delta/go-git.git/test/codegen/strings.go, branch dev.go2go

cmd/compile: apply optimization for readonly globals on wasm

2019-08-28T05:55:52+00:00

Extend the optimization introduced in CL 141118 to the wasm architecture.

And for reference, the rules trigger 212 times while building std and cmd

$GOOS=js GOARCH=wasm gotip build std cmd
$grep -E "Wasm.rules:44(1|2|3|4)" rulelog | wc -l
212

Updates #26498

Change-Id: I153684a2b98589ae812b42268da08b65679e09d1
Reviewed-on: https://go-review.googlesource.com/c/go/+/185477
Run-TryBot: Agniva De Sarker 
TryBot-Result: Gobot Gobot 
Reviewed-by: Cherry Zhang 
Reviewed-by: Richard Musiol

cmd/compile: implement some moves using non-overlapping reads&writes

2018-10-30T20:27:03+00:00

For moves >8,<16 bytes, do a move using non-overlapping loads/stores
if it would require no more instructions.

This helps a bit with the case when the move is from a static
constant, because then the code to materialize the value being moved
is smaller.

Change-Id: Ie47a5a7c654afeb4973142b0a9922faea13c9b54
Reviewed-on: https://go-review.googlesource.com/c/146019
Run-TryBot: Keith Randall 
TryBot-Result: Gobot Gobot 
Reviewed-by: Cherry Zhang

cmd/compile: optimize loads from readonly globals into constants

2018-10-14T02:54:40+00:00

Instead of
   MOVB go.string."foo"(SB), AX
do
   MOVB $102, AX

When we know the global we're loading from is readonly, we can
do that read at compile time.

I've made this arch-dependent mostly because the cases where this
happens often are memory->memory moves, and those don't get
decomposed until lowering.

Did amd64/386/arm/arm64. Other architectures could follow.

Update #26498

Change-Id: I41b1dc831b2cd0a52dac9b97f4f4457888a46389
Reviewed-on: https://go-review.googlesource.com/c/141118
Run-TryBot: Keith Randall 
TryBot-Result: Gobot Gobot 
Reviewed-by: Josh Bleecher Snyder

cmd/compile: make []byte("...") more efficient

2018-10-10T16:10:40+00:00

Do []byte(string) conversions more efficiently when the string
is a constant. Instead of calling stringtobyteslice, allocate
just the space we need and encode the initialization directly.

[]byte("foo") rewrites to the following pseudocode:

var s [3]byte // on heap or stack, depending on whether b escapes
s = *(*[3]byte)(&"foo"[0]) // initialize s from the string
b = s[:]

which generates this assembly:

	0x001d 00029 (tmp1.go:9)	LEAQ	type.[3]uint8(SB), AX
	0x0024 00036 (tmp1.go:9)	MOVQ	AX, (SP)
	0x0028 00040 (tmp1.go:9)	CALL	runtime.newobject(SB)
	0x002d 00045 (tmp1.go:9)	MOVQ	8(SP), AX
	0x0032 00050 (tmp1.go:9)	MOVBLZX	go.string."foo"+2(SB), CX
	0x0039 00057 (tmp1.go:9)	MOVWLZX	go.string."foo"(SB), DX
	0x0040 00064 (tmp1.go:9)	MOVW	DX, (AX)
	0x0043 00067 (tmp1.go:9)	MOVB	CL, 2(AX)
// Then the slice is b = {AX, 3, 3}

The generated code is still not optimal, as it still does load/store
from read-only memory instead of constant stores.  Next CL...

Update #26498
Fixes #10170

Change-Id: I4b990b19f9a308f60c8f4f148934acffefe0a5bd
Reviewed-on: https://go-review.googlesource.com/c/140698
Run-TryBot: Keith Randall 
TryBot-Result: Gobot Gobot 
Reviewed-by: Brad Fitzpatrick

cmd/compile: optimize len([]rune(string))

2018-05-06T05:31:01+00:00

Adds a new runtime function to count runes in a string.
Modifies the compiler to detect the pattern len([]rune(string))
and replaces it with the new rune counting runtime function.

RuneCount/lenruneslice/ASCII                  27.8ns ± 2%  14.5ns ± 3%  -47.70%  (p=0.000 n=10+10)
RuneCount/lenruneslice/Japanese                126ns ± 2%    60ns ± 2%  -52.03%  (p=0.000 n=10+10)
RuneCount/lenruneslice/MixedLength             104ns ± 2%    50ns ± 1%  -51.71%  (p=0.000 n=10+9)

Fixes #24923

Change-Id: Ie9c7e7391a4e2cca675c5cdcc1e5ce7d523948b9
Reviewed-on: https://go-review.googlesource.com/108985
Run-TryBot: Martin Möhrmann 
TryBot-Result: Gobot Gobot 
Reviewed-by: Josh Bleecher Snyder