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-rw-r--r--lib/Transforms/Scalar/DeadStoreElimination.cpp203
1 files changed, 127 insertions, 76 deletions
diff --git a/lib/Transforms/Scalar/DeadStoreElimination.cpp b/lib/Transforms/Scalar/DeadStoreElimination.cpp
index 8b1283f..736cc05 100644
--- a/lib/Transforms/Scalar/DeadStoreElimination.cpp
+++ b/lib/Transforms/Scalar/DeadStoreElimination.cpp
@@ -29,7 +29,8 @@
#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/Analysis/MemoryDependenceAnalysis.h"
#include "llvm/Analysis/ValueTracking.h"
-#include "llvm/Target/TargetData.h"
+#include "llvm/DataLayout.h"
+#include "llvm/Target/TargetLibraryInfo.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Support/Debug.h"
#include "llvm/ADT/SetVector.h"
@@ -45,6 +46,7 @@ namespace {
AliasAnalysis *AA;
MemoryDependenceAnalysis *MD;
DominatorTree *DT;
+ const TargetLibraryInfo *TLI;
static char ID; // Pass identification, replacement for typeid
DSE() : FunctionPass(ID), AA(0), MD(0), DT(0) {
@@ -55,6 +57,7 @@ namespace {
AA = &getAnalysis<AliasAnalysis>();
MD = &getAnalysis<MemoryDependenceAnalysis>();
DT = &getAnalysis<DominatorTree>();
+ TLI = AA->getTargetLibraryInfo();
bool Changed = false;
for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
@@ -106,6 +109,7 @@ FunctionPass *llvm::createDeadStoreEliminationPass() { return new DSE(); }
///
static void DeleteDeadInstruction(Instruction *I,
MemoryDependenceAnalysis &MD,
+ const TargetLibraryInfo *TLI,
SmallSetVector<Value*, 16> *ValueSet = 0) {
SmallVector<Instruction*, 32> NowDeadInsts;
@@ -130,7 +134,7 @@ static void DeleteDeadInstruction(Instruction *I,
if (!Op->use_empty()) continue;
if (Instruction *OpI = dyn_cast<Instruction>(Op))
- if (isInstructionTriviallyDead(OpI))
+ if (isInstructionTriviallyDead(OpI, TLI))
NowDeadInsts.push_back(OpI);
}
@@ -143,7 +147,7 @@ static void DeleteDeadInstruction(Instruction *I,
/// hasMemoryWrite - Does this instruction write some memory? This only returns
/// true for things that we can analyze with other helpers below.
-static bool hasMemoryWrite(Instruction *I) {
+static bool hasMemoryWrite(Instruction *I, const TargetLibraryInfo *TLI) {
if (isa<StoreInst>(I))
return true;
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
@@ -158,6 +162,26 @@ static bool hasMemoryWrite(Instruction *I) {
return true;
}
}
+ if (CallSite CS = I) {
+ if (Function *F = CS.getCalledFunction()) {
+ if (TLI && TLI->has(LibFunc::strcpy) &&
+ F->getName() == TLI->getName(LibFunc::strcpy)) {
+ return true;
+ }
+ if (TLI && TLI->has(LibFunc::strncpy) &&
+ F->getName() == TLI->getName(LibFunc::strncpy)) {
+ return true;
+ }
+ if (TLI && TLI->has(LibFunc::strcat) &&
+ F->getName() == TLI->getName(LibFunc::strcat)) {
+ return true;
+ }
+ if (TLI && TLI->has(LibFunc::strncat) &&
+ F->getName() == TLI->getName(LibFunc::strncat)) {
+ return true;
+ }
+ }
+ }
return false;
}
@@ -175,7 +199,7 @@ getLocForWrite(Instruction *Inst, AliasAnalysis &AA) {
// If we don't have target data around, an unknown size in Location means
// that we should use the size of the pointee type. This isn't valid for
// memset/memcpy, which writes more than an i8.
- if (Loc.Size == AliasAnalysis::UnknownSize && AA.getTargetData() == 0)
+ if (Loc.Size == AliasAnalysis::UnknownSize && AA.getDataLayout() == 0)
return AliasAnalysis::Location();
return Loc;
}
@@ -189,7 +213,7 @@ getLocForWrite(Instruction *Inst, AliasAnalysis &AA) {
// If we don't have target data around, an unknown size in Location means
// that we should use the size of the pointee type. This isn't valid for
// init.trampoline, which writes more than an i8.
- if (AA.getTargetData() == 0) return AliasAnalysis::Location();
+ if (AA.getDataLayout() == 0) return AliasAnalysis::Location();
// FIXME: We don't know the size of the trampoline, so we can't really
// handle it here.
