Re: [PATCH][AArch64] PR target/65491: Classify V1TF vectors as AAPCS64 short vectors rather than composite types

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

Hi James,

On 19/05/15 12:18, James Greenhalgh wrote:
> On Mon, Apr 20, 2015 at 11:16:02AM +0100, Kyrylo Tkachov wrote:
>> Hi all,
>>
>> The ICE in the PR happens when we pass a 1x(128-bit float) vector as an
>> argument.
>> The aarch64 backend erroneously classifies it as a composite type when in
>> fact it
>> is a short vector according to AAPCS64
>> (section 4.1.2 from
>> http://infocenter.arm.com/help/topic/com.arm.doc.ihi0055b/IHI0055B_aapcs64.p
>> df).
> Agreed.
>
>> The solution in this patch is to check aarch64_composite_type_p for a short
>> vector with
>> aarch64_short_vector_p rather than the other way around (check for
>> aarch64_short_vector_p
>> in aarch64_composite_type_p).
> I think I understand what you are saying, but your patch does the
> opposite (ADDS a check for aarch64_short_vector_p in
> aarch64_composite_type_p, REMOVES a check for aarch64_composite_type_p,
> in aarch64_short_vector_p)...

Yeah, I just worded it wrong in the cover letter, sorry about that.
As you say, the logic is pretty hairy.

>
> This logic is pretty hairy, and I'm struggling to convince myself that
> your change only hits the bug you described above. I think I've worked
> it through and it does, but if you can find any additional ABI tests
> which stress the Vector/Floating-Point passing rules that would help
> settle my nerves.

The aapcs64.exp stuff seems to test the existing rules
quite well...

>
> The patch is OK. I wouldn't think we would want to backport it to
> release branches as there is no regression to fix.

Ok, I've committed it with r223577.
I agree that it's not a regression fix, so messing with ABI code
in the release branches is not desirable.

Thanks for the review.

Kyrill

>
> Thanks,
> James
>
>> 2015-04-20  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
>>
>>      PR target/65491
>>      * config/aarch64/aarch64.c (aarch64_short_vector_p): Move above
>>      aarch64_composite_type_p.  Remove check for aarch64_composite_type_p.
>>      (aarch64_composite_type_p): Return false if given type and mode are
>>      for a short vector.
>>
>> 2015-04-20  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
>>
>>      PR target/65491
>>      * gcc.target/aarch64/pr65491_1.c: New test.
>>      * gcc.target/aarch64/aapcs64/type-def.h (vlf1_t): New typedef.
>>      * gcc.target/aarch64/aapcs64/func-ret-1.c: Add test for vlf1_t.