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Teach DAGCombine to convert (sext x) to (zext x) when the
sign-bit of x is known to be zero. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@50357 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -2887,6 +2887,10 @@ SDOperand DAGCombiner::visitSIGN_EXTEND(SDNode *N) {
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if (SCC.Val) return SCC;
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}
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// fold (sext x) -> (zext x) if the sign bit is known zero.
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if (DAG.SignBitIsZero(N0))
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return DAG.getNode(ISD::ZERO_EXTEND, VT, N0);
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return SDOperand();
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}
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