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image: optimize bounds checking for At and Set methods
Use a subslice of the pixel data to give the compiler hints for bounds checking. Only do this for image formats that require 4 or more slice reads/writes. See #27857 for discussion of small cap sizes. name old time/op new time/op delta At/rgba-8 18.8ns ± 2% 18.5ns ± 1% -1.49% (p=0.026 n=10+10) At/rgba64-8 22.2ns ± 2% 21.1ns ± 3% -4.51% (p=0.000 n=10+10) At/nrgba-8 18.8ns ± 2% 18.7ns ± 2% ~ (p=0.467 n=10+10) At/nrgba64-8 21.9ns ± 2% 21.0ns ± 2% -4.15% (p=0.000 n=10+9) At/alpha-8 14.3ns ± 1% 14.3ns ± 2% ~ (p=0.543 n=10+10) At/alpha16-8 6.43ns ± 1% 6.47ns ± 1% ~ (p=0.053 n=10+10) At/gray-8 14.4ns ± 2% 14.6ns ± 5% ~ (p=0.194 n=10+10) At/gray16-8 6.52ns ± 1% 6.55ns ± 2% ~ (p=0.610 n=10+10) At/paletted-8 4.17ns ± 1% 4.21ns ± 2% ~ (p=0.095 n=9+10) Set/rgba-8 39.2ns ± 2% 40.1ns ± 4% +2.45% (p=0.007 n=10+10) Set/rgba64-8 46.2ns ± 3% 43.3ns ± 3% -6.11% (p=0.000 n=10+10) Set/nrgba-8 39.2ns ± 1% 39.7ns ± 5% ~ (p=0.407 n=10+10) Set/nrgba64-8 45.6ns ± 3% 42.9ns ± 3% -5.83% (p=0.000 n=9+10) Set/alpha-8 35.0ns ± 3% 34.1ns ± 2% -2.43% (p=0.017 n=10+10) Set/alpha16-8 36.3ns ± 4% 35.8ns ± 5% ~ (p=0.254 n=10+10) Set/gray-8 19.8ns ± 1% 19.7ns ± 0% -0.69% (p=0.002 n=8+6) Set/gray16-8 36.0ns ± 1% 36.4ns ± 2% +1.08% (p=0.037 n=10+10) Set/paletted-8 39.1ns ± 0% 39.6ns ± 1% +1.30% (p=0.000 n=10+10) RGBAAt-8 3.72ns ± 1% 3.58ns ± 1% -3.76% (p=0.000 n=9+10) RGBASetRGBA-8 4.35ns ± 1% 3.70ns ± 1% -14.92% (p=0.000 n=10+10) RGBA64At-8 5.08ns ± 1% 3.69ns ± 1% -27.40% (p=0.000 n=9+9) RGBA64SetRGBA64-8 6.65ns ± 2% 3.63ns ± 0% -45.35% (p=0.000 n=10+9) NRGBAAt-8 3.72ns ± 1% 3.59ns ± 1% -3.55% (p=0.000 n=10+10) NRGBASetNRGBA-8 4.05ns ± 0% 3.71ns ± 1% -8.57% (p=0.000 n=9+10) NRGBA64At-8 4.99ns ± 1% 3.69ns ± 0% -26.07% (p=0.000 n=10+9) NRGBA64SetNRGBA64-8 6.66ns ± 1% 3.64ns ± 1% -45.40% (p=0.000 n=10+10) AlphaAt-8 1.44ns ± 1% 1.44ns ± 0% ~ (p=0.176 n=10+7) AlphaSetAlpha-8 1.60ns ± 2% 1.56ns ± 0% -2.62% (p=0.000 n=10+6) Alpha16At-8 2.87ns ± 1% 2.92ns ± 2% +1.67% (p=0.001 n=10+10) AlphaSetAlpha16-8 3.26ns ± 1% 3.35ns ± 1% +2.68% (p=0.012 n=8+3) Fixes #14884 Change-Id: Ia0383530596a550e1b1c7aafce5220e5e0935a53 Reviewed-on: https://go-review.googlesource.com/137495 Reviewed-by: Brad Fitzpatrick <[email protected]>
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‎src/image/image.go

