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cmd/compile: make a type-specialized copy of encoding/binary.ReadUvarint

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This is to get better escape analysis for a frequently-allocated object.

Change-Id: I1942a4e1c3cd1f0fa870bc8433a0165c18ce9c75
Reviewed-on: https://go-review.googlesource.com/c/go/+/435336
Reviewed-by: Keith Randall <khr@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
Run-TryBot: David Chase <drchase@google.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
This commit is contained in:
David Chase 2022-09-27 14:37:35 -04:00
parent e8afb29111
commit caa8e1f977
1 changed files with 30 additions and 1 deletions
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31
src/internal/pkgbits/decoder.go
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@ -6,6 +6,7 @@ package pkgbits
import (
"encoding/binary"
"errors"
"fmt"
"go/constant"
"go/token"
@ -246,11 +247,39 @@ func (r *Decoder) checkErr(err error) {
}
func (r *Decoder) rawUvarint() uint64 {
x, err := binary.ReadUvarint(&r.Data)
x, err := readUvarint(&r.Data)
r.checkErr(err)
return x
}
// readUvarint is a type-specialized copy of encoding/binary.ReadUvarint.
// This avoids the interface conversion and thus has better escape properties,
// which flows up the stack.
func readUvarint(r *strings.Reader) (uint64, error) {
var x uint64
var s uint
for i := 0; i < binary.MaxVarintLen64; i++ {
b, err := r.ReadByte()
if err != nil {
if i > 0 && err == io.EOF {
err = io.ErrUnexpectedEOF
}
return x, err
}
if b < 0x80 {
if i == binary.MaxVarintLen64-1 && b > 1 {
return x, overflow
}
return x | uint64(b)<<s, nil
}
x |= uint64(b&0x7f) << s
s += 7
}
return x, overflow
}
var overflow = errors.New("pkgbits: readUvarint overflows a 64-bit integer")
func (r *Decoder) rawVarint() int64 {
ux := r.rawUvarint()