUsedByUsesOtherThan
+ // queries are more precise.
+ for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
+ LSRUse &LU = Uses[LUIdx];
+ for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
+ GenerateReassociations(LU, LUIdx, LU.Formulae[i]);
+ for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
+ GenerateCombinations(LU, LUIdx, LU.Formulae[i]);
+ }
+ for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
+ LSRUse &LU = Uses[LUIdx];
+ for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
+ GenerateSymbolicOffsets(LU, LUIdx, LU.Formulae[i]);
+ for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
+ GenerateConstantOffsets(LU, LUIdx, LU.Formulae[i]);
+ for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
+ GenerateICmpZeroScales(LU, LUIdx, LU.Formulae[i]);
+ for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
+ GenerateScales(LU, LUIdx, LU.Formulae[i]);
+ }
+ for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
+ LSRUse &LU = Uses[LUIdx];
+ for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
+ GenerateTruncates(LU, LUIdx, LU.Formulae[i]);
+ }
+
+ GenerateCrossUseConstantOffsets();
+
+ DEBUG(dbgs() << "\n"
+ "After generating reuse formulae:\n";
+ print_uses(dbgs()));
+}
+
+/// If there are multiple formulae with the same set of registers used
+/// by other uses, pick the best one and delete the others.
+void LSRInstance::FilterOutUndesirableDedicatedRegisters() {
+ DenseSet<const SCEV *> VisitedRegs;
+ SmallPtrSet<const SCEV *, 16> Regs;
+ SmallPtrSet<const SCEV *, 16> LoserRegs;
+#ifndef NDEBUG
+ bool ChangedFormulae = false;
+#endif
+
+ // Collect the best formula for each unique set of shared registers. This
+ // is reset for each use.
+ typedef DenseMap<SmallVector<const SCEV *, 2>, size_t, UniquifierDenseMapInfo>
+ BestFormulaeTy;
+ BestFormulaeTy BestFormulae;
+
+ for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
+ LSRUse &LU = Uses[LUIdx];
+ DEBUG(dbgs() << "Filtering for use "; LU.print(dbgs()); dbgs() << '\n');
+
+ bool Any = false;
+ for (size_t FIdx = 0, NumForms = LU.Formulae.size();
+ FIdx != NumForms; ++FIdx) {
+ Formula &F = LU.Formulae[FIdx];
+
+ // Some formulas are instant losers. For example, they may depend on
+ // nonexistent AddRecs from other loops. These need to be filtered
+ // immediately, otherwise heuristics could choose them over others leading
+ // to an unsatisfactory solution. Passing LoserRegs into RateFormula here
+ // avoids the need to recompute this information across formulae using the
+ // same bad AddRec. Passing LoserRegs is also essential unless we remove
+ // the corresponding bad register from the Regs set.
+ Cost CostF;
+ Regs.clear();
+ CostF.RateFormula(F, Regs, VisitedRegs, L, LU.Offsets, SE, DT,
+ &LoserRegs);
+ if (CostF.isLoser()) {
+ // During initial formula generation, undesirable formulae are generated
+ // by uses within other loops that have some non-trivial address mode or
+ // use the postinc form of the IV. LSR needs to provide these formulae
+ // as the basis of rediscovering the desired formula that uses an AddRec
+ // corresponding to the existing phi. Once all formulae have been
+ // generated, these initial losers may be pruned.
+ DEBUG(dbgs() << " Filtering loser "; F.print(dbgs());
+ dbgs() << "\n");
+ }
+ else {
+ SmallVector<const SCEV *, 2> Key;
+ for (SmallVectorImpl<const SCEV *>::const_iterator J = F.BaseRegs.begin(),
+ JE = F.BaseRegs.end(); J != JE; ++J) {
+ const SCEV *Reg = *J;
+ if (RegUses.isRegUsedByUsesOtherThan(Reg, LUIdx))
+ Key.push_back(Reg);
+ }
+ if (F.ScaledReg &&
+ RegUses.isRegUsedByUsesOtherThan(F.ScaledReg, LUIdx))
+ Key.push_back(F.ScaledReg);
+ // Unstable sort by host order ok, because this is only used for
+ // uniquifying.
+ std::sort(Key.begin(), Key.end());
+
+ std::pair<BestFormulaeTy::const_iterator, bool> P =
+ BestFormulae.insert(std::make_pair(Key, FIdx));
+ if (P.second)
+ continue;
+
+ Formula &Best = LU.Formulae[P.first->second];
+
+ Cost CostBest;
+ Regs.clear();
+ CostBest.RateFormula(Best, Regs, VisitedRegs, L, LU.Offsets, SE, DT);
+ if (CostF < CostBest)
+ std::swap(F, Best);
+ DEBUG(dbgs() << " Filtering out formula "; F.print(dbgs());
+ dbgs() << "\n"
+ " in favor of formula "; Best.print(dbgs());
+ dbgs() << '\n');
+ }
+#ifndef NDEBUG
+ ChangedFormulae = true;
+#endif
+ LU.DeleteFormula(F);
+ --FIdx;
+ --NumForms;
+ Any = true;
+ }
+
+ // Now that we've filtered out some formulae, recompute the Regs set.
+ if (Any)
+ LU.RecomputeRegs(LUIdx, RegUses);
+
+ // Reset this to prepare for the next use.
+ BestFormulae.clear();
+ }
+
+ DEBUG(if (ChangedFormulae) {
+ dbgs() << "\n"
+ "After filtering out undesirable candidates:\n";
+ print_uses(dbgs());
+ });
+}
+
+// This is a rough guess that seems to work fairly well.
+static const size_t ComplexityLimit = UINT16_MAX;
+
+/// EstimateSearchSpaceComplexity - Estimate the worst-case number of
+/// solutions the solver might have to consider. It almost never considers
+/// this many solutions because it prune the search space, but the pruning
+/// isn't always sufficient.
