code review 8174047: cmd/gc: do not reuse bool temporaries for composite equ...

cmd/gc: do not reuse bool temporaries for composite equality.

Reusing it when multiple comparisons occurred in the same
function call led to bad overwriting.

Fixes issue 5162.

[remyoudompheng, 2013-03-31 09:21:00]

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

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

[remyoudompheng, 2013-03-31 09:21:13]

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

Please take another look.

[DMorsing, 2013-03-31 10:16:00]

You can do this without bloating the stack frame. If you make a temporary for
each equality and move the results after the call, the regopt pass can then
remove all the new temporaries.

https://codereview.appspot.com/8174047/diff/6003/src/cmd/gc/walk.c
File src/cmd/gc/walk.c (right):

https://codereview.appspot.com/8174047/diff/6003/src/cmd/gc/walk.c#newcode2856
src/cmd/gc/walk.c:2856: *init = list(*init, call);
Make a new temporary and put a nod(OAS, newtemp, tempbool) at the end of this
list.

https://codereview.appspot.com/8174047/diff/6003/src/cmd/gc/walk.c#newcode2859
src/cmd/gc/walk.c:2859: r = tempbool;
use newtemp here and below.

[remyoudompheng, 2013-03-31 10:25:49]

2013/3/31  <daniel.morsing@gmail.com>:
> You can do this without bloating the stack frame. If you make a
> temporary for each equality and move the results after the call, the
> regopt pass can then remove all the new temporaries.
>

You're right, it will be much nicer.

Rémy.

[remyoudompheng, 2013-03-31 19:33:17]

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

Please take another look.

[DMorsing, 2013-03-31 19:40:14]

LGTM

[remyoudompheng, 2013-04-01 19:02:19]

*** Submitted as https://code.google.com/p/go/source/detail?r=33176241a02b ***

cmd/gc: do not reuse bool temporaries for composite equality.

Reusing it when multiple comparisons occurred in the same
function call led to bad overwriting.

Fixes issue 5162.

R=golang-dev, daniel.morsing
CC=golang-dev
https://codereview.appspot.com/8174047