[PATCH] D27932: InstSimplify: Eliminate fabs on known positive

[Eli Friedman via Phabricator via llvm-commits]

efriedma added inline comments.


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Comment at: lib/Analysis/ValueTracking.cpp:2592
+    return !CFP->getValueAPF().isNegative() ||
+           (IncludeNeg0 && CFP->getValueAPF().isZero());
+  }
----------------
Maybe explicitly handle NaNs here to make it more clear?


================
Comment at: lib/Analysis/ValueTracking.cpp:2614
     if (I->getOperand(0) == I->getOperand(1))
       return true;
     LLVM_FALLTHROUGH;
----------------
IIRC, A*A->A if A is a NaN, so fabs(x*x) isn't equivalent to x*x.


https://reviews.llvm.org/D27932