@@ -205,7 +229,8 @@ getLocForWrite(Instruction *Inst, AliasAnalysis &AA) {
/// instruction if any.
static AliasAnalysis::Location
getLocForRead(Instruction *Inst, AliasAnalysis &AA) {
- assert(hasMemoryWrite(Inst) && "Unknown instruction case");
+ assert(hasMemoryWrite(Inst, AA.getTargetLibraryInfo()) &&
+ "Unknown instruction case");
// The only instructions that both read and write are the mem transfer
// instructions (memcpy/memmove).
@@ -222,23 +247,29 @@ static bool isRemovable(Instruction *I) {
if (StoreInst *SI = dyn_cast<StoreInst>(I))
return SI->isUnordered();
- IntrinsicInst *II = cast<IntrinsicInst>(I);
- switch (II->getIntrinsicID()) {
- default: llvm_unreachable("doesn't pass 'hasMemoryWrite' predicate");
- case Intrinsic::lifetime_end:
- // Never remove dead lifetime_end's, e.g. because it is followed by a
- // free.
- return false;
- case Intrinsic::init_trampoline:
- // Always safe to remove init_trampoline.
- return true;
+ if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
+ switch (II->getIntrinsicID()) {
+ default: llvm_unreachable("doesn't pass 'hasMemoryWrite' predicate");
+ case Intrinsic::lifetime_end:
+ // Never remove dead lifetime_end's, e.g. because it is followed by a
+ // free.
+ return false;
+ case Intrinsic::init_trampoline:
+ // Always safe to remove init_trampoline.
+ return true;
- case Intrinsic::memset:
- case Intrinsic::memmove:
- case Intrinsic::memcpy:
- // Don't remove volatile memory intrinsics.
- return !cast<MemIntrinsic>(II)->isVolatile();
+ case Intrinsic::memset:
+ case Intrinsic::memmove:
+ case Intrinsic::memcpy:
+ // Don't remove volatile memory intrinsics.
+ return !cast<MemIntrinsic>(II)->isVolatile();
+ }
}
+
+ if (CallSite CS = I)
+ return CS.getInstruction()->use_empty();
+
+ return false;
}
@@ -249,14 +280,19 @@ static bool isShortenable(Instruction *I) {
if (isa<StoreInst>(I))
return false;
- IntrinsicInst *II = cast<IntrinsicInst>(I);
- switch (II->getIntrinsicID()) {
- default: return false;
- case Intrinsic::memset:
- case Intrinsic::memcpy:
- // Do shorten memory intrinsics.
- return true;
+ if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
+ switch (II->getIntrinsicID()) {
+ default: return false;
+ case Intrinsic::memset:
+ case Intrinsic::memcpy:
+ // Do shorten memory intrinsics.
+ return true;
+ }
}
+
+ // Don't shorten libcalls calls for now.
+
+ return false;
}
/// getStoredPointerOperand - Return the pointer that is being written to.
@@ -266,17 +302,23 @@ static Value *getStoredPointerOperand(Instruction *I) {
if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(I))
return MI->getDest();
- IntrinsicInst *II = cast<IntrinsicInst>(I);
- switch (II->getIntrinsicID()) {
- default: llvm_unreachable("Unexpected intrinsic!");
- case Intrinsic::init_trampoline:
- return II->getArgOperand(0);
+ if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
+ switch (II->getIntrinsicID()) {
+ default: llvm_unreachable("Unexpected intrinsic!");
+ case Intrinsic::init_trampoline:
+ return II->getArgOperand(0);
+ }
}
+
+ CallSite CS = I;
+ // All the supported functions so far happen to have dest as their first
+ // argument.
+ return CS.getArgument(0);
}
static uint64_t getPointerSize(const Value *V, AliasAnalysis &AA) {
uint64_t Size;
- if (getObjectSize(V, Size, AA.getTargetData()))
+ if (getObjectSize(V, Size, AA.getDataLayout(), AA.getTargetLibraryInfo()))
return Size;
return AliasAnalysis::UnknownSize;
}
@@ -309,10 +351,10 @@ static OverwriteResult isOverwrite(const AliasAnalysis::Location &Later,
// comparison.
if (Later.Size == AliasAnalysis::UnknownSize ||
Earlier.Size == AliasAnalysis::UnknownSize) {
- // If we have no TargetData information around, then the size of the store
+ // If we have no DataLayout information around, then the size of the store
// is inferrable from the pointee type. If they are the same type, then
// we know that the store is safe.
