[PATCH] D84963: [ValueTracking] Add basic computeKnownBits support for llvm.abs intrinsic
Sanjay Patel via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Thu Jul 30 16:02:24 PDT 2020
spatel added a comment.
The SelectionDAG version does the following, so it would make sense to adapt these here:
// If the source's MSB is zero then we know the rest of the bits already.
if (Known2.isNonNegative()) {
Known.Zero = Known2.Zero;
Known.One = Known2.One;
break;
}
// We only know that the absolute values's MSB will be zero iff there is
// a set bit that isn't the sign bit (otherwise it could be INT_MIN).
Known2.One.clearSignBit();
if (Known2.One.getBoolValue()) {
Known.Zero = APInt::getSignMask(BitWidth);
break;
}
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https://reviews.llvm.org/D84963/new/
https://reviews.llvm.org/D84963
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