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Don't zap back to back volatile load/stores

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@41759 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2007-09-07 05:33:03 +00:00
parent 718cb665ca
commit a54c7eb157
2 changed files with 15 additions and 1 deletions
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2
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -9066,7 +9066,7 @@ 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 (LI == Val && LI->getOperand(0) == Ptr) {
if (LI == Val && LI->getOperand(0) == Ptr && !SI.isVolatile()) {
EraseInstFromFunction(SI);
++NumCombined;
return 0;

14
test/Transforms/InstCombine/volatile_store.ll Normal file
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@ -0,0 +1,14 @@
; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {volatile store}
; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {volatile load}
@x = weak global i32 0 ; <i32*> [#uses=2]
define void @self_assign_1() {
entry:
%tmp = volatile load i32* @x ; <i32> [#uses=1]
volatile store i32 %tmp, i32* @x
br label %return
return: ; preds = %entry
ret void
}