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cmd/link: batch writing of bytes

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In best of 10, linking cmd/go shows a ~10% improvement.

tip:              real  0m1.152s user  0m1.005s
this:             real  0m1.065s user  0m0.924s

Change-Id: I303a20b94332feaedc1033c453247a0e4c05c843
Reviewed-on: https://go-review.googlesource.com/19978
Reviewed-by: David Crawshaw <crawshaw@golang.org>
This commit is contained in:
Shahar Kohanim 2016-02-29 11:49:49 +02:00 committed by David Crawshaw
parent 07ccc21295
commit d3b00a8cc4
2 changed files with 32 additions and 20 deletions
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48
src/cmd/link/internal/ld/data.go
View File

@ -708,7 +708,6 @@ func blk(start *LSym, addr int64, size int64) {
}
eaddr := addr + size
var ep []byte
var p []byte
for ; sym != nil; sym = sym.Next {
if sym.Type&obj.SSUB != 0 {
@ -723,18 +722,16 @@ func blk(start *LSym, addr int64, size int64) {
errorexit()
}
for ; addr < sym.Value; addr++ {
Cput(0)
if addr < sym.Value {
strnput("", int(sym.Value-addr))
addr = sym.Value
}
p = sym.P
ep = p[len(sym.P):]
for -cap(p) < -cap(ep) {
Cput(uint8(p[0]))
p = p[1:]
}
Cwrite(p)
addr += int64(len(sym.P))
for ; addr < sym.Value+sym.Size; addr++ {
Cput(0)
if addr < sym.Value+sym.Size {
strnput("", int(sym.Value+sym.Size-addr))
addr = sym.Value + sym.Size
}
if addr != sym.Value+sym.Size {
Diag("phase error: addr=%#x value+size=%#x", int64(addr), int64(sym.Value)+sym.Size)
@ -746,8 +743,8 @@ func blk(start *LSym, addr int64, size int64) {
}
}
for ; addr < eaddr; addr++ {
Cput(0)
if addr < eaddr {
strnput("", int(eaddr-addr))
}
Cflush()
}
@ -899,15 +896,26 @@ func Datblk(addr int64, size int64) {
fmt.Fprintf(&Bso, "\t%.8x|\n", uint(eaddr))
}
func strnput(s string, n int) {
for ; n > 0 && s != ""; s = s[1:] {
Cput(uint8(s[0]))
n--
}
var zeros [512]byte
for n > 0 {
Cput(0)
n--
// strnput writes the first n bytes of s.
// If n is larger then len(s),
// it is padded with NUL bytes.
func strnput(s string, n int) {
if len(s) >= n {
Cwritestring(s[:n])
} else {
Cwritestring(s)
n -= len(s)
for n > 0 {
if len(zeros) >= n {
Cwrite(zeros[:n])
return
} else {
Cwrite(zeros[:])
n -= len(zeros)
}
}
}
}

4
src/cmd/link/internal/ld/lib.go
View File

@ -1850,6 +1850,10 @@ func Cseek(p int64) {
coutbuf.off = p
}
func Cwritestring(s string) {
coutbuf.WriteString(s)
}
func Cwrite(p []byte) {
coutbuf.Write(p)
}