[PATCH][GCC][AArch64] Limit movmem copies to TImode copies.

[Sudakshina Das]

Hi Tamar

On 13/08/18 17:27, Tamar Christina wrote:
> Hi Thomas,
> 
> Thanks for the review.
> 
> I’ll correct the typo before committing if I have no other changes required by a maintainer.
> 
> Regards,
> Tamar.
> 

I am not a maintainer but I would like to point out something in your
patch. I think you test case will fail with -mabi=ilp32

FAIL: gcc.target/aarch64/large_struct_copy_2.c (test for excess errors)
Excess errors:
/work/trunk/src/gcc/gcc/testsuite/gcc.target/aarch64/large_struct_copy_2.c:18:27: 
warning: overflow in conversion from 'long
long int' to 'long int' changes value from '4073709551611' to
'2080555003' [-Woverflow]

We have had more such recent failures and James gave a very neat
way to make sure the mode comes out what you intend it to here:
https://gcc.gnu.org/ml/gcc-patches/2018-08/msg00233.html

I would just ask you to change the data types accordingly and test it
with -mabi=ilp32.

Thanks
Sudi

> From: Thomas Preudhomme <thomas.preudhomme@linaro.org>
> Sent: Monday, August 13, 2018 14:37
> To: Tamar Christina <Tamar.Christina@arm.com>
> Cc: gcc-patches@gcc.gnu.org; nd <nd@arm.com>; James Greenhalgh <James.Greenhalgh@arm.com>; Richard Earnshaw <Richard.Earnshaw@arm.com>; Marcus Shawcroft <Marcus.Shawcroft@arm.com>
> Subject: Re: [PATCH][GCC][AArch64] Limit movmem copies to TImode copies.
> 
> Hi Tamar,
> 
> Thanks for your patch.
> 
> Just one comment about your ChangeLog entry for the testsuiet change: shouldn't it mention that it is a new testcase? The patch you attached seems to create the file.
> 
> Best regards,
> 
> Thomas
> 
> On Mon, 13 Aug 2018 at 10:33, Tamar Christina <tamar.christina@arm.com<mailto:tamar.christina@arm.com>> wrote:
> Hi All,
> 
> On AArch64 we have integer modes larger than TImode, and while we can generate
> moves for these they're not as efficient.
> 
> So instead make sure we limit the maximum we can copy to TImode.  This means
> copying a 16 byte struct will issue 1 TImode copy, which will be done using a
> single STP as we expect but an CImode sized copy won't issue CImode operations.
> 
> Bootstrapped and regtested on aarch4-none-linux-gnu and no issues.
> Crosstested aarch4_be-none-elf and no issues.
> 
> Ok for trunk?
> 
> Thanks,
> Tamar
> 
> gcc/
> 2018-08-13  Tamar Christina  <tamar.christina@arm.com<mailto:tamar.christina@arm.com>>
> 
>          * config/aarch64/aarch64.c (aarch64_expand_movmem): Set TImode max.
> 
> gcc/testsuite/
> 2018-08-13  Tamar Christina  <tamar.christina@arm.com<mailto:tamar.christina@arm.com>>
> 
>          * gcc.target/aarch64/large_struct_copy_2.c: Add assembler scan.
> 
> --
>