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[InstCombine] Reduce visitLoadInst() code duplication. NFCI. 

llvm-svn: 300717
This commit is contained in:
Davide Italiano 2017-04-19 17:26:57 +00:00
parent b2566da849
commit ffcb4df204
1 changed files with 18 additions and 20 deletions
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38
llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
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@ -931,6 +931,18 @@ static Instruction *replaceGEPIdxWithZero(InstCombiner &IC, Value *Ptr,
return nullptr;
}
static bool canSimplifyNullLoadOrGEP(LoadInst &LI, Value *Op) {
if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Op)) {
const Value *GEPI0 = GEPI->getOperand(0);
if (isa<ConstantPointerNull>(GEPI0) && GEPI->getPointerAddressSpace() == 0)
return true;
}
if (isa<UndefValue>(Op) ||
(isa<ConstantPointerNull>(Op) && LI.getPointerAddressSpace() == 0))
return true;
return false;
}
Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
Value *Op = LI.getOperand(0);
@ -979,27 +991,13 @@ Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
if (!LI.isUnordered()) return nullptr;
// load(gep null, ...) -> unreachable
if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Op)) {
const Value *GEPI0 = GEPI->getOperand(0);
// TODO: Consider a target hook for valid address spaces for this xform.
if (isa<ConstantPointerNull>(GEPI0) && GEPI->getPointerAddressSpace() == 0){
// Insert a new store to null instruction before the load to indicate
// that this code is not reachable. We do this instead of inserting
// an unreachable instruction directly because we cannot modify the
// CFG.
new StoreInst(UndefValue::get(LI.getType()),
Constant::getNullValue(Op->getType()), &LI);
return replaceInstUsesWith(LI, UndefValue::get(LI.getType()));
}
}
// load null/undef -> unreachable
// TODO: Consider a target hook for valid address spaces for this xform.
if (isa<UndefValue>(Op) ||
(isa<ConstantPointerNull>(Op) && LI.getPointerAddressSpace() == 0)) {
// Insert a new store to null instruction before the load to indicate that
// this code is not reachable. We do this instead of inserting an
// unreachable instruction directly because we cannot modify the CFG.
// TODO: Consider a target hook for valid address spaces for this xforms.
if (canSimplifyNullLoadOrGEP(LI, Op)) {
// Insert a new store to null instruction before the load to indicate
// that this code is not reachable. We do this instead of inserting
// an unreachable instruction directly because we cannot modify the
// CFG.
new StoreInst(UndefValue::get(LI.getType()),
Constant::getNullValue(Op->getType()), &LI);
return replaceInstUsesWith(LI, UndefValue::get(LI.getType()));