Hi,
On 23 March 2015 at 17:08, Ramana Radhakrishnan
<ramana....@googlemail.com> wrote:
> On Wed, Mar 18, 2015 at 10:19 AM, Yvan Roux <yvan.r...@linaro.org> 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 ?
>
>
> This looks sane. It doesn't look reasonable for alternatives to be
> duplicating each other.
>
> Given I have neither the time nor the hardware to test this patch on,
> I'd rather someone with an interest in iwMMX possibly folks from
> Marvell can pick up testing for this patch.
Ok, Thanks Ramana, I'll wait for somebody able to test it. Notice,
that without this patch on the 4.9 branch, building a cross compiler
which default to iWMMXT architectures ICE on that during LRA while
building of libgcc.
Cheers,
Yvan
> regards
> Ramana
>
>>
>> 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.r...@linaro.org>
>>
>> PR target/64208
>> * config/arm/iwmmxt.md ("*iwmmxt_arm_movdi"): Cleanup redundant
>> alternatives.
