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Re: Special Memory Constraint [was Re: Indirect memory addresses vs. lra]



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.


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