#define DEBUG_TYPE "loop-idiom"
#include "llvm/Transforms/Scalar.h"
-#include "llvm/IntrinsicInst.h"
-#include "llvm/Module.h"
+#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/LoopPass.h"
-#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/Analysis/ScalarEvolutionExpander.h"
+#include "llvm/Analysis/ScalarEvolutionExpressions.h"
+#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/Analysis/ValueTracking.h"
-#include "llvm/Target/TargetData.h"
-#include "llvm/Target/TargetLibraryInfo.h"
-#include "llvm/Transforms/Utils/Local.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
#include "llvm/Support/Debug.h"
-#include "llvm/Support/IRBuilder.h"
#include "llvm/Support/raw_ostream.h"
-#include "llvm/ADT/Statistic.h"
+#include "llvm/Target/TargetLibraryInfo.h"
+#include "llvm/Transforms/Utils/Local.h"
using namespace llvm;
STATISTIC(NumMemSet, "Number of memset's formed from loop stores");
STATISTIC(NumMemCpy, "Number of memcpy's formed from loop load+stores");
namespace {
+
+ class LoopIdiomRecognize;
+
+ /// This class defines some utility functions for loop idiom recognization.
+ class LIRUtil {
+ public:
+ /// Return true iff the block contains nothing but an uncondition branch
+ /// (aka goto instruction).
+ static bool isAlmostEmpty(BasicBlock *);
+
+ static BranchInst *getBranch(BasicBlock *BB) {
+ return dyn_cast<BranchInst>(BB->getTerminator());
+ }
+
+ /// Return the condition of the branch terminating the given basic block.
+ static Value *getBrCondtion(BasicBlock *);
+
+ /// Derive the precondition block (i.e the block that guards the loop
+ /// preheader) from the given preheader.
+ static BasicBlock *getPrecondBb(BasicBlock *PreHead);
+ };
+
+ /// This class is to recoginize idioms of population-count conducted in
+ /// a noncountable loop. Currently it only recognizes this pattern:
+ /// \code
+ /// while(x) {cnt++; ...; x &= x - 1; ...}
+ /// \endcode
+ class NclPopcountRecognize {
+ LoopIdiomRecognize &LIR;
+ Loop *CurLoop;
+ BasicBlock *PreCondBB;
+
+ typedef IRBuilder<> IRBuilderTy;
+
+ public:
+ explicit NclPopcountRecognize(LoopIdiomRecognize &TheLIR);
+ bool recognize();
+
+ private:
+ /// Take a glimpse of the loop to see if we need to go ahead recoginizing
+ /// the idiom.
+ bool preliminaryScreen();
+
+ /// Check if the given conditional branch is based on the comparison
+ /// beween a variable and zero, and if the variable is non-zero, the
+ /// control yeilds to the loop entry. If the branch matches the behavior,
+ /// the variable involved in the comparion is returned. This function will
+ /// be called to see if the precondition and postcondition of the loop
+ /// are in desirable form.
+ Value *matchCondition (BranchInst *Br, BasicBlock *NonZeroTarget) const;
+
+ /// Return true iff the idiom is detected in the loop. and 1) \p CntInst
+ /// is set to the instruction counting the pupulation bit. 2) \p CntPhi
+ /// is set to the corresponding phi node. 3) \p Var is set to the value
+ /// whose population bits are being counted.
+ bool detectIdiom
+ (Instruction *&CntInst, PHINode *&CntPhi, Value *&Var) const;
+
+ /// Insert ctpop intrinsic function and some obviously dead instructions.
+ void transform (Instruction *CntInst, PHINode *CntPhi, Value *Var);
+
+ /// Create llvm.ctpop.* intrinsic function.
