code review 4861042: strconv: put decimal on stack

strconv: put decimal on stack

This makes decimal a good test
case for the escape analysis.

With escape analysis:

benchmark                 old ns/op    new ns/op    delta
BenchmarkAtof64Decimal         1954          243  -87.56%
BenchmarkAtof64Float           2008          293  -85.41%
BenchmarkAtof64FloatExp       10106         8814  -12.78%
BenchmarkAtof64Big             5113         3486  -31.82%

[rsc, 2011-08-25 20:56:34]

Hello golang-dev (cc: golang-dev@googlegroups.com),

I'd like you to review this change to
https://go.googlecode.com/hg

[gri, 2011-08-25 21:02:14]

LGTM

that said, while faster (which is great), it's not really nicer, now that some
results are returned and some are passed back via pointer parameter...

http://codereview.appspot.com/4861042/diff/5001/src/pkg/strconv/atof.go
File src/pkg/strconv/atof.go (right):

http://codereview.appspot.com/4861042/diff/5001/src/pkg/strconv/atof.go#newco...
src/pkg/strconv/atof.go:59: func stringToDecimal(s string, b *decimal) (neg
bool, trunc bool, ok bool) {
should perhaps say that the result is in b?

[rsc, 2011-08-25 21:31:21]

> that said, while faster (which is great), it's not really nicer, now
> that some results are returned and some are passed back via pointer
> parameter...

fair enough.  PTAL

[gri, 2011-08-25 21:46:56]

LGTM

much better!
- gri

[rsc, 2011-08-25 21:54:18]

*** Submitted as http://code.google.com/p/go/source/detail?r=f3f08d7d306e ***

strconv: put decimal on stack

This makes decimal a good test
case for the escape analysis.

With escape analysis:

benchmark                 old ns/op    new ns/op    delta
BenchmarkAtof64Decimal         1954          243  -87.56%
BenchmarkAtof64Float           2008          293  -85.41%
BenchmarkAtof64FloatExp       10106         8814  -12.78%
BenchmarkAtof64Big             5113         3486  -31.82%

R=golang-dev, gri
CC=golang-dev
http://codereview.appspot.com/4861042