code review 5483071: gc: better loopdepth analysis for labels

gc: better loopdepth analysis for labels

This avoids degraded performance caused by extra labels
emitted by inlining (breaking strconv ftoa alloc count unittest) and is better in any case.

[lvd, 2011-12-14 13:36:36]

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

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

[rsc, 2011-12-15 16:09:34]

LGTM

http://codereview.appspot.com/5483071/diff/7001/src/cmd/gc/esc.c
File src/cmd/gc/esc.c (right):

http://codereview.appspot.com/5483071/diff/7001/src/cmd/gc/esc.c#newcode255
src/cmd/gc/esc.c:255: // See case OLABEL in escloopdepth above
Delete or indent // to match rest of code.

http://codereview.appspot.com/5483071/diff/7001/test/escape2.go
File test/escape2.go (right):

http://codereview.appspot.com/5483071/diff/7001/test/escape2.go#newcode1025
test/escape2.go:1025: // a backward jump, must assume new loopdepth for now
s/ for now//
This is correct behavior below: it's a loop.

[rsc, 2011-12-15 16:10:20]

in the CL desc s/beter/better/

[lvd, 2011-12-15 16:27:30]

http://codereview.appspot.com/5483071/diff/7001/src/cmd/gc/esc.c
File src/cmd/gc/esc.c (right):

http://codereview.appspot.com/5483071/diff/7001/src/cmd/gc/esc.c#newcode255
src/cmd/gc/esc.c:255: // See case OLABEL in escloopdepth above
On 2011/12/15 16:09:35, rsc wrote:
> Delete or indent // to match rest of code. 

Done.

http://codereview.appspot.com/5483071/diff/7001/test/escape2.go
File test/escape2.go (right):

http://codereview.appspot.com/5483071/diff/7001/test/escape2.go#newcode1025
test/escape2.go:1025: // a backward jump, must assume new loopdepth for now
On 2011/12/15 16:09:35, rsc wrote:
> s/ for now//
> This is correct behavior below: it's a loop.

of course.  i must have been thinking about how the goto L1 below doesn't
decrement it.  havent figured out how to do that in the case of random
overlapping ranges.  perhaps not worth it.

[lvd, 2011-12-15 16:36:03]

*** Submitted as http://code.google.com/p/go/source/detail?r=eeffa8344a46 ***

gc: better loopdepth analysis for labels

This avoids degraded performance caused by extra labels
emitted by inlining (breaking strconv ftoa alloc count unittest) and is better
in any case.

R=rsc
CC=golang-dev
http://codereview.appspot.com/5483071