scale_win.cc

/*
 *  Copyright 2013 The LibYuv Project Authors. All rights reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS. All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */

#include "libyuv/row.h"
#include "libyuv/scale_row.h"

#ifdef __cplusplus
namespace libyuv {
extern "C" {
#endif

// This module is for 32 bit Visual C x86 and clangcl
#if !defined(LIBYUV_DISABLE_X86) && defined(_M_IX86)

// Offsets for source bytes 0 to 9
static uvec8 kShuf0 =
  { 0, 1, 3, 4, 5, 7, 8, 9, 128, 128, 128, 128, 128, 128, 128, 128 };

// Offsets for source bytes 11 to 20 with 8 subtracted = 3 to 12.
static uvec8 kShuf1 =
  { 3, 4, 5, 7, 8, 9, 11, 12, 128, 128, 128, 128, 128, 128, 128, 128 };

// Offsets for source bytes 21 to 31 with 16 subtracted = 5 to 31.
static uvec8 kShuf2 =
  { 5, 7, 8, 9, 11, 12, 13, 15, 128, 128, 128, 128, 128, 128, 128, 128 };

// Offsets for source bytes 0 to 10
static uvec8 kShuf01 =
  { 0, 1, 1, 2, 2, 3, 4, 5, 5, 6, 6, 7, 8, 9, 9, 10 };

// Offsets for source bytes 10 to 21 with 8 subtracted = 3 to 13.
static uvec8 kShuf11 =
  { 2, 3, 4, 5, 5, 6, 6, 7, 8, 9, 9, 10, 10, 11, 12, 13 };

// Offsets for source bytes 21 to 31 with 16 subtracted = 5 to 31.
static uvec8 kShuf21 =
  { 5, 6, 6, 7, 8, 9, 9, 10, 10, 11, 12, 13, 13, 14, 14, 15 };

// Coefficients for source bytes 0 to 10
static uvec8 kMadd01 =
  { 3, 1, 2, 2, 1, 3, 3, 1, 2, 2, 1, 3, 3, 1, 2, 2 };

// Coefficients for source bytes 10 to 21
static uvec8 kMadd11 =
  { 1, 3, 3, 1, 2, 2, 1, 3, 3, 1, 2, 2, 1, 3, 3, 1 };

// Coefficients for source bytes 21 to 31
static uvec8 kMadd21 =
  { 2, 2, 1, 3, 3, 1, 2, 2, 1, 3, 3, 1, 2, 2, 1, 3 };

// Coefficients for source bytes 21 to 31
static vec16 kRound34 =
  { 2, 2, 2, 2, 2, 2, 2, 2 };

static uvec8 kShuf38a =
  { 0, 3, 6, 8, 11, 14, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128 };

static uvec8 kShuf38b =
  { 128, 128, 128, 128, 128, 128, 0, 3, 6, 8, 11, 14, 128, 128, 128, 128 };

// Arrange words 0,3,6 into 0,1,2
static uvec8 kShufAc =
  { 0, 1, 6, 7, 12, 13, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128 };

// Arrange words 0,3,6 into 3,4,5
static uvec8 kShufAc3 =
  { 128, 128, 128, 128, 128, 128, 0, 1, 6, 7, 12, 13, 128, 128, 128, 128 };

// Scaling values for boxes of 3x3 and 2x3
static uvec16 kScaleAc33 =
  { 65536 / 9, 65536 / 9, 65536 / 6, 65536 / 9, 65536 / 9, 65536 / 6, 0, 0 };

// Arrange first value for pixels 0,1,2,3,4,5
static uvec8 kShufAb0 =
  { 0, 128, 3, 128, 6, 128, 8, 128, 11, 128, 14, 128, 128, 128, 128, 128 };

// Arrange second value for pixels 0,1,2,3,4,5
static uvec8 kShufAb1 =
  { 1, 128, 4, 128, 7, 128, 9, 128, 12, 128, 15, 128, 128, 128, 128, 128 };

// Arrange third value for pixels 0,1,2,3,4,5
static uvec8 kShufAb2 =
  { 2, 128, 5, 128, 128, 128, 10, 128, 13, 128, 128, 128, 128, 128, 128, 128 };

// Scaling values for boxes of 3x2 and 2x2
static uvec16 kScaleAb2 =
  { 65536 / 3, 65536 / 3, 65536 / 2, 65536 / 3, 65536 / 3, 65536 / 2, 0, 0 };

// Reads 32 pixels, throws half away and writes 16 pixels.
__declspec(naked)
void ScaleRowDown2_SSE2(const uint8* src_ptr, ptrdiff_t src_stride,
                        uint8* dst_ptr, int dst_width) {
  __asm {
    mov        eax, [esp + 4]        // src_ptr
                                     // src_stride ignored
    mov        edx, [esp + 12]       // dst_ptr
    mov        ecx, [esp + 16]       // dst_width

  wloop:
    movdqu     xmm0, [eax]
    movdqu     xmm1, [eax + 16]
    lea        eax,  [eax + 32]
    psrlw      xmm0, 8               // isolate odd pixels.
    psrlw      xmm1, 8
    packuswb   xmm0, xmm1
    movdqu     [edx], xmm0
    lea        edx, [edx + 16]
    sub        ecx, 16
    jg         wloop

    ret
  }
}

// Blends 32x1 rectangle to 16x1.
__declspec(naked)
void ScaleRowDown2Linear_SSE2(const uint8* src_ptr, ptrdiff_t src_stride,
                              uint8* dst_ptr, int dst_width) {
  __asm {
    mov        eax, [esp + 4]        // src_ptr
                                     // src_stride
    mov        edx, [esp + 12]       // dst_ptr
    mov        ecx, [esp + 16]       // dst_width
    pcmpeqb    xmm5, xmm5            // generate mask 0x00ff00ff
    psrlw      xmm5, 8

  wloop:
    movdqu     xmm0, [eax]
    movdqu     xmm1, [eax + 16]
    lea        eax,  [eax + 32]

    movdqa     xmm2, xmm0            // average columns (32 to 16 pixels)
    psrlw      xmm0, 8
    movdqa     xmm3, xmm1
    psrlw      xmm1, 8
    pand       xmm2, xmm5
    pand       xmm3, xmm5
    pavgw      xmm0, xmm2
    pavgw      xmm1, xmm3
    packuswb   xmm0, xmm1

    movdqu     [edx], xmm0
    lea        edx, [edx + 16]
    sub        ecx, 16
    jg         wloop

