IntrinsicInst *II = cast<IntrinsicInst>(I);
switch (II->getIntrinsicID()) {
- default: assert(0 && "doesn't pass 'hasMemoryWrite' predicate");
+ 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.
}
}
+
+/// isShortenable - Returns true if this instruction can be safely shortened in
+/// length.
+static bool isShortenable(Instruction *I) {
+ // Don't shorten stores for now
+ 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;
+ }
+}
+
/// getStoredPointerOperand - Return the pointer that is being written to.
static Value *getStoredPointerOperand(Instruction *I) {
if (StoreInst *SI = dyn_cast<StoreInst>(I))
IntrinsicInst *II = cast<IntrinsicInst>(I);
switch (II->getIntrinsicID()) {
- default: assert(false && "Unexpected intrinsic!");
+ default: llvm_unreachable("Unexpected intrinsic!");
case Intrinsic::init_trampoline:
return II->getArgOperand(0);
}
}
-static uint64_t getPointerSize(Value *V, AliasAnalysis &AA) {
+static uint64_t getPointerSize(const Value *V, AliasAnalysis &AA) {
const TargetData *TD = AA.getTargetData();
- if (CallInst *CI = dyn_cast<CallInst>(V)) {
- assert(isMalloc(CI) && "Expected Malloc call!");
- if (ConstantInt *C = dyn_cast<ConstantInt>(CI->getArgOperand(0)))
+ if (const CallInst *CI = extractMallocCall(V)) {
+ if (const ConstantInt *C = dyn_cast<ConstantInt>(CI->getArgOperand(0)))
return C->getZExtValue();
- return AliasAnalysis::UnknownSize;
}
if (TD == 0)
return AliasAnalysis::UnknownSize;
- if (AllocaInst *A = dyn_cast<AllocaInst>(V)) {
+ if (
const AllocaInst *A = dyn_cast<AllocaInst>(V)) {
// Get size information for the alloca
- if (ConstantInt *C = dyn_cast<ConstantInt>(A->getArraySize()))
+ if (const ConstantInt *C = dyn_cast<ConstantInt>(A->getArraySize()))
return C->getZExtValue() * TD->getTypeAllocSize(A->getAllocatedType());
- return AliasAnalysis::UnknownSize;
}
- assert(isa<Argument>(V) && "Expected AllocaInst, malloc call or Argument!");
- PointerType *PT = cast<PointerType>(V->getType());
- return TD->getTypeAllocSize(PT->getElementType());
+ if (const Argument *A = dyn_cast<Argument>(V)) {
+ if (A->hasByValAttr())
+ if (PointerType *PT = dyn_cast<PointerType>(A->getType()))
+ return TD->getTypeAllocSize(PT->getElementType());
+ }
+
+ if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) {
+ if (!GV->mayBeOverridden())
+ return TD->getTypeAllocSize(GV->getType()->getElementType());
+ }
+
+ return AliasAnalysis::UnknownSize;
}
-/// isObjectPointerWithTrustworthySize - Return true if the specified Value* is
-/// pointing to an object with a pointer size we can trust.
-static bool isObjectPointerWithTrustworthySize(const Value *V) {
- if (const AllocaInst *AI = dyn_cast<AllocaInst>(V))
- return !AI->isArrayAllocation();
- if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
- return !GV->mayBeOverridden();
- if (const Argument *A = dyn_cast<Argument>(V))
- return A->hasByValAttr();
- if (isMalloc(V))
- return true;
- return false;
+namespace {
+ enum OverwriteResult
+ {
+ OverwriteComplete,
+ OverwriteEnd,
+ OverwriteUnknown
+ };
}
-/// isCompleteOverwrite - Return true if a store to the 'Later' location
+/// isOverwrite - Return 'OverwriteComplete' if a store to the 'Later' location
/// completely overwrites a store to the 'Earlier' location.
-static bool isCompleteOverwrite(const AliasAnalysis::Location &Later,
- const AliasAnalysis::Location &Earlier,
- AliasAnalysis &AA) {
+/// 'OverwriteEnd' if the end of the 'Earlier' location is completely
+/// overwritten by 'Later', or 'OverwriteUnknown' if nothing can be determined
+static OverwriteResult isOverwrite(const AliasAnalysis::Location &Later,
+ const AliasAnalysis::Location &Earlier,
+ AliasAnalysis &AA,
+ int64_t &EarlierOff,
+ int64_t &LaterOff) {
const Value *P1 = Earlier.Ptr->stripPointerCasts();
const Value *P2 = Later.Ptr->stripPointerCasts();
// If we have no TargetData 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)
- return Later.Ptr->getType() == Earlier.Ptr->getType();
- return false;
+ if (AA.getTargetData() == 0 &&
+ Later.Ptr->getType() == Earlier.Ptr->getType())
+ return OverwriteComplete;
+
+ return OverwriteUnknown;
}
// Make sure that the Later size is >= the Earlier size.
- if (Later.Size < Earlier.Size)
- return false;
- return true;
+ if (Later.Size >= Earlier.Size)
+ return OverwriteComplete;
}
// Otherwise, we have to have size information, and the later store has to be
// larger than the earlier one.
if (Later.Size == AliasAnalysis::UnknownSize ||
Earlier.Size == AliasAnalysis::UnknownSize ||
- Later.Size <= Earlier.Size || AA.getTargetData() == 0)
- return false;
+ AA.getTargetData() == 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
// If we can't resolve the same pointers to the same object, then we can't
// analyze them at all.
if (UO1 != UO2)
- return false;
+ return OverwriteUnknown;
// If the "Later" store is to a recognizable object, get its size.
