Re: reload in incompatible constraints

[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