[llvm-commits] [llvm] r167912 - in /llvm/trunk: lib/CodeGen/SelectionDAG/DAGCombiner.cpp test/CodeGen/X86/pr14333.ll

[Rafael Espíndola]

Can we include this in 3.2?

On 14 November 2012 00:08, Rafael Espindola <rafael.espindola at gmail.com> wrote:
> Author: rafael
> Date: Tue Nov 13 23:08:56 2012
> New Revision: 167912
>
> URL: http://llvm.org/viewvc/llvm-project?rev=167912&view=rev
> Log:
> Handle DAG CSE adding new uses during ReplaceAllUsesWith. Fixes PR14333.
>
> Added:
>     llvm/trunk/test/CodeGen/X86/pr14333.ll
> Modified:
>     llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
>
> Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=167912&r1=167911&r2=167912&view=diff
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
> +++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Tue Nov 13 23:08:56 2012
> @@ -7728,7 +7728,18 @@
>        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);
>      }
>
> Added: llvm/trunk/test/CodeGen/X86/pr14333.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/pr14333.ll?rev=167912&view=auto
> ==============================================================================
> --- llvm/trunk/test/CodeGen/X86/pr14333.ll (added)
> +++ llvm/trunk/test/CodeGen/X86/pr14333.ll Tue Nov 13 23:08:56 2012
> @@ -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
>
>
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