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Evan pointed out that folding sext to zext may not be correct

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if the zext is not legal.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@50368 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2008-04-28 18:47:17 +00:00
parent ebc3a3a3b2
commit 187db7b950
1 changed files with 2 additions and 1 deletions
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3
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -2888,7 +2888,8 @@ SDOperand DAGCombiner::visitSIGN_EXTEND(SDNode *N) {
}
// fold (sext x) -> (zext x) if the sign bit is known zero.
if (DAG.SignBitIsZero(N0))
if ((!AfterLegalize || TLI.isOperationLegal(ISD::ZERO_EXTEND, VT)) &&
DAG.SignBitIsZero(N0))
return DAG.getNode(ISD::ZERO_EXTEND, VT, N0);
return SDOperand();