Lines changed: 82 additions & 67 deletions
Original file line numberDiff line numberDiff line change
@@ -80,7 +80,8 @@ func (p *RGBA) RGBAAt(x, y int) color.RGBA {
8080
return color.RGBA{}
8181
}
8282
i := p.PixOffset(x, y)
83-
return color.RGBA{p.Pix[i+0], p.Pix[i+1], p.Pix[i+2], p.Pix[i+3]}
83+
s := p.Pix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857
84+
return color.RGBA{s[0], s[1], s[2], s[3]}
8485
}
8586

8687
// PixOffset returns the index of the first element of Pix that corresponds to
@@ -95,21 +96,23 @@ func (p *RGBA) Set(x, y int, c color.Color) {
9596
}
9697
i := p.PixOffset(x, y)
9798
c1 := color.RGBAModel.Convert(c).(color.RGBA)
98-
p.Pix[i+0] = c1.R
99-
p.Pix[i+1] = c1.G
100-
p.Pix[i+2] = c1.B
101-
p.Pix[i+3] = c1.A
99+
s := p.Pix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857
100+
s[0] = c1.R
101+
s[1] = c1.G
102+
s[2] = c1.B
103+
s[3] = c1.A
102104
}
103105

104106
func (p *RGBA) SetRGBA(x, y int, c color.RGBA) {
105107
if !(Point{x, y}.In(p.Rect)) {
106108
return
107109
}
108110
i := p.PixOffset(x, y)
109-
p.Pix[i+0] = c.R
110-
p.Pix[i+1] = c.G
111-
p.Pix[i+2] = c.B
112-
p.Pix[i+3] = c.A
111+
s := p.Pix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857
112+
s[0] = c.R
113+
s[1] = c.G
114+
s[2] = c.B
115+
s[3] = c.A
113116
}
114117

115118
// SubImage returns an image representing the portion of the image p visible
@@ -179,11 +182,12 @@ func (p *RGBA64) RGBA64At(x, y int) color.RGBA64 {
179182
return color.RGBA64{}
180183
}
181184
i := p.PixOffset(x, y)
185+
s := p.Pix[i : i+8 : i+8] // Small cap improves performance, see https://golang.org/issue/27857
182186
return color.RGBA64{
183-
uint16(p.Pix[i+0])<<8 | uint16(p.Pix[i+1]),
184-
uint16(p.Pix[i+2])<<8 | uint16(p.Pix[i+3]),
185-
uint16(p.Pix[i+4])<<8 | uint16(p.Pix[i+5]),
186-
uint16(p.Pix[i+6])<<8 | uint16(p.Pix[i+7]),
187+
uint16(s[0])<<8 | uint16(s[1]),
188+
uint16(s[2])<<8 | uint16(s[3]),
189+
uint16(s[4])<<8 | uint16(s[5]),
190+
uint16(s[6])<<8 | uint16(s[7]),
187191
}
188192
}
189193

@@ -199,29 +203,31 @@ func (p *RGBA64) Set(x, y int, c color.Color) {
199203
}
200204
i := p.PixOffset(x, y)
201205
c1 := color.RGBA64Model.Convert(c).(color.RGBA64)
202-
p.Pix[i+0] = uint8(c1.R >> 8)
203-
p.Pix[i+1] = uint8(c1.R)
204-
p.Pix[i+2] = uint8(c1.G >> 8)
205-
p.Pix[i+3] = uint8(c1.G)
206-
p.Pix[i+4] = uint8(c1.B >> 8)
207-
p.Pix[i+5] = uint8(c1.B)
208-
p.Pix[i+6] = uint8(c1.A >> 8)
209-
p.Pix[i+7] = uint8(c1.A)
206+
s := p.Pix[i : i+8 : i+8] // Small cap improves performance, see https://golang.org/issue/27857
207+
s[0] = uint8(c1.R >> 8)
208+
s[1] = uint8(c1.R)
209+
s[2] = uint8(c1.G >> 8)
210+
s[3] = uint8(c1.G)
211+
s[4] = uint8(c1.B >> 8)
212+
s[5] = uint8(c1.B)
213+
s[6] = uint8(c1.A >> 8)
214+
s[7] = uint8(c1.A)
210215
}
211216