    ret
  }
}

// Blends 32x2 rectangle to 16x1.
__declspec(naked)
void ScaleRowDown2Box_SSE2(const uint8* src_ptr, ptrdiff_t src_stride,
                           uint8* dst_ptr, int dst_width) {
  __asm {
    push       esi
    mov        eax, [esp + 4 + 4]    // src_ptr
    mov        esi, [esp + 4 + 8]    // src_stride
    mov        edx, [esp + 4 + 12]   // dst_ptr
    mov        ecx, [esp + 4 + 16]   // dst_width
    pcmpeqb    xmm5, xmm5            // generate mask 0x00ff00ff
    psrlw      xmm5, 8

  wloop:
    movdqu     xmm0, [eax]
    movdqu     xmm1, [eax + 16]
    movdqu     xmm2, [eax + esi]
    movdqu     xmm3, [eax + esi + 16]
    lea        eax,  [eax + 32]
    pavgb      xmm0, xmm2            // average rows
    pavgb      xmm1, xmm3

    movdqa     xmm2, xmm0            // average columns (32 to 16 pixels)
    psrlw      xmm0, 8
    movdqa     xmm3, xmm1
    psrlw      xmm1, 8
    pand       xmm2, xmm5
    pand       xmm3, xmm5
    pavgw      xmm0, xmm2
    pavgw      xmm1, xmm3
    packuswb   xmm0, xmm1

    movdqu     [edx], xmm0
    lea        edx, [edx + 16]
    sub        ecx, 16
    jg         wloop

    pop        esi
    ret
  }
}

#ifdef HAS_SCALEROWDOWN2_AVX2
// Reads 64 pixels, throws half away and writes 32 pixels.
__declspec(naked)
void ScaleRowDown2_AVX2(const uint8* src_ptr, ptrdiff_t src_stride,
                        uint8* dst_ptr, int dst_width) {
  __asm {
    mov        eax, [esp + 4]        // src_ptr
                                     // src_stride ignored
    mov        edx, [esp + 12]       // dst_ptr
    mov        ecx, [esp + 16]       // dst_width

  wloop:
    vmovdqu     ymm0, [eax]
    vmovdqu     ymm1, [eax + 32]
    lea         eax,  [eax + 64]
    vpsrlw      ymm0, ymm0, 8        // isolate odd pixels.
    vpsrlw      ymm1, ymm1, 8
    vpackuswb   ymm0, ymm0, ymm1
    vpermq      ymm0, ymm0, 0xd8     // unmutate vpackuswb
    vmovdqu     [edx], ymm0
    lea         edx, [edx + 32]
    sub         ecx, 32
    jg          wloop

    vzeroupper
    ret
  }
}

// Blends 64x1 rectangle to 32x1.
__declspec(naked)
void ScaleRowDown2Linear_AVX2(const uint8* src_ptr, ptrdiff_t src_stride,
                              uint8* dst_ptr, int dst_width) {
  __asm {
    mov         eax, [esp + 4]        // src_ptr
                                      // src_stride
    mov         edx, [esp + 12]       // dst_ptr
    mov         ecx, [esp + 16]       // dst_width

    vpcmpeqb    ymm4, ymm4, ymm4      // '1' constant, 8b
    vpsrlw      ymm4, ymm4, 15
    vpackuswb   ymm4, ymm4, ymm4
    vpxor       ymm5, ymm5, ymm5      // constant 0

  wloop:
    vmovdqu     ymm0, [eax]
    vmovdqu     ymm1, [eax + 32]
    lea         eax,  [eax + 64]

    vpmaddubsw  ymm0, ymm0, ymm4      // average horizontally
    vpmaddubsw  ymm1, ymm1, ymm4
    vpavgw      ymm0, ymm0, ymm5      // (x + 1) / 2
    vpavgw      ymm1, ymm1, ymm5
    vpackuswb   ymm0, ymm0, ymm1
    vpermq      ymm0, ymm0, 0xd8      // unmutate vpackuswb

    vmovdqu     [edx], ymm0
    lea         edx, [edx + 32]
    sub         ecx, 32
    jg          wloop

    vzeroupper
    ret
  }
}

// Blends 64x2 rectangle to 32x1.
__declspec(naked)
void ScaleRowDown2Box_AVX2(const uint8* src_ptr, ptrdiff_t src_stride,
                           uint8* dst_ptr, int dst_width) {
  __asm {
    push        esi
    mov         eax, [esp + 4 + 4]    // src_ptr
    mov         esi, [esp + 4 + 8]    // src_stride
    mov         edx, [esp + 4 + 12]   // dst_ptr
    mov         ecx, [esp + 4 + 16]   // dst_width

    vpcmpeqb    ymm4, ymm4, ymm4      // '1' constant, 8b
    vpsrlw      ymm4, ymm4, 15
    vpackuswb   ymm4, ymm4, ymm4
    vpxor       ymm5, ymm5, ymm5      // constant 0

  wloop:
    vmovdqu     ymm0, [eax]           // average rows
    vmovdqu     ymm1, [eax + 32]
    vpavgb      ymm0, ymm0, [eax + esi]
    vpavgb      ymm1, ymm1, [eax + esi + 32]
    lea         eax,  [eax + 64]

    vpmaddubsw  ymm0, ymm0, ymm4      // average horizontally
    vpmaddubsw  ymm1, ymm1, ymm4
    vpavgw      ymm0, ymm0, ymm5      // (x + 1) / 2
    vpavgw      ymm1, ymm1, ymm5
    vpackuswb   ymm0, ymm0, ymm1
    vpermq      ymm0, ymm0, 0xd8      // unmutate vpackuswb

    vmovdqu     [edx], ymm0
    lea         edx, [edx + 32]
    sub         ecx, 32
    jg          wloop

    pop         esi
    vzeroupper
    ret
  }
}
#endif  // HAS_SCALEROWDOWN2_AVX2

// Point samples 32 pixels to 8 pixels.
__declspec(naked)
void ScaleRowDown4_SSE2(const uint8* src_ptr, ptrdiff_t src_stride,
                        uint8* dst_ptr, int dst_width) {
  __asm {
    mov        eax, [esp + 4]        // src_ptr
                                     // src_stride ignored
    mov        edx, [esp + 12]       // dst_ptr
    mov        ecx, [esp + 16]       // dst_width
    pcmpeqb    xmm5, xmm5            // generate mask 0x00ff0000
    psrld      xmm5, 24
    pslld      xmm5, 16

  wloop:
    movdqu     xmm0, [eax]
    movdqu     xmm1, [eax + 16]
    lea        eax,  [eax + 32]
    pand       xmm0, xmm5
    pand       xmm1, xmm5
    packuswb   xmm0, xmm1
    psrlw      xmm0, 8
    packuswb   xmm0, xmm0
    movq       qword ptr [edx], xmm0
    lea        edx, [edx + 8]
    sub        ecx, 8
    jg         wloop

