bool runOnFunction(Function &F);
public:
static char ID; // Pass identification, replacement for typeid
- MemCpyOpt() : FunctionPass(&ID) {}
+ MemCpyOpt() : FunctionPass(ID) {
+ initializeMemCpyOptPass(*PassRegistry::getPassRegistry());
+ }
private:
// This transformation requires dominator postdominator info
bool processStore(StoreInst *SI, BasicBlock::iterator &BBI);
bool processMemCpy(MemCpyInst *M);
bool processMemMove(MemMoveInst *M);
- bool performCallSlotOptzn(MemCpyInst *cpy, CallInst *C);
+ bool performCallSlotOptzn(Instruction *cpy, Value *cpyDst, Value *cpySrc,
+ uint64_t cpyLen, CallInst *C);
bool iterateOnFunction(Function &F);
};
// createMemCpyOptPass - The public interface to this file...
FunctionPass *llvm::createMemCpyOptPass() { return new MemCpyOpt(); }
-INITIALIZE_PASS(MemCpyOpt, "memcpyopt", "MemCpy Optimization", false, false);
-
-
+INITIALIZE_PASS_BEGIN(MemCpyOpt, "memcpyopt", "MemCpy Optimization",
+ false, false)
+INITIALIZE_PASS_DEPENDENCY(DominatorTree)
+INITIALIZE_PASS_DEPENDENCY(MemoryDependenceAnalysis)
+INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
+INITIALIZE_PASS_END(MemCpyOpt, "memcpyopt", "MemCpy Optimization",
+ false, false)
/// processStore - When GVN is scanning forward over instructions, we look for
/// some other patterns to fold away. In particular, this looks for stores to
bool MemCpyOpt::processStore(StoreInst *SI, BasicBlock::iterator &BBI) {
if (SI->isVolatile()) return false;
+ TargetData *TD = getAnalysisIfAvailable<TargetData>();
+ if (!TD) return false;
+
+ // Detect cases where we're performing call slot forwarding, but
+ // happen to be using a load-store pair to implement it, rather than
+ // a memcpy.
+ if (LoadInst *LI = dyn_cast<LoadInst>(SI->getOperand(0))) {
+ if (!LI->isVolatile() && LI->hasOneUse()) {
+ MemoryDependenceAnalysis &MD = getAnalysis<MemoryDependenceAnalysis>();
+
+ MemDepResult dep = MD.getDependency(LI);
+ CallInst *C = 0;
+ if (dep.isClobber() && !isa<MemCpyInst>(dep.getInst()))
+ C = dyn_cast<CallInst>(dep.getInst());
+
+ if (C) {
+ bool changed = performCallSlotOptzn(LI,
+ SI->getPointerOperand()->stripPointerCasts(),
+ LI->getPointerOperand()->stripPointerCasts(),
+ TD->getTypeStoreSize(SI->getOperand(0)->getType()), C);
+ if (changed) {
+ MD.removeInstruction(SI);
+ SI->eraseFromParent();
+ LI->eraseFromParent();
+ ++NumMemCpyInstr;
+ return true;
+ }
+ }
+ }
+ }
+
LLVMContext &Context = SI->getContext();
// There are two cases that are interesting for this code to handle: memcpy
if (!ByteVal)
return false;
- TargetData *TD = getAnalysisIfAvailable<TargetData>();
- if (!TD) return false;
AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
Module *M = SI->getParent()->getParent()->getParent();
/// performCallSlotOptzn - takes a memcpy and a call that it depends on,
/// and checks for the possibility of a call slot optimization by having
/// the call write its result directly into the destination of the memcpy.
-bool MemCpyOpt::performCallSlotOptzn(MemCpyInst *cpy, CallInst *C) {
+bool MemCpyOpt::performCallSlotOptzn(Instruction *cpy,
+ Value *cpyDest, Value *cpySrc,
+ uint64_t cpyLen, CallInst *C) {
// The general transformation to keep in mind is
//
// call @func(..., src, ...)
// Deliberately get the source and destination with bitcasts stripped away,
// because we'll need to do type comparisons based on the underlying type.
- Value *cpyDest = cpy->getDest();
- Value *cpySrc = cpy->getSource();
- CallSite CS = CallSite::get(C);
-
- // We need to be able to reason about the size of the memcpy, so we require
- // that it be a constant.
