[PATCH] D16696: InstCombine: fabs(x) * fabs(x) -> x * x

[David Kreitzer via llvm-commits]

DavidKreitzer added inline comments.

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Comment at: lib/Transforms/InstCombine/InstCombineMulDivRem.cpp:621
@@ -620,1 +620,3 @@
 
+      // fabs(X) * fabs(X) -> X * X
+      if (II->getIntrinsicID() == Intrinsic::fabs) {
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arsenm wrote:
> I'm pretty sure this is always safe
If X is -NaN, this transform will change the result of fabs(X) * fabs(X) from +NaN to -NaN. (In all other cases, it will produce the same result.)

So my recommendation is to guard this transformation by I.hasNoNaNs().



http://reviews.llvm.org/D16696