    ret
  }
}

// Blends 32x4 rectangle to 8x1.
__declspec(naked)
void ScaleRowDown4Box_SSE2(const uint8* src_ptr, ptrdiff_t src_stride,
                           uint8* dst_ptr, int dst_width) {
  __asm {
    push       esi
    push       edi
    mov        eax, [esp + 8 + 4]    // src_ptr
    mov        esi, [esp + 8 + 8]    // src_stride
    mov        edx, [esp + 8 + 12]   // dst_ptr
    mov        ecx, [esp + 8 + 16]   // dst_width
    lea        edi, [esi + esi * 2]  // src_stride * 3
    pcmpeqb    xmm7, xmm7            // generate mask 0x00ff00ff
    psrlw      xmm7, 8

  wloop:
    movdqu     xmm0, [eax]           // average rows
    movdqu     xmm1, [eax + 16]
    movdqu     xmm2, [eax + esi]
    movdqu     xmm3, [eax + esi + 16]
    pavgb      xmm0, xmm2
    pavgb      xmm1, xmm3
    movdqu     xmm2, [eax + esi * 2]
    movdqu     xmm3, [eax + esi * 2 + 16]
    movdqu     xmm4, [eax + edi]
    movdqu     xmm5, [eax + edi + 16]
    lea        eax, [eax + 32]
    pavgb      xmm2, xmm4
    pavgb      xmm3, xmm5
    pavgb      xmm0, xmm2
    pavgb      xmm1, xmm3

    movdqa     xmm2, xmm0            // average columns (32 to 16 pixels)
    psrlw      xmm0, 8
    movdqa     xmm3, xmm1
    psrlw      xmm1, 8
    pand       xmm2, xmm7
    pand       xmm3, xmm7
    pavgw      xmm0, xmm2
    pavgw      xmm1, xmm3
    packuswb   xmm0, xmm1

    movdqa     xmm2, xmm0            // average columns (16 to 8 pixels)
    psrlw      xmm0, 8
    pand       xmm2, xmm7
    pavgw      xmm0, xmm2
    packuswb   xmm0, xmm0

    movq       qword ptr [edx], xmm0
    lea        edx, [edx + 8]
    sub        ecx, 8
    jg         wloop

    pop        edi
    pop        esi
    ret
  }
}

#ifdef HAS_SCALEROWDOWN4_AVX2
// Point samples 64 pixels to 16 pixels.
__declspec(naked)
void ScaleRowDown4_AVX2(const uint8* src_ptr, ptrdiff_t src_stride,
                        uint8* dst_ptr, int dst_width) {
  __asm {
    mov         eax, [esp + 4]        // src_ptr
                                      // src_stride ignored
    mov         edx, [esp + 12]       // dst_ptr
    mov         ecx, [esp + 16]       // dst_width
    vpcmpeqb    ymm5, ymm5, ymm5      // generate mask 0x00ff0000
    vpsrld      ymm5, ymm5, 24
    vpslld      ymm5, ymm5, 16

  wloop:
    vmovdqu     ymm0, [eax]
    vmovdqu     ymm1, [eax + 32]
    lea         eax,  [eax + 64]
    vpand       ymm0, ymm0, ymm5
    vpand       ymm1, ymm1, ymm5
    vpackuswb   ymm0, ymm0, ymm1
    vpermq      ymm0, ymm0, 0xd8      // unmutate vpackuswb
    vpsrlw      ymm0, ymm0, 8
    vpackuswb   ymm0, ymm0, ymm0
    vpermq      ymm0, ymm0, 0xd8      // unmutate vpackuswb
    vmovdqu     [edx], xmm0
    lea         edx, [edx + 16]
    sub         ecx, 16
    jg          wloop

    vzeroupper
    ret
  }
}

// Blends 64x4 rectangle to 16x1.
__declspec(naked)
void ScaleRowDown4Box_AVX2(const uint8* src_ptr, ptrdiff_t src_stride,
                           uint8* dst_ptr, int dst_width) {
  __asm {
    push        esi
    push        edi
    mov         eax, [esp + 8 + 4]    // src_ptr
    mov         esi, [esp + 8 + 8]    // src_stride
    mov         edx, [esp + 8 + 12]   // dst_ptr
    mov         ecx, [esp + 8 + 16]   // dst_width
    lea         edi, [esi + esi * 2]  // src_stride * 3
    vpcmpeqb    ymm7, ymm7, ymm7      // generate mask 0x00ff00ff
    vpsrlw      ymm7, ymm7, 8

  wloop:
    vmovdqu     ymm0, [eax]           // average rows
    vmovdqu     ymm1, [eax + 32]
    vpavgb      ymm0, ymm0, [eax + esi]
    vpavgb      ymm1, ymm1, [eax + esi + 32]
    vmovdqu     ymm2, [eax + esi * 2]
    vmovdqu     ymm3, [eax + esi * 2 + 32]
    vpavgb      ymm2, ymm2, [eax + edi]
    vpavgb      ymm3, ymm3, [eax + edi + 32]
    lea         eax, [eax + 64]
    vpavgb      ymm0, ymm0, ymm2
    vpavgb      ymm1, ymm1, ymm3

    vpand       ymm2, ymm0, ymm7      // average columns (64 to 32 pixels)
    vpand       ymm3, ymm1, ymm7
    vpsrlw      ymm0, ymm0, 8
    vpsrlw      ymm1, ymm1, 8
    vpavgw      ymm0, ymm0, ymm2
    vpavgw      ymm1, ymm1, ymm3
    vpackuswb   ymm0, ymm0, ymm1
    vpermq      ymm0, ymm0, 0xd8      // unmutate vpackuswb

    vpand       ymm2, ymm0, ymm7      // average columns (32 to 16 pixels)
    vpsrlw      ymm0, ymm0, 8
    vpavgw      ymm0, ymm0, ymm2
    vpackuswb   ymm0, ymm0, ymm0
    vpermq      ymm0, ymm0, 0xd8      // unmutate vpackuswb

    vmovdqu     [edx], xmm0
    lea         edx, [edx + 16]
    sub         ecx, 16
    jg          wloop

    pop        edi
    pop        esi
    vzeroupper
    ret
  }
}
#endif  // HAS_SCALEROWDOWN4_AVX2

// Point samples 32 pixels to 24 pixels.
// Produces three 8 byte values. For each 8 bytes, 16 bytes are read.
// Then shuffled to do the scaling.

