mirror of https://github.com/golang/go.git
image/jpeg: reduce bound checks from idct and fdct
Before - $gotip build -gcflags="-d=ssa/check_bce/debug=1" fdct.go idct.go ./fdct.go:89:10: Found IsInBounds ./fdct.go:90:10: Found IsInBounds ./fdct.go:91:10: Found IsInBounds ./fdct.go:92:10: Found IsInBounds ./fdct.go:93:10: Found IsInBounds ./fdct.go:94:10: Found IsInBounds ./fdct.go:95:10: Found IsInBounds ./fdct.go:96:10: Found IsInBounds ./idct.go:77:9: Found IsInBounds ./idct.go:77:27: Found IsInBounds ./idct.go:77:45: Found IsInBounds ./idct.go:78:7: Found IsInBounds ./idct.go:78:25: Found IsInBounds ./idct.go:78:43: Found IsInBounds ./idct.go:78:61: Found IsInBounds ./idct.go:79:13: Found IsInBounds ./idct.go:92:13: Found IsInBounds ./idct.go:93:12: Found IsInBounds ./idct.go:94:12: Found IsInBounds ./idct.go:95:12: Found IsInBounds ./idct.go:97:12: Found IsInBounds ./idct.go:98:12: Found IsInBounds ./idct.go:99:12: Found IsInBounds After - $gotip build -gcflags="-d=ssa/check_bce/debug=1" fdct.go idct.go ./fdct.go:90:9: Found IsSliceInBounds ./idct.go:76:11: Found IsSliceInBounds ./idct.go:145:11: Found IsSliceInBounds name old time/op new time/op delta FDCT-4 1.85µs ± 2% 1.74µs ± 1% -5.95% (p=0.000 n=10+10) IDCT-4 1.94µs ± 2% 1.89µs ± 1% -2.67% (p=0.000 n=10+9) DecodeBaseline-4 1.45ms ± 2% 1.46ms ± 1% ~ (p=0.156 n=9+10) DecodeProgressive-4 2.21ms ± 1% 2.21ms ± 1% ~ (p=0.796 n=10+10) EncodeRGBA-4 24.9ms ± 1% 25.0ms ± 1% ~ (p=0.075 n=10+10) EncodeYCbCr-4 26.1ms ± 1% 26.2ms ± 1% ~ (p=0.573 n=8+10) name old speed new speed delta DecodeBaseline-4 42.5MB/s ± 2% 42.4MB/s ± 1% ~ (p=0.162 n=9+10) DecodeProgressive-4 27.9MB/s ± 1% 27.9MB/s ± 1% ~ (p=0.796 n=10+10) EncodeRGBA-4 49.4MB/s ± 1% 49.1MB/s ± 1% ~ (p=0.066 n=10+10) EncodeYCbCr-4 35.3MB/s ± 1% 35.2MB/s ± 1% ~ (p=0.586 n=8+10) name old alloc/op new alloc/op delta DecodeBaseline-4 63.0kB ± 0% 63.0kB ± 0% ~ (all equal) DecodeProgressive-4 260kB ± 0% 260kB ± 0% ~ (all equal) EncodeRGBA-4 4.40kB ± 0% 4.40kB ± 0% ~ (all equal) EncodeYCbCr-4 4.40kB ± 0% 4.40kB ± 0% ~ (all equal) name old allocs/op new allocs/op delta DecodeBaseline-4 5.00 ± 0% 5.00 ± 0% ~ (all equal) DecodeProgressive-4 13.0 ± 0% 13.0 ± 0% ~ (all equal) EncodeRGBA-4 4.00 ± 0% 4.00 ± 0% ~ (all equal) EncodeYCbCr-4 4.00 ± 0% 4.00 ± 0% ~ (all equal) Updates #24499 Change-Id: I6828d077b851817503a7c1a08235763f81bdadf9 Reviewed-on: https://go-review.googlesource.com/c/go/+/167417 Run-TryBot: Agniva De Sarker <agniva.quicksilver@gmail.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Nigel Tao <nigeltao@golang.org>
This commit is contained in:
Agniva De Sarker
Nigel Tao
parent
2da9659158
commit
64f22e4bd6
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@ -86,14 +86,16 @@ const (
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func fdct(b *block) {
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// Pass 1: process rows.
