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image/draw: optimize bounds checks in loops
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Use subslices with known length and cap to give bounds checking hints
to the compiler. Improves over the earlier pointer based optimizations
in https://go-review.googlesource.com/c/go/+/14093 for GlyphOver but
not for FillOver so the latter is left unchanged.

See #27857 for discussion of small caps used in subslices.

name               old time/op  new time/op  delta
FillOver-8          607µs ± 1%   609µs ± 1%     ~     (p=0.447 n=9+10)
FillSrc-8          23.0µs ± 1%  22.9µs ± 2%     ~     (p=0.412 n=9+10)
CopyOver-8          647µs ± 0%   560µs ± 0%  -13.43%  (p=0.000 n=9+10)
CopySrc-8          19.3µs ± 1%  19.1µs ± 2%   -0.66%  (p=0.029 n=10+10)
NRGBAOver-8         697µs ± 1%   651µs ± 1%   -6.64%  (p=0.000 n=10+10)
NRGBASrc-8          405µs ± 1%   347µs ± 0%  -14.23%  (p=0.000 n=10+10)
YCbCr-8             432µs ± 2%   431µs ± 1%     ~     (p=0.764 n=10+9)
Gray-8              164µs ± 1%   139µs ± 1%  -15.44%  (p=0.000 n=10+10)
CMYK-8              498µs ± 0%   461µs ± 0%   -7.49%  (p=0.000 n=10+9)
GlyphOver-8         220µs ± 0%   199µs ± 0%   -9.52%  (p=0.000 n=9+10)
RGBA-8             3.81ms ± 5%  3.79ms ± 5%     ~     (p=0.549 n=9+10)
Paletted-8         1.73ms ± 0%  1.73ms ± 1%     ~     (p=0.278 n=10+9)
GenericOver-8      11.0ms ± 2%  11.0ms ± 1%     ~     (p=0.842 n=9+10)
GenericMaskOver-8  5.29ms ± 1%  5.30ms ± 0%     ~     (p=0.182 n=9+10)
GenericSrc-8       4.24ms ± 1%  4.24ms ± 0%     ~     (p=0.436 n=9+9)
GenericMaskSrc-8   7.89ms ± 1%  7.90ms ± 2%     ~     (p=0.631 n=10+10)

Change-Id: I6fe1b21bb5e255826cbfdd2e73efd5858cd5557c
Reviewed-on: https://go-review.googlesource.com/136935
Reviewed-by: Brad Fitzpatrick <[email protected]>
Run-TryBot: Brad Fitzpatrick <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>
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@iand @bradfitz
iand authored and bradfitz committed Sep 25, 2018
1 parent e945623 commit 5bba505
Showing 1 changed file with 63 additions and 63 deletions.
126 changes: 63 additions & 63 deletions src/image/draw/draw.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -309,23 +309,20 @@ func drawCopyOver(dst *image.RGBA, r image.Rectangle, src *image.RGBA, sp image.
dpix := dst.Pix[d0:]
spix := src.Pix[s0:]
for i := i0; i != i1; i += idelta {
sr := uint32(spix[i+0]) * 0x101
sg := uint32(spix[i+1]) * 0x101
sb := uint32(spix[i+2]) * 0x101
sa := uint32(spix[i+3]) * 0x101

dr := &dpix[i+0]
dg := &dpix[i+1]
db := &dpix[i+2]
da := &dpix[i+3]
s := spix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857
sr := uint32(s[0]) * 0x101
sg := uint32(s[1]) * 0x101
sb := uint32(s[2]) * 0x101
sa := uint32(s[3]) * 0x101

