Re: [PATCH] rs6000: Fix restored rs6000_long_double_type_size.

[Segher Boessenkool <segher@kernel.crashing.org>]

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?

> >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)

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.

> 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?

> --- 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 :-/

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

> 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.

Thanks,


Segher