On Sat, Sep 23, 2017 at 11:16 PM, H.J. Lu <hjl.to...@gmail.com> wrote:
> Since the upper 32 bits of stack register are always zero for x32, we
> can encode %esp as %rsp to avoid 0x67 prefix in address if there is no
> index or base register.
>
> Tested on x86-64. OK for trunk?
>
> H.J.
> ----
> gcc/
>
> PR target/82267
> * config/i386/i386.c (ix86_print_operand_address_as): Encode
> %esp as %rsp to avoid 0x67 prefix if there is no index or base
> register.
>
> gcc/testsuite/
>
> PR target/82267
> * gcc.target/i386/pr82267.c: New tests.
> ---
> gcc/config/i386/i386.c | 17 +++++++++++++++++
> gcc/testsuite/gcc.target/i386/pr82267.c | 14 ++++++++++++++
> 2 files changed, 31 insertions(+)
> create mode 100644 gcc/testsuite/gcc.target/i386/pr82267.c
>
> diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
> index 5e8f58c5e9f..519fdb0ffae 100644
> --- a/gcc/config/i386/i386.c
> +++ b/gcc/config/i386/i386.c
> @@ -19849,6 +19849,23 @@ ix86_print_operand_address_as (FILE *file, rtx addr,
> disp = parts.disp;
> scale = parts.scale;
>
> + /* 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)
> + && index != base)
> + {
> + if (base)
> + {
> + if (REGNO (base) == SP_REG)
> + base = gen_rtx_REG (DImode, SP_REG);
> + }
> + else if (REGNO (index) == SP_REG)
> + index = gen_rtx_REG (DImode, SP_REG);
> + }
> +
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)
