won't fix: 2009/01

2009-01-29

Another MMX/SSE/SSE2 optimization bugs

All SSE2 platform

416157 - Add JPEG SSE2 color processing for ycc_rgb_convert_argb
MichelのコードはIFASTに変更してるから良くないけど、YCC -> RGBの変換は使えるんじゃないかなぁと
APNG SSE2? (previous entry).

All SSE2 platform except to Windows

475225 - Add JPEG optimization for x86_64 platform
Windows x86でしかSSE2使ってないので、GCC系のプラットフォームにも移植する予定。といっても、Fedoraとかだと、--with-system-jpegつけてビルドするからオフィシャルビルドとかしか影響しないけど。

For Windows x64 only (will be only on mozilla-central)

475227 - LCMS SSE2 optimization for Windows x64
GCC向けとMSVCのx86向けはもう入ってる。
Pixman optimization (MQに入れてある。http://hg.mozilla-x86-64.com/mozilla2-win64-mq/)

2009-01-28

ふと思ったmozillaのSSE2最適化

/modules/libpr0n/decoders/png/nsPNGDecoder.cpp

695 void
696 row_callback(png_structp png_ptr, png_bytep new_row,
697              png_uint_32 row_num, int pass)
698 {
 :
 :
793     case gfxIFormats::RGB_A1:
794       {
795         for (PRUint32 x=iwidth; x>0; --x) {
796           *cptr32++ = GFX_PACKED_PIXEL(line[3]?0xFF:0x00, line[0], line[1], line[2]);
797           if (line[3] == 0)
798             rowHasNoAlpha = PR_FALSE;
799           line += 4;
800         }
801       }
802       break;
803     case gfxIFormats::RGB_A8:
804       {
805         for (PRUint32 x=width; x>0; --x) {
806           *cptr32++ = GFX_PACKED_PIXEL(line[3], line[0], line[1], line[2]);
807           if (line[3] != 0xff)
808             rowHasNoAlpha = PR_FALSE;
809           line += 4;
810         }
811       }

ここで使ってる GFX_PACKED_PIXEL のマクロってどうなっているかと思ったら、

/gfx/thebes/public/gfxColor.h

118 /**
119  * Fast approximate division by 255. It has the property that
120  * for all 0 <= n <= 255*255, FAST_DIVIDE_BY_255(n) == n/255.
121  * But it only uses two adds and two shifts instead of an 
122  * integer division (which is expensive on many processors).
123  *
124  * equivalent to ((v)/255)
125  */
126 #define GFX_DIVIDE_BY_255(v)  \
127      (((((unsigned)(v)) << 8) + ((unsigned)(v)) + 255) >> 16)
128 
129 /**
130  * Fast premultiply macro
131  *
132  * equivalent to (((c)*(a))/255)
133  */
134 #define GFX_PREMULTIPLY(c,a) GFX_DIVIDE_BY_255((c)*(a))
135 
136 /** 
137  * Macro to pack the 4 8-bit channels (A,R,G,B) 
138  * into a 32-bit packed premultiplied pixel.
139  *
140  * The checks for 0 alpha or max alpha ensure that the
141  * compiler selects the quicked calculation when alpha is constant.
142  */
143 #define GFX_PACKED_PIXEL(a,r,g,b)                                       \
144     ((a) == 0x00) ? 0x00000000 :                                        \
145     ((a) == 0xFF) ? ((0xFF << 24) | ((r) << 16) | ((g) << 8) | (b))     \
146                   : ((a) << 24) |                                       \
147                     (GFX_PREMULTIPLY(r,a) << 16) |                      \
148                     (GFX_PREMULTIPLY(g,a) << 8) |                       \
149                     (GFX_PREMULTIPLY(b,a))

だから、アルファブレンディングしたPNGを持ってくると遅すぎじゃないかな？

こんな感じのパックドコードをSSE2で実装すれば約2倍くらいは速くなるような。

xmm0080 = _mm_set1_epi16(0x0080);
xmm0101 = _mm_set1_epi16(0x0101);
xmmAlpha = _mm_set_epi32(0x00ff0000, 0x00000000, 0x00ff0000, 0x00000000);

data = _mm_loadu_si128((__m128i*)src);
dataLo = _mm_unpacklo_epi8 (data, _mm_setzero_si128 ());
dataHi = _mm_unpackhi_epi8 (data, _mm_setzero_si128 ());

alphaLo = _mm_shufflelo_epi16 (dataLo, _MM_SHUFFLE(3, 3, 3, 3));
alphaHi = _mm_shufflelo_epi16 (dataHi, _MM_SHUFFLE(3, 3, 3, 3));
alphaLo = _mm_shufflehi_epi16 (alphaLo, _MM_SHUFFLE(3, 3, 3, 3));
alphaHi = _mm_shufflehi_epi16 (alphaHi, _MM_SHUFFLE(3, 3, 3, 3));

alphaLo = _mm_or_si128(alphaLo, xmmAlpha);
alphaHi = _mm_or_si128(alphaHi, xmmAlpha);

dataLo = _mm_shufflelo_epi16 (dataLo, _MM_SHUFFLE(3, 0, 1, 2));
dataLo = _mm_shufflehi_epi16 (dataLo, _MM_SHUFFLE(3, 0, 1, 2));
dataHi = _mm_shufflelo_epi16 (dataHi, _MM_SHUFFLE(3, 0, 1, 2));
dataHi = _mm_shufflehi_epi16 (dataHi, _MM_SHUFFLE(3, 0, 1, 2));

dataLo = _mm_mullo_epi16(dataLo, alphaLo);
dataHi = _mm_mullo_epi16(dataHi, alphaHi);

dataLo = _mm_adds_epu16(dataLo, xmm0080);
dataHi = _mm_adds_epu16(dataHi, xmm0080);

dataLo = _mm_mulhi_epu16(dataLo, xmm0101);
dataHi = _mm_mulhi_epu16(dataHi, xmm0101);

data = _mm_packus_epi16 (dataLo, dataHi);
_mm_storeu_si128((__m128i*)dst, data);

今度テストしてみよう。