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Re: [PATCH i386] Move CLOBBERED_REGS earlier in register class list
- From: Uros Bizjak <ubizjak at gmail dot com>
- To: Jan Hubicka <hubicka at ucw dot cz>
- Cc: Alexander Monakov <amonakov at ispras dot ru>, "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>, Rich Felker <dalias at libc dot org>, Vladimir Makarov <vmakarov at redhat dot com>
- Date: Sun, 10 May 2015 19:51:17 +0200
- Subject: Re: [PATCH i386] Move CLOBBERED_REGS earlier in register class list
- Authentication-results: sourceware.org; auth=none
- References: <1430757479-14241-1-git-send-email-amonakov at ispras dot ru> <1430757479-14241-3-git-send-email-amonakov at ispras dot ru> <20150510164402 dot GG9659 at atrey dot karlin dot mff dot cuni dot cz>
On Sun, May 10, 2015 at 6:44 PM, Jan Hubicka <email@example.com> 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
> which contains a rationale, too.
> I am adding Uros and Vladimir to CC just in case they missed the email :)
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.