#define DEBUG_TYPE "iv-users"
#include "llvm/Analysis/IVUsers.h"
-#include "llvm/Constants.h"
-#include "llvm/Instructions.h"
-#include "llvm/Type.h"
-#include "llvm/DerivedTypes.h"
-#include "llvm/Analysis/Dominators.h"
+#include "llvm/ADT/STLExtras.h"
#include "llvm/Analysis/LoopPass.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
-#include "llvm/Assembly/AsmAnnotationWriter.h"
-#include "llvm/ADT/STLExtras.h"
+#include "llvm/Analysis/ValueTracking.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/Dominators.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Type.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
using namespace llvm;
char IVUsers::ID = 0;
-INITIALIZE_PASS(IVUsers, "iv-users", "Induction Variable Users", false, true);
+INITIALIZE_PASS_BEGIN(IVUsers, "iv-users",
+ "Induction Variable Users", false, true)
+INITIALIZE_PASS_DEPENDENCY(LoopInfo)
+INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
+INITIALIZE_PASS_DEPENDENCY(ScalarEvolution)
+INITIALIZE_PASS_END(IVUsers, "iv-users",
+ "Induction Variable Users", false, true)
Pass *llvm::createIVUsersPass() {
return new IVUsers();
}
-/// findInterestingAddRec - Test whether the given expression is interesting.
-/// Return the addrec with the current loop which makes it interesting, or
-/// null if it is not interesting.
-const SCEVAddRecExpr *IVUsers::findInterestingAddRec(const SCEV *S) const {
+/// isInteresting - Test whether the given expression is "interesting" when
+/// used by the given expression, within the context of analyzing the
+/// given loop.
+static bool isInteresting(const SCEV *S, const Instruction *I, const Loop *L,
+ ScalarEvolution *SE, LoopInfo *LI) {
// An addrec is interesting if it's affine or if it has an interesting start.
if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
- // Keep things simple. Don't touch loop-variant strides.
+ // Keep things simple. Don't touch loop-variant strides unless they're
+ // only used outside the loop and we can simplify them.
if (AR->getLoop() == L)
- return AR;
- // We don't yet know how to do effective SCEV expansions for addrecs
- // with interesting steps.
- if (findInterestingAddRec(AR->getStepRecurrence(*SE)))
- return 0;
- // Otherwise recurse to see if the start value is interesting.
- return findInterestingAddRec(AR->getStart());
+ return AR->isAffine() ||
+ (!L->contains(I) &&
+ SE->getSCEVAtScope(AR, LI->getLoopFor(I->getParent())) != AR);
+ // Otherwise recurse to see if the start value is interesting, and that
+ // the step value is not interesting, since we don't yet know how to
+ // do effective SCEV expansions for addrecs with interesting steps.
+ return isInteresting(AR->getStart(), I, L, SE, LI) &&
+ !isInteresting(AR->getStepRecurrence(*SE), I, L, SE, LI);
}
// An add is interesting if exactly one of its operands is interesting.
if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
+ bool AnyInterestingYet = false;
for (SCEVAddExpr::op_iterator OI = Add->op_begin(), OE = Add->op_end();
OI != OE; ++OI)
- if (const SCEVAddRecExpr *AR = findInterestingAddRec(*OI))
- return AR;
- return 0;
+ if (isInteresting(*OI, I, L, SE, LI)) {
+ if (AnyInterestingYet)
+ return false;
+ AnyInterestingYet = true;
+ }
+ return AnyInterestingYet;
}
// Nothing else is interesting here.
- return 0;
+ return false;
}
-bool IVUsers::isInterestingUser(const Instruction *User) const {
- // Void and FP expressions cannot be reduced.
- if (!SE->isSCEVable(User->getType()))
- return false;
-
- // LSR is not APInt clean, do not touch integers bigger than 64-bits.
- if (SE->getTypeSizeInBits(User->getType()) > 64)
- return false;
-
- // Don't descend into PHI nodes outside the current loop.
