Commit f6af8ffd authored by Pawel Wodnicki's avatar Pawel Wodnicki
Browse files

Merging r167912: into the 3.2 release branch. 

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

llvm-svn: 168596
parent 3fbacb3b

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

+12 −1
Original line number Diff line number Diff line
@@ -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);

    }

llvm/test/CodeGen/X86/pr14333.ll

0 → 100644
+12 −0
Original line number Diff line number Diff line 
; 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