#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Support/CFG.h"
#include "llvm/Transforms/Utils/Local.h"
-#include "Support/CommandLine.h"
-#include "Support/Statistic.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/ADT/Statistic.h"
using namespace llvm;
+namespace {
+ /// SCEVExpander - This class uses information about analyze scalars to
+ /// rewrite expressions in canonical form.
+ ///
+ /// Clients should create an instance of this class when rewriting is needed,
+ /// and destroying it when finished to allow the release of the associated
+ /// memory.
+ struct SCEVExpander : public SCEVVisitor<SCEVExpander, Value*> {
+ ScalarEvolution &SE;
+ LoopInfo &LI;
+ std::map<SCEVHandle, Value*> InsertedExpressions;
+ std::set<Instruction*> InsertedInstructions;
+
+ Instruction *InsertPt;
+
+ friend class SCEVVisitor<SCEVExpander, Value*>;
+ public:
+ SCEVExpander(ScalarEvolution &se, LoopInfo &li) : SE(se), LI(li) {}
+
+ /// isInsertedInstruction - Return true if the specified instruction was
+ /// inserted by the code rewriter. If so, the client should not modify the
+ /// instruction.
+ bool isInsertedInstruction(Instruction *I) const {
+ return InsertedInstructions.count(I);
+ }
+
+ /// getOrInsertCanonicalInductionVariable - This method returns the
+ /// canonical induction variable of the specified type for the specified
+ /// loop (inserting one if there is none). A canonical induction variable
+ /// starts at zero and steps by one on each iteration.
+ Value *getOrInsertCanonicalInductionVariable(const Loop *L, const Type *Ty){
+ assert((Ty->isInteger() || Ty->isFloatingPoint()) &&
+ "Can only insert integer or floating point induction variables!");
+ SCEVHandle H = SCEVAddRecExpr::get(SCEVUnknown::getIntegerSCEV(0, Ty),
+ SCEVUnknown::getIntegerSCEV(1, Ty), L);
+ return expand(H);
+ }
+
+ /// addInsertedValue - Remember the specified instruction as being the
+ /// canonical form for the specified SCEV.
+ void addInsertedValue(Instruction *I, SCEV *S) {
+ InsertedExpressions[S] = (Value*)I;
+ InsertedInstructions.insert(I);
+ }
+
+ /// expandCodeFor - Insert code to directly compute the specified SCEV
+ /// expression into the program. The inserted code is inserted into the
+ /// specified block.
+ ///
+ /// If a particular value sign is required, a type may be specified for the
+ /// result.
+ Value *expandCodeFor(SCEVHandle SH, Instruction *IP, const Type *Ty = 0) {
+ // Expand the code for this SCEV.
+ this->InsertPt = IP;
+ return expandInTy(SH, Ty);
+ }
+
+ protected:
+ Value *expand(SCEV *S) {
+ // Check to see if we already expanded this.
+ std::map<SCEVHandle, Value*>::iterator I = InsertedExpressions.find(S);
+ if (I != InsertedExpressions.end())
+ return I->second;
+
+ Value *V = visit(S);
+ InsertedExpressions[S] = V;
+ return V;
+ }
+
+ Value *expandInTy(SCEV *S, const Type *Ty) {
+ Value *V = expand(S);
+ if (Ty && V->getType() != Ty) {
+ // FIXME: keep track of the cast instruction.
+ if (Constant *C = dyn_cast<Constant>(V))
+ return ConstantExpr::getCast(C, Ty);
+ else if (Instruction *I = dyn_cast<Instruction>(V)) {
+ // Check to see if there is already a cast. If there is, use it.
+ for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
+ UI != E; ++UI) {
+ if ((*UI)->getType() == Ty)
+ if (CastInst *CI = dyn_cast<CastInst>(cast<Instruction>(*UI))) {
+ BasicBlock::iterator It = I; ++It;
+ while (isa<PHINode>(It)) ++It;
+ if (It != BasicBlock::iterator(CI)) {
+ // Splice the cast immediately after the operand in question.
