code review 3993041: runtime: fix arm reflect.call boundary case

runtime: fix arm reflect.call boundary case

The fault was lucky: when it wasn't faulting it was silently
copying a word from some other block and later putting
that same word back.  If some other goroutine had changed
that word of memory in the interim, too bad.

The ARM code was inconsistent about whether the
"argument frame" included the saved LR.  Including it made
some things more regular but mostly just caused confusion
in the places where the regularity broke.  Now the rule
reflects reality: argp is always a pointer to arguments,
never a saved link register.

Renamed struct fields to make meaning clearer.

Running ARM in QEMU, package time's gotest:
  * before: 27/58 failed
  * after: 0/50

[rsc, 2011-01-13 19:33:22]

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

I'd like you to review this change.

[r, 2011-01-13 19:45:46]

LGTM
although the big comment is mostly describing code that doesn't exist.
can you make it more prescriptive rather than recollective?

[rsc, 2011-01-13 19:51:21]

only the 3rd paragraph is referring to removed code.
i can delete it

[r2, 2011-01-13 19:56:50]

On Jan 13, 2011, at 11:51 AM, Russ Cox wrote:

> only the 3rd paragraph is referring to removed code.
> i can delete it

yes please

[rsc, 2011-01-13 22:50:32]

Hello r, r2 (cc: golang-dev@googlegroups.com),

Please take another look.

[r, 2011-01-13 22:57:51]

LGTM

[rsc, 2011-01-14 19:05:23]

*** Submitted as http://code.google.com/p/go/source/detail?r=2f6f904b13b1 ***

runtime: fix arm reflect.call boundary case

The fault was lucky: when it wasn't faulting it was silently
copying a word from some other block and later putting
that same word back.  If some other goroutine had changed
that word of memory in the interim, too bad.

The ARM code was inconsistent about whether the
"argument frame" included the saved LR.  Including it made
some things more regular but mostly just caused confusion
in the places where the regularity broke.  Now the rule
reflects reality: argp is always a pointer to arguments,
never a saved link register.

Renamed struct fields to make meaning clearer.

Running ARM in QEMU, package time's gotest:
  * before: 27/58 failed
  * after: 0/50

R=r, r2
CC=golang-dev
http://codereview.appspot.com/3993041