+ CallInst *createPopcntIntrinsic(IRBuilderTy &IRB, Value *Val, DebugLoc DL);
+ };
+
class LoopIdiomRecognize : public LoopPass {
Loop *CurLoop;
- const TargetData *TD;
+ const DataLayout *TD;
DominatorTree *DT;
ScalarEvolution *SE;
TargetLibraryInfo *TLI;
+ const TargetTransformInfo *TTI;
public:
static char ID;
explicit LoopIdiomRecognize() : LoopPass(ID) {
initializeLoopIdiomRecognizePass(*PassRegistry::getPassRegistry());
+ TD = 0; DT = 0; SE = 0; TLI = 0; TTI = 0;
}
bool runOnLoop(Loop *L, LPPassManager &LPM);
AU.addRequired<DominatorTree>();
AU.addRequired<TargetLibraryInfo>();
}
+
+ const DataLayout *getDataLayout() {
+ return TD ? TD : TD=getAnalysisIfAvailable<DataLayout>();
+ }
+
+ DominatorTree *getDominatorTree() {
+ return DT ? DT : (DT=&getAnalysis<DominatorTree>());
+ }
+
+ ScalarEvolution *getScalarEvolution() {
+ return SE ? SE : (SE = &getAnalysis<ScalarEvolution>());
+ }
+
+ TargetLibraryInfo *getTargetLibraryInfo() {
+ return TLI ? TLI : (TLI = &getAnalysis<TargetLibraryInfo>());
+ }
+
+ const TargetTransformInfo *getTargetTransformInfo() {
+ if (!TTI)
+ TTI = getAnalysisIfAvailable<TargetTransformInfo>();
+ return TTI;
+ }
+
+ Loop *getLoop() const { return CurLoop; }
+
+ private:
+ bool runOnNoncountableLoop();
+ bool runOnCountableLoop();
};
}
Pass *llvm::createLoopIdiomPass() { return new LoopIdiomRecognize(); }
-/// DeleteDeadInstruction - Delete this instruction. Before we do, go through
+/// deleteDeadInstruction - Delete this instruction. Before we do, go through
/// and zero out all the operands of this instruction. If any of them become
/// dead, delete them and the computation tree that feeds them.
///
-static void DeleteDeadInstruction(Instruction *I, ScalarEvolution &SE) {
+static void deleteDeadInstruction(Instruction *I, ScalarEvolution &SE,
+ const TargetLibraryInfo *TLI) {
SmallVector<Instruction*, 32> NowDeadInsts;
NowDeadInsts.push_back(I);
if (!Op->use_empty()) continue;
if (Instruction *OpI = dyn_cast<Instruction>(Op))
- if (isInstructionTriviallyDead(OpI))
+ if (isInstructionTriviallyDead(OpI, TLI))
NowDeadInsts.push_back(OpI);
}
} while (!NowDeadInsts.empty());
}
-bool LoopIdiomRecognize::runOnLoop(Loop *L, LPPassManager &LPM) {
- CurLoop = L;
+/// deleteIfDeadInstruction - If the specified value is a dead instruction,
+/// delete it and any recursively used instructions.
+static void deleteIfDeadInstruction(Value *V, ScalarEvolution &SE,
+ const TargetLibraryInfo *TLI) {
+ if (Instruction *I = dyn_cast<Instruction>(V))
+ if (isInstructionTriviallyDead(I, TLI))
+ deleteDeadInstruction(I, SE, TLI);
+}
- // The trip count of the loop must be analyzable.
- SE = &getAnalysis<ScalarEvolution>();
- if (!SE->hasLoopInvariantBackedgeTakenCount(L))
+//===----------------------------------------------------------------------===//
+//
+// Implementation of LIRUtil
+//
+//===----------------------------------------------------------------------===//
+
+// This fucntion will return true iff the given block contains nothing but goto.
+// A typical usage of this function is to check if the preheader fucntion is
+// "almost" empty such that generated intrinsic function can be moved across
+// preheader and to be placed at the end of the preconditiona block without
+// concerning of breaking data dependence.
+bool LIRUtil::isAlmostEmpty(BasicBlock *BB) {
+ if (BranchInst *Br = getBranch(BB)) {
+ return Br->isUnconditional() && BB->size() == 1;
+ }
+ return false;
+}
+
+Value *LIRUtil::getBrCondtion(BasicBlock *BB) {
+ BranchInst *Br = getBranch(BB);
+ return Br ? Br->getCondition() : 0;
+}
+
+BasicBlock *LIRUtil::getPrecondBb(BasicBlock *PreHead) {
+ if (BasicBlock *BB = PreHead->getSinglePredecessor()) {
+ BranchInst *Br = getBranch(BB);
+ return Br && Br->isConditional() ? BB : 0;
+ }
+ return 0;
+}
+
+//===----------------------------------------------------------------------===//
+//
+// Implementation of NclPopcountRecognize
+//
+//===----------------------------------------------------------------------===//
+
+NclPopcountRecognize::NclPopcountRecognize(LoopIdiomRecognize &TheLIR):
+ LIR(TheLIR), CurLoop(TheLIR.getLoop()), PreCondBB(0) {
+}
+
+bool NclPopcountRecognize::preliminaryScreen() {
+ const TargetTransformInfo *TTI = LIR.getTargetTransformInfo();
+ if (TTI->getPopcntSupport(32) != TargetTransformInfo::PSK_FastHardware)
+ return false;
+
+ // Counting population are usually conducted by few arithmetic instrutions.