- if (isObjectPointerWithTrustworthySize(UO2)) {
- uint64_t ObjectSize =
- TD.getTypeAllocSize(cast<PointerType>(UO2->getType())->getElementType());
- if (ObjectSize == Later.Size)
- return true;
- }
+ uint64_t ObjectSize = getPointerSize(UO2, AA);
+ if (ObjectSize != AliasAnalysis::UnknownSize)
+ if (ObjectSize == Later.Size && ObjectSize >= Earlier.Size)
+ return OverwriteComplete;
// Okay, we have stores to two completely different pointers. Try to
// decompose the pointer into a "base + constant_offset" form. If the base
// pointers are equal, then we can reason about the two stores.
- int64_t EarlierOff = 0, LaterOff = 0;
+ EarlierOff = 0;
+ LaterOff = 0;
const Value *BP1 = GetPointerBaseWithConstantOffset(P1, EarlierOff, TD);
const Value *BP2 = GetPointerBaseWithConstantOffset(P2, LaterOff, TD);
// If the base pointers still differ, we have two completely different stores.
if (BP1 != BP2)
- return false;
+ return OverwriteUnknown;
// The later store completely overlaps the earlier store if:
//
//
// We have to be careful here as *Off is signed while *.Size is unsigned.
if (EarlierOff >= LaterOff &&
+ Later.Size > Earlier.Size &&
uint64_t(EarlierOff - LaterOff) + Earlier.Size <= Later.Size)
- return true;
+ return OverwriteComplete;
+
+ // The other interesting case is if the later store overwrites the end of
+ // the earlier store
+ //
+ // |--earlier--|
+ // |-- later --|
+ //
+ // In this case we may want to trim the size of earlier to avoid generating
+ // writes to addresses which will definitely be overwritten later
+ if (LaterOff > EarlierOff &&
+ LaterOff < int64_t(EarlierOff + Earlier.Size) &&
+ int64_t(LaterOff + Later.Size) >= int64_t(EarlierOff + Earlier.Size))
+ return OverwriteEnd;
// Otherwise, they don't completely overlap.
- return false;
+ return OverwriteUnknown;
}
/// isPossibleSelfRead - If 'Inst' might be a self read (i.e. a noop copy of a
// If we find a write that is a) removable (i.e., non-volatile), b) is
// completely obliterated by the store to 'Loc', and c) which we know that
// 'Inst' doesn't load from, then we can remove it.
- if (isRemovable(DepWrite) && isCompleteOverwrite(Loc, DepLoc, *AA) &&
+ if (isRemovable(DepWrite) &&
!isPossibleSelfRead(Inst, Loc, DepWrite, *AA)) {
- DEBUG(dbgs() << "DSE: Remove Dead Store:\n DEAD: "
- << *DepWrite << "\n KILLER: " << *Inst << '\n');
-
- // Delete the store and now-dead instructions that feed it.
- DeleteDeadInstruction(DepWrite, *MD);
- ++NumFastStores;
- MadeChange = true;
-
- // DeleteDeadInstruction can delete the current instruction in loop
- // cases, reset BBI.
- BBI = Inst;
- if (BBI != BB.begin())
- --BBI;
- break;
+ int64_t InstWriteOffset, DepWriteOffset;
+ OverwriteResult OR = isOverwrite(Loc, DepLoc, *AA,
+ DepWriteOffset, InstWriteOffset);
+ if (OR == OverwriteComplete) {
+ DEBUG(dbgs() << "DSE: Remove Dead Store:\n DEAD: "
+ << *DepWrite << "\n KILLER: " << *Inst << '\n');
+
+ // Delete the store and now-dead instructions that feed it.
+ DeleteDeadInstruction(DepWrite, *MD);
+ ++NumFastStores;
+ MadeChange = true;
+
+ // DeleteDeadInstruction can delete the current instruction in loop
+ // cases, reset BBI.
+ BBI = Inst;
+ if (BBI != BB.begin())
+ --BBI;
+ break;
+ } else if (OR == OverwriteEnd && isShortenable(DepWrite)) {
+ // TODO: base this on the target vector size so that if the earlier
+ // store was too small to get vector writes anyway then its likely
+ // a good idea to shorten it
+ // Power of 2 vector writes are probably always a bad idea to optimize
+ // as any store/memset/memcpy is likely using vector instructions so
+ // shortening it to not vector size is likely to be slower
+ MemIntrinsic* DepIntrinsic = cast<MemIntrinsic>(DepWrite);
+ unsigned DepWriteAlign = DepIntrinsic->getAlignment();
+ if (llvm::isPowerOf2_64(InstWriteOffset) ||
+ ((DepWriteAlign != 0) && InstWriteOffset % DepWriteAlign == 0)) {
+
+ DEBUG(dbgs() << "DSE: Remove Dead Store:\n OW END: "
+ << *DepWrite << "\n KILLER (offset "
+ << InstWriteOffset << ", "
+ << DepLoc.Size << ")"
+ << *Inst << '\n');
+
+ Value* DepWriteLength = DepIntrinsic->getLength();
+ Value* TrimmedLength = ConstantInt::get(DepWriteLength->getType(),
+ InstWriteOffset -
+ DepWriteOffset);
+ DepIntrinsic->setLength(TrimmedLength);
+ MadeChange = true;
+ }
+ }
}
// If this is a may-aliased store that is clobbering the store value, we
BasicBlock *BB, DominatorTree *DT) {
for (pred_iterator I = pred_begin(BB), E = pred_end(BB); I != E; ++I) {
BasicBlock *Pred = *I;
+ if (Pred == BB) continue;
TerminatorInst *PredTI = Pred->getTerminator();
if (PredTI->getNumSuccessors() != 1)
continue;
I != E; ++I)
DeadStackObjects.erase(*I);
}
-
projects / oota-llvm.git / blobdiff