+ I->getParent()->getInstList().splice(It,
+ CI->getParent()->getInstList(),
+ CI);
+ }
+ return CI;
+ }
+ }
+ BasicBlock::iterator IP = I; ++IP;
+ if (InvokeInst *II = dyn_cast<InvokeInst>(I))
+ IP = II->getNormalDest()->begin();
+ while (isa<PHINode>(IP)) ++IP;
+ return new CastInst(V, Ty, V->getName(), IP);
+ } else {
+ // FIXME: check to see if there is already a cast!
+ return new CastInst(V, Ty, V->getName(), InsertPt);
+ }
+ }
+ return V;
+ }
+
+ Value *visitConstant(SCEVConstant *S) {
+ return S->getValue();
+ }
+
+ Value *visitTruncateExpr(SCEVTruncateExpr *S) {
+ Value *V = expand(S->getOperand());
+ return new CastInst(V, S->getType(), "tmp.", InsertPt);
+ }
+
+ Value *visitZeroExtendExpr(SCEVZeroExtendExpr *S) {
+ Value *V = expandInTy(S->getOperand(),S->getType()->getUnsignedVersion());
+ return new CastInst(V, S->getType(), "tmp.", InsertPt);
+ }
+
+ Value *visitAddExpr(SCEVAddExpr *S) {
+ const Type *Ty = S->getType();
+ Value *V = expandInTy(S->getOperand(S->getNumOperands()-1), Ty);
+
+ // Emit a bunch of add instructions
+ for (int i = S->getNumOperands()-2; i >= 0; --i)
+ V = BinaryOperator::createAdd(V, expandInTy(S->getOperand(i), Ty),
+ "tmp.", InsertPt);
+ return V;
+ }
+
+ Value *visitMulExpr(SCEVMulExpr *S);
+
+ Value *visitUDivExpr(SCEVUDivExpr *S) {
+ const Type *Ty = S->getType();
+ Value *LHS = expandInTy(S->getLHS(), Ty);
+ Value *RHS = expandInTy(S->getRHS(), Ty);
+ return BinaryOperator::createDiv(LHS, RHS, "tmp.", InsertPt);
+ }
+
+ Value *visitAddRecExpr(SCEVAddRecExpr *S);
+
+ Value *visitUnknown(SCEVUnknown *S) {
+ return S->getValue();
+ }
+ };
+}
+
+Value *SCEVExpander::visitMulExpr(SCEVMulExpr *S) {
+ const Type *Ty = S->getType();
+ int FirstOp = 0; // Set if we should emit a subtract.
+ if (SCEVConstant *SC = dyn_cast<SCEVConstant>(S->getOperand(0)))
+ if (SC->getValue()->isAllOnesValue())
+ FirstOp = 1;
+
+ int i = S->getNumOperands()-2;
+ Value *V = expandInTy(S->getOperand(i+1), Ty);
+
+ // Emit a bunch of multiply instructions
+ for (; i >= FirstOp; --i)
+ V = BinaryOperator::createMul(V, expandInTy(S->getOperand(i), Ty),
+ "tmp.", InsertPt);
+ // -1 * ... ---> 0 - ...
+ if (FirstOp == 1)
+ V = BinaryOperator::createNeg(V, "tmp.", InsertPt);
+ return V;
+}
+
+Value *SCEVExpander::visitAddRecExpr(SCEVAddRecExpr *S) {
+ const Type *Ty = S->getType();
+ const Loop *L = S->getLoop();
+ // We cannot yet do fp recurrences, e.g. the xform of {X,+,F} --> X+{0,+,F}
+ assert(Ty->isIntegral() && "Cannot expand fp recurrences yet!");
+
+ // {X,+,F} --> X + {0,+,F}
+ if (!isa<SCEVConstant>(S->getStart()) ||
+ !cast<SCEVConstant>(S->getStart())->getValue()->isNullValue()) {
+ Value *Start = expandInTy(S->getStart(), Ty);
+ std::vector<SCEVHandle> NewOps(S->op_begin(), S->op_end());
+ NewOps[0] = SCEVUnknown::getIntegerSCEV(0, Ty);
+ Value *Rest = expandInTy(SCEVAddRecExpr::get(NewOps, L), Ty);
+
+ // FIXME: look for an existing add to use.
