Re: [PATCH] x86: Use ud2 assembly mnemonic when available.

[Andrew Pinski <pinskia at gmail dot com>]

On Thu, Feb 13, 2014 at 3:46 PM, Roland McGrath <mcgrathr@google.com> wrote:
> Non-ancient assemblers support the "ud2" mnemonic, so there is no need
> to emit the literal opcode as data.
>
> OK for trunk and 4.8?

I changed this to use .word due to openbsd3.1:
http://gcc.gnu.org/ml/gcc-patches/2005-07/msg01347.html .  I no longer
have access to this older openbsd box so I don't object to this
change.  In fact I doubt we support any binutils that are pre 2.0 any
more; so maybe move over unconditionally to ud.

Thanks,
Andrew Pinski

>
>
> Thanks,
> Roland
>
>
> gcc/
> 2014-02-13  Roland McGrath  <mcgrathr@google.com>
>
>         * configure.ac (HAVE_AS_IX86_UD2): New test for 'ud2' mnemonic.
>         * configure: Regenerated.
>         * config.in: Regenerated.
>         * config/i386/i386.md (trap) [HAVE_AS_IX86_UD2]: Use the mnemonic
>         instead of ASM_SHORT.
>
> --- a/gcc/config.in
> +++ b/gcc/config.in
> @@ -375,6 +375,12 @@
>  #endif
>
>
> +/* Define if your assembler supports the 'ud2' mnemonic. */
> +#ifndef USED_FOR_TARGET
> +#undef HAVE_AS_IX86_UD2
> +#endif
> +
> +
>  /* Define if your assembler supports the lituse_jsrdirect relocation. */
>  #ifndef USED_FOR_TARGET
>  #undef HAVE_AS_JSRDIRECT_RELOCS
> --- a/gcc/config/i386/i386.md
> +++ b/gcc/config/i386/i386.md
> @@ -17843,7 +17843,13 @@
>  (define_insn "trap"
>    [(trap_if (const_int 1) (const_int 6))]
>    ""
> -  { return ASM_SHORT "0x0b0f"; }
> +{
> +#ifdef HAVE_AS_IX86_UD2
> +  return "ud2";
> +#else
> +  return ASM_SHORT "0x0b0f";
> +#endif
> +}
>    [(set_attr "length" "2")])
>
>  (define_expand "prefetch"
> --- a/gcc/configure
> +++ b/gcc/configure
> @@ -25109,6 +25109,37 @@ $as_echo "#define
> HAVE_AS_IX86_REP_LOCK_PREFIX 1" >>confdefs.h
>
>  fi
>
> +    { $as_echo "$as_me:${as_lineno-$LINENO}: checking assembler for
> ud2 mnemonic" >&5
> +$as_echo_n "checking assembler for ud2 mnemonic... " >&6; }
> +if test "${gcc_cv_as_ix86_ud2+set}" = set; then :
> +  $as_echo_n "(cached) " >&6
> +else
> +  gcc_cv_as_ix86_ud2=no
> +  if test x$gcc_cv_as != x; then
> +    $as_echo 'ud2' > conftest.s
> +    if { ac_try='$gcc_cv_as $gcc_cv_as_flags  -o conftest.o conftest.s >&5'
> +  { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
> +  (eval $ac_try) 2>&5
> +  ac_status=$?
> +  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
> +  test $ac_status = 0; }; }
> +    then
> +       gcc_cv_as_ix86_ud2=yes
> +    else
> +      echo "configure: failed program was" >&5
> +      cat conftest.s >&5
> +    fi
> +    rm -f conftest.o conftest.s
> +  fi
> +fi
> +{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $gcc_cv_as_ix86_ud2" >&5
> +$as_echo "$gcc_cv_as_ix86_ud2" >&6; }
> +if test $gcc_cv_as_ix86_ud2 = yes; then
> +
> +$as_echo "#define HAVE_AS_IX86_UD2 1" >>confdefs.h
> +
> +fi
> +
>      { $as_echo "$as_me:${as_lineno-$LINENO}: checking assembler for
> R_386_TLS_GD_PLT reloc" >&5
>  $as_echo_n "checking assembler for R_386_TLS_GD_PLT reloc... " >&6; }
>  if test "${gcc_cv_as_ix86_tlsgdplt+set}" = set; then :
> --- a/gcc/configure.ac
> +++ b/gcc/configure.ac
> @@ -3895,6 +3895,12 @@ foo:     nop
>          [AC_DEFINE(HAVE_AS_IX86_REP_LOCK_PREFIX, 1,
>            [Define if the assembler supports 'rep <insn>, lock <insn>'.])])
>
> +    gcc_GAS_CHECK_FEATURE([ud2 mnemonic],
> +       gcc_cv_as_ix86_ud2,,,
> +       [ud2],,
> +      [AC_DEFINE(HAVE_AS_IX86_UD2, 1,
> +       [Define if your assembler supports the 'ud2' mnemonic.])])
> +
>      gcc_GAS_CHECK_FEATURE([R_386_TLS_GD_PLT reloc],
>          gcc_cv_as_ix86_tlsgdplt,,,
>         [call    tls_gd@tlsgdplt],