+size_t LSRInstance::EstimateSearchSpaceComplexity() const {
+ size_t Power = 1;
+ for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
+ E = Uses.end(); I != E; ++I) {
+ size_t FSize = I->Formulae.size();
+ if (FSize >= ComplexityLimit) {
+ Power = ComplexityLimit;
+ break;
+ }
+ Power *= FSize;
+ if (Power >= ComplexityLimit)
+ break;
+ }
+ return Power;
+}
+
+/// NarrowSearchSpaceByDetectingSupersets - When one formula uses a superset
+/// of the registers of another formula, it won't help reduce register
+/// pressure (though it may not necessarily hurt register pressure); remove
+/// it to simplify the system.
+void LSRInstance::NarrowSearchSpaceByDetectingSupersets() {
+ if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
+ DEBUG(dbgs() << "The search space is too complex.\n");
+
+ DEBUG(dbgs() << "Narrowing the search space by eliminating formulae "
+ "which use a superset of registers used by other "
+ "formulae.\n");
+
+ for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
+ LSRUse &LU = Uses[LUIdx];
+ bool Any = false;
+ for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
+ Formula &F = LU.Formulae[i];
+ // Look for a formula with a constant or GV in a register. If the use
+ // also has a formula with that same value in an immediate field,
+ // delete the one that uses a register.
+ for (SmallVectorImpl<const SCEV *>::const_iterator
+ I = F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I) {
+ if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*I)) {
+ Formula NewF = F;
+ NewF.AM.BaseOffs += C->getValue()->getSExtValue();
+ NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
+ (I - F.BaseRegs.begin()));
+ if (LU.HasFormulaWithSameRegs(NewF)) {
+ DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n');
+ LU.DeleteFormula(F);
+ --i;
+ --e;
+ Any = true;
+ break;
+ }
+ } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(*I)) {
+ if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue()))
+ if (!F.AM.BaseGV) {
+ Formula NewF = F;
+ NewF.AM.BaseGV = GV;
+ NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
+ (I - F.BaseRegs.begin()));
+ if (LU.HasFormulaWithSameRegs(NewF)) {
+ DEBUG(dbgs() << " Deleting "; F.print(dbgs());
+ dbgs() << '\n');
+ LU.DeleteFormula(F);
+ --i;
+ --e;
+ Any = true;
+ break;
+ }
+ }
+ }
+ }
+ }
+ if (Any)
+ LU.RecomputeRegs(LUIdx, RegUses);
+ }
+
+ DEBUG(dbgs() << "After pre-selection:\n";
+ print_uses(dbgs()));
+ }
+}
+
+/// NarrowSearchSpaceByCollapsingUnrolledCode - When there are many registers
+/// for expressions like A, A+1, A+2, etc., allocate a single register for
+/// them.
+void LSRInstance::NarrowSearchSpaceByCollapsingUnrolledCode() {
+ if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
+ DEBUG(dbgs() << "The search space is too complex.\n");
+
+ DEBUG(dbgs() << "Narrowing the search space by assuming that uses "
+ "separated by a constant offset will use the same "
+ "registers.\n");
+
+ // This is especially useful for unrolled loops.
+
+ for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
+ LSRUse &LU = Uses[LUIdx];
+ for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(),
+ E = LU.Formulae.end(); I != E; ++I) {
+ const Formula &F = *I;
+ if (F.AM.BaseOffs != 0 && F.AM.Scale == 0) {
+ if (LSRUse *LUThatHas = FindUseWithSimilarFormula(F, LU)) {
+ if (reconcileNewOffset(*LUThatHas, F.AM.BaseOffs,
+ /*HasBaseReg=*/false,
+ LU.Kind, LU.AccessTy)) {
+ DEBUG(dbgs() << " Deleting use "; LU.print(dbgs());
+ dbgs() << '\n');
+
+ LUThatHas->AllFixupsOutsideLoop &= LU.AllFixupsOutsideLoop;
+
+ // Update the relocs to reference the new use.
+ for (SmallVectorImpl<LSRFixup>::iterator I = Fixups.begin(),
+ E = Fixups.end(); I != E; ++I) {
+ LSRFixup &Fixup = *I;
+ if (Fixup.LUIdx == LUIdx) {
+ Fixup.LUIdx = LUThatHas - &Uses.front();
+ Fixup.Offset += F.AM.BaseOffs;
+ // Add the new offset to LUThatHas' offset list.
+ if (LUThatHas->Offsets.back() != Fixup.Offset) {
+ LUThatHas->Offsets.push_back(Fixup.Offset);
+ if (Fixup.Offset > LUThatHas->MaxOffset)
+ LUThatHas->MaxOffset = Fixup.Offset;
+ if (Fixup.Offset < LUThatHas->MinOffset)
+ LUThatHas->MinOffset = Fixup.Offset;
+ }
+ DEBUG(dbgs() << "New fixup has offset "
+ << Fixup.Offset << '\n');
+ }
+ if (Fixup.LUIdx == NumUses-1)
+ Fixup.LUIdx = LUIdx;
+ }
+
+ // Delete formulae from the new use which are no longer legal.
+ bool Any = false;
+ for (size_t i = 0, e = LUThatHas->Formulae.size(); i != e; ++i) {
+ Formula &F = LUThatHas->Formulae[i];
+ if (!isLegalUse(F.AM,
+ LUThatHas->MinOffset, LUThatHas->MaxOffset,
+ LUThatHas->Kind, LUThatHas->AccessTy, TLI)) {
+ DEBUG(dbgs() << " Deleting "; F.print(dbgs());
+ dbgs() << '\n');
+ LUThatHas->DeleteFormula(F);
+ --i;
+ --e;
+ Any = true;
+ }
+ }
+ if (Any)
+ LUThatHas->RecomputeRegs(LUThatHas - &Uses.front(), RegUses);
+
+ // Delete the old use.
+ DeleteUse(LU, LUIdx);
+ --LUIdx;
+ --NumUses;
+ break;
+ }
+ }
+ }
+ }
+ }
+
+ DEBUG(dbgs() << "After pre-selection:\n";
+ print_uses(dbgs()));
+ }
+}
+
+/// NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters - Call
+/// FilterOutUndesirableDedicatedRegisters again, if necessary, now that
+/// we've done more filtering, as it may be able to find more formulae to
+/// eliminate.