+ return BinaryOperator::createAdd(Rest, Start, "tmp.", InsertPt);
+ }
+
+ // {0,+,1} --> Insert a canonical induction variable into the loop!
+ if (S->getNumOperands() == 2 &&
+ S->getOperand(1) == SCEVUnknown::getIntegerSCEV(1, Ty)) {
+ // Create and insert the PHI node for the induction variable in the
+ // specified loop.
+ BasicBlock *Header = L->getHeader();
+ PHINode *PN = new PHINode(Ty, "indvar", Header->begin());
+ PN->addIncoming(Constant::getNullValue(Ty), L->getLoopPreheader());
+
+ pred_iterator HPI = pred_begin(Header);
+ assert(HPI != pred_end(Header) && "Loop with zero preds???");
+ if (!L->contains(*HPI)) ++HPI;
+ assert(HPI != pred_end(Header) && L->contains(*HPI) &&
+ "No backedge in loop?");
+
+ // Insert a unit add instruction right before the terminator corresponding
+ // to the back-edge.
+ Constant *One = Ty->isFloatingPoint() ? (Constant*)ConstantFP::get(Ty, 1.0)
+ : ConstantInt::get(Ty, 1);
+ Instruction *Add = BinaryOperator::createAdd(PN, One, "indvar.next",
+ (*HPI)->getTerminator());
+
+ pred_iterator PI = pred_begin(Header);
+ if (*PI == L->getLoopPreheader())
+ ++PI;
+ PN->addIncoming(Add, *PI);
+ return PN;
+ }
+
+ // Get the canonical induction variable I for this loop.
+ Value *I = getOrInsertCanonicalInductionVariable(L, Ty);
+
+ if (S->getNumOperands() == 2) { // {0,+,F} --> i*F
+ Value *F = expandInTy(S->getOperand(1), Ty);
+ return BinaryOperator::createMul(I, F, "tmp.", InsertPt);
+ }
+
+ // If this is a chain of recurrences, turn it into a closed form, using the
+ // folders, then expandCodeFor the closed form. This allows the folders to
+ // simplify the expression without having to build a bunch of special code
+ // into this folder.
+ SCEVHandle IH = SCEVUnknown::get(I); // Get I as a "symbolic" SCEV.
+
+ SCEVHandle V = S->evaluateAtIteration(IH);
+ //std::cerr << "Evaluated: " << *this << "\n to: " << *V << "\n";
+
+ return expandInTy(V, Ty);
+}
+
+
namespace {
Statistic<> NumRemoved ("indvars", "Number of aux indvars removed");
Statistic<> NumPointer ("indvars", "Number of pointer indvars promoted");
void EliminatePointerRecurrence(PHINode *PN, BasicBlock *Preheader,
std::set<Instruction*> &DeadInsts);
void LinearFunctionTestReplace(Loop *L, SCEV *IterationCount,
- ScalarEvolutionRewriter &RW);
+ SCEVExpander &RW);
void RewriteLoopExitValues(Loop *L);
void DeleteTriviallyDeadInstructions(std::set<Instruction*> &Insts);
return new IndVarSimplify();
}
-
/// 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.
// Insert a new integer PHI node into the top of the block.
PHINode *NewPhi = new PHINode(AddedVal->getType(),
PN->getName()+".rec", PN);
- NewPhi->addIncoming(Constant::getNullValue(NewPhi->getType()),
- Preheader);
+ NewPhi->addIncoming(Constant::getNullValue(NewPhi->getType()), Preheader);
+
// Create the new add instruction.
- Value *NewAdd = BinaryOperator::create(Instruction::Add, NewPhi,
- AddedVal,
- GEPI->getName()+".rec", GEPI);
+ Value *NewAdd = BinaryOperator::createAdd(NewPhi, AddedVal,
+ GEPI->getName()+".rec", GEPI);
NewPhi->addIncoming(NewAdd, PN->getIncomingBlock(BackedgeIdx));
// Update the existing GEP to use the recurrence.
