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>
func fdct(b *block) {
// Pass 1: process rows.
for y := 0; y < 8; y++ {
- x0 := b[y*8+0]
- x1 := b[y*8+1]
- x2 := b[y*8+2]
- x3 := b[y*8+3]
- x4 := b[y*8+4]
- x5 := b[y*8+5]
- x6 := b[y*8+6]
- x7 := b[y*8+7]
+ y8 := y * 8
+ s := b[y8 : y8+8 : y8+8] // Small cap improves performance, see https://golang.org/issue/27857
+ x0 := s[0]
+ x1 := s[1]
+ x2 := s[2]
+ x3 := s[3]
+ x4 := s[4]
+ x5 := s[5]
+ x6 := s[6]
+ x7 := s[7]
tmp0 := x0 + x7
tmp1 := x1 + x6
tmp2 = x2 - x5
tmp3 = x3 - x4
- b[y*8+0] = (tmp10 + tmp11 - 8*centerJSample) << pass1Bits
- b[y*8+4] = (tmp10 - tmp11) << pass1Bits
+ s[0] = (tmp10 + tmp11 - 8*centerJSample) << pass1Bits
+ s[4] = (tmp10 - tmp11) << pass1Bits
z1 := (tmp12 + tmp13) * fix_0_541196100
z1 += 1 << (constBits - pass1Bits - 1)
- b[y*8+2] = (z1 + tmp12*fix_0_765366865) >> (constBits - pass1Bits)
- b[y*8+6] = (z1 - tmp13*fix_1_847759065) >> (constBits - pass1Bits)
+ s[2] = (z1 + tmp12*fix_0_765366865) >> (constBits - pass1Bits)
+ s[6] = (z1 - tmp13*fix_1_847759065) >> (constBits - pass1Bits)
tmp10 = tmp0 + tmp3
tmp11 = tmp1 + tmp2
tmp12 += z1
tmp13 += z1
- b[y*8+1] = (tmp0 + tmp10 + tmp12) >> (constBits - pass1Bits)
- b[y*8+3] = (tmp1 + tmp11 + tmp13) >> (constBits - pass1Bits)
- b[y*8+5] = (tmp2 + tmp11 + tmp12) >> (constBits - pass1Bits)
- b[y*8+7] = (tmp3 + tmp10 + tmp13) >> (constBits - pass1Bits)
+ s[1] = (tmp0 + tmp10 + tmp12) >> (constBits - pass1Bits)
+ s[3] = (tmp1 + tmp11 + tmp13) >> (constBits - pass1Bits)
+ s[5] = (tmp2 + tmp11 + tmp12) >> (constBits - pass1Bits)
+ s[7] = (tmp3 + tmp10 + tmp13) >> (constBits - pass1Bits)
}
// Pass 2: process columns.
// We remove pass1Bits scaling, but leave results scaled up by an overall factor of 8.
// Horizontal 1-D IDCT.
for y := 0; y < 8; y++ {
y8 := y * 8
+ s := src[y8 : y8+8 : y8+8] // Small cap improves performance, see https://golang.org/issue/27857
// If all the AC components are zero, then the IDCT is trivial.
- if src[y8+1] == 0 && src[y8+2] == 0 && src[y8+3] == 0 &&
- src[y8+4] == 0 && src[y8+5] == 0 && src[y8+6] == 0 && src[y8+7] == 0 {
- dc := src[y8+0] << 3
- src[y8+0] = dc
- src[y8+1] = dc
- src[y8+2] = dc
- src[y8+3] = dc
- src[y8+4] = dc
- src[y8+5] = dc
- src[y8+6] = dc
- src[y8+7] = dc
+ if s[1] == 0 && s[2] == 0 && s[3] == 0 &&
+ s[4] == 0 && s[5] == 0 && s[6] == 0 && s[7] == 0 {
+ dc := s[0] << 3
+ s[0] = dc
+ s[1] = dc
+ s[2] = dc
+ s[3] = dc
+ s[4] = dc
+ s[5] = dc
+ s[6] = dc
+ s[7] = dc
continue
}
// Prescale.
- x0 := (src[y8+0] << 11) + 128
- x1 := src[y8+4] << 11
- x2 := src[y8+6]
- x3 := src[y8+2]
- x4 := src[y8+1]
- x5 := src[y8+7]
- x6 := src[y8+5]
- x7 := src[y8+3]
+ x0 := (s[0] << 11) + 128
+ x1 := s[4] << 11
+ x2 := s[6]
+ x3 := s[2]
+ x4 := s[1]
+ x5 := s[7]
+ x6 := s[5]
+ x7 := s[3]
// Stage 1.
x8 := w7 * (x4 + x5)
x4 = (r2*(x4-x5) + 128) >> 8
// Stage 4.
- src[y8+0] = (x7 + x1) >> 8
- src[y8+1] = (x3 + x2) >> 8
- src[y8+2] = (x0 + x4) >> 8
- src[y8+3] = (x8 + x6) >> 8
- src[y8+4] = (x8 - x6) >> 8
- src[y8+5] = (x0 - x4) >> 8
- src[y8+6] = (x3 - x2) >> 8
- src[y8+7] = (x7 - x1) >> 8
+ s[0] = (x7 + x1) >> 8
+ s[1] = (x3 + x2) >> 8
+ s[2] = (x0 + x4) >> 8
+ s[3] = (x8 + x6) >> 8
+ s[4] = (x8 - x6) >> 8
+ s[5] = (x0 - x4) >> 8
+ s[6] = (x3 - x2) >> 8
+ s[7] = (x7 - x1) >> 8
}
// Vertical 1-D IDCT.
// Similar to the horizontal 1-D IDCT case, if all the AC components are zero, then the IDCT is trivial.
// However, after performing the horizontal 1-D IDCT, there are typically non-zero AC components, so
// we do not bother to check for the all-zero case.
+ s := src[x : x+57 : x+57] // Small cap improves performance, see https://golang.org/issue/27857
// Prescale.
- y0 := (src[8*0+x] << 8) + 8192
- y1 := src[8*4+x] << 8
- y2 := src[8*6+x]
- y3 := src[8*2+x]
- y4 := src[8*1+x]
- y5 := src[8*7+x]
- y6 := src[8*5+x]
- y7 := src[8*3+x]
+ y0 := (s[8*0] << 8) + 8192
+ y1 := s[8*4] << 8
+ y2 := s[8*6]
+ y3 := s[8*2]
+ y4 := s[8*1]
+ y5 := s[8*7]
+ y6 := s[8*5]
+ y7 := s[8*3]
// Stage 1.
y8 := w7*(y4+y5) + 4
y4 = (r2*(y4-y5) + 128) >> 8
// Stage 4.
- src[8*0+x] = (y7 + y1) >> 14
- src[8*1+x] = (y3 + y2) >> 14
- src[8*2+x] = (y0 + y4) >> 14
- src[8*3+x] = (y8 + y6) >> 14
- src[8*4+x] = (y8 - y6) >> 14
- src[8*5+x] = (y0 - y4) >> 14
- src[8*6+x] = (y3 - y2) >> 14
- src[8*7+x] = (y7 - y1) >> 14
+ s[8*0] = (y7 + y1) >> 14
+ s[8*1] = (y3 + y2) >> 14
+ s[8*2] = (y0 + y4) >> 14
+ s[8*3] = (y8 + y6) >> 14
+ s[8*4] = (y8 - y6) >> 14
+ s[8*5] = (y0 - y4) >> 14
+ s[8*6] = (y3 - y2) >> 14
+ s[8*7] = (y7 - y1) >> 14
}
}