__declspec(naked)
void ScaleRowDown34_SSSE3(const uint8* src_ptr, ptrdiff_t src_stride,
                          uint8* dst_ptr, int dst_width) {
  __asm {
    mov        eax, [esp + 4]        // src_ptr
                                     // src_stride ignored
    mov        edx, [esp + 12]       // dst_ptr
    mov        ecx, [esp + 16]       // dst_width
    movdqa     xmm3, xmmword ptr kShuf0
    movdqa     xmm4, xmmword ptr kShuf1
    movdqa     xmm5, xmmword ptr kShuf2

  wloop:
    movdqu     xmm0, [eax]
    movdqu     xmm1, [eax + 16]
    lea        eax,  [eax + 32]
    movdqa     xmm2, xmm1
    palignr    xmm1, xmm0, 8
    pshufb     xmm0, xmm3
    pshufb     xmm1, xmm4
    pshufb     xmm2, xmm5
    movq       qword ptr [edx], xmm0
    movq       qword ptr [edx + 8], xmm1
    movq       qword ptr [edx + 16], xmm2
    lea        edx, [edx + 24]
    sub        ecx, 24
    jg         wloop

    ret
  }
}

// Blends 32x2 rectangle to 24x1
// Produces three 8 byte values. For each 8 bytes, 16 bytes are read.
// Then shuffled to do the scaling.

// Register usage:
// xmm0 src_row 0
// xmm1 src_row 1
// xmm2 shuf 0
// xmm3 shuf 1
// xmm4 shuf 2
// xmm5 madd 0
// xmm6 madd 1
// xmm7 kRound34

// Note that movdqa+palign may be better than movdqu.
__declspec(naked)
void ScaleRowDown34_1_Box_SSSE3(const uint8* src_ptr,
                                ptrdiff_t src_stride,
                                uint8* dst_ptr, int dst_width) {
  __asm {
    push       esi
    mov        eax, [esp + 4 + 4]    // src_ptr
    mov        esi, [esp + 4 + 8]    // src_stride
    mov        edx, [esp + 4 + 12]   // dst_ptr
    mov        ecx, [esp + 4 + 16]   // dst_width
    movdqa     xmm2, xmmword ptr kShuf01
    movdqa     xmm3, xmmword ptr kShuf11
    movdqa     xmm4, xmmword ptr kShuf21
    movdqa     xmm5, xmmword ptr kMadd01
    movdqa     xmm6, xmmword ptr kMadd11
    movdqa     xmm7, xmmword ptr kRound34

  wloop:
    movdqu     xmm0, [eax]           // pixels 0..7
    movdqu     xmm1, [eax + esi]
    pavgb      xmm0, xmm1
    pshufb     xmm0, xmm2
    pmaddubsw  xmm0, xmm5
    paddsw     xmm0, xmm7
    psrlw      xmm0, 2
    packuswb   xmm0, xmm0
    movq       qword ptr [edx], xmm0
    movdqu     xmm0, [eax + 8]       // pixels 8..15
    movdqu     xmm1, [eax + esi + 8]
    pavgb      xmm0, xmm1
    pshufb     xmm0, xmm3
    pmaddubsw  xmm0, xmm6
    paddsw     xmm0, xmm7
    psrlw      xmm0, 2
    packuswb   xmm0, xmm0
    movq       qword ptr [edx + 8], xmm0
    movdqu     xmm0, [eax + 16]      // pixels 16..23
    movdqu     xmm1, [eax + esi + 16]
    lea        eax, [eax + 32]
    pavgb      xmm0, xmm1
    pshufb     xmm0, xmm4
    movdqa     xmm1, xmmword ptr kMadd21
    pmaddubsw  xmm0, xmm1
    paddsw     xmm0, xmm7
    psrlw      xmm0, 2
    packuswb   xmm0, xmm0
    movq       qword ptr [edx + 16], xmm0
    lea        edx, [edx + 24]
    sub        ecx, 24
    jg         wloop

    pop        esi
    ret
  }
}

// Note that movdqa+palign may be better than movdqu.
__declspec(naked)
void ScaleRowDown34_0_Box_SSSE3(const uint8* src_ptr,
                                ptrdiff_t src_stride,
                                uint8* dst_ptr, int dst_width) {
  __asm {
    push       esi
    mov        eax, [esp + 4 + 4]    // src_ptr
    mov        esi, [esp + 4 + 8]    // src_stride
    mov        edx, [esp + 4 + 12]   // dst_ptr
    mov        ecx, [esp + 4 + 16]   // dst_width
    movdqa     xmm2, xmmword ptr kShuf01
    movdqa     xmm3, xmmword ptr kShuf11
    movdqa     xmm4, xmmword ptr kShuf21
    movdqa     xmm5, xmmword ptr kMadd01
    movdqa     xmm6, xmmword ptr kMadd11
    movdqa     xmm7, xmmword ptr kRound34

  wloop:
    movdqu     xmm0, [eax]           // pixels 0..7
    movdqu     xmm1, [eax + esi]
    pavgb      xmm1, xmm0
    pavgb      xmm0, xmm1
    pshufb     xmm0, xmm2
    pmaddubsw  xmm0, xmm5
    paddsw     xmm0, xmm7
    psrlw      xmm0, 2
    packuswb   xmm0, xmm0
    movq       qword ptr [edx], xmm0
    movdqu     xmm0, [eax + 8]       // pixels 8..15
    movdqu     xmm1, [eax + esi + 8]
    pavgb      xmm1, xmm0
    pavgb      xmm0, xmm1
    pshufb     xmm0, xmm3
    pmaddubsw  xmm0, xmm6
    paddsw     xmm0, xmm7
    psrlw      xmm0, 2
    packuswb   xmm0, xmm0
    movq       qword ptr [edx + 8], xmm0
    movdqu     xmm0, [eax + 16]      // pixels 16..23
    movdqu     xmm1, [eax + esi + 16]
    lea        eax, [eax + 32]
    pavgb      xmm1, xmm0
    pavgb      xmm0, xmm1
    pshufb     xmm0, xmm4
    movdqa     xmm1, xmmword ptr kMadd21
    pmaddubsw  xmm0, xmm1
    paddsw     xmm0, xmm7
    psrlw      xmm0, 2
    packuswb   xmm0, xmm0
    movq       qword ptr [edx + 16], xmm0
    lea        edx, [edx+24]
    sub        ecx, 24
    jg         wloop

    pop        esi
    ret
  }
}

// 3/8 point sampler

// Scale 32 pixels to 12
__declspec(naked)
void ScaleRowDown38_SSSE3(const uint8* src_ptr, ptrdiff_t src_stride,
                          uint8* dst_ptr, int dst_width) {
  __asm {
    mov        eax, [esp + 4]        // src_ptr
                                     // src_stride ignored
    mov        edx, [esp + 12]       // dst_ptr
    mov        ecx, [esp + 16]       // dst_width
    movdqa     xmm4, xmmword ptr kShuf38a
    movdqa     xmm5, xmmword ptr kShuf38b

