Re: [PATCH] middle-end/61747 - conditional move expansion and constants

[Jakub Jelinek <jakub@redhat.com>]

On Wed, Jul 19, 2023 at 01:36:23PM +0000, Richard Biener wrote:
> > If we have a match between at least one of the comparison operands and
> > op2/op3, I think having equivalency there is perhaps more important than
> > the canonicalization, but it would be nice not to break it even if there
> > is no match.  So, perhaps force_reg only if there is a match?
> > force_reg (cmpmode, force_reg (cmpmode, x)) is equivalent to
> > force_reg (cmpmode, x), so perhaps:
> > 	    {
> > 	      if (rtx_equal_p (orig_op0, op2))
> > 		op2p = XEXP (comparison, 0) = force_reg (cmpmode, orig_op0);
> > 	      if (rtx_equal_p (orig_op0, op3))
> > 		op3p = XEXP (comparison, 0)
> > 		  = force_reg (cmpmode, XEXP (comparison, 0));
> > 	    }
> > and similarly for the other body?
> 
> I don't think we'll have op3 == op2 == orig_op0 because if
> op2 == op3 the 
> 
>   /* If the two source operands are identical, that's just a move.  */
> 
>   if (rtx_equal_p (op2, op3))
>     {
>       if (!target)
>         target = gen_reg_rtx (mode);
> 
>       emit_move_insn (target, op3);
>       return target;
> 
> code should have triggered.  So we should know we invoke force_reg
> only once for each comparison operand check?
> 
> So I'm going to test the following ontop of the patch.

Please use else if instead of the second if then.
Ok with that change.

> --- a/gcc/optabs.cc
> +++ b/gcc/optabs.cc
> @@ -5131,11 +5131,10 @@ emit_conditional_move (rtx target, struct 
> rtx_comparison comp,
>                   > COSTS_N_INSNS (1))
>               && can_create_pseudo_p ())
>             {
> -             XEXP (comparison, 0) = force_reg (cmpmode, orig_op0);
>               if (rtx_equal_p (orig_op0, op2))
> -               op2p = XEXP (comparison, 0);
> +               op2p = XEXP (comparison, 0) = force_reg (cmpmode, 
> orig_op0);
>               if (rtx_equal_p (orig_op0, op3))
> -               op3p = XEXP (comparison, 0);
> +               op3p = XEXP (comparison, 0) = force_reg (cmpmode, 
> orig_op0);
>             }
>           if (CONSTANT_P (orig_op1) && optimize
>               && (rtx_cost (orig_op1, mode, COMPARE, 0,
> @@ -5143,11 +5142,10 @@ emit_conditional_move (rtx target, struct 
> rtx_comparison comp,
>                   > COSTS_N_INSNS (1))
>               && can_create_pseudo_p ())
>             {
> -             XEXP (comparison, 1) = force_reg (cmpmode, orig_op1);
>               if (rtx_equal_p (orig_op1, op2))
> -               op2p = XEXP (comparison, 1);
> +               op2p = XEXP (comparison, 1) = force_reg (cmpmode, 
> orig_op1);
>               if (rtx_equal_p (orig_op1, op3))
> -               op3p = XEXP (comparison, 1);
> +               op3p = XEXP (comparison, 1) = force_reg (cmpmode, 
> orig_op1);
>             }
>           prepare_cmp_insn (XEXP (comparison, 0), XEXP (comparison, 1),
>                             GET_CODE (comparison), NULL_RTX, unsignedp,

	Jakub