- ConstantInt *cpyLength = dyn_cast<ConstantInt>(cpy->getLength());
- if (!cpyLength)
- return false;
+ CallSite CS(C);
// Require that src be an alloca. This simplifies the reasoning considerably.
AllocaInst *srcAlloca = dyn_cast<AllocaInst>(cpySrc);
uint64_t srcSize = TD->getTypeAllocSize(srcAlloca->getAllocatedType()) *
srcArraySize->getZExtValue();
- if (cpyLength->getZExtValue() < srcSize)
+ if (cpyLen < srcSize)
return false;
// Check that accessing the first srcSize bytes of dest will not cause a
// the use analysis, we also need to know that it does not sneakily
// access dest. We rely on AA to figure this out for us.
AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
- if (AA.getModRefInfo(C, cpy->getRawDest(), srcSize) !=
+ if (AA.getModRefInfo(C, cpyDest, srcSize) !=
AliasAnalysis::NoModRef)
return false;
// Remove the memcpy
MD.removeInstruction(cpy);
- cpy->eraseFromParent();
++NumMemCpyInstr;
return true;
}
-/// processMemCpy - perform simplication of memcpy's. If we have memcpy A which
-/// copies X to Y, and memcpy B which copies Y to Z, then we can rewrite B to be
-/// a memcpy from X to Z (or potentially a memmove, depending on circumstances).
-/// This allows later passes to remove the first memcpy altogether.
+/// processMemCpy - perform simplification of memcpy's. If we have memcpy A
+/// which copies X to Y, and memcpy B which copies Y to Z, then we can rewrite
+/// B to be a memcpy from X to Z (or potentially a memmove, depending on
+/// circumstances). This allows later passes to remove the first memcpy
+/// altogether.
bool MemCpyOpt::processMemCpy(MemCpyInst *M) {
MemoryDependenceAnalysis &MD = getAnalysis<MemoryDependenceAnalysis>();
+ // We can only optimize statically-sized memcpy's.
+ ConstantInt *cpyLen = dyn_cast<ConstantInt>(M->getLength());
+ if (!cpyLen) return false;
+
// The are two possible optimizations we can do for memcpy:
// a) memcpy-memcpy xform which exposes redundance for DSE.
// b) call-memcpy xform for return slot optimization.
if (!dep.isClobber())
return false;
if (!isa<MemCpyInst>(dep.getInst())) {
- if (CallInst *C = dyn_cast<CallInst>(dep.getInst()))
- return performCallSlotOptzn(M, C);
+ if (CallInst *C = dyn_cast<CallInst>(dep.getInst())) {
+ bool changed = performCallSlotOptzn(M, M->getDest(), M->getSource(),
+ cpyLen->getZExtValue(), C);
+ if (changed) M->eraseFromParent();
+ return changed;
+ }
return false;
}
M->getParent()->getParent()->getParent(),
M->getIntrinsicID(), ArgTys, 3);
+ // Make sure to use the lesser of the alignment of the source and the dest
+ // since we're changing where we're reading from, but don't want to increase
+ // the alignment past what can be read from or written to.
+ // TODO: Is this worth it if we're creating a less aligned memcpy? For
+ // example we could be moving from movaps -> movq on x86.
+ unsigned Align = std::min(MDep->getAlignmentCst()->getZExtValue(),
+ M->getAlignmentCst()->getZExtValue());
+ LLVMContext &Context = M->getContext();
+ ConstantInt *AlignCI = ConstantInt::get(Type::getInt32Ty(Context), Align);
Value *Args[5] = {
M->getRawDest(), MDep->getRawSource(), M->getLength(),
- M->getAlignmentCst(), M->getVolatileCst()
+ AlignCI, M->getVolatileCst()
};
-
CallInst *C = CallInst::Create(MemCpyFun, Args, Args+5, "", M);
-
// If C and M don't interfere, then this is a valid transformation. If they
// did, this would mean that the two sources overlap, which would be bad.
if (MD.getDependency(C) == dep) {
// If the memmove is a constant size, use it for the alias query, this allows
// us to optimize things like: memmove(P, P+64, 64);
- uint64_t MemMoveSize = ~0ULL;
+ unsigned MemMoveSize = AliasAnalysis::UnknownSize;
if (ConstantInt *Len = dyn_cast<ConstantInt>(M->getLength()))
MemMoveSize = Len->getZExtValue();
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