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[IRCE][NFC] Add no wrap flags to no-wrapping SCEV calculation 

In a lambda where we expect to have result within bounds, add respective `nsw/nuw` flags to
help SCEV just in case if it fails to figure them out on its own.

Differential Revision: https://reviews.llvm.org/D40168

llvm-svn: 318898
This commit is contained in:
Max Kazantsev 2017-11-23 06:14:39 +00:00
parent 69b903eecb
commit 716e647d74
1 changed files with 3 additions and 2 deletions
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5
llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
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@ -1667,7 +1667,8 @@ InductiveRangeCheck::computeSafeIterationSpace(
// Rule 3: Y <s (X - SINT_MAX) ---> (X - SINT_MAX).
// It gives us smax(Y, X - SINT_MAX) to substract in all cases.
const SCEV *XMinusSIntMax = SE.getMinusSCEV(X, SIntMax);
return SE.getMinusSCEV(X, SE.getSMaxExpr(Y, XMinusSIntMax));
return SE.getMinusSCEV(X, SE.getSMaxExpr(Y, XMinusSIntMax),
SCEV::FlagNSW);
} else
// X is a number from unsigned range, Y is interpreted as signed.
// Even if Y is SINT_MIN, (X - Y) does not reach UINT_MAX. So the only
@ -1679,7 +1680,7 @@ InductiveRangeCheck::computeSafeIterationSpace(
// If 0 <= X < Y, we should stop at 0 and can only substract X.
// Rule 3: Y >s X ---> X.
// It gives us smin(X, Y) to substract in all cases.
return SE.getMinusSCEV(X, SE.getSMinExpr(X, Y));
return SE.getMinusSCEV(X, SE.getSMinExpr(X, Y), SCEV::FlagNUW);
};
const SCEV *M = SE.getMinusSCEV(C, A);
const SCEV *Zero = SE.getZero(M->getType());