// The 0x101 is here for the same reason as in drawRGBA.
a := (m - sa) * 0x101

*dr = uint8((uint32(*dr)*a/m + sr) >> 8)
*dg = uint8((uint32(*dg)*a/m + sg) >> 8)
*db = uint8((uint32(*db)*a/m + sb) >> 8)
*da = uint8((uint32(*da)*a/m + sa) >> 8)
d := dpix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857
d[0] = uint8((uint32(d[0])*a/m + sr) >> 8)
d[1] = uint8((uint32(d[1])*a/m + sg) >> 8)
d[2] = uint8((uint32(d[2])*a/m + sb) >> 8)
d[3] = uint8((uint32(d[3])*a/m + sa) >> 8)
}
d0 += ddelta
s0 += sdelta
Expand Down Expand Up @@ -372,23 +369,25 @@ func drawNRGBAOver(dst *image.RGBA, r image.Rectangle, src *image.NRGBA, sp imag

for i, si := i0, si0; i < i1; i, si = i+4, si+4 {
// Convert from non-premultiplied color to pre-multiplied color.
sa := uint32(spix[si+3]) * 0x101
sr := uint32(spix[si+0]) * sa / 0xff
sg := uint32(spix[si+1]) * sa / 0xff
sb := uint32(spix[si+2]) * sa / 0xff

dr := uint32(dpix[i+0])
dg := uint32(dpix[i+1])
db := uint32(dpix[i+2])
da := uint32(dpix[i+3])
s := spix[si : si+4 : si+4] // Small cap improves performance, see https://golang.org/issue/27857
sa := uint32(s[3]) * 0x101
sr := uint32(s[0]) * sa / 0xff
sg := uint32(s[1]) * sa / 0xff
sb := uint32(s[2]) * sa / 0xff

d := dpix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857
dr := uint32(d[0])
dg := uint32(d[1])
db := uint32(d[2])
da := uint32(d[3])

// The 0x101 is here for the same reason as in drawRGBA.
a := (m - sa) * 0x101

dpix[i+0] = uint8((dr*a/m + sr) >> 8)
dpix[i+1] = uint8((dg*a/m + sg) >> 8)
dpix[i+2] = uint8((db*a/m + sb) >> 8)
dpix[i+3] = uint8((da*a/m + sa) >> 8)
d[0] = uint8((dr*a/m + sr) >> 8)
d[1] = uint8((dg*a/m + sg) >> 8)
d[2] = uint8((db*a/m + sb) >> 8)
d[3] = uint8((da*a/m + sa) >> 8)
}
}
}
Expand All @@ -407,15 +406,17 @@ func drawNRGBASrc(dst *image.RGBA, r image.Rectangle, src *image.NRGBA, sp image

for i, si := i0, si0; i < i1; i, si = i+4, si+4 {
// Convert from non-premultiplied color to pre-multiplied color.
sa := uint32(spix[si+3]) * 0x101
sr := uint32(spix[si+0]) * sa / 0xff
sg := uint32(spix[si+1]) * sa / 0xff
sb := uint32(spix[si+2]) * sa / 0xff

dpix[i+0] = uint8(sr >> 8)
dpix[i+1] = uint8(sg >> 8)
dpix[i+2] = uint8(sb >> 8)
dpix[i+3] = uint8(sa >> 8)
s := spix[si : si+4 : si+4] // Small cap improves performance, see https://golang.org/issue/27857
sa := uint32(s[3]) * 0x101
sr := uint32(s[0]) * sa / 0xff
sg := uint32(s[1]) * sa / 0xff
sb := uint32(s[2]) * sa / 0xff

d := dpix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857
d[0] = uint8(sr >> 8)
d[1] = uint8(sg >> 8)
d[2] = uint8(sb >> 8)
d[3] = uint8(sa >> 8)
}
}
}
Expand All @@ -434,10 +435,11 @@ func drawGray(dst *image.RGBA, r image.Rectangle, src *image.Gray, sp image.Poin

for i, si := i0, si0; i < i1; i, si = i+4, si+1 {
p := spix[si]
dpix[i+0] = p
dpix[i+1] = p
dpix[i+2] = p
dpix[i+3] = 255
d := dpix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857
d[0] = p
d[1] = p
d[2] = p
d[3] = 255
}
}
}
Expand All @@ -455,9 +457,10 @@ func drawCMYK(dst *image.RGBA, r image.Rectangle, src *image.CMYK, sp image.Poin
spix := src.Pix[sy*src.Stride:]

