[PATCH] D47041: [ValueTracking] Teach computeKnownBits that the result of an absolute value pattern that uses nsw flag is always positive.

[Craig Topper via Phabricator via llvm-commits]

craig.topper added inline comments.


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Comment at: lib/Analysis/ValueTracking.cpp:1085
+      // will be 0 because that makes abs(INT_MIN) undefined.
+      if (cast<Instruction>(RHS)->hasNoSignedWrap())
+        MaxHighZeros = 1;
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dmgreen wrote:
> Can't RHS be a const?
This patch is dependent on another patch where I made matchSelectPattern return the negation portion in RHS. Previously it always returned a 0, 1, or -1 constant which was failry useless.


https://reviews.llvm.org/D47041