On Mon, Aug 19, 2019 at 09:14:22AM -0400, Vladimir Makarov wrote:
> On 2019-08-19 3:35 a.m., John Darrington wrote:
> >On Fri, Aug 16, 2019 at 10:50:13AM -0400, Vladimir Makarov wrote:
> > No I meant something like that
> >
> > (define_special_memory_constraint "a" ...)
> > (define_predicate "my_special_predicate" ...
> >
> > {
> > if (lra_in_progress_p)
> > return REG_P (op) && REGNO (op) >= FIRST_PSEUDO_REGISTER &&
> > reg_renumber[REGNO(op)] < 0;
> > return true if memory with sp addressing;
> > })
> >
> > I think LRA spills pseudo-register and it will be memory addressed
> > by sp
> > at the end of LRA.
> >
> >What I've done is this:
> >
> >(define_predicate "my_special_predicate"
> > (match_operand 0 "memory_operand")
> > {
> > debug_rtx (op);
> > gcc_assert (MEM_P (op));
> > op = XEXP (op, 0);
> > if (GET_CODE (op) == PLUS)
> > op = XEXP (op, 0);
> >
> > if (lra_in_progress)
> > {
> > fprintf (stderr, "%s:%d\n", __FILE__, __LINE__);
> > return REG_P (op) && REGNO (op) >= FIRST_PSEUDO_REGISTER &&
> > reg_renumber[REGNO(op)] < 0;
> > }
> >
> >
> > if (REG_P (op))
> > {
> > int regno = REGNO (op);
> > return (regno == 10); // register is the stack pointer
> > }
> >
> > return true;
> > })
> >
> > (and many variations) Unfortunately, any moderately complicated input
> > still results in a (mem (reg) ) insn repeatedly entering the
> > lra_in_progress case and returning false, and eventually terminating with
> >
> > "internal compiler error: maximum number of generated reload insns per
> > insn achieved (90)"
> >
> >
> >Any other ideas?
> As I remember there were a few other ideas from Richard Biener and
> Segher Boessenkool. I also proposed to add a new address register which
> will be always a fixed stack memory slot at the end. Unfortunately I am
> not familiar with the target and the port to say in details how to do
> it. But I think it is worth to try.
The m68hc11 port used the fake Z register approach, and I believe it had
some special machine pass to get rid of it right before assembler output.
(r171302 is when it was removed -- last version was
https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=gcc/config/m68hc11/m68hc11.c;h=1e414102c3f1fed985e4fb8db7954342e965190b;hb=bae8bb65d842d7ffefe990c1f0ac004491f3c105#l4061
for the machine reorg stuff).
No idea how well it works... But it's only needed if you are forced to
have a frame pointer IIUC?
Segher