+void LSRInstance::NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters(){
+ if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
+ DEBUG(dbgs() << "The search space is too complex.\n");
+
+ DEBUG(dbgs() << "Narrowing the search space by re-filtering out "
+ "undesirable dedicated registers.\n");
+
+ FilterOutUndesirableDedicatedRegisters();
+
+ DEBUG(dbgs() << "After pre-selection:\n";
+ print_uses(dbgs()));
+ }
+}
+
+/// NarrowSearchSpaceByPickingWinnerRegs - Pick a register which seems likely
+/// to be profitable, and then in any use which has any reference to that
+/// register, delete all formulae which do not reference that register.
+void LSRInstance::NarrowSearchSpaceByPickingWinnerRegs() {
+ // With all other options exhausted, loop until the system is simple
+ // enough to handle.
+ SmallPtrSet<const SCEV *, 4> Taken;
+ while (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
+ // Ok, we have too many of formulae on our hands to conveniently handle.
+ // Use a rough heuristic to thin out the list.
+ DEBUG(dbgs() << "The search space is too complex.\n");
+
+ // Pick the register which is used by the most LSRUses, which is likely
+ // to be a good reuse register candidate.
+ const SCEV *Best = 0;
+ unsigned BestNum = 0;
+ for (RegUseTracker::const_iterator I = RegUses.begin(), E = RegUses.end();
+ I != E; ++I) {
+ const SCEV *Reg = *I;
+ if (Taken.count(Reg))
+ continue;
+ if (!Best)
+ Best = Reg;
+ else {
+ unsigned Count = RegUses.getUsedByIndices(Reg).count();
+ if (Count > BestNum) {
+ Best = Reg;
+ BestNum = Count;
+ }
+ }
+ }
+
+ DEBUG(dbgs() << "Narrowing the search space by assuming " << *Best
+ << " will yield profitable reuse.\n");
+ Taken.insert(Best);
+
+ // In any use with formulae which references this register, delete formulae
+ // which don't reference it.
+ for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
+ LSRUse &LU = Uses[LUIdx];
+ if (!LU.Regs.count(Best)) continue;
+
+ bool Any = false;
+ for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
+ Formula &F = LU.Formulae[i];
+ if (!F.referencesReg(Best)) {
+ DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n');
+ LU.DeleteFormula(F);
+ --e;
+ --i;
+ Any = true;
+ assert(e != 0 && "Use has no formulae left! Is Regs inconsistent?");
+ continue;
+ }
+ }
+
+ if (Any)
+ LU.RecomputeRegs(LUIdx, RegUses);
+ }
+
+ DEBUG(dbgs() << "After pre-selection:\n";
+ print_uses(dbgs()));
+ }
+}
+
+/// NarrowSearchSpaceUsingHeuristics - If there are an extraordinary number of
+/// formulae to choose from, use some rough heuristics to prune down the number
+/// of formulae. This keeps the main solver from taking an extraordinary amount
+/// of time in some worst-case scenarios.
+void LSRInstance::NarrowSearchSpaceUsingHeuristics() {
+ NarrowSearchSpaceByDetectingSupersets();
+ NarrowSearchSpaceByCollapsingUnrolledCode();
+ NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
+ NarrowSearchSpaceByPickingWinnerRegs();
+}
+
+/// SolveRecurse - This is the recursive solver.
+void LSRInstance::SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
+ Cost &SolutionCost,
+ SmallVectorImpl<const Formula *> &Workspace,
+ const Cost &CurCost,
+ const SmallPtrSet<const SCEV *, 16> &CurRegs,
+ DenseSet<const SCEV *> &VisitedRegs) const {
+ // Some ideas:
+ // - prune more:
+ // - use more aggressive filtering
+ // - sort the formula so that the most profitable solutions are found first
+ // - sort the uses too
+ // - search faster:
+ // - don't compute a cost, and then compare. compare while computing a cost
+ // and bail early.
+ // - track register sets with SmallBitVector
+
+ const LSRUse &LU = Uses[Workspace.size()];
+
+ // If this use references any register that's already a part of the
+ // in-progress solution, consider it a requirement that a formula must
+ // reference that register in order to be considered. This prunes out
+ // unprofitable searching.
+ SmallSetVector<const SCEV *, 4> ReqRegs;
+ for (SmallPtrSet<const SCEV *, 16>::const_iterator I = CurRegs.begin(),
+ E = CurRegs.end(); I != E; ++I)
+ if (LU.Regs.count(*I))
+ ReqRegs.insert(*I);
+
+ SmallPtrSet<const SCEV *, 16> NewRegs;
+ Cost NewCost;
+ for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(),
+ E = LU.Formulae.end(); I != E; ++I) {
+ const Formula &F = *I;
+
+ // Ignore formulae which do not use any of the required registers.
+ bool SatisfiedReqReg = true;
+ for (SmallSetVector<const SCEV *, 4>::const_iterator J = ReqRegs.begin(),
+ JE = ReqRegs.end(); J != JE; ++J) {
+ const SCEV *Reg = *J;
+ if ((!F.ScaledReg || F.ScaledReg != Reg) &&
+ std::find(F.BaseRegs.begin(), F.BaseRegs.end(), Reg) ==
+ F.BaseRegs.end()) {
+ SatisfiedReqReg = false;
+ break;
+ }
+ }
+ if (!SatisfiedReqReg) {
+ // If none of the formulae satisfied the required registers, then we could
+ // clear ReqRegs and try again. Currently, we simply give up in this case.
+ continue;
+ }
+
+ // Evaluate the cost of the current formula. If it's already worse than
+ // the current best, prune the search at that point.
+ NewCost = CurCost;
+ NewRegs = CurRegs;
+ NewCost.RateFormula(F, NewRegs, VisitedRegs, L, LU.Offsets, SE, DT);
+ if (NewCost < SolutionCost) {
+ Workspace.push_back(&F);
+ if (Workspace.size() != Uses.size()) {
+ SolveRecurse(Solution, SolutionCost, Workspace, NewCost,
+ NewRegs, VisitedRegs);
+ if (F.getNumRegs() == 1 && Workspace.size() == 1)
+ VisitedRegs.insert(F.ScaledReg ? F.ScaledReg : F.BaseRegs[0]);
+ } else {
+ DEBUG(dbgs() << "New best at "; NewCost.print(dbgs());
+ dbgs() << ".\n Regs:";
+ for (SmallPtrSet<const SCEV *, 16>::const_iterator
+ I = NewRegs.begin(), E = NewRegs.end(); I != E; ++I)
+ dbgs() << ' ' << **I;
+ dbgs() << '\n');
+
+ SolutionCost = NewCost;
+ Solution = Workspace;
+ }
+ Workspace.pop_back();
+ }
+ }
+}
+
+/// Solve - Choose one formula from each use. Return the results in the given
+/// Solution vector.
