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Re: [PATCH i386] Move CLOBBERED_REGS earlier in register class list


On Sun, May 10, 2015 at 6:44 PM, Jan Hubicka <hubicka@ucw.cz> wrote:
>> On 32-bit x86, register class CLOBBERED_REGS is a proper subset of
>> LEGACY_REGS, which causes IRA not to consider it separately for register
>> allocation, even when it has lower cost than other classes.  This patch is
>> useful to fix code generation problem that appears with no-PLT PIC tailcalls.
>>
>> Was there a specific reason for CLOBBERED_REGS class to be listed as late as
>> it is?  On 32-bit this class contains only EAX, ECX, EDX.
>
> Uros moved CLOBBERED_REGS late in
> https://gcc.gnu.org/ml/gcc-patches/2012-08/msg00796.html
> which contains a rationale, too.
>
> I am adding Uros and Vladimir to CC just in case they missed the email :)
> Honza

Uh, I don't remember that far, but from the context of the referred
patch, it looks like a "cleanup" of some sort. My atch matched 32bit
to 64bit, but could be also in the opposite way. Let's try the patch
and see what breaks.

Uros.


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