  xloop:
    movdqu     xmm0, [eax]           // 16 pixels -> 0,1,2,3,4,5
    movdqu     xmm1, [eax + 16]      // 16 pixels -> 6,7,8,9,10,11
    lea        eax, [eax + 32]
    pshufb     xmm0, xmm4
    pshufb     xmm1, xmm5
    paddusb    xmm0, xmm1

    movq       qword ptr [edx], xmm0  // write 12 pixels
    movhlps    xmm1, xmm0
    movd       [edx + 8], xmm1
    lea        edx, [edx + 12]
    sub        ecx, 12
    jg         xloop

    ret
  }
}

// Scale 16x3 pixels to 6x1 with interpolation
__declspec(naked)
void ScaleRowDown38_3_Box_SSSE3(const uint8* src_ptr,
                                ptrdiff_t src_stride,
                                uint8* dst_ptr, int dst_width) {
  __asm {
    push       esi
    mov        eax, [esp + 4 + 4]    // src_ptr
    mov        esi, [esp + 4 + 8]    // src_stride
    mov        edx, [esp + 4 + 12]   // dst_ptr
    mov        ecx, [esp + 4 + 16]   // dst_width
    movdqa     xmm2, xmmword ptr kShufAc
    movdqa     xmm3, xmmword ptr kShufAc3
    movdqa     xmm4, xmmword ptr kScaleAc33
    pxor       xmm5, xmm5

  xloop:
    movdqu     xmm0, [eax]           // sum up 3 rows into xmm0/1
    movdqu     xmm6, [eax + esi]
    movhlps    xmm1, xmm0
    movhlps    xmm7, xmm6
    punpcklbw  xmm0, xmm5
    punpcklbw  xmm1, xmm5
    punpcklbw  xmm6, xmm5
    punpcklbw  xmm7, xmm5
    paddusw    xmm0, xmm6
    paddusw    xmm1, xmm7
    movdqu     xmm6, [eax + esi * 2]
    lea        eax, [eax + 16]
    movhlps    xmm7, xmm6
    punpcklbw  xmm6, xmm5
    punpcklbw  xmm7, xmm5
    paddusw    xmm0, xmm6
    paddusw    xmm1, xmm7

    movdqa     xmm6, xmm0            // 8 pixels -> 0,1,2 of xmm6
    psrldq     xmm0, 2
    paddusw    xmm6, xmm0
    psrldq     xmm0, 2
    paddusw    xmm6, xmm0
    pshufb     xmm6, xmm2

    movdqa     xmm7, xmm1            // 8 pixels -> 3,4,5 of xmm6
    psrldq     xmm1, 2
    paddusw    xmm7, xmm1
    psrldq     xmm1, 2
    paddusw    xmm7, xmm1
    pshufb     xmm7, xmm3
    paddusw    xmm6, xmm7

    pmulhuw    xmm6, xmm4            // divide by 9,9,6, 9,9,6
    packuswb   xmm6, xmm6

    movd       [edx], xmm6           // write 6 pixels
    psrlq      xmm6, 16
    movd       [edx + 2], xmm6
    lea        edx, [edx + 6]
    sub        ecx, 6
    jg         xloop

    pop        esi
    ret
  }
}

// Scale 16x2 pixels to 6x1 with interpolation
__declspec(naked)
void ScaleRowDown38_2_Box_SSSE3(const uint8* src_ptr,
                                ptrdiff_t src_stride,
                                uint8* dst_ptr, int dst_width) {
  __asm {
    push       esi
    mov        eax, [esp + 4 + 4]    // src_ptr
    mov        esi, [esp + 4 + 8]    // src_stride
    mov        edx, [esp + 4 + 12]   // dst_ptr
    mov        ecx, [esp + 4 + 16]   // dst_width
    movdqa     xmm2, xmmword ptr kShufAb0
    movdqa     xmm3, xmmword ptr kShufAb1
    movdqa     xmm4, xmmword ptr kShufAb2
    movdqa     xmm5, xmmword ptr kScaleAb2

  xloop:
    movdqu     xmm0, [eax]           // average 2 rows into xmm0
    movdqu     xmm1, [eax + esi]
    lea        eax, [eax + 16]
    pavgb      xmm0, xmm1

    movdqa     xmm1, xmm0            // 16 pixels -> 0,1,2,3,4,5 of xmm1
    pshufb     xmm1, xmm2
    movdqa     xmm6, xmm0
    pshufb     xmm6, xmm3
    paddusw    xmm1, xmm6
    pshufb     xmm0, xmm4
    paddusw    xmm1, xmm0

    pmulhuw    xmm1, xmm5            // divide by 3,3,2, 3,3,2
    packuswb   xmm1, xmm1

    movd       [edx], xmm1           // write 6 pixels
    psrlq      xmm1, 16
    movd       [edx + 2], xmm1
    lea        edx, [edx + 6]
    sub        ecx, 6
    jg         xloop

    pop        esi
    ret
  }
}

// Reads 16 bytes and accumulates to 16 shorts at a time.
__declspec(naked)
void ScaleAddRow_SSE2(const uint8* src_ptr, uint16* dst_ptr, int src_width) {
  __asm {
    mov        eax, [esp + 4]   // src_ptr
    mov        edx, [esp + 8]   // dst_ptr
    mov        ecx, [esp + 12]  // src_width
    pxor       xmm5, xmm5

  // sum rows
  xloop:
    movdqu     xmm3, [eax]       // read 16 bytes
    lea        eax, [eax + 16]
    movdqu     xmm0, [edx]       // read 16 words from destination
    movdqu     xmm1, [edx + 16]
    movdqa     xmm2, xmm3
    punpcklbw  xmm2, xmm5
    punpckhbw  xmm3, xmm5
    paddusw    xmm0, xmm2        // sum 16 words
    paddusw    xmm1, xmm3
    movdqu     [edx], xmm0       // write 16 words to destination
    movdqu     [edx + 16], xmm1
    lea        edx, [edx + 32]
    sub        ecx, 16
    jg         xloop
    ret
  }
}

#ifdef HAS_SCALEADDROW_AVX2
// Reads 32 bytes and accumulates to 32 shorts at a time.
__declspec(naked)
void ScaleAddRow_AVX2(const uint8* src_ptr, uint16* dst_ptr, int src_width) {
  __asm {
    mov         eax, [esp + 4]   // src_ptr
    mov         edx, [esp + 8]   // dst_ptr
    mov         ecx, [esp + 12]  // src_width
    vpxor       ymm5, ymm5, ymm5