+ // Such instructions can be easilly "absorbed" by vacant slots in a
+ // non-compact loop. Therefore, recognizing popcount idiom only makes sense
+ // in a compact loop.
+
+ // Give up if the loop has multiple blocks or multiple backedges.
+ if (CurLoop->getNumBackEdges() != 1 || CurLoop->getNumBlocks() != 1)
+ return false;
+
+ BasicBlock *LoopBody = *(CurLoop->block_begin());
+ if (LoopBody->size() >= 20) {
+ // The loop is too big, bail out.
+ return false;
+ }
+
+ // It should have a preheader containing nothing but a goto instruction.
+ BasicBlock *PreHead = CurLoop->getLoopPreheader();
+ if (!PreHead || !LIRUtil::isAlmostEmpty(PreHead))
+ return false;
+
+ // It should have a precondition block where the generated popcount instrinsic
+ // function will be inserted.
+ PreCondBB = LIRUtil::getPrecondBb(PreHead);
+ if (!PreCondBB)
return false;
- const SCEV *BECount = SE->getBackedgeTakenCount(L);
+
+ return true;
+}
+
+Value *NclPopcountRecognize::matchCondition (BranchInst *Br,
+ BasicBlock *LoopEntry) const {
+ if (!Br || !Br->isConditional())
+ return 0;
+
+ ICmpInst *Cond = dyn_cast<ICmpInst>(Br->getCondition());
+ if (!Cond)
+ return 0;
+
+ ConstantInt *CmpZero = dyn_cast<ConstantInt>(Cond->getOperand(1));
+ if (!CmpZero || !CmpZero->isZero())
+ return 0;
+
+ ICmpInst::Predicate Pred = Cond->getPredicate();
+ if ((Pred == ICmpInst::ICMP_NE && Br->getSuccessor(0) == LoopEntry) ||
+ (Pred == ICmpInst::ICMP_EQ && Br->getSuccessor(1) == LoopEntry))
+ return Cond->getOperand(0);
+
+ return 0;
+}
+
+bool NclPopcountRecognize::detectIdiom(Instruction *&CntInst,
+ PHINode *&CntPhi,
+ Value *&Var) const {
+ // Following code tries to detect this idiom:
+ //
+ // if (x0 != 0)
+ // goto loop-exit // the precondition of the loop
+ // cnt0 = init-val;
+ // do {
+ // x1 = phi (x0, x2);
+ // cnt1 = phi(cnt0, cnt2);
+ //
+ // cnt2 = cnt1 + 1;
+ // ...
+ // x2 = x1 & (x1 - 1);
+ // ...
+ // } while(x != 0);
+ //
+ // loop-exit:
+ //
+
+ // step 1: Check to see if the look-back branch match this pattern:
+ // "if (a!=0) goto loop-entry".
+ BasicBlock *LoopEntry;
+ Instruction *DefX2, *CountInst;
+ Value *VarX1, *VarX0;
+ PHINode *PhiX, *CountPhi;
+
+ DefX2 = CountInst = 0;
+ VarX1 = VarX0 = 0;
+ PhiX = CountPhi = 0;
+ LoopEntry = *(CurLoop->block_begin());
+
+ // step 1: Check if the loop-back branch is in desirable form.