- if (LI->getLoopFor(User->getParent()) != L &&
- isa<PHINode>(User))
- return false;
-
- // Otherwise, it may be interesting.
+/// Return true if all loop headers that dominate this block are in simplified
+/// form.
+static bool isSimplifiedLoopNest(BasicBlock *BB, const DominatorTree *DT,
+ const LoopInfo *LI,
+ SmallPtrSet<Loop*,16> &SimpleLoopNests) {
+ Loop *NearestLoop = 0;
+ for (DomTreeNode *Rung = DT->getNode(BB);
+ Rung; Rung = Rung->getIDom()) {
+ BasicBlock *DomBB = Rung->getBlock();
+ Loop *DomLoop = LI->getLoopFor(DomBB);
+ if (DomLoop && DomLoop->getHeader() == DomBB) {
+ // If the domtree walk reaches a loop with no preheader, return false.
+ if (!DomLoop->isLoopSimplifyForm())
+ return false;
+ // If we have already checked this loop nest, stop checking.
+ if (SimpleLoopNests.count(DomLoop))
+ break;
+ // If we have not already checked this loop nest, remember the loop
+ // header nearest to BB. The nearest loop may not contain BB.
+ if (!NearestLoop)
+ NearestLoop = DomLoop;
+ }
+ }
+ if (NearestLoop)
+ SimpleLoopNests.insert(NearestLoop);
return true;
}
-/// AddUsersIfInteresting - Inspect the specified instruction. If it is a
+/// AddUsersImpl - Inspect the specified instruction. If it is a
/// reducible SCEV, recursively add its users to the IVUsesByStride set and
/// return true. Otherwise, return false.
-void IVUsers::AddUsersIfInteresting(Instruction *I) {
- // Stop if we've seen this before.
+bool IVUsers::AddUsersImpl(Instruction *I,
+ SmallPtrSet<Loop*,16> &SimpleLoopNests) {
+ // Add this IV user to the Processed set before returning false to ensure that
+ // all IV users are members of the set. See IVUsers::isIVUserOrOperand.
if (!Processed.insert(I))
- return;
+ return true; // Instruction already handled.
- // If this PHI node is not SCEVable, ignore it.
if (!SE->isSCEVable(I->getType()))
- return;
-
- // If this PHI node is not an addrec for this loop, ignore it.
- const SCEVAddRecExpr *Expr = findInterestingAddRec(SE->getSCEV(I));
- if (!Expr)
- return;
-
- // Walk the def-use graph.
- SmallVector<std::pair<Instruction *, const SCEVAddRecExpr *>, 16> Worklist;
- Worklist.push_back(std::make_pair(I, Expr));
- do {
- std::pair<Instruction *, const SCEVAddRecExpr *> P =
- Worklist.pop_back_val();
- Instruction *Op = P.first;
- const SCEVAddRecExpr *OpAR = P.second;
-
- // Visit Op's users.
- SmallPtrSet<Instruction *, 8> VisitedUsers;
- for (Value::use_iterator UI = Op->use_begin(), E = Op->use_end();
- UI != E; ++UI) {
- // Don't visit any individual user more than once.
- Instruction *User = cast<Instruction>(*UI);
- if (!VisitedUsers.insert(User))
- continue;
-
- // If it's an affine addrec (which we can pretty safely re-expand) inside
- // the loop, or a potentially non-affine addrec outside the loop (which
- // we can evaluate outside of the loop), follow it.
- if (OpAR->isAffine() || !L->contains(User)) {
- if (isInterestingUser(User)) {
- const SCEV *UserExpr = SE->getSCEV(User);
-
- if (const SCEVAddRecExpr *AR = findInterestingAddRec(UserExpr)) {
- // Interesting. Keep searching.
- if (Processed.insert(User))
- Worklist.push_back(std::make_pair(User, AR));
- continue;
- }
- }
+ return false; // Void and FP expressions cannot be reduced.
