[PATCH] x86: Don't pad .tfloat output

[H.J. Lu]

On Sun, Aug 15, 2021 at 11:48 PM Jan Beulich <jbeulich@suse.com> wrote:
>
> On 15.08.2021 22:34, H.J. Lu wrote:
> > .tfloat output should always be 10 bytes without padding, independent
> > of psABIs.
>
> I disagree. It's been a long standing bug. I can see that affecting
> existing code isn't nice, so I could see us emit e.g. a warning for
> the time being. In the worst case we might add a command line option
> to drive the behavior.
>
> >  In glibc, x86 assembly codes expect 10-byte .tfloat output.
> > This also changes .ds.x output and .tfloat output with hex input to
> > match .tfloat output.
>
> This leaves users without any ABI-conforming way to produce double
> extended precision values, short of hand-coding the padding. Even if
> you were really going to insist that retaining the broken behavior
> of .tfloat is necessary, a directive providing correct behavior
> should be available. This might then be .d{c,cb,s}.x, or something
> new. But as said - to me this really would only be a last resort.
> Whoever introduced .tfloat in its present way screwed up, and
> whoever forgot to fix .tfloat for x86-64 didn't even pay attention
> to the ABI difference.
>
> >       PR gas/28230
> >       * config/tc-i386.c (x86_tfloat_pad): Removed.
> >       * config/tc-i386.h (X_PRECISION_PAD): Changed to 0.
> >       (x86_tfloat_pad): Removed.
> >       * testsuite/gas/i386/fp.s: If NO_TFLOAT_PADDING isn't defined,
> >       add explicit paddings after .tfloat, .ds.x, .dc.x and .dcb.x
> >       directives.
> >       * testsuite/gas/i386/i386.exp (ASFLAGS): Append
> >       "--defsym NO_TFLOAT_PADDING=1" when running the fp test.
>
> I'm afraid I don't understand the games you play here: If you
> really thought .tfloat should not emit ABI-conforming data, then
> why would you bother introducing NO_TFLOAT_PADDING to allow for
> alternative behavior?

Since I don't want to change fp-elf32.d nor fp-elf64.d, I added paddings
manually.  fp.d doesn't expect paddings.

-- 
H.J.