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for y := 0; y < 8; y++ {
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x0 := b[y*8+0]
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x1 := b[y*8+1]
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x2 := b[y*8+2]
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x3 := b[y*8+3]
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x4 := b[y*8+4]
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x5 := b[y*8+5]
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x6 := b[y*8+6]
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x7 := b[y*8+7]
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y8 := y * 8
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s := b[y8 : y8+8 : y8+8] // Small cap improves performance, see https://golang.org/issue/27857
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x0 := s[0]
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x1 := s[1]
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x2 := s[2]
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x3 := s[3]
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x4 := s[4]
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x5 := s[5]
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x6 := s[6]
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x7 := s[7]
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tmp0 := x0 + x7
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tmp1 := x1 + x6
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@ -110,12 +112,12 @@ func fdct(b *block) {
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tmp2 = x2 - x5
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tmp3 = x3 - x4
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b[y*8+0] = (tmp10 + tmp11 - 8*centerJSample) << pass1Bits
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b[y*8+4] = (tmp10 - tmp11) << pass1Bits
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s[0] = (tmp10 + tmp11 - 8*centerJSample) << pass1Bits
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s[4] = (tmp10 - tmp11) << pass1Bits
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z1 := (tmp12 + tmp13) * fix_0_541196100
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z1 += 1 << (constBits - pass1Bits - 1)
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b[y*8+2] = (z1 + tmp12*fix_0_765366865) >> (constBits - pass1Bits)
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b[y*8+6] = (z1 - tmp13*fix_1_847759065) >> (constBits - pass1Bits)
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s[2] = (z1 + tmp12*fix_0_765366865) >> (constBits - pass1Bits)
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s[6] = (z1 - tmp13*fix_1_847759065) >> (constBits - pass1Bits)
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tmp10 = tmp0 + tmp3
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tmp11 = tmp1 + tmp2
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@ -134,10 +136,10 @@ func fdct(b *block) {
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tmp12 += z1
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tmp13 += z1
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b[y*8+1] = (tmp0 + tmp10 + tmp12) >> (constBits - pass1Bits)
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b[y*8+3] = (tmp1 + tmp11 + tmp13) >> (constBits - pass1Bits)
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b[y*8+5] = (tmp2 + tmp11 + tmp12) >> (constBits - pass1Bits)
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b[y*8+7] = (tmp3 + tmp10 + tmp13) >> (constBits - pass1Bits)
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s[1] = (tmp0 + tmp10 + tmp12) >> (constBits - pass1Bits)
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s[3] = (tmp1 + tmp11 + tmp13) >> (constBits - pass1Bits)
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s[5] = (tmp2 + tmp11 + tmp12) >> (constBits - pass1Bits)
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s[7] = (tmp3 + tmp10 + tmp13) >> (constBits - pass1Bits)
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}
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// Pass 2: process columns.
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// We remove pass1Bits scaling, but leave results scaled up by an overall factor of 8.
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@ -73,30 +73,31 @@ func idct(src *block) {
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// Horizontal 1-D IDCT.
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for y := 0; y < 8; y++ {
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y8 := y * 8
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s := src[y8 : y8+8 : y8+8] // Small cap improves performance, see https://golang.org/issue/27857
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// If all the AC components are zero, then the IDCT is trivial.
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if src[y8+1] == 0 && src[y8+2] == 0 && src[y8+3] == 0 &&
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src[y8+4] == 0 && src[y8+5] == 0 && src[y8+6] == 0 && src[y8+7] == 0 {
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dc := src[y8+0] << 3
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src[y8+0] = dc
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src[y8+1] = dc
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src[y8+2] = dc
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src[y8+3] = dc
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src[y8+4] = dc
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src[y8+5] = dc
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src[y8+6] = dc
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src[y8+7] = dc
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if s[1] == 0 && s[2] == 0 && s[3] == 0 &&
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s[4] == 0 && s[5] == 0 && s[6] == 0 && s[7] == 0 {
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dc := s[0] << 3
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s[0] = dc
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s[1] = dc
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s[2] = dc
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s[3] = dc
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s[4] = dc
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s[5] = dc
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s[6] = dc
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s[7] = dc
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continue
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}
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// Prescale.