212217
func (p *RGBA64) SetRGBA64(x, y int, c color.RGBA64) {
213218
if !(Point{x, y}.In(p.Rect)) {
214219
return
215220
}
216221
i := p.PixOffset(x, y)
217-
p.Pix[i+0] = uint8(c.R >> 8)
218-
p.Pix[i+1] = uint8(c.R)
219-
p.Pix[i+2] = uint8(c.G >> 8)
220-
p.Pix[i+3] = uint8(c.G)
221-
p.Pix[i+4] = uint8(c.B >> 8)
222-
p.Pix[i+5] = uint8(c.B)
223-
p.Pix[i+6] = uint8(c.A >> 8)
224-
p.Pix[i+7] = uint8(c.A)
222+
s := p.Pix[i : i+8 : i+8] // Small cap improves performance, see https://golang.org/issue/27857
223+
s[0] = uint8(c.R >> 8)
224+
s[1] = uint8(c.R)
225+
s[2] = uint8(c.G >> 8)
226+
s[3] = uint8(c.G)
227+
s[4] = uint8(c.B >> 8)
228+
s[5] = uint8(c.B)
229+
s[6] = uint8(c.A >> 8)
230+
s[7] = uint8(c.A)
225231
}
226232

227233
// SubImage returns an image representing the portion of the image p visible
@@ -291,7 +297,8 @@ func (p *NRGBA) NRGBAAt(x, y int) color.NRGBA {
291297
return color.NRGBA{}
292298
}
293299
i := p.PixOffset(x, y)
294-
return color.NRGBA{p.Pix[i+0], p.Pix[i+1], p.Pix[i+2], p.Pix[i+3]}
300+
s := p.Pix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857
301+
return color.NRGBA{s[0], s[1], s[2], s[3]}
295302
}
296303

297304
// PixOffset returns the index of the first element of Pix that corresponds to
@@ -306,21 +313,23 @@ func (p *NRGBA) Set(x, y int, c color.Color) {
306313
}
307314
i := p.PixOffset(x, y)
308315
c1 := color.NRGBAModel.Convert(c).(color.NRGBA)
309-
p.Pix[i+0] = c1.R
310-
p.Pix[i+1] = c1.G
311-
p.Pix[i+2] = c1.B
312-
p.Pix[i+3] = c1.A
316+
s := p.Pix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857
317+
s[0] = c1.R
318+
s[1] = c1.G
319+
s[2] = c1.B
320+
s[3] = c1.A
313321
}
314322

315323
func (p *NRGBA) SetNRGBA(x, y int, c color.NRGBA) {
316324
if !(Point{x, y}.In(p.Rect)) {
317325
return
318326
}
319327
i := p.PixOffset(x, y)
320-
p.Pix[i+0] = c.R
321-
p.Pix[i+1] = c.G
322-
p.Pix[i+2] = c.B
323-
p.Pix[i+3] = c.A
328+
s := p.Pix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857
329+
s[0] = c.R
330+
s[1] = c.G
331+
s[2] = c.B
332+
s[3] = c.A
324333
}
325334

326335
// SubImage returns an image representing the portion of the image p visible
@@ -390,11 +399,12 @@ func (p *NRGBA64) NRGBA64At(x, y int) color.NRGBA64 {
390399
return color.NRGBA64{}
391400
}
392401
i := p.PixOffset(x, y)
402+
s := p.Pix[i : i+8 : i+8] // Small cap improves performance, see https://golang.org/issue/27857
393403
return color.NRGBA64{
394-
uint16(p.Pix[i+0])<<8 | uint16(p.Pix[i+1]),
395-
uint16(p.Pix[i+2])<<8 | uint16(p.Pix[i+3]),
396-
uint16(p.Pix[i+4])<<8 | uint16(p.Pix[i+5]),
397-
uint16(p.Pix[i+6])<<8 | uint16(p.Pix[i+7]),
404+
uint16(s[0])<<8 | uint16(s[1]),
405+
uint16(s[2])<<8 | uint16(s[3]),
406+
uint16(s[4])<<8 | uint16(s[5]),
407+
uint16(s[6])<<8 | uint16(s[7]),
398408
}
399409
}
400410

