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go/test/codegen/strings.go
Keith Randall 653a4bd8d4 cmd/compile: optimize loads from readonly globals into constants
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 <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
2018-10-14 02:54:40 +00:00

50 lines
1.4 KiB
Go

// asmcheck
// Copyright 2018 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package codegen
// This file contains code generation tests related to the handling of
// string types.
func CountRunes(s string) int { // Issue #24923
// amd64:`.*countrunes`
return len([]rune(s))
}
func ToByteSlice() []byte { // Issue #24698
// amd64:`LEAQ\ttype\.\[3\]uint8`
// amd64:`CALL\truntime\.newobject`
// amd64:-`.*runtime.stringtoslicebyte`
return []byte("foo")
}
// Loading from read-only symbols should get transformed into constants.
func ConstantLoad() {
// 12592 = 0x3130
// 50 = 0x32
// amd64:`MOVW\t\$12592, \(`,`MOVB\t\$50, 2\(`
// 386:`MOVW\t\$12592, \(`,`MOVB\t\$50, 2\(`
// arm:`MOVW\t\$48`,`MOVW\t\$49`,`MOVW\t\$50`
// arm64:`MOVD\t\$12592`,`MOVD\t\$50`
bsink = []byte("012")
// 858927408 = 0x33323130
// 13620 = 0x3534
// amd64:`MOVL\t\$858927408`,`MOVW\t\$13620, 4\(`
// 386:`MOVL\t\$858927408`,`MOVW\t\$13620, 4\(`
// arm64:`MOVD\t\$858927408`,`MOVD\t\$13620`
bsink = []byte("012345")
// 3978425819141910832 = 0x3736353433323130
// 7306073769690871863 = 0x6564636261393837
// amd64:`MOVQ\t\$3978425819141910832`,`MOVQ\t\$7306073769690871863`
// 386:`MOVL\t\$858927408, \(`,`DUFFCOPY`
// arm64:`MOVD\t\$3978425819141910832`,`MOVD\t\$1650538808`,`MOVD\t\$25699`,`MOVD\t\$101`
bsink = []byte("0123456789abcde")
}
var bsink []byte