[PATCH] x32: Encode %esp as %rsp to avoid 0x67 prefix

[Uros Bizjak]

On Tue, Sep 26, 2017 at 2:19 PM, Jakub Jelinek <jakub@redhat.com> wrote:
> On Sun, Sep 24, 2017 at 11:25:34AM +0200, Uros Bizjak wrote:
>> We can use 'q' modifier just before register output part (plus a small
>> simplification).
>>
>> Can you try the attached (untested) patch?
>>
>> Uros.
>
>> Index: i386.c
>> ===================================================================
>> --- i386.c    (revision 253118)
>> +++ i386.c    (working copy)
>> @@ -19953,6 +19953,14 @@ ix86_print_operand_address_as (FILE *file, rtx add
>>         code = 'k';
>>       }
>>
>> +      /* Since the upper 32 bits of RSP are always zero for x32, we can
>> +      encode %esp as %rsp to avoid 0x67 prefix if there is no index or
>> +      base register.  */
>> +      if (TARGET_X32 && Pmode == SImode
>> +       && ((!index && base && REGNO (base) == SP_REG)
>> +           || (!base && index && REGNO (index) == SP_REG)))
>> +     code = 'q';
>> +
>>        if (ASSEMBLER_DIALECT == ASM_ATT)
>>       {
>>         if (disp)
>
> This broke
> +FAIL: gcc.target/i386/pr55049-1.c (internal compiler error)
> +FAIL: gcc.target/i386/pr55049-1.c (test for excess errors)
> +FAIL: gcc.target/i386/pr59034-1.c (internal compiler error)
> +FAIL: gcc.target/i386/pr59034-1.c (test for excess errors)
> +FAIL: g++.dg/other/pr59492.C  -std=gnu++11 (internal compiler error)
> +FAIL: g++.dg/other/pr59492.C  -std=gnu++11 (test for excess errors)
> +FAIL: g++.dg/other/pr59492.C  -std=gnu++14 (internal compiler error)
> +FAIL: g++.dg/other/pr59492.C  -std=gnu++14 (test for excess errors)
> +FAIL: g++.dg/other/pr59492.C  -std=gnu++98 (internal compiler error)
> +FAIL: g++.dg/other/pr59492.C  -std=gnu++98 (test for excess errors)
> with --enable-checking=yes,rtl,extra.
>
> While I believe non-NULL index must be a REG, that is not the case for base,
> which can be pc_rtx.  A few lines later it calls print_reg on base and/or
> index (if non-NULL) and that assumes it is pc_rtx or uses REGNO on it,
> so I think we can't see a SUBREG or something similar there.
>
> Fixed thusly, ok for trunk?
>
> 2017-09-26  Jakub Jelinek  <jakub@redhat.com>
>
>         PR target/82267
>         * config/i386/i386.c (ix86_print_operand_address_as): Only test
>         REGNO (base) == SP_REG if base is a REG.

OK.

Thanks,
Uros.

> --- gcc/config/i386/i386.c.jj   2017-09-26 11:38:54.000000000 +0200
> +++ gcc/config/i386/i386.c      2017-09-26 14:04:51.444459554 +0200
> @@ -19957,7 +19957,7 @@ ix86_print_operand_address_as (FILE *fil
>          encode %esp as %rsp to avoid 0x67 prefix if there is no index or
>          base register.  */
>        if (TARGET_X32 && Pmode == SImode
> -         && ((!index && base && REGNO (base) == SP_REG)
> +         && ((!index && base && REG_P (base) && REGNO (base) == SP_REG)
>               || (!base && index && REGNO (index) == SP_REG)))
>         code = 'q';
>
>
>
>         Jakub