54789eff38
Static branch prediction guesses that forward branches aren't taken.
Since stacks are rarely grown, make the forward branch mean grow.
While we're here, remove the debug-only instruction
saving the frame size in the temp register.
Sample disassembly for
func f() {
_ = [128]byte{}
}
Before:
0x4008248 ldr x1, [x28, #0x10]
0x400824c sub x2, sp, #0x90
0x4008250 cmp x2, x1
0x4008254 b.hi 0x4008268
0x4008258 mov x3, x30
0x400825c movz x27, #0x90
0x4008260 bl runtime.morestack_noctxt
0x4008264 b main.f
0x4008268 sub sp, sp, #0x90
0x400826c add x16, sp, #0x10
0x4008270 str xzr, [x16]
0x4008274 str xzr, [x16, #0x8]
0x4008278 str xzr, [x16, #0x10]
0x400827c str xzr, [x16, #0x18]
0x4008280 str xzr, [x16, #0x20]
0x4008284 str xzr, [x16, #0x28]
0x4008288 str xzr, [x16, #0x30]
0x400828c str xzr, [x16, #0x38]
0x4008290 str xzr, [x16, #0x40]
0x4008294 str xzr, [x16, #0x48]
0x4008298 str xzr, [x16, #0x50]
0x400829c str xzr, [x16, #0x58]
0x40082a0 str xzr, [x16, #0x60]
0x40082a4 str xzr, [x16, #0x68]
0x40082a8 str xzr, [x16, #0x70]
0x40082ac str xzr, [x16, #0x78]
0x40082b0 add sp, sp, #0x90
0x40082b4 ret
After:
0x4004bc8 ldr x1, [x28, #0x10]
0x4004bcc sub x2, sp, #0x90
0x4004bd0 cmp x2, x1
0x4004bd4 b.ls 0x4004c28
0x4004bd8 sub sp, sp, #0x90
0x4004bdc add x16, sp, #0x10
0x4004be0 str xzr, [x16]
0x4004be4 str xzr, [x16, #0x8]
0x4004be8 str xzr, [x16, #0x10]
0x4004bec str xzr, [x16, #0x18]
0x4004bf0 str xzr, [x16, #0x20]
0x4004bf4 str xzr, [x16, #0x28]
0x4004bf8 str xzr, [x16, #0x30]
0x4004bfc str xzr, [x16, #0x38]
0x4004c00 str xzr, [x16, #0x40]
0x4004c04 str xzr, [x16, #0x48]
0x4004c08 str xzr, [x16, #0x50]
0x4004c0c str xzr, [x16, #0x58]
0x4004c10 str xzr, [x16, #0x60]
0x4004c14 str xzr, [x16, #0x68]
0x4004c18 str xzr, [x16, #0x70]
0x4004c1c str xzr, [x16, #0x78]
0x4004c20 add sp, sp, #0x90
0x4004c24 ret
0x4004c28 mov x3, x30
0x4004c2c bl runtime.morestack_noctxt
0x4004c30 b main.f
Updates #10587.
Package sort benchmarks using an iPhone 6:
name old time/op new time/op delta
SearchWrappers 355ns ± 1% 328ns ± 1% -7.57% (p=0.000 n=25+19)
SortString1K 580µs ± 1% 577µs ± 1% -0.48% (p=0.000 n=25+25)
StableString1K 1.04ms ± 0% 1.04ms ± 0% ~ (p=0.851 n=24+25)
SortInt1K 251µs ± 1% 247µs ± 1% -1.52% (p=0.000 n=23+25)
StableInt1K 267µs ± 2% 261µs ± 2% -2.02% (p=0.000 n=25+25)
SortInt64K 23.8ms ± 1% 23.6ms ± 0% -0.97% (p=0.000 n=25+23)
StableInt64K 22.8ms ± 0% 22.4ms ± 1% -1.76% (p=0.000 n=24+25)
Sort1e2 123µs ± 1% 124µs ± 1% ~ (p=0.256 n=23+23)
Stable1e2 248µs ± 1% 247µs ± 1% -0.69% (p=0.000 n=23+25)
Sort1e4 24.3ms ± 2% 24.6ms ± 5% +1.36% (p=0.017 n=22+25)
Stable1e4 77.2ms ± 6% 76.2ms ± 5% -1.36% (p=0.020 n=25+25)
Sort1e6 3.95s ± 8% 3.95s ± 8% ~ (p=0.863 n=25+25)
Stable1e6 15.7s ± 1% 15.5s ± 1% -1.11% (p=0.000 n=22+23)
Change-Id: I377b3817af2ed27ddeecf24edef97fad91fc1afc
Reviewed-on: https://go-review.googlesource.com/10500
Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Dave Cheney <dave@cheney.net>
|
||
|---|---|---|
| api | ||
| doc | ||
| lib/time | ||
| misc | ||
| src | ||
| test | ||
| .gitattributes | ||
| .gitignore | ||
| AUTHORS | ||
| CONTRIBUTING.md | ||
| CONTRIBUTORS | ||
| favicon.ico | ||
| LICENSE | ||
| PATENTS | ||
| README.md | ||
| robots.txt | ||
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For example, if you extracted the tar file into $HOME/go, you might put the following in your .profile:
export GOROOT=$HOME/go
export PATH=$PATH:$GOROOT/bin
See https://golang.org/doc/install or doc/install.html for more details.