+ {
+ if (Value *T = matchCondition (LIRUtil::getBranch(LoopEntry), LoopEntry))
+ DefX2 = dyn_cast<Instruction>(T);
+ else
+ return false;
+ }
+
+ // step 2: detect instructions corresponding to "x2 = x1 & (x1 - 1)"
+ {
+ if (DefX2->getOpcode() != Instruction::And)
+ return false;
+
+ BinaryOperator *SubOneOp;
+
+ if ((SubOneOp = dyn_cast<BinaryOperator>(DefX2->getOperand(0))))
+ VarX1 = DefX2->getOperand(1);
+ else {
+ VarX1 = DefX2->getOperand(0);
+ SubOneOp = dyn_cast<BinaryOperator>(DefX2->getOperand(1));
+ }
+ if (!SubOneOp)
+ return false;
+
+ Instruction *SubInst = cast<Instruction>(SubOneOp);
+ ConstantInt *Dec = dyn_cast<ConstantInt>(SubInst->getOperand(1));
+ if (!Dec ||
+ !((SubInst->getOpcode() == Instruction::Sub && Dec->isOne()) ||
+ (SubInst->getOpcode() == Instruction::Add && Dec->isAllOnesValue()))) {
+ return false;
+ }
+ }
+
+ // step 3: Check the recurrence of variable X
+ {
+ PhiX = dyn_cast<PHINode>(VarX1);
+ if (!PhiX ||
+ (PhiX->getOperand(0) != DefX2 && PhiX->getOperand(1) != DefX2)) {
+ return false;
+ }
+ }
+
+ // step 4: Find the instruction which count the population: cnt2 = cnt1 + 1
+ {
+ CountInst = NULL;
+ for (BasicBlock::iterator Iter = LoopEntry->getFirstNonPHI(),
+ IterE = LoopEntry->end(); Iter != IterE; Iter++) {
+ Instruction *Inst = Iter;
+ if (Inst->getOpcode() != Instruction::Add)
+ continue;
+
+ ConstantInt *Inc = dyn_cast<ConstantInt>(Inst->getOperand(1));
+ if (!Inc || !Inc->isOne())
+ continue;
+
+ PHINode *Phi = dyn_cast<PHINode>(Inst->getOperand(0));
+ if (!Phi || Phi->getParent() != LoopEntry)
+ continue;
+
+ // Check if the result of the instruction is live of the loop.
+ bool LiveOutLoop = false;
+ for (Value::use_iterator I = Inst->use_begin(), E = Inst->use_end();
+ I != E; I++) {
+ if ((cast<Instruction>(*I))->getParent() != LoopEntry) {
+ LiveOutLoop = true; break;
+ }
+ }
+
+ if (LiveOutLoop) {
+ CountInst = Inst;
+ CountPhi = Phi;
+ break;
+ }
+ }
+
+ if (!CountInst)
+ return false;
+ }
+
+ // step 5: check if the precondition is in this form:
+ // "if (x != 0) goto loop-head ; else goto somewhere-we-don't-care;"
+ {
+ BranchInst *PreCondBr = LIRUtil::getBranch(PreCondBB);
+ Value *T = matchCondition (PreCondBr, CurLoop->getLoopPreheader());
+ if (T != PhiX->getOperand(0) && T != PhiX->getOperand(1))
+ return false;
+
+ CntInst = CountInst;
+ CntPhi = CountPhi;
+ Var = T;
+ }
+
+ return true;
+}
+
+void NclPopcountRecognize::transform(Instruction *CntInst,
+ PHINode *CntPhi, Value *Var) {
+
+ ScalarEvolution *SE = LIR.getScalarEvolution();
+ TargetLibraryInfo *TLI = LIR.getTargetLibraryInfo();
+ BasicBlock *PreHead = CurLoop->getLoopPreheader();
+ BranchInst *PreCondBr = LIRUtil::getBranch(PreCondBB);
+ const DebugLoc DL = CntInst->getDebugLoc();
+
+ // Assuming before transformation, the loop is following:
+ // if (x) // the precondition
+ // do { cnt++; x &= x - 1; } while(x);
+
+ // Step 1: Insert the ctpop instruction at the end of the precondition block
+ IRBuilderTy Builder(PreCondBr);
+ Value *PopCnt, *PopCntZext, *NewCount, *TripCnt;
+ {
+ PopCnt = createPopcntIntrinsic(Builder, Var, DL);
+ NewCount = PopCntZext =
+ Builder.CreateZExtOrTrunc(PopCnt, cast<IntegerType>(CntPhi->getType()));
+
+ if (NewCount != PopCnt)
+ (cast<Instruction>(NewCount))->setDebugLoc(DL);
+
+ // TripCnt is exactly the number of iterations the loop has
+ TripCnt = NewCount;
+
+ // If the popoulation counter's initial value is not zero, insert Add Inst.
