diff options
Diffstat (limited to 'include/private/SkFloatingPoint.h')
-rw-r--r-- | include/private/SkFloatingPoint.h | 23 |
1 files changed, 8 insertions, 15 deletions
diff --git a/include/private/SkFloatingPoint.h b/include/private/SkFloatingPoint.h index ffed5c0747..f7ee816b12 100644 --- a/include/private/SkFloatingPoint.h +++ b/include/private/SkFloatingPoint.h @@ -127,28 +127,20 @@ extern const uint32_t gIEEENegativeInfinity; #define SK_FloatInfinity (*SkTCast<const float*>(&gIEEEInfinity)) #define SK_FloatNegativeInfinity (*SkTCast<const float*>(&gIEEENegativeInfinity)) -static inline float sk_float_rsqrt_portable(float x) { - // Get initial estimate. - int i = *SkTCast<int*>(&x); - i = 0x5F1FFFF9 - (i>>1); - float estimate = *SkTCast<float*>(&i); - - // One step of Newton's method to refine. - const float estimate_sq = estimate*estimate; - estimate *= 0.703952253f*(2.38924456f-x*estimate_sq); - return estimate; -} +// We forward declare this to break an #include cycle. +// (SkScalar -> SkFloatingPoint -> SkOpts.h -> SkXfermode -> SkColor -> SkScalar) +namespace SkOpts { extern float (*rsqrt)(float); } // Fast, approximate inverse square root. // Compare to name-brand "1.0f / sk_float_sqrt(x)". Should be around 10x faster on SSE, 2x on NEON. -static inline float sk_float_rsqrt(float x) { +static inline float sk_float_rsqrt(const float x) { // We want all this inlined, so we'll inline SIMD and just take the hit when we don't know we've got // it at compile time. This is going to be too fast to productively hide behind a function pointer. // -// We do one step of Newton's method to refine the estimates in the NEON and portable paths. No +// We do one step of Newton's method to refine the estimates in the NEON and null paths. No // refinement is faster, but very innacurate. Two steps is more accurate, but slower than 1/sqrt. // -// Optimized constants in the portable path courtesy of http://rrrola.wz.cz/inv_sqrt.html +// Optimized constants in the null path courtesy of http://rrrola.wz.cz/inv_sqrt.html #if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE1 return _mm_cvtss_f32(_mm_rsqrt_ss(_mm_set_ss(x))); #elif defined(SK_ARM_HAS_NEON) @@ -161,7 +153,8 @@ static inline float sk_float_rsqrt(float x) { estimate = vmul_f32(estimate, vrsqrts_f32(xx, estimate_sq)); return vget_lane_f32(estimate, 0); // 1 will work fine too; the answer's in both places. #else - return sk_float_rsqrt_portable(x); + // Perhaps runtime-detected NEON, or a portable fallback. + return SkOpts::rsqrt(x); #endif } |