/// SCEV analysis can determine a loop-invariant trip count of the loop, which
/// is actually a much broader range than just linear tests.
void IndVarSimplify::LinearFunctionTestReplace(Loop *L, SCEV *IterationCount,
- ScalarEvolutionRewriter &RW) {
+ SCEVExpander &RW) {
// Find the exit block for the loop. We can currently only handle loops with
// a single exit.
std::vector<BasicBlock*> ExitBlocks;
// Expand the code for the iteration count into the preheader of the loop.
BasicBlock *Preheader = L->getLoopPreheader();
- Value *ExitCnt = RW.ExpandCodeFor(TripCount, Preheader->getTerminator(),
+ Value *ExitCnt = RW.expandCodeFor(TripCount, Preheader->getTerminator(),
IndVar->getType());
// Insert a new setne or seteq instruction before the branch.
// Scan all of the instructions in the loop, looking at those that have
// extra-loop users and which are recurrences.
- ScalarEvolutionRewriter Rewriter(*SE, *LI);
+ SCEVExpander Rewriter(*SE, *LI);
// We insert the code into the preheader of the loop if the loop contains
// multiple exit blocks, or in the exit block if there is exactly one.
if (!isa<SCEVCouldNotCompute>(ExitValue)) {
Changed = true;
++NumReplaced;
- Value *NewVal = Rewriter.ExpandCodeFor(ExitValue, InsertPt,
+ Value *NewVal = Rewriter.expandCodeFor(ExitValue, InsertPt,
I->getType());
// Rewrite any users of the computed value outside of the loop
if (PN->getType()->isInteger()) { // FIXME: when we have fast-math, enable!
SCEVHandle SCEV = SE->getSCEV(PN);
if (SCEV->hasComputableLoopEvolution(L))
- if (SE->shouldSubstituteIndVar(SCEV)) // HACK!
- IndVars.push_back(std::make_pair(PN, SCEV));
+ // FIXME: Without a strength reduction pass, it is an extremely bad idea
+ // to indvar substitute anything more complex than a linear induction
+ // variable. Doing so will put expensive multiply instructions inside
+ // of the loop. For now just disable indvar subst on anything more
+ // complex than a linear addrec.
+ if (SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(SCEV))
+ if (AR->getNumOperands() == 2 && isa<SCEVConstant>(AR->getOperand(1)))
+ IndVars.push_back(std::make_pair(PN, SCEV));
}
// If there are no induction variables in the loop, there is nothing more to
// Actually, if we know how many times the loop iterates, lets insert a
// canonical induction variable to help subsequent passes.
if (!isa<SCEVCouldNotCompute>(IterationCount)) {
- ScalarEvolutionRewriter Rewriter(*SE, *LI);
- Rewriter.GetOrInsertCanonicalInductionVariable(L,
+ SCEVExpander Rewriter(*SE, *LI);
+ Rewriter.getOrInsertCanonicalInductionVariable(L,
IterationCount->getType());
LinearFunctionTestReplace(L, IterationCount, Rewriter);
}
}
// Create a rewriter object which we'll use to transform the code with.
- ScalarEvolutionRewriter Rewriter(*SE, *LI);
+ SCEVExpander Rewriter(*SE, *LI);
// Now that we know the largest of of the induction variables in this loop,
// insert a canonical induction variable of the largest size.
LargestType = LargestType->getUnsignedVersion();
- Value *IndVar = Rewriter.GetOrInsertCanonicalInductionVariable(L,LargestType);
+ Value *IndVar = Rewriter.getOrInsertCanonicalInductionVariable(L,LargestType);
++NumInserted;
Changed = true;
std::map<unsigned, Value*> InsertedSizes;
while (!IndVars.empty()) {
PHINode *PN = IndVars.back().first;
- Value *NewVal = Rewriter.ExpandCodeFor(IndVars.back().second, InsertPt,
+ Value *NewVal = Rewriter.expandCodeFor(IndVars.back().second, InsertPt,
PN->getType());
std::string Name = PN->getName();
PN->setName("");
!I->use_empty() &&
!Rewriter.isInsertedInstruction(I)) {
SCEVHandle SH = SE->getSCEV(I);
- Value *V = Rewriter.ExpandCodeFor(SH, I, I->getType());
+ Value *V = Rewriter.expandCodeFor(SH, I, I->getType());
if (V != I) {
if (isa<Instruction>(V)) {
std::string Name = I->getName();
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