+ Value *CntInitVal = CntPhi->getIncomingValueForBlock(PreHead);
+ ConstantInt *InitConst = dyn_cast<ConstantInt>(CntInitVal);
+ if (!InitConst || !InitConst->isZero()) {
+ NewCount = Builder.CreateAdd(NewCount, CntInitVal);
+ (cast<Instruction>(NewCount))->setDebugLoc(DL);
+ }
+ }
+
+ // Step 2: Replace the precondition from "if(x == 0) goto loop-exit" to
+ // "if(NewCount == 0) loop-exit". Withtout this change, the intrinsic
+ // function would be partial dead code, and downstream passes will drag
+ // it back from the precondition block to the preheader.
+ {
+ ICmpInst *PreCond = cast<ICmpInst>(PreCondBr->getCondition());
+
+ Value *Opnd0 = PopCntZext;
+ Value *Opnd1 = ConstantInt::get(PopCntZext->getType(), 0);
+ if (PreCond->getOperand(0) != Var)
+ std::swap(Opnd0, Opnd1);
+
+ ICmpInst *NewPreCond =
+ cast<ICmpInst>(Builder.CreateICmp(PreCond->getPredicate(), Opnd0, Opnd1));
+ PreCond->replaceAllUsesWith(NewPreCond);
+
+ deleteDeadInstruction(PreCond, *SE, TLI);
+ }
+
+ // Step 3: Note that the population count is exactly the trip count of the
+ // loop in question, which enble us to to convert the loop from noncountable
+ // loop into a countable one. The benefit is twofold:
+ //
+ // - If the loop only counts population, the entire loop become dead after
+ // the transformation. It is lots easier to prove a countable loop dead
+ // than to prove a noncountable one. (In some C dialects, a infite loop
+ // isn't dead even if it computes nothing useful. In general, DCE needs
+ // to prove a noncountable loop finite before safely delete it.)
+ //
+ // - If the loop also performs something else, it remains alive.
+ // Since it is transformed to countable form, it can be aggressively
+ // optimized by some optimizations which are in general not applicable
+ // to a noncountable loop.
+ //
+ // After this step, this loop (conceptually) would look like following:
+ // newcnt = __builtin_ctpop(x);
+ // t = newcnt;
+ // if (x)
+ // do { cnt++; x &= x-1; t--) } while (t > 0);
+ BasicBlock *Body = *(CurLoop->block_begin());
+ {
+ BranchInst *LbBr = LIRUtil::getBranch(Body);
+ ICmpInst *LbCond = cast<ICmpInst>(LbBr->getCondition());
+ Type *Ty = TripCnt->getType();
+
+ PHINode *TcPhi = PHINode::Create(Ty, 2, "tcphi", Body->begin());
+
+ Builder.SetInsertPoint(LbCond);
+ Value *Opnd1 = cast<Value>(TcPhi);
+ Value *Opnd2 = cast<Value>(ConstantInt::get(Ty, 1));
+ Instruction *TcDec =
+ cast<Instruction>(Builder.CreateSub(Opnd1, Opnd2, "tcdec", false, true));
+
+ TcPhi->addIncoming(TripCnt, PreHead);
+ TcPhi->addIncoming(TcDec, Body);
+
+ CmpInst::Predicate Pred = (LbBr->getSuccessor(0) == Body) ?
+ CmpInst::ICMP_UGT : CmpInst::ICMP_SLE;
+ LbCond->setPredicate(Pred);
+ LbCond->setOperand(0, TcDec);
+ LbCond->setOperand(1, cast<Value>(ConstantInt::get(Ty, 0)));
+ }
+
+ // Step 4: All the references to the original population counter outside
+ // the loop are replaced with the NewCount -- the value returned from
+ // __builtin_ctpop().
+ {
+ SmallVector<Value *, 4> CntUses;
+ for (Value::use_iterator I = CntInst->use_begin(), E = CntInst->use_end();
+ I != E; I++) {
+ if (cast<Instruction>(*I)->getParent() != Body)
+ CntUses.push_back(*I);
+ }
+ for (unsigned Idx = 0; Idx < CntUses.size(); Idx++) {
+ (cast<Instruction>(CntUses[Idx]))->replaceUsesOfWith(CntInst, NewCount);
+ }
+ }
+
+ // step 5: Forget the "non-computable" trip-count SCEV associated with the
+ // loop. The loop would otherwise not be deleted even if it becomes empty.