+void LSRInstance::Solve(SmallVectorImpl<const Formula *> &Solution) const {
+ SmallVector<const Formula *, 8> Workspace;
+ Cost SolutionCost;
+ SolutionCost.Loose();
+ Cost CurCost;
+ SmallPtrSet<const SCEV *, 16> CurRegs;
+ DenseSet<const SCEV *> VisitedRegs;
+ Workspace.reserve(Uses.size());
+
+ // SolveRecurse does all the work.
+ SolveRecurse(Solution, SolutionCost, Workspace, CurCost,
+ CurRegs, VisitedRegs);
+ if (Solution.empty()) {
+ DEBUG(dbgs() << "\nNo Satisfactory Solution\n");
+ return;
+ }
+
+ // Ok, we've now made all our decisions.
+ DEBUG(dbgs() << "\n"
+ "The chosen solution requires "; SolutionCost.print(dbgs());
+ dbgs() << ":\n";
+ for (size_t i = 0, e = Uses.size(); i != e; ++i) {
+ dbgs() << " ";
+ Uses[i].print(dbgs());
+ dbgs() << "\n"
+ " ";
+ Solution[i]->print(dbgs());
+ dbgs() << '\n';
+ });
+
+ assert(Solution.size() == Uses.size() && "Malformed solution!");
+}
+
+/// HoistInsertPosition - Helper for AdjustInsertPositionForExpand. Climb up
+/// the dominator tree far as we can go while still being dominated by the
+/// input positions. This helps canonicalize the insert position, which
+/// encourages sharing.
+BasicBlock::iterator
+LSRInstance::HoistInsertPosition(BasicBlock::iterator IP,
+ const SmallVectorImpl<Instruction *> &Inputs)
+ const {
+ for (;;) {
+ const Loop *IPLoop = LI.getLoopFor(IP->getParent());
+ unsigned IPLoopDepth = IPLoop ? IPLoop->getLoopDepth() : 0;
+
+ BasicBlock *IDom;
+ for (DomTreeNode *Rung = DT.getNode(IP->getParent()); ; ) {
+ if (!Rung) return IP;
+ Rung = Rung->getIDom();
+ if (!Rung) return IP;
+ IDom = Rung->getBlock();
+
+ // Don't climb into a loop though.
+ const Loop *IDomLoop = LI.getLoopFor(IDom);
+ unsigned IDomDepth = IDomLoop ? IDomLoop->getLoopDepth() : 0;
+ if (IDomDepth <= IPLoopDepth &&
+ (IDomDepth != IPLoopDepth || IDomLoop == IPLoop))
+ break;
+ }
+
+ bool AllDominate = true;
+ Instruction *BetterPos = 0;
+ Instruction *Tentative = IDom->getTerminator();
+ for (SmallVectorImpl<Instruction *>::const_iterator I = Inputs.begin(),
+ E = Inputs.end(); I != E; ++I) {
+ Instruction *Inst = *I;
+ if (Inst == Tentative || !DT.dominates(Inst, Tentative)) {
+ AllDominate = false;
+ break;
+ }
+ // Attempt to find an insert position in the middle of the block,
+ // instead of at the end, so that it can be used for other expansions.
+ if (IDom == Inst->getParent() &&
+ (!BetterPos || !DT.dominates(Inst, BetterPos)))
+ BetterPos = llvm::next(BasicBlock::iterator(Inst));
+ }
+ if (!AllDominate)
+ break;
+ if (BetterPos)
+ IP = BetterPos;
+ else
+ IP = Tentative;
+ }
+
+ return IP;
+}
+
+/// AdjustInsertPositionForExpand - Determine an input position which will be
+/// dominated by the operands and which will dominate the result.
+BasicBlock::iterator
+LSRInstance::AdjustInsertPositionForExpand(BasicBlock::iterator LowestIP,
+ const LSRFixup &LF,
+ const LSRUse &LU,
+ SCEVExpander &Rewriter) const {
+ // Collect some instructions which must be dominated by the
+ // expanding replacement. These must be dominated by any operands that
+ // will be required in the expansion.
+ SmallVector<Instruction *, 4> Inputs;
+ if (Instruction *I = dyn_cast<Instruction>(LF.OperandValToReplace))
+ Inputs.push_back(I);
+ if (LU.Kind == LSRUse::ICmpZero)
+ if (Instruction *I =
+ dyn_cast<Instruction>(cast<ICmpInst>(LF.UserInst)->getOperand(1)))
+ Inputs.push_back(I);
+ if (LF.PostIncLoops.count(L)) {
+ if (LF.isUseFullyOutsideLoop(L))
+ Inputs.push_back(L->getLoopLatch()->getTerminator());
+ else
+ Inputs.push_back(IVIncInsertPos);
+ }
+ // The expansion must also be dominated by the increment positions of any
+ // loops it for which it is using post-inc mode.
+ for (PostIncLoopSet::const_iterator I = LF.PostIncLoops.begin(),
+ E = LF.PostIncLoops.end(); I != E; ++I) {
+ const Loop *PIL = *I;
+ if (PIL == L) continue;
+
+ // Be dominated by the loop exit.
+ SmallVector<BasicBlock *, 4> ExitingBlocks;
+ PIL->getExitingBlocks(ExitingBlocks);
+ if (!ExitingBlocks.empty()) {
+ BasicBlock *BB = ExitingBlocks[0];
+ for (unsigned i = 1, e = ExitingBlocks.size(); i != e; ++i)
+ BB = DT.findNearestCommonDominator(BB, ExitingBlocks[i]);
+ Inputs.push_back(BB->getTerminator());
+ }
+ }
+
+ assert(!isa<PHINode>(LowestIP) && !isa<LandingPadInst>(LowestIP)
+ && !isa<DbgInfoIntrinsic>(LowestIP) &&
+ "Insertion point must be a normal instruction");
+
+ // Then, climb up the immediate dominator tree as far as we can go while
+ // still being dominated by the input positions.
