[llvm-dev] FENV_ACCESS and floating point LibFunc calls

Tim Northover via llvm-dev
Fri, 12 May 2017 01:48:28 -0000

On 11 May 2017 at 18:30, Michael Clark via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> I note that on your bug that you have stated that the branch is faster than
> the conditional move. Faster code is a side effect of the fix in this
> particular case.

On the contrary: the faster code is pretty much the only reason this
can happen before the rest of the FENV support lands.

It's been said before, but I'll reiterate: LLVM IR does not model the
FENV on its instructions. CodeGen and other passes are free to
de-conditionalize exceptions, remove them, or add spurious ones just
for the giggles. What LLVM does now is not incorrect.

Tim.