+
+ // IVUsers is used by LSR which assumes that all SCEV expressions are safe to
+ // pass to SCEVExpander. Expressions are not safe to expand if they represent
+ // operations that are not safe to speculate, namely integer division.
+ if (!isa<PHINode>(I) && !isSafeToSpeculativelyExecute(I, DL))
+ return false;
+
+ // LSR is not APInt clean, do not touch integers bigger than 64-bits.
+ // Also avoid creating IVs of non-native types. For example, we don't want a
+ // 64-bit IV in 32-bit code just because the loop has one 64-bit cast.
+ uint64_t Width = SE->getTypeSizeInBits(I->getType());
+ if (Width > 64 || (DL && !DL->isLegalInteger(Width)))
+ return false;
+
+ // Get the symbolic expression for this instruction.
+ const SCEV *ISE = SE->getSCEV(I);
+
+ // If we've come to an uninteresting expression, stop the traversal and
+ // call this a user.
+ if (!isInteresting(ISE, I, L, SE, LI))
+ return false;
+
+ SmallPtrSet<Instruction *, 4> UniqueUsers;
+ for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
+ UI != E; ++UI) {
+ Instruction *User = cast<Instruction>(*UI);
+ if (!UniqueUsers.insert(User))
+ continue;
+
+ // Do not infinitely recurse on PHI nodes.
+ if (isa<PHINode>(User) && Processed.count(User))
+ continue;
+
+ // Only consider IVUsers that are dominated by simplified loop
+ // headers. Otherwise, SCEVExpander will crash.
+ BasicBlock *UseBB = User->getParent();
+ // A phi's use is live out of its predecessor block.
+ if (PHINode *PHI = dyn_cast<PHINode>(User)) {
+ unsigned OperandNo = UI.getOperandNo();
+ unsigned ValNo = PHINode::getIncomingValueNumForOperand(OperandNo);
+ UseBB = PHI->getIncomingBlock(ValNo);
+ }
+ if (!isSimplifiedLoopNest(UseBB, DT, LI, SimpleLoopNests))
+ return false;
+
+ // Descend recursively, but not into PHI nodes outside the current loop.
+ // It's important to see the entire expression outside the loop to get
+ // choices that depend on addressing mode use right, although we won't
+ // consider references outside the loop in all cases.
+ // If User is already in Processed, we don't want to recurse into it again,
+ // but do want to record a second reference in the same instruction.
+ bool AddUserToIVUsers = false;
+ if (LI->getLoopFor(User->getParent()) != L) {
+ if (isa<PHINode>(User) || Processed.count(User) ||
+ !AddUsersImpl(User, SimpleLoopNests)) {
+ DEBUG(dbgs() << "FOUND USER in other loop: " << *User << '\n'
+ << " OF SCEV: " << *ISE << '\n');
+ AddUserToIVUsers = true;
}
+ } else if (Processed.count(User) || !AddUsersImpl(User, SimpleLoopNests)) {
+ DEBUG(dbgs() << "FOUND USER: " << *User << '\n'
+ << " OF SCEV: " << *ISE << '\n');
+ AddUserToIVUsers = true;
+ }
- // Otherwise, this is the point where the def-use chain
- // becomes uninteresting. Call it an IV User.
- AddUser(User, Op);
+ if (AddUserToIVUsers) {
+ // Okay, we found a user that we cannot reduce.
+ IVUses.push_back(new IVStrideUse(this, User, I));
+ IVStrideUse &NewUse = IVUses.back();
+ // Autodetect the post-inc loop set, populating NewUse.PostIncLoops.
+ // The regular return value here is discarded; instead of recording
+ // it, we just recompute it when we need it.
