This is the mail archive of the
gcc-help@gcc.gnu.org
mailing list for the GCC project.
Re: reload in incompatible constraints
2011/6/28 Ian Lance Taylor <iant@google.com>:
> Aurelien Buhrig <aurelien.buhrig.gcc@gmail.com> writes:
>
>> I'm trying to implement TARGET_SECONDARY_RELOAD but I cannot make it
>> work properly.
>> The hook seems to work for preventing from moving from BASE_REG to
>> BASE_REG in HImode by inserting a GENERAL_REG.
>> But I also want to insert a GENERAL_REGS intermediate register when
>> moving between BASE_REGS registers and memory in HImode.
>>
>> So I wrote something like that in my TARGET_SECONDARY_RELOAD:
>> if (MEM_P(x) && (reload_mode == HImode) && reload_class == BASE_REGS)
>> ? ? ?return GENERAL_REGS;
>>
>>
>> But it seems this do not work. For instance with DI function parameter
>> access (movdi reg:DI <-- m) which are (automatically) split into movhi
>> subreg:HI <-- m; then in movhi reg:HI <- m. But the hook do not seem
>> to work since the reg:HI is reloaded into a BASE_REG...
>>
>> So when is this hook called? Is there something specific with spliting
>> insn? Or just a general thing about TARGET_SECONDARY_RELOAD I missed ?
>
> The hook is called during reload, which is run as part of register
> allocation. ?When are you splitting the DImode load?
>
> Ian
>
I have no instruction for it. GCC automatically splits it, and it does
it at the very beginning (131r.expand) by affecting a subreg:HI, and
affects a reg:HI at 139r.subregs, and a hard base_reg at 176r.greg. It
is never changed after.
Would it be a reg class pb ?
For now, I defined BASE_REGS class for address registers which does
not intersect with GENERAL_REGS class (the data registers). Should I
define Address register and data register as general register, with a
class for address register and a new class for data registers (such as
m68k) ?
Does GCC treat GENERALS_REGS differently than other classes ?
Aurélien