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When the control value of a If block is known for a particular inbound edge
because its value can be inferred from the control value of its predecessor,
then this inbound edge can be redirected to the known successor directly,
This CL optimizes this kind of cases to eliminate unnecessary comparision.
For example, the following piece of code comes from runtime.atoi,
if !neg && un > uint(maxInt) {
return 0, false
}
if neg && un > uint(maxInt)+1 {
return 0, false
}
Before this optimization, if the first "if" statement does not return, both
conditions of the second "if" statement will be checked. But obviously the
value of neg is known through the first "if" statement, and there is no need
to check neg repeatedly.
After this optimization, this redundancy check is eliminated, and the execution
logic becomes as follows.
if !neg {
if un > uint(maxInt) {
return 0, false
}
} else {
if un > uint(maxInt)+1 {
return 0, false
}
}
This CL does not bring significant performance changes, but it makes the code
structure look more reasonable.
Statistical data from tool compilecmp on Linux/amd64:
name old time/op new time/op delta
Template 380ms ± 4% 385ms ± 3% +1.16% (p=0.000 n=50+49)
Unicode 168ms ± 9% 169ms ± 9% ~ (p=0.421 n=49+46)
GoTypes 1.99s ± 4% 2.02s ± 4% +1.48% (p=0.000 n=49+49)
Compiler 188ms ± 8% 188ms ± 9% ~ (p=0.997 n=49+50)
SSA 11.8s ± 2% 12.0s ± 2% +1.24% (p=0.000 n=48+50)
Flate 242ms ± 6% 244ms ± 9% ~ (p=0.307 n=46+49)
GoParser 361ms ± 3% 366ms ± 4% +1.23% (p=0.000 n=48+49)
Reflect 836ms ± 3% 842ms ± 3% +0.70% (p=0.004 n=48+48)
Tar 335ms ± 3% 340ms ± 4% +1.47% (p=0.000 n=49+46)
XML 432ms ± 4% 437ms ± 4% +1.11% (p=0.002 n=49+49)
LinkCompiler 701ms ± 4% 704ms ± 5% ~ (p=0.278 n=49+50)
ExternalLinkCompiler 1.83s ± 3% 1.84s ± 3% +0.51% (p=0.034 n=48+49)
LinkWithoutDebugCompiler 436ms ± 6% 438ms ± 6% ~ (p=0.419 n=48+49)
[Geo mean] 612ms 617ms +0.84%
name old alloc/op new alloc/op delta
Template 38.7MB ± 1% 39.1MB ± 1% +1.19% (p=0.000 n=50+50)
Unicode 28.1MB ± 0% 28.1MB ± 0% +0.20% (p=0.000 n=49+45)
GoTypes 168MB ± 1% 170MB ± 1% +1.05% (p=0.000 n=48+49)
Compiler 23.0MB ± 1% 23.1MB ± 1% +0.63% (p=0.000 n=50+50)
SSA 1.54GB ± 1% 1.55GB ± 1% +0.85% (p=0.000 n=50+50)
Flate 23.6MB ± 1% 23.9MB ± 1% +1.36% (p=0.000 n=43+46)
GoParser 35.0MB ± 1% 35.3MB ± 1% +0.94% (p=0.000 n=50+50)
Reflect 84.7MB ± 1% 86.1MB ± 1% +1.72% (p=0.000 n=49+49)
Tar 34.5MB ± 1% 34.9MB ± 1% +1.07% (p=0.000 n=47+48)
XML 44.2MB ± 3% 44.6MB ± 3% +0.70% (p=0.003 n=50+49)
LinkCompiler 128MB ± 0% 128MB ± 0% +0.01% (p=0.004 n=49+50)
ExternalLinkCompiler 120MB ± 0% 120MB ± 0% +0.01% (p=0.000 n=49+50)
LinkWithoutDebugCompiler 77.3MB ± 0% 77.3MB ± 0% +0.02% (p=0.000 n=50+50)
[Geo mean] 69.1MB 69.6MB +0.75%
file before after Δ %
addr2line 4049276 4051308 +2032 +0.050%
api 5248940 5248996 +56 +0.001%
asm 4868093 4868037 -56 -0.001%
buildid 2627666 2626026 -1640 -0.062%
cgo 4614432 4615040 +608 +0.013%
compile 23298888 23301267 +2379 +0.010%
cover 4591609 4591161 -448 -0.010%
dist 3449638 3450254 +616 +0.018%
doc 3925667 3926363 +696 +0.018%
