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improve DSE when TargetData is not around, based on work by

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Hans Wennborg!

llvm-svn: 86067
This commit is contained in:
Chris Lattner 2009-11-04 23:20:12 +00:00
parent 2867641b64
commit a003aee613
3 changed files with 31 additions and 6 deletions
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19
lib/Transforms/Scalar/DeadStoreElimination.cpp
View File

@ -78,6 +78,21 @@ static RegisterPass<DSE> X("dse", "Dead Store Elimination");
FunctionPass *llvm::createDeadStoreEliminationPass() { return new DSE(); }
/// isValueAtLeastAsBigAs - Return true if V1 is greater than or equal to the
/// stored size of V2. This returns false if we don't know.
///
static bool isValueAtLeastAsBigAs(Value *V1, Value *V2, const TargetData *TD) {
const Type *V1Ty = V1->getType(), *V2Ty = V2->getType();
// Exactly the same type, must have exactly the same size.
if (V1Ty == V2Ty) return true;
// If we don't have target data, we don't know.
if (TD == 0) return false;
return TD->getTypeStoreSize(V1Ty) >= TD->getTypeStoreSize(V2Ty);
}
bool DSE::runOnBasicBlock(BasicBlock &BB) {
MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>();
TD = getAnalysisIfAvailable<TargetData>();
@ -118,9 +133,7 @@ bool DSE::runOnBasicBlock(BasicBlock &BB) {
// If this is a store-store dependence, then the previous store is dead so
// long as this store is at least as big as it.
if (StoreInst *DepStore = dyn_cast<StoreInst>(InstDep.getInst()))
if (TD &&
TD->getTypeStoreSize(DepStore->getOperand(0)->getType()) <=
TD->getTypeStoreSize(SI->getOperand(0)->getType())) {
if (isValueAtLeastAsBigAs(SI->getOperand(0), DepStore->getOperand(0),TD)){
// Delete the store and now-dead instructions that feed it.
DeleteDeadInstruction(DepStore);
NumFastStores++;

3
lib/Transforms/Scalar/JumpThreading.cpp
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@ -68,9 +68,6 @@ namespace {
static char ID; // Pass identification
JumpThreading() : FunctionPass(&ID) {}
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
}
bool runOnFunction(Function &F);
void FindLoopHeaders(Function &F);

15
test/Transforms/DeadStoreElimination/no-targetdata.ll Normal file
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@ -0,0 +1,15 @@
; RUN: opt %s -dse -S | FileCheck %s
declare void @test1f()
define void @test1(i32* noalias %p) {
store i32 1, i32* %p;
call void @test1f()
store i32 2, i32 *%p
ret void
; CHECK: define void @test1
; CHECK-NOT: store
; CHECK-NEXT: call void
; CHECK-NEXT: store i32 2
; CHECK-NEXT: ret void
}