search for: replacepowwithsqrt

...quot; returns true. > If there are other errno divergences for edge case values, we may need to > check other conditions. > > On Sat, Sep 12, 2020 at 9:37 PM Hubert Tong via llvm-dev < > llvm-dev at lists.llvm.org> wrote: > >> The transformation in LibCallSimplifier::replacePowWithSqrt with respect >> to -Inf uses a select instruction, which based on the observed behaviour, >> incorporates the side effects of the unchosen branch. This means that (for >> pow) a call to sqrt(-Inf) is materialized. Such a call is specified as >> having a domain error (C17 sub...

...iately erasing that select with the code from the godbolt example. Does the real motivating case have no uses of the pow() result value? On Mon, Sep 14, 2020 at 1:03 PM Sanjay Patel <spatel at rotateright.com> wrote: > Yes, I mean just bail out on the transform in > LibCallSimplifier::replacePowWithSqrt() -> getSqrtCall(). If we can't prove > the call behaves the same with errno, then give up. > I'm not sure where the select / branching happens, but I don't see that > happening in the initial transform (called from -instcombine) > > On Mon, Sep 14, 2020 at 12:58 PM Hu...

The transformation in LibCallSimplifier::replacePowWithSqrt with respect to -Inf uses a select instruction, which based on the observed behaviour, incorporates the side effects of the unchosen branch. This means that (for pow) a call to sqrt(-Inf) is materialized. Such a call is specified as having a domain error (C17 subclause 7.12.7.5) since the operand i...