[PATCH] D49040: [SLC] Simplify pow(x, 0.333...) to cbrt(x)

[Eli Friedman via Phabricator via llvm-commits]

efriedma added a comment.

Missing testcases.

I'm not sure what you mean by "a hard time matching the exponent"; I can't see any reason float would be different from double, assuming you're actually using the right constant.



================
Comment at: llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp:1125
+  // Only in finite and normal math.
+  if (!Pow->hasNoInfs() || !Pow->hasNoNaNs())
+    return nullptr;
----------------
You need nsz: `pow(-0., 1./3)` returns +0, but `cbrt(-0.)` returns -0.

I think I'd prefer to require afn for this; not sure it's necessary, but better to be safe.

Please add explicit comments explaining why you need nnan and ninf (nnan because pow() returns a nan for negative x, ninf for `pow(-inf, 1./3)`).


Repository:
  rL LLVM

https://reviews.llvm.org/D49040