On Tue, Mar 3, 2020 at 6:50 AM Jan Beulich <jbeulich@suse.com> wrote:
>
> On 03.03.2020 15:09, H.J. Lu wrote:
> > I am testing this patch with GCC 8.  I will check it in if it fixes
> > regressions in GCC 8 testsuits:
> >
> > https://gcc.gnu.org/ml/gcc-regression/2020-03/msg00008.html
> >
> > H.J.
> > ---
> > According to gas manual, suffix in instruction mnemonics isn't always
> > required:
> >
> > When there is no sizing suffix and no (suitable) register operands to
> > deduce the size of memory operands, with a few exceptions and where long
> > operand size is possible in the first place, operand size will default
> > to long in 32- and 64-bit modes.
>
> Nothing there says that this defaulting is to happen silently. Yet
> _that's_ what my earlier changes altered. The defaulting is still
> the same. And no - SUCH CASES SHOULD NOT GO SILENTLY, neither here
> nor in the MOVSX/MOVZX case. Ambiguities should _always_ be
> pointed out by the assembler. (There may be [and there is] a mode
> in which this goes silently, to be enabled at the programmer's
> risk.)

It is not going to happen in AT&T syntax.   Gas has to support older GCC
without any warnings.

> > This includes cvtsi2sd, cvtsi2ss, vcvtsi2sd, vcvtsi2ss, vcvtusi2sd and
> > vcvtusi2ss.  Since they are used in GCC 8 and older GCC releases, they
> > must be allowed without suffix in AT&T syntax.
> >
> > gas/
> >
> >       PR gas/25622
> >       * testsuite/gas/i386/i386.exp: Run x86-64-default-suffix and
> >       x86-64-default-suffix-avx.
> >       * testsuite/gas/i386/noreg64.s: Remove cvtsi2sd, cvtsi2ss,
> >       vcvtsi2sd, vcvtsi2ss, vcvtusi2sd and vcvtusi2ss entries.
> >       * testsuite/gas/i386/noreg64.d: Updated.
> >       * testsuite/gas/i386/noreg64.l: Likewise.
> >       * testsuite/gas/i386/x86-64-default-suffix-avx.d: New file.
> >       * testsuite/gas/i386/x86-64-default-suffix.d: Likewise.
> >       * testsuite/gas/i386/x86-64-default-suffix.s: Likewise.
> >
> > opcodes/
> >
> >       PR gas/25622
> >       * i386-opc.tbl: Add IgnoreSize to cvtsi2sd, cvtsi2ss, vcvtsi2sd,
> >       vcvtsi2ss, vcvtusi2sd and vcvtusi2ss for AT&T syntax.
>
> Oh no. I'm trying to clean up the IgnoreSize mess and you want to
> add new instances for no good reason (yes, there are cases where
> this is actually missing; hopefully I'll get to send out the
> series later this week).

Since an instruction template can't have both IgnoreSize and DefaultSize,
I am testing this patch and will check it if there are no regressions.  Then
we can add one value to MnemonicSize.

> I know I can't prevent this going in, but I'm heavily opposed.
> You don't "fix" anything here, you break things.
>

I disagree.


-- 
H.J.