[PATCH 7/7] ira.c validate_equiv_mem

[Alan Modra]

On Wed, Mar 23, 2016 at 01:03:18AM +0100, Bernd Schmidt wrote:
> On 03/21/2016 02:43 AM, Alan Modra wrote:
> >
> >+enum valid_equiv { valid_none, valid_combine, valid_reload };
> >+
> 
> Might be worth documenting that each step represents a superset of the
> previous one.

Fixed.

> >+	  ret = valid_combine;
> >+	  if (! MEM_READONLY_P (memref)
> >+	      && ! RTL_CONST_OR_PURE_CALL_P (insn))
> >+	    return valid_none;
> >+	}
> 
> The gcc style is actually not to have a space after unary "!". None of the
> code in this file follows that, but I think you may want to change that as
> you modify things in your patches, and have new code follow the recommended
> style.

Fixed.

> >@@ -3536,7 +3557,8 @@ update_equiv_regs (void)
> >  		{
> >  		  /* Note that the statement below does not affect the priority
> >  		     in local-alloc!  */
> >-		  REG_LIVE_LENGTH (regno) *= 2;
> >+		  if (note)
> >+		    REG_LIVE_LENGTH (regno) *= 2;
> 
> That's a very suspicious comment. It would be worth testing whether
> REG_LIVE_LENGTH has any effect on our current register allocation at all,
> and remove this code if not.

Yes, REG_LIVE_LENGTH is used in just one place in the whole of gcc,
and that's the test in update_equiv_regs just above the code you
quote.
	      /* Don't mess with things live during setjmp.  */
	      if (REG_LIVE_LENGTH (regno) >= 0 && optimize)

That could be replaced with
	      if (optimize && !bitmap_bit_p (setjmp_crosses, regno))
and outside the loop
  bitmap setjmp_crosses = regstat_get_setjmp_crosses ();

For now, I've removed the REG_LIVE_LENGTH adjustment from patch 7/7.
I'll also prepare a patch to delete REG_LIVE_LENGTH everywhere.

-- 
Alan Modra
Australia Development Lab, IBM