Function ImRsqrt

tutorials/common/imgui/imgui_internal.h:441–441

static inline double ImSign(double x)           { return (x < 0.0) ? -1.0 : (x > 0.0) ? 1.0 : 0.0; }
#ifdef IMGUI_ENABLE_SSE
static inline float  ImRsqrt(float x)           { return _mm_cvtss_f32(_mm_rsqrt_ss(_mm_set_ss(x))); }
#else
static inline float  ImRsqrt(float x)           { return 1.0f / sqrtf(x); }
#endif