  // sum rows
  xloop:
    vmovdqu     ymm3, [eax]       // read 32 bytes
    lea         eax, [eax + 32]
    vpermq      ymm3, ymm3, 0xd8  // unmutate for vpunpck
    vpunpcklbw  ymm2, ymm3, ymm5
    vpunpckhbw  ymm3, ymm3, ymm5
    vpaddusw    ymm0, ymm2, [edx] // sum 16 words
    vpaddusw    ymm1, ymm3, [edx + 32]
    vmovdqu     [edx], ymm0       // write 32 words to destination
    vmovdqu     [edx + 32], ymm1
    lea         edx, [edx + 64]
    sub         ecx, 32
    jg          xloop

    vzeroupper
    ret
  }
}
#endif  // HAS_SCALEADDROW_AVX2

// Bilinear column filtering. SSSE3 version.
__declspec(naked)
void ScaleFilterCols_SSSE3(uint8* dst_ptr, const uint8* src_ptr,
                           int dst_width, int x, int dx) {
  __asm {
    push       ebx
    push       esi
    push       edi
    mov        edi, [esp + 12 + 4]    // dst_ptr
    mov        esi, [esp + 12 + 8]    // src_ptr
    mov        ecx, [esp + 12 + 12]   // dst_width
    movd       xmm2, [esp + 12 + 16]  // x
    movd       xmm3, [esp + 12 + 20]  // dx
    mov        eax, 0x04040000      // shuffle to line up fractions with pixel.
    movd       xmm5, eax
    pcmpeqb    xmm6, xmm6           // generate 0x007f for inverting fraction.
    psrlw      xmm6, 9
    pextrw     eax, xmm2, 1         // get x0 integer. preroll
    sub        ecx, 2
    jl         xloop29

    movdqa     xmm0, xmm2           // x1 = x0 + dx
    paddd      xmm0, xmm3
    punpckldq  xmm2, xmm0           // x0 x1
    punpckldq  xmm3, xmm3           // dx dx
    paddd      xmm3, xmm3           // dx * 2, dx * 2
    pextrw     edx, xmm2, 3         // get x1 integer. preroll

    // 2 Pixel loop.
  xloop2:
    movdqa     xmm1, xmm2           // x0, x1 fractions.
    paddd      xmm2, xmm3           // x += dx
    movzx      ebx, word ptr [esi + eax]  // 2 source x0 pixels
    movd       xmm0, ebx
    psrlw      xmm1, 9              // 7 bit fractions.
    movzx      ebx, word ptr [esi + edx]  // 2 source x1 pixels
    movd       xmm4, ebx
    pshufb     xmm1, xmm5           // 0011
    punpcklwd  xmm0, xmm4
    pxor       xmm1, xmm6           // 0..7f and 7f..0
    pmaddubsw  xmm0, xmm1           // 16 bit, 2 pixels.
    pextrw     eax, xmm2, 1         // get x0 integer. next iteration.
    pextrw     edx, xmm2, 3         // get x1 integer. next iteration.
    psrlw      xmm0, 7              // 8.7 fixed point to low 8 bits.
    packuswb   xmm0, xmm0           // 8 bits, 2 pixels.
    movd       ebx, xmm0
    mov        [edi], bx
    lea        edi, [edi + 2]
    sub        ecx, 2               // 2 pixels
    jge        xloop2

 xloop29:

    add        ecx, 2 - 1
    jl         xloop99

    // 1 pixel remainder
    movzx      ebx, word ptr [esi + eax]  // 2 source x0 pixels
    movd       xmm0, ebx
    psrlw      xmm2, 9              // 7 bit fractions.
    pshufb     xmm2, xmm5           // 0011
    pxor       xmm2, xmm6           // 0..7f and 7f..0
    pmaddubsw  xmm0, xmm2           // 16 bit
    psrlw      xmm0, 7              // 8.7 fixed point to low 8 bits.
    packuswb   xmm0, xmm0           // 8 bits
    movd       ebx, xmm0
    mov        [edi], bl

 xloop99:

    pop        edi
    pop        esi
    pop        ebx
    ret
  }
}

// Reads 16 pixels, duplicates them and writes 32 pixels.
__declspec(naked)
void ScaleColsUp2_SSE2(uint8* dst_ptr, const uint8* src_ptr,
                       int dst_width, int x, int dx) {
  __asm {
    mov        edx, [esp + 4]    // dst_ptr
    mov        eax, [esp + 8]    // src_ptr
    mov        ecx, [esp + 12]   // dst_width

  wloop:
    movdqu     xmm0, [eax]
    lea        eax,  [eax + 16]
    movdqa     xmm1, xmm0
    punpcklbw  xmm0, xmm0
    punpckhbw  xmm1, xmm1
    movdqu     [edx], xmm0
    movdqu     [edx + 16], xmm1
    lea        edx, [edx + 32]
    sub        ecx, 32
    jg         wloop

    ret
  }
}

// Reads 8 pixels, throws half away and writes 4 even pixels (0, 2, 4, 6)
__declspec(naked)
void ScaleARGBRowDown2_SSE2(const uint8* src_argb,
                            ptrdiff_t src_stride,
                            uint8* dst_argb, int dst_width) {
  __asm {
    mov        eax, [esp + 4]        // src_argb
                                     // src_stride ignored
    mov        edx, [esp + 12]       // dst_argb
    mov        ecx, [esp + 16]       // dst_width

  wloop:
    movdqu     xmm0, [eax]
    movdqu     xmm1, [eax + 16]
    lea        eax,  [eax + 32]
    shufps     xmm0, xmm1, 0xdd
    movdqu     [edx], xmm0
    lea        edx, [edx + 16]
    sub        ecx, 4
    jg         wloop

    ret
  }
}

// Blends 8x1 rectangle to 4x1.
__declspec(naked)
void ScaleARGBRowDown2Linear_SSE2(const uint8* src_argb,
                                  ptrdiff_t src_stride,
                                  uint8* dst_argb, int dst_width) {
  __asm {
    mov        eax, [esp + 4]        // src_argb
                                     // src_stride ignored
    mov        edx, [esp + 12]       // dst_argb
    mov        ecx, [esp + 16]       // dst_width

  wloop:
    movdqu     xmm0, [eax]
    movdqu     xmm1, [eax + 16]
    lea        eax,  [eax + 32]
    movdqa     xmm2, xmm0
    shufps     xmm0, xmm1, 0x88      // even pixels
    shufps     xmm2, xmm1, 0xdd      // odd pixels
    pavgb      xmm0, xmm2
    movdqu     [edx], xmm0
    lea        edx, [edx + 16]
    sub        ecx, 4
    jg         wloop

