https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95740
--- Comment #5 from Hongtao.liu <crazylht at gmail dot com> ---
(In reply to Hongtao.liu from comment #4)
> It can be fixed by
>
> 2 files changed, 4 insertions(+), 2 deletions(-)
> gcc/config/i386/i386.c | 2 +-
> gcc/config/i386/i386.h | 4 +++-
>
> modified gcc/config/i386/i386.c
> @@ -19194,7 +19194,7 @@ ix86_preferred_reload_class (rtx x, reg_class_t
> regclass)
>
> /* Prefer SSE regs only, if we can use them for math. */
> if (SSE_FLOAT_MODE_P (mode) && TARGET_SSE_MATH)
> - return SSE_CLASS_P (regclass) ? regclass : NO_REGS;
> + return INT_SSE_CLASS_P (regclass) ? regclass : NO_REGS;
>
> /* Generally when we see PLUS here, it's the function invariant
> (plus soft-fp const_int). Which can only be computed into general
> modified gcc/config/i386/i386.h
> @@ -1283,7 +1283,9 @@ enum reg_class
> reg_class_subset_p ((CLASS), FLOAT_REGS)
> #define SSE_CLASS_P(CLASS) \
> reg_class_subset_p ((CLASS), ALL_SSE_REGS)
> -#define MMX_CLASS_P(CLASS) \
> +#define INT_SSE_CLASS_P(CLASS) \
> + reg_class_subset_p ((CLASS), INT_SSE_REGS)
> +#define MMX_CLASS_P(CLASS) \
> ((CLASS) == MMX_REGS)
> #define MASK_CLASS_P(CLASS) \
> reg_class_subset_p ((CLASS), ALL_MASK_REGS)
>
> I'm testing performance impact.
orginally, ix86_preferred_reload_class (SFmode, GENERAL_REGS) return NO_REG,
and it increase reject by LRA_MAX_REJECT(600) which make it impossible to
reload to general_regs.
---------------------cut from lra-constraints.c------------------------
/* Check strong discouragement of reload of non-constant
into class THIS_ALTERNATIVE. */
if (! CONSTANT_P (op) && ! no_regs_p
&& (targetm.preferred_reload_class
(op, this_alternative) == NO_REGS
|| (curr_static_id->operand[nop].type == OP_OUT
&& (targetm.preferred_output_reload_class
(op, this_alternative) == NO_REGS))))
{
if (offmemok && REG_P (op))
{
if (lra_dump_file != NULL)
fprintf
(lra_dump_file,
" %d Spill pseudo into memory:
reject+=3\n",
nop);
reject += 3;
}
else
{
if (lra_dump_file != NULL)
fprintf
(lra_dump_file,
" %d Non-prefered reload: reject+=%d\n",
nop, LRA_MAX_REJECT);
reject += LRA_MAX_REJECT;
}
}
-------------------------------------------------------
with gcc -O2 test.c -mfpmath=387, trunk gcc can also generate
foo(float):
movd %xmm0, %eax
addl $1, %eax
ret
