[PING^2][PATCH] PR29474: Don't canonicalize commutative operands during reload

[Jeff Law]

Maxim Kuvyrkov wrote:
> Maxim Kuvyrkov wrote:
>> Hello,
>>
>> I'd like to ping patch in 
>> http://gcc.gnu.org/ml/gcc-patches/2007-09/msg00817.html.
>>
>> While testing trunk and 4.3 branch for ColdFire, I noticed several 
>> failures in gcc.c-torture testsuite, which the above patch fixes.
>>
>> The patch was tested on m68k-linux-gnu and m68k-elf (both for 
>> coldfire) with no new regressions.
>
> Ping.
>
> Without this patch current trunk ICEs in reload when compiling 
> gcc.c-torture/execute/20060420-1.c for m68k/ColdFire.  The fix is safe 
> (as it just reduces optimization space) and it does not affect 
> benchmarks (EEMBC and CSiBE were tested).
>
> Is there any chance of committing this before 4.4 branches or should I 
> ping again when stage1 has started.
>
Given it's a bugfix  I think it's appropriate to pursue at this stage.  
The biggest concern is that this code (reload) can sometimes be rather 
fragile.

I think we want to avoid all simplifications by validate_replace_rtx 
during reload.  I think the easiest way to accomplish this would be to 
make a change from

  validate_replace_rtx_1 (&PATTERN (insn), from, to, insn, true);

to

  validate_replace_rtx_1 (&PATTERN (insn), from, to, insn, 
(reload_in_progress ? false : true));

Within validate_replace_rtx.    This would need some widespread testing 
across multiple targets, but I do think it's the right way to approach 
the problem (or as an alternative, add validate_replace_rtx_nosimplify 
and use that within reload1.c).

Jeff