Re: [PATCH] rs6000: Fix restored rs6000_long_double_type_size.

["Martin Liška" <mliska@suse.cz>]

On 7/12/21 7:20 PM, Segher Boessenkool wrote:
> On Mon, Jun 28, 2021 at 02:19:03PM +0200, Martin Liška wrote:
>> On 6/24/21 12:46 AM, Segher Boessenkool wrote:
>>>> As mentioned in the "Fallout: save/restore target options in
>>>> handle_optimize_attribute"
>>>> thread, we need to support target option restore of
>>>> rs6000_long_double_type_size == FLOAT_PRECISION_TFmode.
>>>
>>> I have no idea?  Could you explain please?
>>
>> Sure. Few weeks ago, we started using cl_target_option_{save,restore} calls
>> even for optimize attributes (and pragma). Motivation was that optimize
>> options
>> can influence target options (and vice versa).
>>
>> Doing that, FLOAT_PRECISION_TFmode must be accepted as a valid option value
>> for rs6000_long_double_type_size.
> 
> 
>>>> --- /dev/null
>>>> +++ b/gcc/testsuite/gcc.target/powerpc/pragma-optimize.c
>>>> @@ -0,0 +1,14 @@
>>>> +/* { dg-do compile { target { powerpc*-*-linux* } } } */
>>>
>>> Why on Linux only?  That doesn't sound right.  Do you need some other
>>> selector(s)?
>>
>> Sorry, I copied the test-case.
> 
> Ugh.  Yes, the status quo is no good either :-(
> 
>>>> +/* { dg-options "-O2 -mlong-double-128 -mabi=ibmlongdouble" } */
>>>> +
>>>> +extern unsigned long int x;
>>>> +extern float f (float);
>>>> +extern __typeof (f) f_power8;
>>>> +extern __typeof (f) f_power9;
>>>> +extern __typeof (f) f __attribute__ ((ifunc ("f_ifunc")));
>>>> +static __attribute__ ((optimize ("-fno-stack-protector"))) __typeof (f) *
>>>
>>> -fno-stack-protector is default.
>>
>> Yes, but one needs an optimize attribute in order to trigger
>> cl_target_option_save/restore
>> mechanism.
> 
> So it behaves differently if you select the default than if you do not
> select anything?  That is wrong, no?

Sorry, I don't get your example, please explain it.

> 
>> >From 1632939853fbf193f72ace3d1024a137d549fef4 Mon Sep 17 00:00:00 2001
>> From: Martin Liska <mliska@suse.cz>
>> Date: Tue, 1 Jun 2021 15:39:14 +0200
>> Subject: [PATCH] rs6000: Fix restored rs6000_long_double_type_size.
> 
> (No full stop at end of subject please)

Done.

> 
> Missing patch description here.  This should be suitable as commit
> message when you eventually commit the patch.
> 
> Please send with that, as a separate mail, not as attachment to another
> thread.

Done.

> 
>> gcc/ChangeLog:
>>
>> 	* config/rs6000/rs6000.c (rs6000_option_override_internal): When
>> 	a target option is restored, it can have
>> 	rs6000_long_double_type_size set to FLOAT_PRECISION_TFmode.
> 
> That does not say what changed?

Updated.

> 
>> --- a/gcc/config/rs6000/rs6000.c
>> +++ b/gcc/config/rs6000/rs6000.c
>> @@ -4185,6 +4185,8 @@ rs6000_option_override_internal (bool global_init_p)
>>         else
>>   	rs6000_long_double_type_size = default_long_double_size;
>>       }
>> +  else if (rs6000_long_double_type_size == FLOAT_PRECISION_TFmode)
>> +    ; /* The option can be restored with cl_target_option_restore.  */
>>     else if (rs6000_long_double_type_size == 128)
>>       rs6000_long_double_type_size = FLOAT_PRECISION_TFmode;
>>     else if (global_options_set.x_rs6000_ieeequad)
> 
> "The option can be restored" is more confusing than helpful.  *Will* be
> restored by it, maybe?  Not that I understand what that means :-/

I updated the wording a bit.

> 
> Does it make more sense to merge the 128 and FLOAT_PRECISION_TFmode
> cases?

Likely not, it's important to assign a reasonable comment to the 128 option value.

> 
>> diff --git a/gcc/testsuite/gcc.target/powerpc/pragma-optimize.c b/gcc/testsuite/gcc.target/powerpc/pragma-optimize.c
>> new file mode 100644
>> index 00000000000..2455fb57138
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.target/powerpc/pragma-optimize.c
>> @@ -0,0 +1,14 @@
>> +/* { dg-do compile { target { powerpc*-*-* } } } */
> 
> No target powerpc*-*-* in gcc.target/powerpc please.  This is enforced
> for everything in there by powerpc.exp already.

Fixed.

Martin

> 
> Thanks,
> 
> 
> Segher
>