+ BasicBlock::iterator IP = HoistInsertPosition(LowestIP, Inputs);
+
+ // Don't insert instructions before PHI nodes.
+ while (isa<PHINode>(IP)) ++IP;
+
+ // Ignore landingpad instructions.
+ while (isa<LandingPadInst>(IP)) ++IP;
+
+ // Ignore debug intrinsics.
+ while (isa<DbgInfoIntrinsic>(IP)) ++IP;
+
+ // Set IP below instructions recently inserted by SCEVExpander. This keeps the
+ // IP consistent across expansions and allows the previously inserted
+ // instructions to be reused by subsequent expansion.
+ while (Rewriter.isInsertedInstruction(IP) && IP != LowestIP) ++IP;
+
+ return IP;
+}
+
+/// Expand - Emit instructions for the leading candidate expression for this
+/// LSRUse (this is called "expanding").
+Value *LSRInstance::Expand(const LSRFixup &LF,
+ const Formula &F,
+ BasicBlock::iterator IP,
+ SCEVExpander &Rewriter,
+ SmallVectorImpl<WeakVH> &DeadInsts) const {
+ const LSRUse &LU = Uses[LF.LUIdx];
+
+ // Determine an input position which will be dominated by the operands and
+ // which will dominate the result.
+ IP = AdjustInsertPositionForExpand(IP, LF, LU, Rewriter);
+
+ // Inform the Rewriter if we have a post-increment use, so that it can
+ // perform an advantageous expansion.
+ Rewriter.setPostInc(LF.PostIncLoops);
+
+ // This is the type that the user actually needs.
+ Type *OpTy = LF.OperandValToReplace->getType();
+ // This will be the type that we'll initially expand to.
+ Type *Ty = F.getType();
+ if (!Ty)
+ // No type known; just expand directly to the ultimate type.
+ Ty = OpTy;
+ else if (SE.getEffectiveSCEVType(Ty) == SE.getEffectiveSCEVType(OpTy))
+ // Expand directly to the ultimate type if it's the right size.
+ Ty = OpTy;
+ // This is the type to do integer arithmetic in.
+ Type *IntTy = SE.getEffectiveSCEVType(Ty);
+
+ // Build up a list of operands to add together to form the full base.
+ SmallVector<const SCEV *, 8> Ops;
+
+ // Expand the BaseRegs portion.
+ for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
+ E = F.BaseRegs.end(); I != E; ++I) {
+ const SCEV *Reg = *I;
+ assert(!Reg->isZero() && "Zero allocated in a base register!");
+
+ // If we're expanding for a post-inc user, make the post-inc adjustment.
+ PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops);
+ Reg = TransformForPostIncUse(Denormalize, Reg,
+ LF.UserInst, LF.OperandValToReplace,
+ Loops, SE, DT);
+
+ Ops.push_back(SE.getUnknown(Rewriter.expandCodeFor(Reg, 0, IP)));
+ }
+
+ // Flush the operand list to suppress SCEVExpander hoisting.
+ if (!Ops.empty()) {
+ Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP);
+ Ops.clear();
+ Ops.push_back(SE.getUnknown(FullV));
+ }
+
+ // Expand the ScaledReg portion.
+ Value *ICmpScaledV = 0;
+ if (F.AM.Scale != 0) {
+ const SCEV *ScaledS = F.ScaledReg;
+
+ // If we're expanding for a post-inc user, make the post-inc adjustment.
+ PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops);
+ ScaledS = TransformForPostIncUse(Denormalize, ScaledS,
+ LF.UserInst, LF.OperandValToReplace,
+ Loops, SE, DT);
+
+ if (LU.Kind == LSRUse::ICmpZero) {
+ // An interesting way of "folding" with an icmp is to use a negated
+ // scale, which we'll implement by inserting it into the other operand
+ // of the icmp.
+ assert(F.AM.Scale == -1 &&
+ "The only scale supported by ICmpZero uses is -1!");
+ ICmpScaledV = Rewriter.expandCodeFor(ScaledS, 0, IP);
+ } else {
+ // Otherwise just expand the scaled register and an explicit scale,
+ // which is expected to be matched as part of the address.
+ ScaledS = SE.getUnknown(Rewriter.expandCodeFor(ScaledS, 0, IP));
+ ScaledS = SE.getMulExpr(ScaledS,
+ SE.getConstant(ScaledS->getType(), F.AM.Scale));
+ Ops.push_back(ScaledS);
+
+ // Flush the operand list to suppress SCEVExpander hoisting.
+ Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP);
+ Ops.clear();
+ Ops.push_back(SE.getUnknown(FullV));
+ }
+ }
+
+ // Expand the GV portion.
+ if (F.AM.BaseGV) {
+ Ops.push_back(SE.getUnknown(F.AM.BaseGV));
+
+ // Flush the operand list to suppress SCEVExpander hoisting.
+ Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP);
+ Ops.clear();
+ Ops.push_back(SE.getUnknown(FullV));
+ }
+
+ // Expand the immediate portion.
+ int64_t Offset = (uint64_t)F.AM.BaseOffs + LF.Offset;
+ if (Offset != 0) {
+ if (LU.Kind == LSRUse::ICmpZero) {
+ // The other interesting way of "folding" with an ICmpZero is to use a
+ // negated immediate.
+ if (!ICmpScaledV)
+ ICmpScaledV = ConstantInt::get(IntTy, -(uint64_t)Offset);
+ else {
+ Ops.push_back(SE.getUnknown(ICmpScaledV));
+ ICmpScaledV = ConstantInt::get(IntTy, Offset);
+ }
+ } else {
+ // Just add the immediate values. These again are expected to be matched
+ // as part of the address.
+ Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy, Offset)));
+ }
+ }
+
+ // Expand the unfolded offset portion.
+ int64_t UnfoldedOffset = F.UnfoldedOffset;
+ if (UnfoldedOffset != 0) {
+ // Just add the immediate values.
+ Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy,
+ UnfoldedOffset)));
+ }
+
+ // Emit instructions summing all the operands.
+ const SCEV *FullS = Ops.empty() ?
+ SE.getConstant(IntTy, 0) :
+ SE.getAddExpr(Ops);
+ Value *FullV = Rewriter.expandCodeFor(FullS, Ty, IP);
+
+ // We're done expanding now, so reset the rewriter.
+ Rewriter.clearPostInc();
+
+ // An ICmpZero Formula represents an ICmp which we're handling as a
+ // comparison against zero. Now that we've expanded an expression for that
+ // form, update the ICmp's other operand.
+ if (LU.Kind == LSRUse::ICmpZero) {
+ ICmpInst *CI = cast<ICmpInst>(LF.UserInst);
+ DeadInsts.push_back(CI->getOperand(1));
+ assert(!F.AM.BaseGV && "ICmp does not support folding a global value and "
+ "a scale at the same time!");
+ if (F.AM.Scale == -1) {
+ if (ICmpScaledV->getType() != OpTy) {
+ Instruction *Cast =
+ CastInst::Create(CastInst::getCastOpcode(ICmpScaledV, false,
+ OpTy, false),
+ ICmpScaledV, OpTy, "tmp", CI);
+ ICmpScaledV = Cast;
+ }
+ CI->setOperand(1, ICmpScaledV);
+ } else {
+ assert(F.AM.Scale == 0 &&
+ "ICmp does not support folding a global value and "
+ "a scale at the same time!");
+ Constant *C = ConstantInt::getSigned(SE.getEffectiveSCEVType(OpTy),
+ -(uint64_t)Offset);
+ if (C->getType() != OpTy)
+ C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
+ OpTy, false),
+ C, OpTy);
+
+ CI->setOperand(1, C);
+ }
+ }
+
+ return FullV;
+}
+
+/// RewriteForPHI - Helper for Rewrite. PHI nodes are special because the use
+/// of their operands effectively happens in their predecessor blocks, so the
+/// expression may need to be expanded in multiple places.
+void LSRInstance::RewriteForPHI(PHINode *PN,
+ const LSRFixup &LF,
+ const Formula &F,
+ SCEVExpander &Rewriter,
+ SmallVectorImpl<WeakVH> &DeadInsts,
+ Pass *P) const {
+ DenseMap<BasicBlock *, Value *> Inserted;
+ for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
+ if (PN->getIncomingValue(i) == LF.OperandValToReplace) {
+ BasicBlock *BB = PN->getIncomingBlock(i);
+
+ // If this is a critical edge, split the edge so that we do not insert
+ // the code on all predecessor/successor paths. We do this unless this
+ // is the canonical backedge for this loop, which complicates post-inc
+ // users.
+ if (e != 1 && BB->getTerminator()->getNumSuccessors() > 1 &&
+ !isa<IndirectBrInst>(BB->getTerminator())) {
+ BasicBlock *Parent = PN->getParent();
+ Loop *PNLoop = LI.getLoopFor(Parent);
+ if (!PNLoop || Parent != PNLoop->getHeader()) {
+ // Split the critical edge.
+ BasicBlock *NewBB = 0;
+ if (!Parent->isLandingPad()) {
+ NewBB = SplitCriticalEdge(BB, Parent, P,
+ /*MergeIdenticalEdges=*/true,
+ /*DontDeleteUselessPhis=*/true);
+ } else {
+ SmallVector<BasicBlock*, 2> NewBBs;
+ SplitLandingPadPredecessors(Parent, BB, "", "", P, NewBBs);
+ NewBB = NewBBs[0];
+ }
+
+ // If PN is outside of the loop and BB is in the loop, we want to
+ // move the block to be immediately before the PHI block, not
+ // immediately after BB.
+ if (L->contains(BB) && !L->contains(PN))
+ NewBB->moveBefore(PN->getParent());
+
+ // Splitting the edge can reduce the number of PHI entries we have.
+ e = PN->getNumIncomingValues();
+ BB = NewBB;
+ i = PN->getBasicBlockIndex(BB);
+ }
+ }
+
+ std::pair<DenseMap<BasicBlock *, Value *>::iterator, bool> Pair =
+ Inserted.insert(std::make_pair(BB, static_cast<Value *>(0)));
+ if (!Pair.second)
+ PN->setIncomingValue(i, Pair.first->second);
+ else {
+ Value *FullV = Expand(LF, F, BB->getTerminator(), Rewriter, DeadInsts);
+
+ // If this is reuse-by-noop-cast, insert the noop cast.
+ Type *OpTy = LF.OperandValToReplace->getType();
+ if (FullV->getType() != OpTy)
+ FullV =
+ CastInst::Create(CastInst::getCastOpcode(FullV, false,
+ OpTy, false),
+ FullV, LF.OperandValToReplace->getType(),
+ "tmp", BB->getTerminator());
+
+ PN->setIncomingValue(i, FullV);
+ Pair.first->second = FullV;
+ }
+ }
+}
+
+/// Rewrite - Emit instructions for the leading candidate expression for this
+/// LSRUse (this is called "expanding"), and update the UserInst to reference
+/// the newly expanded value.
+void LSRInstance::Rewrite(const LSRFixup &LF,
+ const Formula &F,
+ SCEVExpander &Rewriter,
+ SmallVectorImpl<WeakVH> &DeadInsts,
+ Pass *P) const {
+ // First, find an insertion point that dominates UserInst. For PHI nodes,
+ // find the nearest block which dominates all the relevant uses.
+ if (PHINode *PN = dyn_cast<PHINode>(LF.UserInst)) {
+ RewriteForPHI(PN, LF, F, Rewriter, DeadInsts, P);
+ } else {
+ Value *FullV = Expand(LF, F, LF.UserInst, Rewriter, DeadInsts);
+
+ // If this is reuse-by-noop-cast, insert the noop cast.