+ SE->forgetLoop(CurLoop);
+}
+
+CallInst *NclPopcountRecognize::createPopcntIntrinsic(IRBuilderTy &IRBuilder,
+ Value *Val, DebugLoc DL) {
+ Value *Ops[] = { Val };
+ Type *Tys[] = { Val->getType() };
+
+ Module *M = (*(CurLoop->block_begin()))->getParent()->getParent();
+ Value *Func = Intrinsic::getDeclaration(M, Intrinsic::ctpop, Tys);
+ CallInst *CI = IRBuilder.CreateCall(Func, Ops);
+ CI->setDebugLoc(DL);
+
+ return CI;
+}
+
+/// recognize - detect population count idiom in a non-countable loop. If
+/// detected, transform the relevant code to popcount intrinsic function
+/// call, and return true; otherwise, return false.
+bool NclPopcountRecognize::recognize() {
+
+ if (!LIR.getTargetTransformInfo())
+ return false;
+
+ LIR.getScalarEvolution();
+
+ if (!preliminaryScreen())
+ return false;
+
+ Instruction *CntInst;
+ PHINode *CntPhi;
+ Value *Val;
+ if (!detectIdiom(CntInst, CntPhi, Val))
+ return false;
+
+ transform(CntInst, CntPhi, Val);
+ return true;
+}
+
+//===----------------------------------------------------------------------===//
+//
+// Implementation of LoopIdiomRecognize
+//
+//===----------------------------------------------------------------------===//
+
+bool LoopIdiomRecognize::runOnCountableLoop() {
+ const SCEV *BECount = SE->getBackedgeTakenCount(CurLoop);
if (isa<SCEVCouldNotCompute>(BECount)) return false;
// If this loop executes exactly one time, then it should be peeled, not
return false;
// We require target data for now.
- TD = getAnalysisIfAvailable<TargetData>();
- if (TD == 0) return false;
+ if (!getDataLayout())
+ return false;
+
+ // set DT
+ (void)getDominatorTree();
- DT = &getAnalysis<DominatorTree>();
LoopInfo &LI = getAnalysis<LoopInfo>();
TLI = &getAnalysis<TargetLibraryInfo>();
+ // set TLI
+ (void)getTargetLibraryInfo();
+
SmallVector<BasicBlock*, 8> ExitBlocks;
CurLoop->getUniqueExitBlocks(ExitBlocks);
DEBUG(dbgs() << "loop-idiom Scanning: F["
- << L->getHeader()->getParent()->getName()
- << "] Loop %" << L->getHeader()->getName() << "\n");
+ << CurLoop->getHeader()->getParent()->getName()
+ << "] Loop %" << CurLoop->getHeader()->getName() << "\n");
bool MadeChange = false;
// Scan all the blocks in the loop that are not in subloops.
- for (Loop::block_iterator BI = L->block_begin(), E = L->block_end(); BI != E;
- ++BI) {
+ for (Loop::block_iterator BI = CurLoop->block_begin(),
+ E = CurLoop->block_end(); BI != E; ++BI) {
// Ignore blocks in subloops.
if (LI.getLoopFor(*BI) != CurLoop)
continue;
return MadeChange;
}
+bool LoopIdiomRecognize::runOnNoncountableLoop() {
+ NclPopcountRecognize Popcount(*this);
+ if (Popcount.recognize())
+ return true;
+
+ return false;
+}
+
+bool LoopIdiomRecognize::runOnLoop(Loop *L, LPPassManager &LPM) {
+ CurLoop = L;
+
+ // If the loop could not be converted to canonical form, it must have an
+ // indirectbr in it, just give up.
+ if (!L->getLoopPreheader())
+ return false;
+
+ // Disable loop idiom recognition if the function's name is a common idiom.
+ StringRef Name = L->getHeader()->getParent()->getName();
+ if (Name == "memset" || Name == "memcpy")
+ return false;
+
+ SE = &getAnalysis<ScalarEvolution>();
+ if (SE->hasLoopInvariantBackedgeTakenCount(L))
+ return runOnCountableLoop();
+ return runOnNoncountableLoop();
+}
+
/// runOnLoopBlock - Process the specified block, which lives in a counted loop
/// with the specified backedge count. This block is known to be in the current
/// loop and not in any subloops.