- if (AA.getTargetData() == 0 &&
+ if (AA.getDataLayout() == 0 &&
Later.Ptr->getType() == Earlier.Ptr->getType())
return OverwriteComplete;
@@ -328,13 +370,13 @@ static OverwriteResult isOverwrite(const AliasAnalysis::Location &Later,
// larger than the earlier one.
if (Later.Size == AliasAnalysis::UnknownSize ||
Earlier.Size == AliasAnalysis::UnknownSize ||
- AA.getTargetData() == 0)
+ AA.getDataLayout() == 0)
return OverwriteUnknown;
// Check to see if the later store is to the entire object (either a global,
// an alloca, or a byval argument). If so, then it clearly overwrites any
// other store to the same object.
- const TargetData &TD = *AA.getTargetData();
+ const DataLayout &TD = *AA.getDataLayout();
const Value *UO1 = GetUnderlyingObject(P1, &TD),
*UO2 = GetUnderlyingObject(P2, &TD);
@@ -454,13 +496,13 @@ bool DSE::runOnBasicBlock(BasicBlock &BB) {
Instruction *Inst = BBI++;
// Handle 'free' calls specially.
- if (CallInst *F = isFreeCall(Inst)) {
+ if (CallInst *F = isFreeCall(Inst, TLI)) {
MadeChange |= HandleFree(F);
continue;
}
// If we find something that writes memory, get its memory dependence.
- if (!hasMemoryWrite(Inst))
+ if (!hasMemoryWrite(Inst, TLI))
continue;
MemDepResult InstDep = MD->getDependency(Inst);
@@ -483,7 +525,7 @@ bool DSE::runOnBasicBlock(BasicBlock &BB) {
// in case we need it.
WeakVH NextInst(BBI);
- DeleteDeadInstruction(SI, *MD);
+ DeleteDeadInstruction(SI, *MD, TLI);
if (NextInst == 0) // Next instruction deleted.
BBI = BB.begin();
@@ -530,7 +572,7 @@ bool DSE::runOnBasicBlock(BasicBlock &BB) {
<< *DepWrite << "\n KILLER: " << *Inst << '\n');
// Delete the store and now-dead instructions that feed it.
- DeleteDeadInstruction(DepWrite, *MD);
+ DeleteDeadInstruction(DepWrite, *MD, TLI);
++NumFastStores;
MadeChange = true;
@@ -627,7 +669,7 @@ bool DSE::HandleFree(CallInst *F) {
MemDepResult Dep = MD->getPointerDependencyFrom(Loc, false, InstPt, BB);
while (Dep.isDef() || Dep.isClobber()) {
Instruction *Dependency = Dep.getInst();
- if (!hasMemoryWrite(Dependency) || !isRemovable(Dependency))
+ if (!hasMemoryWrite(Dependency, TLI) || !isRemovable(Dependency))
break;
Value *DepPointer =
@@ -640,7 +682,7 @@ bool DSE::HandleFree(CallInst *F) {
Instruction *Next = llvm::next(BasicBlock::iterator(Dependency));
// DCE instructions only used to calculate that store
- DeleteDeadInstruction(Dependency, *MD);
+ DeleteDeadInstruction(Dependency, *MD, TLI);
++NumFastStores;
MadeChange = true;
@@ -659,6 +701,22 @@ bool DSE::HandleFree(CallInst *F) {
return MadeChange;
}
+namespace {
+ struct CouldRef {
+ typedef Value *argument_type;
+ const CallSite CS;
+ AliasAnalysis *AA;
+
+ bool operator()(Value *I) {
+ // See if the call site touches the value.
+ AliasAnalysis::ModRefResult A =
+ AA->getModRefInfo(CS, I, getPointerSize(I, *AA));
+
+ return A == AliasAnalysis::ModRef || A == AliasAnalysis::Ref;
+ }
+ };
+}
+
/// handleEndBlock - Remove dead stores to stack-allocated locations in the
/// function end block. Ex:
/// %A = alloca i32
@@ -680,7 +738,7 @@ bool DSE::handleEndBlock(BasicBlock &BB) {
// Okay, so these are dead heap objects, but if the pointer never escapes
// then it's leaked by this function anyways.
- else if (isAllocLikeFn(I) && !PointerMayBeCaptured(I, true, true))
+ else if (isAllocLikeFn(I, TLI) && !PointerMayBeCaptured(I, true, true))
DeadStackObjects.insert(I);
}
@@ -696,7 +754,7 @@ bool DSE::handleEndBlock(BasicBlock &BB) {
--BBI;
// If we find a store, check to see if it points into a dead stack value.
