http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56195
--- Comment #7 from Vladimir Makarov <vmakarov at redhat dot com> 2013-02-07
20:08:47 UTC ---
(In reply to comment #6)
> Actually, that one doesn't really work, because we have pseudo rather than
> hard
> reg at that point, which will never simplify.
>
> With this:
>
> --- lra-constraints.c.jj 2013-02-07 18:34:39.000000000 +0100
> +++ lra-constraints.c 2013-02-07 20:58:25.558920536 +0100
> @@ -421,8 +421,20 @@ get_reload_reg (enum op_type type, enum
> if (rtx_equal_p (curr_insn_input_reloads[i].input, original)
> && in_class_p (curr_insn_input_reloads[i].reg, rclass, &new_class))
> {
> - *result_reg = curr_insn_input_reloads[i].reg;
> - regno = REGNO (*result_reg);
> + rtx reg = curr_insn_input_reloads[i].reg;
> + regno = REGNO (reg);
> + /* If input is equal to original and both are VOIDmode,
> + GET_MODE (reg) might be still different from mode.
> + Ensure we don't return *result_reg with wrong mode. */
> + if (GET_MODE (reg) != mode)
> + {
> + if (GET_MODE_SIZE (GET_MODE (reg)) < GET_MODE_SIZE (mode))
> + continue;
> + reg = lowpart_subreg (mode, reg, GET_MODE (reg));
> + if (reg == NULL_RTX || GET_CODE (reg) != SUBREG)
> + continue;
> + }
> + *result_reg = reg;
> if (lra_dump_file != NULL)
> {
> fprintf (lra_dump_file, " Reuse r%d for reload ", regno);
>
> the assembly difference is:
>
> - cmpl (%rdi), %rdi
> + cmpl (%rdi), %edi
>
> which is desirable in this case, but not sure if all get_reload_reg callers
> will grok a SUBREG instead of REG returned in *result_reg.
This version of patch looks ok for me. I have no worry about get_reload_reg
callers. It should work fine (that is a difference from reload pass when you
should care about secondary reloads etc).
Thanks for working on this, Jakub,