@@ -410,29 +420,31 @@ func (p *NRGBA64) Set(x, y int, c color.Color) {
410420
}
411421
i := p.PixOffset(x, y)
412422
c1 := color.NRGBA64Model.Convert(c).(color.NRGBA64)
413-
p.Pix[i+0] = uint8(c1.R >> 8)
414-
p.Pix[i+1] = uint8(c1.R)
415-
p.Pix[i+2] = uint8(c1.G >> 8)
416-
p.Pix[i+3] = uint8(c1.G)
417-
p.Pix[i+4] = uint8(c1.B >> 8)
418-
p.Pix[i+5] = uint8(c1.B)
419-
p.Pix[i+6] = uint8(c1.A >> 8)
420-
p.Pix[i+7] = uint8(c1.A)
423+
s := p.Pix[i : i+8 : i+8] // Small cap improves performance, see https://golang.org/issue/27857
424+
s[0] = uint8(c1.R >> 8)
425+
s[1] = uint8(c1.R)
426+
s[2] = uint8(c1.G >> 8)
427+
s[3] = uint8(c1.G)
428+
s[4] = uint8(c1.B >> 8)
429+
s[5] = uint8(c1.B)
430+
s[6] = uint8(c1.A >> 8)
431+
s[7] = uint8(c1.A)
421432
}
422433

423434
func (p *NRGBA64) SetNRGBA64(x, y int, c color.NRGBA64) {
424435
if !(Point{x, y}.In(p.Rect)) {
425436
return
426437
}
427438
i := p.PixOffset(x, y)
428-
p.Pix[i+0] = uint8(c.R >> 8)
429-
p.Pix[i+1] = uint8(c.R)
430-
p.Pix[i+2] = uint8(c.G >> 8)
431-
p.Pix[i+3] = uint8(c.G)
432-
p.Pix[i+4] = uint8(c.B >> 8)
433-
p.Pix[i+5] = uint8(c.B)
434-
p.Pix[i+6] = uint8(c.A >> 8)
435-
p.Pix[i+7] = uint8(c.A)
439+
s := p.Pix[i : i+8 : i+8] // Small cap improves performance, see https://golang.org/issue/27857
440+
s[0] = uint8(c.R >> 8)
441+
s[1] = uint8(c.R)
442+
s[2] = uint8(c.G >> 8)
443+
s[3] = uint8(c.G)
444+
s[4] = uint8(c.B >> 8)
445+
s[5] = uint8(c.B)
446+
s[6] = uint8(c.A >> 8)
447+
s[7] = uint8(c.A)
436448
}
437449

438450
// SubImage returns an image representing the portion of the image p visible
@@ -850,7 +862,8 @@ func (p *CMYK) CMYKAt(x, y int) color.CMYK {
850862
return color.CMYK{}
851863
}
852864
i := p.PixOffset(x, y)
853-
return color.CMYK{p.Pix[i+0], p.Pix[i+1], p.Pix[i+2], p.Pix[i+3]}
865+
s := p.Pix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857
866+
return color.CMYK{s[0], s[1], s[2], s[3]}
854867
}
855868

856869
// PixOffset returns the index of the first element of Pix that corresponds to
@@ -865,21 +878,23 @@ func (p *CMYK) Set(x, y int, c color.Color) {
865878
}
866879
i := p.PixOffset(x, y)
867880
c1 := color.CMYKModel.Convert(c).(color.CMYK)
868-
p.Pix[i+0] = c1.C
869-
p.Pix[i+1] = c1.M
870-
p.Pix[i+2] = c1.Y
871-
p.Pix[i+3] = c1.K
881+
s := p.Pix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857
882+
s[0] = c1.C
883+
s[1] = c1.M
884+
s[2] = c1.Y
885+
s[3] = c1.K
872886
}
873887

874888
func (p *CMYK) SetCMYK(x, y int, c color.CMYK) {
875889
if !(Point{x, y}.In(p.Rect)) {
876890
return
877891
}
878892
i := p.PixOffset(x, y)
879-
p.Pix[i+0] = c.C
880-
p.Pix[i+1] = c.M
881-
p.Pix[i+2] = c.Y
882-
p.Pix[i+3] = c.K
893+
s := p.Pix[i : i+4 : i+4] // Small cap improves performance, see https://golang.org/issue/27857
894+
s[0] = c.C
895+
s[1] = c.M
896+
s[2] = c.Y
897+
s[3] = c.K
883898
}
884899

885900
// SubImage returns an image representing the portion of the image p visible

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