fix 3322936 3323464 +528 +0.016%
link 6628632 6629560 +928 +0.014%
nm 3991753 3996497 +4744 +0.119%
objdump 4396119 4395615 -504 -0.011%
pack 2399719 2399535 -184 -0.008%
pprof 13616418 13622866 +6448 +0.047%
test2json 2646121 2646081 -40 -0.002%
trace 10233087 10226359 -6728 -0.066%
vet 7117994 7121066 +3072 +0.043%
total 111026988 111039495 +12507 +0.011%
On linux arm64:
name old time/op new time/op delta
Template 284ms ± 1% 286ms ± 1% +0.70% (p=0.000 n=49+50)
Unicode 125ms ± 3% 125ms ± 2% ~ (p=0.548 n=50+50)
GoTypes 1.69s ± 1% 1.71s ± 1% +1.02% (p=0.000 n=49+49)
Compiler 125ms ± 1% 124ms ± 2% -0.35% (p=0.020 n=50+50)
SSA 12.7s ± 1% 12.8s ± 1% +1.21% (p=0.000 n=49+49)
Flate 172ms ± 1% 173ms ± 1% +0.20% (p=0.047 n=50+50)
GoParser 265ms ± 1% 266ms ± 1% +0.64% (p=0.000 n=50+50)
Reflect 651ms ± 1% 650ms ± 1% ~ (p=0.079 n=48+48)
Tar 246ms ± 1% 246ms ± 1% ~ (p=0.202 n=50+46)
XML 328ms ± 1% 332ms ± 1% +1.28% (p=0.000 n=50+49)
LinkCompiler 600ms ± 1% 599ms ± 1% ~ (p=0.264 n=50+50)
ExternalLinkCompiler 1.88s ± 1% 1.90s ± 0% +1.36% (p=0.000 n=50+50)
LinkWithoutDebugCompiler 365ms ± 1% 365ms ± 1% ~ (p=0.602 n=50+46)
[Geo mean] 490ms 492ms +0.47%
name old alloc/op new alloc/op delta
Template 38.8MB ± 1% 39.1MB ± 1% +0.92% (p=0.000 n=44+42)
Unicode 28.4MB ± 0% 28.4MB ± 0% +0.22% (p=0.000 n=44+45)
GoTypes 169MB ± 1% 171MB ± 1% +1.12% (p=0.000 n=50+50)
Compiler 23.2MB ± 1% 23.3MB ± 1% +0.56% (p=0.000 n=42+43)
SSA 1.55GB ± 0% 1.56GB ± 0% +0.91% (p=0.000 n=48+49)
Flate 23.7MB ± 2% 24.0MB ± 1% +1.20% (p=0.000 n=50+50)
GoParser 35.3MB ± 1% 35.6MB ± 1% +0.88% (p=0.000 n=50+50)
Reflect 85.0MB ± 0% 86.5MB ± 0% +1.70% (p=0.000 n=49+48)
Tar 34.5MB ± 1% 34.9MB ± 1% +1.03% (p=0.000 n=47+50)
XML 43.8MB ± 2% 44.0MB ± 0% +0.41% (p=0.002 n=49+38)
LinkCompiler 136MB ± 0% 136MB ± 0% +0.01% (p=0.006 n=50+49)
ExternalLinkCompiler 127MB ± 0% 127MB ± 0% +0.02% (p=0.000 n=49+50)
LinkWithoutDebugCompiler 84.1MB ± 0% 84.1MB ± 0% ~ (p=0.534 n=50+50)
[Geo mean] 70.4MB 70.9MB +0.69%
file before after Δ %
addr2line 4006004 4004556 -1448 -0.036%
api 5029716 5028828 -888 -0.018%
asm 4936863 4934943 -1920 -0.039%
buildid 2594947 2594099 -848 -0.033%
cgo 4399702 4399502 -200 -0.005%
compile 22233139 22230486 -2653 -0.012%
cover 4443681 4443881 +200 +0.005%
dist 3365902 3365486 -416 -0.012%
doc 3776175 3776151 -24 -0.001%
fix 3218624 3218600 -24 -0.001%
link 6365001 6361409 -3592 -0.056%
nm 3923345 3923065 -280 -0.007%
objdump 4295473 4296673 +1200 +0.028%
pack 2390561 2389393 -1168 -0.049%
pprof 12866419 12865115 -1304 -0.010%
test2json 2587113 2585561 -1552 -0.060%
trace 9609814 9610846 +1032 +0.011%
vet 6790272 6789760 -512 -0.008%
total 106832751 106818354 -14397 -0.013%
Update: #37608
Change-Id: I2831238b12e3af5aef2261f64f804bf0a8b43f86
Reviewed-on: https://go-review.googlesource.com/c/go/+/244737
Reviewed-by: eric fang <eric.fang@arm.com>
Reviewed-by: Keith Randall <khr@golang.org>
Trust: eric fang <eric.fang@arm.com>
Run-TryBot: eric fang <eric.fang@arm.com>
TryBot-Result: Go Bot <gobot@golang.org>
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