    ret
  }
}

// Blends 8x2 rectangle to 4x1.
__declspec(naked)
void ScaleARGBRowDown2Box_SSE2(const uint8* src_argb,
                               ptrdiff_t src_stride,
                               uint8* dst_argb, int dst_width) {
  __asm {
    push       esi
    mov        eax, [esp + 4 + 4]    // src_argb
    mov        esi, [esp + 4 + 8]    // src_stride
    mov        edx, [esp + 4 + 12]   // dst_argb
    mov        ecx, [esp + 4 + 16]   // dst_width

  wloop:
    movdqu     xmm0, [eax]
    movdqu     xmm1, [eax + 16]
    movdqu     xmm2, [eax + esi]
    movdqu     xmm3, [eax + esi + 16]
    lea        eax,  [eax + 32]
    pavgb      xmm0, xmm2            // average rows
    pavgb      xmm1, xmm3
    movdqa     xmm2, xmm0            // average columns (8 to 4 pixels)
    shufps     xmm0, xmm1, 0x88      // even pixels
    shufps     xmm2, xmm1, 0xdd      // odd pixels
    pavgb      xmm0, xmm2
    movdqu     [edx], xmm0
    lea        edx, [edx + 16]
    sub        ecx, 4
    jg         wloop

    pop        esi
    ret
  }
}

// Reads 4 pixels at a time.
__declspec(naked)
void ScaleARGBRowDownEven_SSE2(const uint8* src_argb, ptrdiff_t src_stride,
                               int src_stepx,
                               uint8* dst_argb, int dst_width) {
  __asm {
    push       ebx
    push       edi
    mov        eax, [esp + 8 + 4]    // src_argb
                                     // src_stride ignored
    mov        ebx, [esp + 8 + 12]   // src_stepx
    mov        edx, [esp + 8 + 16]   // dst_argb
    mov        ecx, [esp + 8 + 20]   // dst_width
    lea        ebx, [ebx * 4]
    lea        edi, [ebx + ebx * 2]

  wloop:
    movd       xmm0, [eax]
    movd       xmm1, [eax + ebx]
    punpckldq  xmm0, xmm1
    movd       xmm2, [eax + ebx * 2]
    movd       xmm3, [eax + edi]
    lea        eax,  [eax + ebx * 4]
    punpckldq  xmm2, xmm3
    punpcklqdq xmm0, xmm2
    movdqu     [edx], xmm0
    lea        edx, [edx + 16]
    sub        ecx, 4
    jg         wloop

    pop        edi
    pop        ebx
    ret
  }
}

// Blends four 2x2 to 4x1.
__declspec(naked)
void ScaleARGBRowDownEvenBox_SSE2(const uint8* src_argb,
                                  ptrdiff_t src_stride,
                                  int src_stepx,
                                  uint8* dst_argb, int dst_width) {
  __asm {
    push       ebx
    push       esi
    push       edi
    mov        eax, [esp + 12 + 4]    // src_argb
    mov        esi, [esp + 12 + 8]    // src_stride
    mov        ebx, [esp + 12 + 12]   // src_stepx
    mov        edx, [esp + 12 + 16]   // dst_argb
    mov        ecx, [esp + 12 + 20]   // dst_width
    lea        esi, [eax + esi]       // row1 pointer
    lea        ebx, [ebx * 4]
    lea        edi, [ebx + ebx * 2]

  wloop:
    movq       xmm0, qword ptr [eax]  // row0 4 pairs
    movhps     xmm0, qword ptr [eax + ebx]
    movq       xmm1, qword ptr [eax + ebx * 2]
    movhps     xmm1, qword ptr [eax + edi]
    lea        eax,  [eax + ebx * 4]
    movq       xmm2, qword ptr [esi]  // row1 4 pairs
    movhps     xmm2, qword ptr [esi + ebx]
    movq       xmm3, qword ptr [esi + ebx * 2]
    movhps     xmm3, qword ptr [esi + edi]
    lea        esi,  [esi + ebx * 4]
    pavgb      xmm0, xmm2            // average rows
    pavgb      xmm1, xmm3
    movdqa     xmm2, xmm0            // average columns (8 to 4 pixels)
    shufps     xmm0, xmm1, 0x88      // even pixels
    shufps     xmm2, xmm1, 0xdd      // odd pixels
    pavgb      xmm0, xmm2
    movdqu     [edx], xmm0
    lea        edx, [edx + 16]
    sub        ecx, 4
    jg         wloop

    pop        edi
    pop        esi
    pop        ebx
    ret
  }
}

// Column scaling unfiltered. SSE2 version.
__declspec(naked)
void ScaleARGBCols_SSE2(uint8* dst_argb, const uint8* src_argb,
                        int dst_width, int x, int dx) {
  __asm {
    push       edi
    push       esi
    mov        edi, [esp + 8 + 4]    // dst_argb
    mov        esi, [esp + 8 + 8]    // src_argb
    mov        ecx, [esp + 8 + 12]   // dst_width
    movd       xmm2, [esp + 8 + 16]  // x
    movd       xmm3, [esp + 8 + 20]  // dx

    pshufd     xmm2, xmm2, 0         // x0 x0 x0 x0
    pshufd     xmm0, xmm3, 0x11      // dx  0 dx  0
    paddd      xmm2, xmm0
    paddd      xmm3, xmm3            // 0, 0, 0,  dx * 2
    pshufd     xmm0, xmm3, 0x05      // dx * 2, dx * 2, 0, 0
    paddd      xmm2, xmm0            // x3 x2 x1 x0
    paddd      xmm3, xmm3            // 0, 0, 0,  dx * 4
    pshufd     xmm3, xmm3, 0         // dx * 4, dx * 4, dx * 4, dx * 4

    pextrw     eax, xmm2, 1          // get x0 integer.
    pextrw     edx, xmm2, 3          // get x1 integer.

    cmp        ecx, 0
    jle        xloop99
    sub        ecx, 4
    jl         xloop49

    // 4 Pixel loop.
 xloop4:
    movd       xmm0, [esi + eax * 4]  // 1 source x0 pixels
    movd       xmm1, [esi + edx * 4]  // 1 source x1 pixels
    pextrw     eax, xmm2, 5           // get x2 integer.
    pextrw     edx, xmm2, 7           // get x3 integer.
    paddd      xmm2, xmm3             // x += dx
    punpckldq  xmm0, xmm1             // x0 x1

    movd       xmm1, [esi + eax * 4]  // 1 source x2 pixels
    movd       xmm4, [esi + edx * 4]  // 1 source x3 pixels
    pextrw     eax, xmm2, 1           // get x0 integer. next iteration.
    pextrw     edx, xmm2, 3           // get x1 integer. next iteration.
    punpckldq  xmm1, xmm4             // x2 x3
    punpcklqdq xmm0, xmm1             // x0 x1 x2 x3
    movdqu     [edi], xmm0
    lea        edi, [edi + 16]
    sub        ecx, 4                 // 4 pixels
    jge        xloop4

 xloop49:
    test       ecx, 2
    je         xloop29

    // 2 Pixels.
    movd       xmm0, [esi + eax * 4]  // 1 source x0 pixels
    movd       xmm1, [esi + edx * 4]  // 1 source x1 pixels
    pextrw     eax, xmm2, 5           // get x2 integer.
    punpckldq  xmm0, xmm1             // x0 x1

    movq       qword ptr [edi], xmm0
    lea        edi, [edi + 8]

 xloop29:
    test       ecx, 1
    je         xloop99

    // 1 Pixels.
    movd       xmm0, [esi + eax * 4]  // 1 source x2 pixels
    movd       dword ptr [edi], xmm0
 xloop99:

    pop        esi
    pop        edi
    ret
  }
}

// Bilinear row filtering combines 2x1 -> 1x1. SSSE3 version.
// TODO(fbarchard): Port to Neon

