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cmd/internal/obj: reuse the varint encoding buffer

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This reduces the number of allocations in the compiler
while building the stdlib by 15.66%.

No functional changes. Passes toolstash -cmp.

Change-Id: Ia21b37134a8906a4e23d53fdc15235b4aa7bbb34
Reviewed-on: https://go-review.googlesource.com/9085
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This commit is contained in:
Josh Bleecher Snyder 2015-04-20 10:20:36 -07:00
parent 3c939b5348
commit 873483c682
1 changed files with 6 additions and 3 deletions
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9
src/cmd/internal/obj/objfile.go
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@ -463,18 +463,21 @@ func writesym(ctxt *Link, b *Biobuf, s *LSym) {
} }
} }
// Reusable buffer to avoid allocations.
// This buffer was responsible for 15% of gc's allocations.
var varintbuf [10]uint8
func wrint(b *Biobuf, sval int64) { func wrint(b *Biobuf, sval int64) {
var v uint64 var v uint64
var buf [10]uint8
uv := (uint64(sval) << 1) ^ uint64(int64(sval>>63)) uv := (uint64(sval) << 1) ^ uint64(int64(sval>>63))
p := buf[:] p := varintbuf[:]
for v = uv; v >= 0x80; v >>= 7 { for v = uv; v >= 0x80; v >>= 7 {
p[0] = uint8(v | 0x80) p[0] = uint8(v | 0x80)
p = p[1:] p = p[1:]
} }
p[0] = uint8(v) p[0] = uint8(v)
p = p[1:] p = p[1:]
Bwrite(b, buf[:len(buf)-len(p)]) Bwrite(b, varintbuf[:len(varintbuf)-len(p)])
} }
func wrstring(b *Biobuf, s string) { func wrstring(b *Biobuf, s string) {