Use `_mm_sincos_ps` where both sin and cos are calculated for same angle

[legends2k]

In //include/cglm/quat.h, we've glm_quatv which calculates a new quaternion from axis and angle; it does

  c = cosf(a);
  s = sinf(a);

This can be optimized by using

1. _mm_sincos_ps
2. For non-SIMD cases, some platforms like Linux support sincos

Moving to this would be a nice (micro-)optimization 😉

[legends2k]

Related discussion on StackOverflow: What is the fastest way to compute sin and cos together?.

[recp]

@legends2k thanks, I like micro optimizations :) we can create a function like glm_sincos() then use _mm_sincos_ps() in for related platforms, I liked the idea

[myfreeer]

It seems compilers can do this optimization for many platforms:

Details

[recp]

@myfreeer thanks for the detailed explanation but I still like glm_sincos() idea which uses sincos internally if available, compilers may optimize this small inline function more easily without doubt rather than complex func I guess:

glm_sincos( ... ) {
  *s = sinf(a);
  *c = cosf(a);
}

let's keep the issue open for a while.

[gottfriedleibniz]

Another benefit to glm_sincos is that most sin/cos approximation functions (e.g., when cross-platform determinism is required) compute both values simultaneously (rather, it is "free" to compute them simultaneously). So it is usually a nice abstraction to have.

[recp]

@gottfriedleibniz thanks for your feedback[s]