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Subject: [Bug rtl-optimization/56195] [4.8 Regression] Error: incorrect register `%rdi' used with `l' suffix (at -O2)
Date: Thu, 07 Feb 2013 19:25:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56195

Vladimir Makarov <vmakarov at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |vmakarov at redhat dot com

--- Comment #4 from Vladimir Makarov <vmakarov at redhat dot com> 2013-02-07 19:24:58 UTC ---
(In reply to comment #3)
> I'd say the bug is in get_reload_reg.
> Changing pseudo 118 in operand 0 of insn 90 on equiv 0
> Changing address in insn 90 r59:DI -- no change
> Changing pseudo 59 in address of insn 90 on equiv 0
>       Creating newreg=137, assigning class GENERAL_REGS to address r137
>          Choosing alt 1 in insn 90:  (0) r  (1) rm
>          Reuse r137 for reload 0, change to class INDEX_REGS for r137
>    90: flags:CCGC=cmp(r137:DI,[r137:DI])
>     Inserting insn reload before:
>   256: r137:DI=0
> 
> 
> 3065          if (get_reload_reg (type, mode, old, goal_alt[i], "", &new_reg)
> 3066              && type != OP_OUT)
> 
> calls it with
> type=OP_IN, mode=SImode, original=const0_rtx, rclass=GENERAL_REGS
> but returns new_reg = (reg:DI 137).
> That is because:
>       if (rtx_equal_p (curr_insn_input_reloads[i].input, original)
>           && in_class_p (curr_insn_input_reloads[i].reg, rclass, &new_class))
> doesn't check any mode if original (and curr_insn_input_reloads[i].input) are
> VOIDmode as in this case.  So, either this can be fixed by doing:
>        if (rtx_equal_p (curr_insn_input_reloads[i].input, original)
> -      && in_class_p (curr_insn_input_reloads[i].reg, rclass, &new_class))
> +      && in_class_p (curr_insn_input_reloads[i].reg, rclass, &new_class)
> +      && GET_MODE (curr_insn_input_reloads[i].reg) == mode)
> , or we could try better, if the GET_MODE (curr_insn_input_reloads[i].reg)
> is wider than mode, see if we can create a lowpart subreg thereof and return
> that, and only give up (i.e. continue looping) if creation of the lowpart
> subreg for some reason failed.
> 
> Vlad, what do you think?

I think, the second solution with lowpart is better.

Would you like to make a patch or may be you prefer that I work on it?