On Mon, 29 Jun 2015, Marek Polacek wrote:
> On Mon, Jun 29, 2015 at 09:36:59AM +0200, Richard Biener wrote:
> > > Anything wrong with this?
> > >
> > > +/* X - (X / Y) * Y is the same as X % Y. */
> > > +(simplify
> > > + (minus (convert? @0) (convert? (mult (trunc_div @0 @1) @1)))
> > > + (if (INTEGRAL_TYPE_P (type) || VECTOR_INTEGER_TYPE_P (type))
> > > + (convert (trunc_mod @0 @1))))
>
> That looks awfully similar to a variant I also tried (but I remember
> having convert1? and convert2? in it). Not sure what was wrong with
> that one; certainly yours seems to work fine.
>
> Not sure whether we need some tree_nop_conversion_p in it. Perhaps not.
>
> > Yes. Eventually even (convert? (mult (convert1? (trunc_div ...)?
> > Of course with matching @0 between the two operands of the minus
> > you constrain types quite a bit.
>
> I'm starting to dislike this whole convert business ;).
;) fold-const.c STRIP_NOPS certainly was both convenient and
error-prone at the same time.
> > I'd say just single-step through fold and see what types it get
> > present when folding a - (unsigned) ((a / b) * b).
>
> I did that. The whole expression has type "unsigned int", arg0
> is "a" of type int and arg1 is "(a / b) * b" of type int.
>
> The following version is what Marc suggests.
>
> Bootstrapped/regtested on x86_64-linux, ok for trunk?
Ok.
Thanks,
Richard.
> 2015-06-29 Marek Polacek <pola...@redhat.com>
> Marc Glisse <marc.gli...@inria.fr>
>
> * fold-const.c (fold_binary_loc): Move X - (X / Y) * Y -> X % Y to ...
> * match.pd: ... pattern here.
>
> diff --git gcc/fold-const.c gcc/fold-const.c
> index 6f12dd0..01e3983 100644
> --- gcc/fold-const.c
> +++ gcc/fold-const.c
> @@ -10509,19 +10509,6 @@ fold_binary_loc (location_t loc,
> fold_convert_loc (loc, type,
> TREE_OPERAND (arg0, 0)));
>
> - /* X - (X / Y) * Y is X % Y. */
> - if ((INTEGRAL_TYPE_P (type) || VECTOR_INTEGER_TYPE_P (type))
> - && TREE_CODE (arg1) == MULT_EXPR
> - && TREE_CODE (TREE_OPERAND (arg1, 0)) == TRUNC_DIV_EXPR
> - && operand_equal_p (arg0,
> - TREE_OPERAND (TREE_OPERAND (arg1, 0), 0), 0)
> - && operand_equal_p (TREE_OPERAND (TREE_OPERAND (arg1, 0), 1),
> - TREE_OPERAND (arg1, 1), 0))
> - return
> - fold_convert_loc (loc, type,
> - fold_build2_loc (loc, TRUNC_MOD_EXPR, TREE_TYPE
> (arg0),
> - arg0, TREE_OPERAND (arg1, 1)));
> -
> if (! FLOAT_TYPE_P (type))
> {
> /* Fold A - (A & B) into ~B & A. */
> diff --git gcc/match.pd gcc/match.pd
> index b2f8429..2bc158b 100644
> --- gcc/match.pd
> +++ gcc/match.pd
> @@ -238,6 +238,12 @@ along with GCC; see the file COPYING3. If not see
> && tree_nop_conversion_p (type, TREE_TYPE (@1)))
> (trunc_mod @0 (convert @1))))
>
> +/* X - (X / Y) * Y is the same as X % Y. */
> +(simplify
> + (minus (convert? @0) (convert? (mult (trunc_div @0 @1) @1)))
> + (if (INTEGRAL_TYPE_P (type) || VECTOR_INTEGER_TYPE_P (type))
> + (convert (trunc_mod @0 @1))))
> +
> /* Optimize TRUNC_MOD_EXPR by a power of two into a BIT_AND_EXPR,
> i.e. "X % C" into "X & (C - 1)", if X and C are positive.
> Also optimize A % (C << N) where C is a power of 2,
>
> Marek
>
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Dilip Upmanyu, Graham
Norton, HRB 21284 (AG Nuernberg)