+ ISE = TransformForPostIncUse(NormalizeAutodetect,
+ ISE, User, I,
+ NewUse.PostIncLoops,
+ *SE, *DT);
+ DEBUG(if (SE->getSCEV(I) != ISE)
+ dbgs() << " NORMALIZED TO: " << *ISE << '\n');
}
- } while (!Worklist.empty());
+ }
+ return true;
+}
+
+bool IVUsers::AddUsersIfInteresting(Instruction *I) {
+ // SCEVExpander can only handle users that are dominated by simplified loop
+ // entries. Keep track of all loops that are only dominated by other simple
+ // loops so we don't traverse the domtree for each user.
+ SmallPtrSet<Loop*,16> SimpleLoopNests;
+
+ return AddUsersImpl(I, SimpleLoopNests);
}
IVStrideUse &IVUsers::AddUser(Instruction *User, Value *Operand) {
IVUses.push_back(new IVStrideUse(this, User, Operand));
- IVStrideUse &NewUse = IVUses.back();
-
- // Auto-detect and remember post-inc loops for this expression.
- const SCEV *S = SE->getSCEV(Operand);
- (void)TransformForPostIncUse(NormalizeAutodetect,
- S, User, Operand,
- NewUse.PostIncLoops,
- *SE, *DT);
- return NewUse;
+ return IVUses.back();
}
IVUsers::IVUsers()
- : LoopPass(ID) {
+ : LoopPass(ID) {
+ initializeIVUsersPass(*PassRegistry::getPassRegistry());
}
void IVUsers::getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<LoopInfo>();
- AU.addRequired<DominatorTree>();
+ AU.addRequired<DominatorTreeWrapperPass>();
AU.addRequired<ScalarEvolution>();
AU.setPreservesAll();
}
L = l;
LI = &getAnalysis<LoopInfo>();
- DT = &getAnalysis<DominatorTree>();
+ DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
SE = &getAnalysis<ScalarEvolution>();
+ DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>();
+ DL = DLP ? &DLP->getDataLayout() : 0;
// Find all uses of induction variables in this loop, and categorize
// them by stride. Start by finding all of the PHI nodes in the header for
// this loop. If they are induction variables, inspect their uses.
for (BasicBlock::iterator I = L->getHeader()->begin(); isa<PHINode>(I); ++I)
- AddUsersIfInteresting(I);
+ (void)AddUsersIfInteresting(I);
return false;
}
void IVUsers::print(raw_ostream &OS, const Module *M) const {
OS << "IV Users for loop ";
- WriteAsOperand(OS, L->getHeader(), false);
+ L->getHeader()->printAsOperand(OS, false);
if (SE->hasLoopInvariantBackedgeTakenCount(L)) {
OS << " with backedge-taken count "
<< *SE->getBackedgeTakenCount(L);
}
OS << ":\n";
- // Use a default AssemblyAnnotationWriter to suppress the default info
- // comments, which aren't relevant here.
- AssemblyAnnotationWriter Annotator;
for (ilist<IVStrideUse>::const_iterator UI = IVUses.begin(),
E = IVUses.end(); UI != E; ++UI) {
OS << " ";
- WriteAsOperand(OS, UI->getOperandValToReplace(), false);
+ UI->getOperandValToReplace()->printAsOperand(OS, false);
OS << " = " << *getReplacementExpr(*UI);
for (PostIncLoopSet::const_iterator
I = UI->PostIncLoops.begin(),
E = UI->PostIncLoops.end(); I != E; ++I) {
OS << " (post-inc with loop ";
- WriteAsOperand(OS, (*I)->getHeader(), false);
+ (*I)->getHeader()->printAsOperand(OS, false);
OS << ")";
}
OS << " in ";
- UI->getUser()->print(OS, &Annotator);
+ UI->getUser()->print(OS);
OS << '\n';
}
}
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
void IVUsers::dump() const {
print(dbgs());
}
+#endif
void IVUsers::releaseMemory() {
Processed.clear();
void IVStrideUse::deleted() {
// Remove this user from the list.
+ Parent->Processed.erase(this->getUser());
Parent->IVUses.erase(this);
// this now dangles!
}
projects / oota-llvm.git / blobdiff