/// processLoopStore - See if this store can be promoted to a memset or memcpy.
bool LoopIdiomRecognize::processLoopStore(StoreInst *SI, const SCEV *BECount) {
- if (SI->isVolatile()) return false;
+ if (!SI->isSimple()) return false;
Value *StoredVal = SI->getValueOperand();
Value *StorePtr = SI->getPointerOperand();
const SCEVAddRecExpr *LoadEv =
dyn_cast<SCEVAddRecExpr>(SE->getSCEV(LI->getOperand(0)));
if (LoadEv && LoadEv->getLoop() == CurLoop && LoadEv->isAffine() &&
- StoreEv->getOperand(1) == LoadEv->getOperand(1) && !LI->isVolatile())
+ StoreEv->getOperand(1) == LoadEv->getOperand(1) && LI->isSimple())
if (processLoopStoreOfLoopLoad(SI, StoreSize, StoreEv, LoadEv, BECount))
return true;
}
///
/// Note that we don't ever attempt to use memset_pattern8 or 4, because these
/// just replicate their input array and then pass on to memset_pattern16.
-static Constant *getMemSetPatternValue(Value *V, const TargetData &TD) {
+static Constant *getMemSetPatternValue(Value *V, const DataLayout &TD) {
// If the value isn't a constant, we can't promote it to being in a constant
// array. We could theoretically do a store to an alloca or something, but
// that doesn't seem worthwhile.
SplatValue = 0;
} else {
// Otherwise, this isn't an idiom we can transform. For example, we can't
- // do anything with a 3-byte store, for example.
+ // do anything with a 3-byte store.
return false;
}
+ // The trip count of the loop and the base pointer of the addrec SCEV is
+ // guaranteed to be loop invariant, which means that it should dominate the
+ // header. This allows us to insert code for it in the preheader.
+ BasicBlock *Preheader = CurLoop->getLoopPreheader();
+ IRBuilder<> Builder(Preheader->getTerminator());
+ SCEVExpander Expander(*SE, "loop-idiom");
// Okay, we have a strided store "p[i]" of a splattable value. We can turn
// this into a memset in the loop preheader now if we want. However, this
// would be unsafe to do if there is anything else in the loop that may read
- // or write to the aliased location. Check for an alias.
- if (mayLoopAccessLocation(DestPtr, AliasAnalysis::ModRef,
- CurLoop, BECount,
- StoreSize, getAnalysis<AliasAnalysis>(), TheStore))
- return false;
-
- // Okay, everything looks good, insert the memset.
- BasicBlock *Preheader = CurLoop->getLoopPreheader();
-
- IRBuilder<> Builder(Preheader->getTerminator());
-
- // The trip count of the loop and the base pointer of the addrec SCEV is
- // guaranteed to be loop invariant, which means that it should dominate the
- // header. Just insert code for it in the preheader.
- SCEVExpander Expander(*SE);
-
+ // or write to the aliased location. Check for any overlap by generating the
+ // base pointer and checking the region.
unsigned AddrSpace = cast<PointerType>(DestPtr->getType())->getAddressSpace();
Value *BasePtr =
Expander.expandCodeFor(Ev->getStart(), Builder.getInt8PtrTy(AddrSpace),
Preheader->getTerminator());
+
+ if (mayLoopAccessLocation(BasePtr, AliasAnalysis::ModRef,
+ CurLoop, BECount,
+ StoreSize, getAnalysis<AliasAnalysis>(), TheStore)){
+ Expander.clear();
+ // If we generated new code for the base pointer, clean up.
+ deleteIfDeadInstruction(BasePtr, *SE, TLI);
+ return false;
+ }
+
+ // Okay, everything looks good, insert the memset.
+
// The # stored bytes is (BECount+1)*Size. Expand the trip count out to
// pointer size if it isn't already.
- const Type *IntPtr = TD->getIntPtrType(DestPtr->getContext());
+ Type *IntPtr = TD->getIntPtrType(DestPtr->getContext());
BECount = SE->getTruncateOrZeroExtend(BECount, IntPtr);
const SCEV *NumBytesS = SE->getAddExpr(BECount, SE->getConstant(IntPtr, 1),
// Okay, the memset has been formed. Zap the original store and anything that
// feeds into it.
