Re: [PATCH, ARM, PR64208] LRA ICE Fix

[Kyrill Tkachov <kyrylo.tkachov@arm.com>]

Hi Yvan,

On 18/03/15 10:19, Yvan Roux wrote:
> Hi,
>
> This is a fix for PR64208 where LRA loops when dealing with
> iwmmxt_arm_movdi insn.  As explain in the PR, the issue was introduced
> on trunk and 4.9 branch by fix of PR rtl-optimization/60969 and then
> workaround by r211798 (-fuse-caller-save enable for ARM).
>
> The changes in IRA cost made by PR60969, changed the register class of
> this insn output from GENERAL_REGS to IWMMXT_REGS, and the
> redundancies in the insn pattern alternatives description force LRA to
> reload the pseudo, which generates the same iwmmxt_arm_movdi insn,
> which can't be resolved, and so on ...
>
> Removing the redundancies fixes the issue, as LRA find that
> alternative 8 (Uy => y) matches.
>
> This issue is present in 4.9 branch, but latent on trunk (the
> clobbering of IP and CC information added during -fuse-caller-save
> patch changed the register allocation).
>
> Cross compiled and regression tested on ARM targets (but not on an
> IWMMXT one), is it ok for trunk and 4.9 branch ?
>
> Rq: I think that adding IP and CC clobbers to
> CALL_INSN_FUNCTION_USAGE, as specified by AAPCS, in 4.9 branch is
> something we need too, I've a patch for that if you agree on that.
>
> Thanks,
> Yvan
>
> 2105-03-17  Yvan Roux  <yvan.roux@linaro.org>
>
>      PR target/64208
>      * config/arm/iwmmxt.md ("*iwmmxt_arm_movdi"): Cleanup redundant
> alternatives.

As a general note, I think this patch should include the testcase from 
the PR.
I can see that it's fairly self-contained.

Cheers,
Kyrill