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Have SCEV turn sext(x) into zext(x) when x is s>= 0. This applies many times in
"make check" alone. llvm-svn: 124046
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@ -1035,6 +1035,10 @@ const SCEV *ScalarEvolution::getSignExtendExpr(const SCEV *Op,
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void *IP = 0;
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if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
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// If the input value is provably positive, build a zext instead.
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if (isKnownNonNegative(Op))
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return getZeroExtendExpr(Op, Ty);
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// If the input value is a chrec scev, and we can prove that the value
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// did not overflow the old, smaller, value, we can sign extend all of the
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// operands (often constants). This allows analysis of something like
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