- DeleteDeadInstruction(TheStore, *SE);
+ deleteDeadInstruction(TheStore, *SE, TLI);
++NumMemSet;
return true;
}
LoadInst *LI = cast<LoadInst>(SI->getValueOperand());
+ // The trip count of the loop and the base pointer of the addrec SCEV is
+ // guaranteed to be loop invariant, which means that it should dominate the
+ // header. This allows us to insert code for it in the preheader.
+ BasicBlock *Preheader = CurLoop->getLoopPreheader();
+ IRBuilder<> Builder(Preheader->getTerminator());
+ SCEVExpander Expander(*SE, "loop-idiom");
+
// Okay, we have a strided store "p[i]" of a loaded value. We can turn
// this into a memcpy in the loop preheader now if we want. However, this
// would be unsafe to do if there is anything else in the loop that may read
- // or write to the stored location (including the load feeding the stores).
- // Check for an alias.
- if (mayLoopAccessLocation(SI->getPointerOperand(), AliasAnalysis::ModRef,
+ // or write the memory region we're storing to. This includes the load that
+ // feeds the stores. Check for an alias by generating the base address and
+ // checking everything.
+ Value *StoreBasePtr =
+ Expander.expandCodeFor(StoreEv->getStart(),
+ Builder.getInt8PtrTy(SI->getPointerAddressSpace()),
+ Preheader->getTerminator());
+
+ if (mayLoopAccessLocation(StoreBasePtr, AliasAnalysis::ModRef,
CurLoop, BECount, StoreSize,
- getAnalysis<AliasAnalysis>(), SI))
+ getAnalysis<AliasAnalysis>(), SI)) {
+ Expander.clear();
+ // If we generated new code for the base pointer, clean up.
+ deleteIfDeadInstruction(StoreBasePtr, *SE, TLI);
return false;
+ }
// For a memcpy, we have to make sure that the input array is not being
// mutated by the loop.
- if (mayLoopAccessLocation(LI->getPointerOperand(), AliasAnalysis::Mod,
- CurLoop, BECount, StoreSize,
- getAnalysis<AliasAnalysis>(), SI))
- return false;
-
- // Okay, everything looks good, insert the memcpy.
- BasicBlock *Preheader = CurLoop->getLoopPreheader();
-
- IRBuilder<> Builder(Preheader->getTerminator());
-
- // The trip count of the loop and the base pointer of the addrec SCEV is
- // guaranteed to be loop invariant, which means that it should dominate the
- // header. Just insert code for it in the preheader.
- SCEVExpander Expander(*SE);
-
Value *LoadBasePtr =
Expander.expandCodeFor(LoadEv->getStart(),
Builder.getInt8PtrTy(LI->getPointerAddressSpace()),
Preheader->getTerminator());
- Value *StoreBasePtr =
- Expander.expandCodeFor(StoreEv->getStart(),
- Builder.getInt8PtrTy(SI->getPointerAddressSpace()),
- Preheader->getTerminator());
+
+ if (mayLoopAccessLocation(LoadBasePtr, AliasAnalysis::Mod, CurLoop, BECount,
+ StoreSize, getAnalysis<AliasAnalysis>(), SI)) {
+ Expander.clear();
+ // If we generated new code for the base pointer, clean up.
+ deleteIfDeadInstruction(LoadBasePtr, *SE, TLI);
+ deleteIfDeadInstruction(StoreBasePtr, *SE, TLI);
+ return false;
+ }
+
+ // Okay, everything is safe, we can transform this!
+
// The # stored bytes is (BECount+1)*Size. Expand the trip count out to
// pointer size if it isn't already.
- const Type *IntPtr = TD->getIntPtrType(SI->getContext());
+ Type *IntPtr = TD->getIntPtrType(SI->getContext());
BECount = SE->getTruncateOrZeroExtend(BECount, IntPtr);
const SCEV *NumBytesS = SE->getAddExpr(BECount, SE->getConstant(IntPtr, 1),
DEBUG(dbgs() << " Formed memcpy: " << *NewCall << "\n"
<< " from load ptr=" << *LoadEv << " at: " << *LI << "\n"
<< " from store ptr=" << *StoreEv << " at: " << *SI << "\n");
-
+
// Okay, the memset has been formed. Zap the original store and anything that
// feeds into it.
- DeleteDeadInstruction(SI, *SE);
+ deleteDeadInstruction(SI, *SE, TLI);
++NumMemCpy;
return true;
}
projects / oota-llvm.git / blobdiff