fmt: speed up 10-20%
The check for Stringer etc. can only fire if the test is not a builtin, so avoid
the expensive check if we know there's no chance.
Also put in a fast path for pad, which saves a more modest amount.
benchmark old ns/op new ns/op delta
BenchmarkSprintfEmpty 148 152 +2.70%
BenchmarkSprintfString 585 497 -15.04%
BenchmarkSprintfInt 441 396 -10.20%
BenchmarkSprintfIntInt 718 603 -16.02%
BenchmarkSprintfPrefixedInt 676 621 -8.14%
BenchmarkSprintfFloat 1003 953 -4.99%
BenchmarkManyArgs 2945 2312 -21.49%
BenchmarkScanInts 1704152 1734441 +1.78%
BenchmarkScanRecursiveInt 1837397 1828920 -0.46%
R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/6245068
diff --git a/src/pkg/fmt/format.go b/src/pkg/fmt/format.go
index caf900d..3c9cd0d 100644
--- a/src/pkg/fmt/format.go
+++ b/src/pkg/fmt/format.go
@@ -110,11 +110,11 @@
// Append b to f.buf, padded on left (w > 0) or right (w < 0 or f.minus)
// clear flags afterwards.
func (f *fmt) pad(b []byte) {
- var padding []byte
- var left, right int
- if f.widPresent && f.wid != 0 {
- padding, left, right = f.computePadding(len(b))
+ if !f.widPresent || f.wid == 0 {
+ f.buf.Write(b)
+ return
}
+ padding, left, right := f.computePadding(len(b))
if left > 0 {
f.writePadding(left, padding)
}
@@ -127,11 +127,11 @@
// append s to buf, padded on left (w > 0) or right (w < 0 or f.minus).
// clear flags afterwards.
func (f *fmt) padString(s string) {
- var padding []byte
- var left, right int
- if f.widPresent && f.wid != 0 {
- padding, left, right = f.computePadding(utf8.RuneCountInString(s))
+ if !f.widPresent || f.wid == 0 {
+ f.buf.WriteString(s)
+ return
}
+ padding, left, right := f.computePadding(utf8.RuneCountInString(s))
if left > 0 {
f.writePadding(left, padding)
}