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x0 := (src[y8+0] << 11) + 128
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x1 := src[y8+4] << 11
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x2 := src[y8+6]
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x3 := src[y8+2]
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x4 := src[y8+1]
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x5 := src[y8+7]
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x6 := src[y8+5]
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x7 := src[y8+3]
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x0 := (s[0] << 11) + 128
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x1 := s[4] << 11
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x2 := s[6]
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x3 := s[2]
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x4 := s[1]
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x5 := s[7]
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x6 := s[5]
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x7 := s[3]
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// Stage 1.
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x8 := w7 * (x4 + x5)
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@ -126,14 +127,14 @@ func idct(src *block) {
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x4 = (r2*(x4-x5) + 128) >> 8
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// Stage 4.
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src[y8+0] = (x7 + x1) >> 8
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src[y8+1] = (x3 + x2) >> 8
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src[y8+2] = (x0 + x4) >> 8
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src[y8+3] = (x8 + x6) >> 8
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src[y8+4] = (x8 - x6) >> 8
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src[y8+5] = (x0 - x4) >> 8
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src[y8+6] = (x3 - x2) >> 8
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src[y8+7] = (x7 - x1) >> 8
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s[0] = (x7 + x1) >> 8
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s[1] = (x3 + x2) >> 8
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s[2] = (x0 + x4) >> 8
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s[3] = (x8 + x6) >> 8
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s[4] = (x8 - x6) >> 8
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s[5] = (x0 - x4) >> 8
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s[6] = (x3 - x2) >> 8
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s[7] = (x7 - x1) >> 8
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}
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// Vertical 1-D IDCT.
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@ -141,16 +142,17 @@ func idct(src *block) {
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// Similar to the horizontal 1-D IDCT case, if all the AC components are zero, then the IDCT is trivial.
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// However, after performing the horizontal 1-D IDCT, there are typically non-zero AC components, so
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// we do not bother to check for the all-zero case.
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s := src[x : x+57 : x+57] // Small cap improves performance, see https://golang.org/issue/27857
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// Prescale.
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y0 := (src[8*0+x] << 8) + 8192
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y1 := src[8*4+x] << 8
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y2 := src[8*6+x]
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y3 := src[8*2+x]
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y4 := src[8*1+x]
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y5 := src[8*7+x]
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y6 := src[8*5+x]
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y7 := src[8*3+x]
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y0 := (s[8*0] << 8) + 8192
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y1 := s[8*4] << 8
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y2 := s[8*6]
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y3 := s[8*2]
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y4 := s[8*1]
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y5 := s[8*7]
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y6 := s[8*5]
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y7 := s[8*3]
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// Stage 1.
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y8 := w7*(y4+y5) + 4
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@ -180,13 +182,13 @@ func idct(src *block) {
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y4 = (r2*(y4-y5) + 128) >> 8
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// Stage 4.
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src[8*0+x] = (y7 + y1) >> 14
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src[8*1+x] = (y3 + y2) >> 14
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src[8*2+x] = (y0 + y4) >> 14
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src[8*3+x] = (y8 + y6) >> 14
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src[8*4+x] = (y8 - y6) >> 14
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src[8*5+x] = (y0 - y4) >> 14
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src[8*6+x] = (y3 - y2) >> 14
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src[8*7+x] = (y7 - y1) >> 14
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s[8*0] = (y7 + y1) >> 14
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s[8*1] = (y3 + y2) >> 14
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s[8*2] = (y0 + y4) >> 14
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s[8*3] = (y8 + y6) >> 14
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s[8*4] = (y8 - y6) >> 14
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s[8*5] = (y0 - y4) >> 14
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s[8*6] = (y3 - y2) >> 14
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s[8*7] = (y7 - y1) >> 14
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}
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}
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