- if (hasMemoryWrite(BBI) && isRemovable(BBI)) {
+ if (hasMemoryWrite(BBI, TLI) && isRemovable(BBI)) {
// See through pointer-to-pointer bitcasts
SmallVector<Value *, 4> Pointers;
GetUnderlyingObjects(getStoredPointerOperand(BBI), Pointers);
@@ -724,7 +782,7 @@ bool DSE::handleEndBlock(BasicBlock &BB) {
dbgs() << '\n');
// DCE instructions only used to calculate that store.
- DeleteDeadInstruction(Dead, *MD, &DeadStackObjects);
+ DeleteDeadInstruction(Dead, *MD, TLI, &DeadStackObjects);
++NumFastStores;
MadeChange = true;
continue;
@@ -732,9 +790,9 @@ bool DSE::handleEndBlock(BasicBlock &BB) {
}
// Remove any dead non-memory-mutating instructions.
- if (isInstructionTriviallyDead(BBI)) {
+ if (isInstructionTriviallyDead(BBI, TLI)) {
Instruction *Inst = BBI++;
- DeleteDeadInstruction(Inst, *MD, &DeadStackObjects);
+ DeleteDeadInstruction(Inst, *MD, TLI, &DeadStackObjects);
++NumFastOther;
MadeChange = true;
continue;
@@ -750,7 +808,7 @@ bool DSE::handleEndBlock(BasicBlock &BB) {
if (CallSite CS = cast<Value>(BBI)) {
// Remove allocation function calls from the list of dead stack objects;
// there can't be any references before the definition.
- if (isAllocLikeFn(BBI))
+ if (isAllocLikeFn(BBI, TLI))
DeadStackObjects.remove(BBI);
// If this call does not access memory, it can't be loading any of our
@@ -760,20 +818,8 @@ bool DSE::handleEndBlock(BasicBlock &BB) {
// If the call might load from any of our allocas, then any store above
// the call is live.
- SmallVector<Value*, 8> LiveAllocas;
- for (SmallSetVector<Value*, 16>::iterator I = DeadStackObjects.begin(),
- E = DeadStackObjects.end(); I != E; ++I) {
- // See if the call site touches it.
- AliasAnalysis::ModRefResult A =
- AA->getModRefInfo(CS, *I, getPointerSize(*I, *AA));
-
- if (A == AliasAnalysis::ModRef || A == AliasAnalysis::Ref)
- LiveAllocas.push_back(*I);
- }
-
- for (SmallVector<Value*, 8>::iterator I = LiveAllocas.begin(),
- E = LiveAllocas.end(); I != E; ++I)
- DeadStackObjects.remove(*I);
+ CouldRef Pred = { CS, AA };
+ DeadStackObjects.remove_if(Pred);
// If all of the allocas were clobbered by the call then we're not going
// to find anything else to process.
@@ -816,6 +862,20 @@ bool DSE::handleEndBlock(BasicBlock &BB) {
return MadeChange;
}
+namespace {
+ struct CouldAlias {
+ typedef Value *argument_type;
+ const AliasAnalysis::Location &LoadedLoc;
+ AliasAnalysis *AA;
+
+ bool operator()(Value *I) {
+ // See if the loaded location could alias the stack location.
+ AliasAnalysis::Location StackLoc(I, getPointerSize(I, *AA));
+ return !AA->isNoAlias(StackLoc, LoadedLoc);
+ }
+ };
+}
+
/// RemoveAccessedObjects - Check to see if the specified location may alias any
/// of the stack objects in the DeadStackObjects set. If so, they become live
/// because the location is being loaded.
@@ -834,16 +894,7 @@ void DSE::RemoveAccessedObjects(const AliasAnalysis::Location &LoadedLoc,
return;
}
- SmallVector<Value*, 16> NowLive;
- for (SmallSetVector<Value*, 16>::iterator I = DeadStackObjects.begin(),
- E = DeadStackObjects.end(); I != E; ++I) {
- // See if the loaded location could alias the stack location.
- AliasAnalysis::Location StackLoc(*I, getPointerSize(*I, *AA));
- if (!AA->isNoAlias(StackLoc, LoadedLoc))
- NowLive.push_back(*I);
- }
-
- for (SmallVector<Value*, 16>::iterator I = NowLive.begin(), E = NowLive.end();
- I != E; ++I)
- DeadStackObjects.remove(*I);
+ // Remove objects that could alias LoadedLoc.
+ CouldAlias Pred = { LoadedLoc, AA };
+ DeadStackObjects.remove_if(Pred);
}
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