for i, si := i0, si0; i < i1; i, si = i+4, si+4 {
dpix[i+0], dpix[i+1], dpix[i+2] =
color.CMYKToRGB(spix[si+0], spix[si+1], spix[si+2], spix[si+3])
dpix[i+3] = 255
s := spix[si : si+4 : si+4] // Small cap improves performance, see https://golang.org/issue/27857
d := dpix[i : i+4 : i+4]
d[0], d[1], d[2] = color.CMYKToRGB(s[0], s[1], s[2], s[3])
d[3] = 255
}
}
}
Expand All @@ -475,18 +478,14 @@ func drawGlyphOver(dst *image.RGBA, r image.Rectangle, src *image.Uniform, mask
}
ma |= ma << 8

dr := &dst.Pix[i+0]
dg := &dst.Pix[i+1]
db := &dst.Pix[i+2]
da := &dst.Pix[i+3]

// The 0x101 is here for the same reason as in drawRGBA.
a := (m - (sa * ma / m)) * 0x101

*dr = uint8((uint32(*dr)*a + sr*ma) / m >> 8)
*dg = uint8((uint32(*dg)*a + sg*ma) / m >> 8)
*db = uint8((uint32(*db)*a + sb*ma) / m >> 8)
*da = uint8((uint32(*da)*a + sa*ma) / m >> 8)
d := dst.Pix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857
d[0] = uint8((uint32(d[0])*a + sr*ma) / m >> 8)
d[1] = uint8((uint32(d[1])*a + sg*ma) / m >> 8)
d[2] = uint8((uint32(d[2])*a + sb*ma) / m >> 8)
d[3] = uint8((uint32(d[3])*a + sa*ma) / m >> 8)
}
i0 += dst.Stride
i1 += dst.Stride
Expand Down Expand Up @@ -518,11 +517,12 @@ func drawRGBA(dst *image.RGBA, r image.Rectangle, src image.Image, sp image.Poin
_, _, _, ma = mask.At(mx, my).RGBA()
}
sr, sg, sb, sa := src.At(sx, sy).RGBA()
d := dst.Pix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857
if op == Over {
dr := uint32(dst.Pix[i+0])
dg := uint32(dst.Pix[i+1])
db := uint32(dst.Pix[i+2])
da := uint32(dst.Pix[i+3])
dr := uint32(d[0])
dg := uint32(d[1])
db := uint32(d[2])
da := uint32(d[3])

// dr, dg, db and da are all 8-bit color at the moment, ranging in [0,255].
// We work in 16-bit color, and so would normally do:
Expand All @@ -532,16 +532,16 @@ func drawRGBA(dst *image.RGBA, r image.Rectangle, src image.Image, sp image.Poin
// This yields the same result, but is fewer arithmetic operations.
a := (m - (sa * ma / m)) * 0x101

dst.Pix[i+0] = uint8((dr*a + sr*ma) / m >> 8)
dst.Pix[i+1] = uint8((dg*a + sg*ma) / m >> 8)
dst.Pix[i+2] = uint8((db*a + sb*ma) / m >> 8)
dst.Pix[i+3] = uint8((da*a + sa*ma) / m >> 8)
d[0] = uint8((dr*a + sr*ma) / m >> 8)
d[1] = uint8((dg*a + sg*ma) / m >> 8)
d[2] = uint8((db*a + sb*ma) / m >> 8)
d[3] = uint8((da*a + sa*ma) / m >> 8)

} else {
dst.Pix[i+0] = uint8(sr * ma / m >> 8)
dst.Pix[i+1] = uint8(sg * ma / m >> 8)
dst.Pix[i+2] = uint8(sb * ma / m >> 8)
dst.Pix[i+3] = uint8(sa * ma / m >> 8)
d[0] = uint8(sr * ma / m >> 8)
d[1] = uint8(sg * ma / m >> 8)
d[2] = uint8(sb * ma / m >> 8)
d[3] = uint8(sa * ma / m >> 8)
}
}
i0 += dy * dst.Stride
Expand Down

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