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This case is solved by Scalar Replacement of Aggregates (DT) and

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Early CSE pass so this patch reverts it to original source code.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127574 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jin-Gu Kang 2011-03-14 01:21:00 +00:00
parent c2ec0f974d
commit 948d9e7ec7
1 changed files with 3 additions and 25 deletions
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28
lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
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@ -429,31 +429,9 @@ Instruction *InstCombiner::visitStoreInst(StoreInst &SI) {
// the pointer we're loading and is producing the pointer we're storing,
// then *this* store is dead (X = load P; store X -> P).
if (LoadInst *LI = dyn_cast<LoadInst>(BBI)) {
if (equivalentAddressValues(LI->getOperand(0), Ptr) &&
!SI.isVolatile()) {
if (LI == Val)
return EraseInstFromFunction(SI);
// load and store reference same memory location, the memory location
// is represented by getelementptr with two uses (load and store) and
// the getelementptr's base is alloca with single use. At this point,
// instructions from alloca to store can be removed.
// (this pattern is generated when bitfield is accessed.)
// For example,
// %u = alloca %struct.test, align 4 ; [#uses=1]
// %0 = getelementptr inbounds %struct.test* %u, i32 0, i32 0;[#uses=2]
// %1 = load i8* %0, align 4 ; [#uses=1]
// %2 = and i8 %1, -16 ; [#uses=1]
// %3 = or i8 %2, 5 ; [#uses=1]
// store i8 %3, i8* %0, align 4
if (Ptr->hasNUses(2)) {
if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Ptr)) {
if (isa<AllocaInst>(GEP->getOperand(0))) {
if (GEP->getOperand(0)->hasOneUse())
return EraseInstFromFunction(SI);
}
}
}
}
if (LI == Val && equivalentAddressValues(LI->getOperand(0), Ptr) &&
!SI.isVolatile())
return EraseInstFromFunction(SI);
// Otherwise, this is a load from some other location. Stores before it
// may not be dead.