+ Type *OpTy = LF.OperandValToReplace->getType();
+ if (FullV->getType() != OpTy) {
+ Instruction *Cast =
+ CastInst::Create(CastInst::getCastOpcode(FullV, false, OpTy, false),
+ FullV, OpTy, "tmp", LF.UserInst);
+ FullV = Cast;
+ }
+
+ // Update the user. ICmpZero is handled specially here (for now) because
+ // Expand may have updated one of the operands of the icmp already, and
+ // its new value may happen to be equal to LF.OperandValToReplace, in
+ // which case doing replaceUsesOfWith leads to replacing both operands
+ // with the same value. TODO: Reorganize this.
+ if (Uses[LF.LUIdx].Kind == LSRUse::ICmpZero)
+ LF.UserInst->setOperand(0, FullV);
+ else
+ LF.UserInst->replaceUsesOfWith(LF.OperandValToReplace, FullV);
+ }
+
+ DeadInsts.push_back(LF.OperandValToReplace);
+}
+
+/// ImplementSolution - Rewrite all the fixup locations with new values,
+/// following the chosen solution.
+void
+LSRInstance::ImplementSolution(const SmallVectorImpl<const Formula *> &Solution,
+ Pass *P) {
+ // Keep track of instructions we may have made dead, so that
+ // we can remove them after we are done working.
+ SmallVector<WeakVH, 16> DeadInsts;
+
+ SCEVExpander Rewriter(SE, "lsr");
+#ifndef NDEBUG
+ Rewriter.setDebugType(DEBUG_TYPE);
+#endif
+ Rewriter.disableCanonicalMode();
+ Rewriter.enableLSRMode();
+ Rewriter.setIVIncInsertPos(L, IVIncInsertPos);
+
+ // Mark phi nodes that terminate chains so the expander tries to reuse them.
+ for (SmallVectorImpl<IVChain>::const_iterator ChainI = IVChainVec.begin(),
+ ChainE = IVChainVec.end(); ChainI != ChainE; ++ChainI) {
+ if (PHINode *PN = dyn_cast<PHINode>(ChainI->tailUserInst()))
+ Rewriter.setChainedPhi(PN);
+ }
+
+ // Expand the new value definitions and update the users.
+ for (SmallVectorImpl<LSRFixup>::const_iterator I = Fixups.begin(),
+ E = Fixups.end(); I != E; ++I) {
+ const LSRFixup &Fixup = *I;
+
+ Rewrite(Fixup, *Solution[Fixup.LUIdx], Rewriter, DeadInsts, P);
+
+ Changed = true;
+ }
+
+ for (SmallVectorImpl<IVChain>::const_iterator ChainI = IVChainVec.begin(),
+ ChainE = IVChainVec.end(); ChainI != ChainE; ++ChainI) {
+ GenerateIVChain(*ChainI, Rewriter, DeadInsts);
+ Changed = true;
+ }
+ // Clean up after ourselves. This must be done before deleting any
+ // instructions.
+ Rewriter.clear();
+
+ Changed |= DeleteTriviallyDeadInstructions(DeadInsts);
+}
+
+LSRInstance::LSRInstance(const TargetLowering *tli, Loop *l, Pass *P)
+ : IU(P->getAnalysis<IVUsers>()),
+ SE(P->getAnalysis<ScalarEvolution>()),
+ DT(P->getAnalysis<DominatorTree>()),
+ LI(P->getAnalysis<LoopInfo>()),
+ TLI(tli), L(l), Changed(false), IVIncInsertPos(0) {
+
+ // If LoopSimplify form is not available, stay out of trouble.
+ if (!L->isLoopSimplifyForm())
+ return;
+
+ // If there's no interesting work to be done, bail early.
+ if (IU.empty()) return;
+
+ // If there's too much analysis to be done, bail early. We won't be able to
+ // model the problem anyway.
+ unsigned NumUsers = 0;
+ for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) {
+ if (++NumUsers > MaxIVUsers) {
+ DEBUG(dbgs() << "LSR skipping loop, too many IV Users in " << *L
+ << "\n");
+ return;
+ }
+ }
+
+#ifndef NDEBUG
+ // All dominating loops must have preheaders, or SCEVExpander may not be able
+ // to materialize an AddRecExpr whose Start is an outer AddRecExpr.
+ //
+ // IVUsers analysis should only create users that are dominated by simple loop
+ // headers. Since this loop should dominate all of its users, its user list
+ // should be empty if this loop itself is not within a simple loop nest.
+ for (DomTreeNode *Rung = DT.getNode(L->getLoopPreheader());
+ Rung; Rung = Rung->getIDom()) {
+ BasicBlock *BB = Rung->getBlock();
+ const Loop *DomLoop = LI.getLoopFor(BB);
+ if (DomLoop && DomLoop->getHeader() == BB) {
+ assert(DomLoop->getLoopPreheader() && "LSR needs a simplified loop nest");
+ }
+ }
+#endif // DEBUG
+
+ DEBUG(dbgs() << "\nLSR on loop ";
+ WriteAsOperand(dbgs(), L->getHeader(), /*PrintType=*/false);
+ dbgs() << ":\n");
+
+ // First, perform some low-level loop optimizations.
+ OptimizeShadowIV();
+ OptimizeLoopTermCond();
+
+ // If loop preparation eliminates all interesting IV users, bail.
+ if (IU.empty()) return;
+
+ // Skip nested loops until we can model them better with formulae.
+ if (!L->empty()) {
+ DEBUG(dbgs() << "LSR skipping outer loop " << *L << "\n");
+ return;
+ }
+
+ // Start collecting data and preparing for the solver.
+ CollectChains();
+ CollectInterestingTypesAndFactors();
+ CollectFixupsAndInitialFormulae();
+ CollectLoopInvariantFixupsAndFormulae();
+
+ assert(!Uses.empty() && "IVUsers reported at least one use");
+ DEBUG(dbgs() << "LSR found " << Uses.size() << " uses:\n";
+ print_uses(dbgs()));
+
+ // Now use the reuse data to generate a bunch of interesting ways
+ // to formulate the values needed for the uses.
+ GenerateAllReuseFormulae();
+
+ FilterOutUndesirableDedicatedRegisters();
+ NarrowSearchSpaceUsingHeuristics();
+
+ SmallVector<const Formula *, 8> Solution;
+ Solve(Solution);
+
+ // Release memory that is no longer needed.