// Shuffle table for arranging 2 pixels into pairs for pmaddubsw
static uvec8 kShuffleColARGB = {
  0u, 4u, 1u, 5u, 2u, 6u, 3u, 7u,  // bbggrraa 1st pixel
  8u, 12u, 9u, 13u, 10u, 14u, 11u, 15u  // bbggrraa 2nd pixel
};

// Shuffle table for duplicating 2 fractions into 8 bytes each
static uvec8 kShuffleFractions = {
  0u, 0u, 0u, 0u, 0u, 0u, 0u, 0u, 4u, 4u, 4u, 4u, 4u, 4u, 4u, 4u,
};

__declspec(naked)
void ScaleARGBFilterCols_SSSE3(uint8* dst_argb, const uint8* src_argb,
                               int dst_width, int x, int dx) {
  __asm {
    push       esi
    push       edi
    mov        edi, [esp + 8 + 4]    // dst_argb
    mov        esi, [esp + 8 + 8]    // src_argb
    mov        ecx, [esp + 8 + 12]   // dst_width
    movd       xmm2, [esp + 8 + 16]  // x
    movd       xmm3, [esp + 8 + 20]  // dx
    movdqa     xmm4, xmmword ptr kShuffleColARGB
    movdqa     xmm5, xmmword ptr kShuffleFractions
    pcmpeqb    xmm6, xmm6           // generate 0x007f for inverting fraction.
    psrlw      xmm6, 9
    pextrw     eax, xmm2, 1         // get x0 integer. preroll
    sub        ecx, 2
    jl         xloop29

    movdqa     xmm0, xmm2           // x1 = x0 + dx
    paddd      xmm0, xmm3
    punpckldq  xmm2, xmm0           // x0 x1
    punpckldq  xmm3, xmm3           // dx dx
    paddd      xmm3, xmm3           // dx * 2, dx * 2
    pextrw     edx, xmm2, 3         // get x1 integer. preroll

    // 2 Pixel loop.
  xloop2:
    movdqa     xmm1, xmm2           // x0, x1 fractions.
    paddd      xmm2, xmm3           // x += dx
    movq       xmm0, qword ptr [esi + eax * 4]  // 2 source x0 pixels
    psrlw      xmm1, 9              // 7 bit fractions.
    movhps     xmm0, qword ptr [esi + edx * 4]  // 2 source x1 pixels
    pshufb     xmm1, xmm5           // 0000000011111111
    pshufb     xmm0, xmm4           // arrange pixels into pairs
    pxor       xmm1, xmm6           // 0..7f and 7f..0
    pmaddubsw  xmm0, xmm1           // argb_argb 16 bit, 2 pixels.
    pextrw     eax, xmm2, 1         // get x0 integer. next iteration.
    pextrw     edx, xmm2, 3         // get x1 integer. next iteration.
    psrlw      xmm0, 7              // argb 8.7 fixed point to low 8 bits.
    packuswb   xmm0, xmm0           // argb_argb 8 bits, 2 pixels.
    movq       qword ptr [edi], xmm0
    lea        edi, [edi + 8]
    sub        ecx, 2               // 2 pixels
    jge        xloop2

 xloop29:

    add        ecx, 2 - 1
    jl         xloop99

    // 1 pixel remainder
    psrlw      xmm2, 9              // 7 bit fractions.
    movq       xmm0, qword ptr [esi + eax * 4]  // 2 source x0 pixels
    pshufb     xmm2, xmm5           // 00000000
    pshufb     xmm0, xmm4           // arrange pixels into pairs
    pxor       xmm2, xmm6           // 0..7f and 7f..0
    pmaddubsw  xmm0, xmm2           // argb 16 bit, 1 pixel.
    psrlw      xmm0, 7
    packuswb   xmm0, xmm0           // argb 8 bits, 1 pixel.
    movd       [edi], xmm0

 xloop99:

    pop        edi
    pop        esi
    ret
  }
}

// Reads 4 pixels, duplicates them and writes 8 pixels.
__declspec(naked)
void ScaleARGBColsUp2_SSE2(uint8* dst_argb, const uint8* src_argb,
                           int dst_width, int x, int dx) {
  __asm {
    mov        edx, [esp + 4]    // dst_argb
    mov        eax, [esp + 8]    // src_argb
    mov        ecx, [esp + 12]   // dst_width

  wloop:
    movdqu     xmm0, [eax]
    lea        eax,  [eax + 16]
    movdqa     xmm1, xmm0
    punpckldq  xmm0, xmm0
    punpckhdq  xmm1, xmm1
    movdqu     [edx], xmm0
    movdqu     [edx + 16], xmm1
    lea        edx, [edx + 32]
    sub        ecx, 8
    jg         wloop

    ret
  }
}

// Divide num by div and return as 16.16 fixed point result.
__declspec(naked)
int FixedDiv_X86(int num, int div) {
  __asm {
    mov        eax, [esp + 4]    // num
    cdq                          // extend num to 64 bits
    shld       edx, eax, 16      // 32.16
    shl        eax, 16
    idiv       dword ptr [esp + 8]
    ret
  }
}

// Divide num by div and return as 16.16 fixed point result.
__declspec(naked)
int FixedDiv1_X86(int num, int div) {
  __asm {
    mov        eax, [esp + 4]    // num
    mov        ecx, [esp + 8]    // denom
    cdq                          // extend num to 64 bits
    shld       edx, eax, 16      // 32.16
    shl        eax, 16
    sub        eax, 0x00010001
    sbb        edx, 0
    sub        ecx, 1
    idiv       ecx
    ret
  }
}
#endif  // !defined(LIBYUV_DISABLE_X86) && defined(_M_IX86)

#ifdef __cplusplus
}  // extern "C"
}  // namespace libyuv
#endif