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Handle DAG CSE adding new uses during ReplaceAllUsesWith. Fixes PR14333.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167912 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Rafael Espindola 2012-11-14 05:08:56 +00:00
parent c35ce700fe
commit 8e2b8ae3b1
2 changed files with 24 additions and 1 deletions
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13
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -7728,7 +7728,18 @@ bool DAGCombiner::MergeConsecutiveStores(StoreSDNode* St) {
if (StoreNodes[i].MemNode == EarliestOp)
continue;
StoreSDNode *St = cast<StoreSDNode>(StoreNodes[i].MemNode);
DAG.ReplaceAllUsesOfValueWith(SDValue(St, 0), St->getChain());
// ReplaceAllUsesWith will replace all uses that existed when it was
// called, but graph optimizations may cause new ones to appear. For
// example, the case in pr14333 looks like
//
// St's chain -> St -> another store -> X
//
// And the only difference from St to the other store is the chain.
// When we change it's chain to be St's chain they become identical,
// get CSEed and the net result is that X is now a use of St.
// Since we know that St is redundant, just iterate.
while (!St->use_empty())
DAG.ReplaceAllUsesWith(SDValue(St, 0), St->getChain());
removeFromWorkList(St);
DAG.DeleteNode(St);
}

12
test/CodeGen/X86/pr14333.ll Normal file
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@ -0,0 +1,12 @@
; RUN: llc -mtriple=x86_64-unknown-unknown < %s
%foo = type { i64, i64 }
define void @bar(%foo* %zed) {
%tmp = getelementptr inbounds %foo* %zed, i64 0, i32 0
store i64 0, i64* %tmp, align 8
%tmp2 = getelementptr inbounds %foo* %zed, i64 0, i32 1
store i64 0, i64* %tmp2, align 8
%tmp3 = bitcast %foo* %zed to i8*
call void @llvm.memset.p0i8.i64(i8* %tmp3, i8 0, i64 16, i32 8, i1 false)
ret void
}
declare void @llvm.memset.p0i8.i64(i8* nocapture, i8, i64, i32, i1) nounwind