+ Factors.clear();
+ Types.clear();
+ RegUses.clear();
+
+ if (Solution.empty())
+ return;
+
+#ifndef NDEBUG
+ // Formulae should be legal.
+ for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
+ E = Uses.end(); I != E; ++I) {
+ const LSRUse &LU = *I;
+ for (SmallVectorImpl<Formula>::const_iterator J = LU.Formulae.begin(),
+ JE = LU.Formulae.end(); J != JE; ++J)
+ assert(isLegalUse(J->AM, LU.MinOffset, LU.MaxOffset,
+ LU.Kind, LU.AccessTy, TLI) &&
+ "Illegal formula generated!");
+ };
+#endif
+
+ // Now that we've decided what we want, make it so.
+ ImplementSolution(Solution, P);
+}
+
+void LSRInstance::print_factors_and_types(raw_ostream &OS) const {
+ if (Factors.empty() && Types.empty()) return;
+
+ OS << "LSR has identified the following interesting factors and types: ";
+ bool First = true;
+
+ for (SmallSetVector<int64_t, 8>::const_iterator
+ I = Factors.begin(), E = Factors.end(); I != E; ++I) {
+ if (!First) OS << ", ";
+ First = false;
+ OS << '*' << *I;
+ }
+
+ for (SmallSetVector<Type *, 4>::const_iterator
+ I = Types.begin(), E = Types.end(); I != E; ++I) {
+ if (!First) OS << ", ";
+ First = false;
+ OS << '(' << **I << ')';
+ }
+ OS << '\n';
+}
+
+void LSRInstance::print_fixups(raw_ostream &OS) const {
+ OS << "LSR is examining the following fixup sites:\n";
+ for (SmallVectorImpl<LSRFixup>::const_iterator I = Fixups.begin(),
+ E = Fixups.end(); I != E; ++I) {
+ dbgs() << " ";
+ I->print(OS);
+ OS << '\n';
+ }
+}
+
+void LSRInstance::print_uses(raw_ostream &OS) const {
+ OS << "LSR is examining the following uses:\n";
+ for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
+ E = Uses.end(); I != E; ++I) {
+ const LSRUse &LU = *I;
+ dbgs() << " ";
+ LU.print(OS);
+ OS << '\n';
+ for (SmallVectorImpl<Formula>::const_iterator J = LU.Formulae.begin(),
+ JE = LU.Formulae.end(); J != JE; ++J) {
+ OS << " ";
+ J->print(OS);
+ OS << '\n';
+ }
+ }
+}
+
+void LSRInstance::print(raw_ostream &OS) const {
+ print_factors_and_types(OS);
+ print_fixups(OS);
+ print_uses(OS);
+}
+
+void LSRInstance::dump() const {
+ print(errs()); errs() << '\n';
+}
+
+namespace {
+
+class LoopStrengthReduce : public LoopPass {
+ /// TLI - Keep a pointer of a TargetLowering to consult for determining
+ /// transformation profitability.
+ const TargetLowering *const TLI;
+
+public:
+ static char ID; // Pass ID, replacement for typeid
+ explicit LoopStrengthReduce(const TargetLowering *tli = 0);
+
+private:
+ bool runOnLoop(Loop *L, LPPassManager &LPM);
+ void getAnalysisUsage(AnalysisUsage &AU) const;
+};
+
+}
+
+char LoopStrengthReduce::ID = 0;
+INITIALIZE_PASS_BEGIN(LoopStrengthReduce, "loop-reduce",
+ "Loop Strength Reduction", false, false)
+INITIALIZE_PASS_DEPENDENCY(DominatorTree)
+INITIALIZE_PASS_DEPENDENCY(ScalarEvolution)
+INITIALIZE_PASS_DEPENDENCY(IVUsers)
+INITIALIZE_PASS_DEPENDENCY(LoopInfo)
+INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
+INITIALIZE_PASS_END(LoopStrengthReduce, "loop-reduce",
+ "Loop Strength Reduction", false, false)
+
+
+Pass *llvm::createLoopStrengthReducePass(const TargetLowering *TLI) {
+ return new LoopStrengthReduce(TLI);
+}
+
+LoopStrengthReduce::LoopStrengthReduce(const TargetLowering *tli)
+ : LoopPass(ID), TLI(tli) {
+ initializeLoopStrengthReducePass(*PassRegistry::getPassRegistry());
+ }
+
+void LoopStrengthReduce::getAnalysisUsage(AnalysisUsage &AU) const {
+ // We split critical edges, so we change the CFG. However, we do update
+ // many analyses if they are around.
+ AU.addPreservedID(LoopSimplifyID);
+
+ AU.addRequired<LoopInfo>();
+ AU.addPreserved<LoopInfo>();
+ AU.addRequiredID(LoopSimplifyID);
+ AU.addRequired<DominatorTree>();
+ AU.addPreserved<DominatorTree>();
+ AU.addRequired<ScalarEvolution>();
+ AU.addPreserved<ScalarEvolution>();
+ // Requiring LoopSimplify a second time here prevents IVUsers from running
+ // twice, since LoopSimplify was invalidated by running ScalarEvolution.
+ AU.addRequiredID(LoopSimplifyID);
+ AU.addRequired<IVUsers>();
+ AU.addPreserved<IVUsers>();
+}
+
+bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager & /*LPM*/) {
+ bool Changed = false;
+
+ // Run the main LSR transformation.
+ Changed |= LSRInstance(TLI, L, this).getChanged();
+
+ // Remove any extra phis created by processing inner loops.
+ Changed |= DeleteDeadPHIs(L->getHeader());
+ if (EnablePhiElim) {
+ SmallVector<WeakVH, 16> DeadInsts;
+ SCEVExpander Rewriter(getAnalysis<ScalarEvolution>(), "lsr");
+#ifndef NDEBUG
+ Rewriter.setDebugType(DEBUG_TYPE);
+#endif
+ unsigned numFolded = Rewriter.
+ replaceCongruentIVs(L, &getAnalysis<DominatorTree>(), DeadInsts, TLI);
+ if (numFolded) {
+ Changed = true;
+ DeleteTriviallyDeadInstructions(DeadInsts);
+ DeleteDeadPHIs(L->getHeader());
+ }
+ }
return Changed;
}
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