On Wed, Jan 27, 2016 at 8:29 AM, Ilya Enkovich <enkovich....@gmail.com> wrote:
> 2016-01-27 19:18 GMT+03:00 H.J. Lu <hjl.to...@gmail.com>:
>> On Wed, Jan 27, 2016 at 8:11 AM, Ilya Enkovich <enkovich....@gmail.com>
>> wrote:
>>> On 27 Jan 16:44, Jakub Jelinek wrote:
>>>> On Wed, Jan 27, 2016 at 06:34:41PM +0300, Ilya Enkovich wrote:
>>>> > @@ -5453,6 +5443,11 @@ ix86_option_override_internal (bool main_args_p,
>>>> > opts->x_target_flags |= MASK_VZEROUPPER;
>>>> > if (!(opts_set->x_target_flags & MASK_STV))
>>>> > opts->x_target_flags |= MASK_STV;
>>>> > + /* Disable STV if -mpreferred-stack-boundary={2,3} - the needed
>>>>
>>>> The comment doesn't match the code, you disable STV only for
>>>> -mpreferred-stack-boundary=2.
>>>
>>> Thanks, here is an updated version.
>>>
>>> Ilya
>>> --
>>> gcc/
>>>
>>> 2016-01-27 Jakub Jelinek <ja...@redhat.com>
>>> Ilya Enkovich <enkovich....@gmail.com>
>>>
>>> PR target/69454
>>> * config/i386/i386.c (convert_scalars_to_vector): Remove
>>> stack alignment fixes.
>>> (ix86_option_override_internal): Disable TARGET_STV if stack
>>> is not properly aligned.
>>>
>>> gcc/testsuite/
>>>
>>> 2016-01-27 Ilya Enkovich <enkovich....@gmail.com>
>>>
>>> PR target/69454
>>> * gcc.target/i386/pr69454-1.c: New test.
>>> * gcc.target/i386/pr69454-2.c: New test.
>>>
>>>
>>> diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
>>> index 34b57a4..9fb8db8 100644
>>> --- a/gcc/config/i386/i386.c
>>> +++ b/gcc/config/i386/i386.c
>>> @@ -3588,16 +3588,6 @@ convert_scalars_to_vector ()
>>> bitmap_obstack_release (NULL);
>>> df_process_deferred_rescans ();
>>>
>>> - /* Conversion means we may have 128bit register spills/fills
>>> - which require aligned stack. */
>>> - if (converted_insns)
>>> - {
>>> - if (crtl->stack_alignment_needed < 128)
>>> - crtl->stack_alignment_needed = 128;
>>> - if (crtl->stack_alignment_estimated < 128)
>>> - crtl->stack_alignment_estimated = 128;
>>> - }
>>> -
>>> return 0;
>>> }
>>>
>>> @@ -5453,6 +5443,11 @@ ix86_option_override_internal (bool main_args_p,
>>> opts->x_target_flags |= MASK_VZEROUPPER;
>>> if (!(opts_set->x_target_flags & MASK_STV))
>>> opts->x_target_flags |= MASK_STV;
>>> + /* Disable STV if -mpreferred-stack-boundary=2 - the needed
>>> + stack realignment will be extra cost the pass doesn't take into
>>> + account and the pass can't realign the stack. */
>>> + if (ix86_preferred_stack_boundary < 64)
>>> + opts->x_target_flags &= ~MASK_STV;
>>> if (!ix86_tune_features[X86_TUNE_AVX256_UNALIGNED_LOAD_OPTIMAL]
>>> && !(opts_set->x_target_flags & MASK_AVX256_SPLIT_UNALIGNED_LOAD))
>>> opts->x_target_flags |= MASK_AVX256_SPLIT_UNALIGNED_LOAD;
>>
>> MINIMUM_ALIGNMENT keeps track stack alignment. It is OK
>> to disable STV for -mpreferred-stack-boundary=2. But you should
>> also update ix86_minimum_alignment to make sure that STV is
>> disabled before returning 32 for DImode.
>
> If -mpreferred-stack-boundary=2 then STV is disabled, if STV is enabled then
> -mpreferred-stack-boundary>=3 and this condition in
> ix86_minimum_alignment works:
>
> if (TARGET_64BIT || align != 64 || ix86_preferred_stack_boundary >= 64)
> return align;
>
No, you shouldn't make assumptions in ix86_minimum_alignment. You
should check explicitly that STV is disabled in ix86_minimum_alignment.
--
H.J.
