[cfe-dev] clang does not use sincos with -O2 but gcc does

[René J.V. Bertin via cfe-dev]

On Thursday May 18 2017 10:09:14 Dennis Luehring via cfe-dev wrote:

>why do clang needs the -ffast-math option to use the sincos function here?
>gcc uses the sincos function without -ffast-math

It may have something to do with the fact that sincos() is a GNU extension to the standard math lib?

Also, I hope it doesn't expand to a call to the x87 FPU instruction, but IIRC that one is actually slower than 2 calls to modern sin() and cos() implementations :)

R.