| /* |
| * Copyright 2014 Google Inc. |
| * |
| * Use of this source code is governed by a BSD-style license that can be |
| * found in the LICENSE file. |
| */ |
| |
| #include "include/private/SkFloatBits.h" |
| #include "include/private/SkHalf.h" |
| |
| uint16_t halfMantissa(SkHalf h) { |
| return h & 0x03ff; |
| } |
| |
| uint16_t halfExponent(SkHalf h) { |
| return (h >> 10) & 0x001f; |
| } |
| |
| uint16_t halfSign(SkHalf h) { |
| return h >> 15; |
| } |
| |
| union FloatUIntUnion { |
| uint32_t fUInt; // this must come first for the initializations below to work |
| float fFloat; |
| }; |
| |
| // based on Fabien Giesen's float_to_half_fast3() |
| // see https://gist.github.com/rygorous/2156668 |
| SkHalf SkFloatToHalf(float f) { |
| static const uint32_t f32infty = { 255 << 23 }; |
| static const uint32_t f16infty = { 31 << 23 }; |
| static const FloatUIntUnion magic = { 15 << 23 }; |
| static const uint32_t sign_mask = 0x80000000u; |
| static const uint32_t round_mask = ~0xfffu; |
| SkHalf o = 0; |
| |
| FloatUIntUnion floatUnion; |
| floatUnion.fFloat = f; |
| |
| uint32_t sign = floatUnion.fUInt & sign_mask; |
| floatUnion.fUInt ^= sign; |
| |
| // NOTE all the integer compares in this function can be safely |
| // compiled into signed compares since all operands are below |
| // 0x80000000. Important if you want fast straight SSE2 code |
| // (since there's no unsigned PCMPGTD). |
| |
| // Inf or NaN (all exponent bits set) |
| if (floatUnion.fUInt >= f32infty) |
| // NaN->qNaN and Inf->Inf |
| o = (floatUnion.fUInt > f32infty) ? 0x7e00 : 0x7c00; |
| // (De)normalized number or zero |
| else { |
| floatUnion.fUInt &= round_mask; |
| floatUnion.fFloat *= magic.fFloat; |
| floatUnion.fUInt -= round_mask; |
| // Clamp to signed infinity if overflowed |
| if (floatUnion.fUInt > f16infty) { |
| floatUnion.fUInt = f16infty; |
| } |
| |
| o = floatUnion.fUInt >> 13; // Take the bits! |
| } |
| |
| o |= sign >> 16; |
| return o; |
| } |
| |
| // based on Fabien Giesen's half_to_float_fast2() |
| // see https://fgiesen.wordpress.com/2012/03/28/half-to-float-done-quic/ |
| float SkHalfToFloat(SkHalf h) { |
| static const FloatUIntUnion magic = { 126 << 23 }; |
| FloatUIntUnion o; |
| |
| if (halfExponent(h) == 0) |
| { |
| // Zero / Denormal |
| o.fUInt = magic.fUInt + halfMantissa(h); |
| o.fFloat -= magic.fFloat; |
| } |
| else |
| { |
| // Set mantissa |
| o.fUInt = halfMantissa(h) << 13; |
| // Set exponent |
| if (halfExponent(h) == 0x1f) |
| // Inf/NaN |
| o.fUInt |= (255 << 23); |
| else |
| o.fUInt |= ((127 - 15 + halfExponent(h)) << 23); |
| } |
| |
| // Set sign |
| o.fUInt |= (halfSign(h) << 31); |
| return o.fFloat; |
| } |