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Re: Fix X - (X / Y) * Y in match.pd
- From: Richard Biener <richard dot guenther at gmail dot com>
- To: Marc Glisse <marc dot glisse at inria dot fr>
- Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>
- Date: Thu, 29 Oct 2015 16:25:14 +0100
- Subject: Re: Fix X - (X / Y) * Y in match.pd
- Authentication-results: sourceware.org; auth=none
- References: <alpine dot DEB dot 2 dot 02 dot 1510291540100 dot 19735 at laptop-mg dot saclay dot inria dot fr>
On Thu, Oct 29, 2015 at 4:06 PM, Marc Glisse <marc.glisse@inria.fr> wrote:
> Hello,
>
> before we completely forget about it, this fixes the pattern as discussed
> around https://gcc.gnu.org/ml/gcc-patches/2015-10/msg01459.html .
>
> Note that, as seen in https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68008#c1
> , we would sometimes like to allow a conversion between trunc_div and mult,
> but that's a separate generalization and I did not want to think of the
> proper conditions for its validity.
>
> Bootstrap+regtest on ppc64le-redhat-linux.
Ok, can you add a comment why we can't use matching captures before
the operand_equal_p? Just in case somebody stumbles across this...
Richard.
> 2015-10-30 Marc Glisse <marc.glisse@inria.fr>
>
> * match.pd (X-(X/Y)*Y): Properly handle conversions and
> commutativity.
>
> --
> Marc Glisse
> Index: gcc/match.pd
> ===================================================================
> --- gcc/match.pd (revision 229478)
> +++ gcc/match.pd (working copy)
> @@ -311,24 +311,24 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> /* X % -Y is the same as X % Y. */
> (simplify
> (trunc_mod @0 (convert? (negate @1)))
> (if (!TYPE_UNSIGNED (type)
> && !TYPE_OVERFLOW_TRAPS (type)
> && 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 (convert1? @0) (convert2? (mult (trunc_div @0 @1) @1)))
> - (if ((INTEGRAL_TYPE_P (type) || VECTOR_INTEGER_TYPE_P (type))
> - && TYPE_UNSIGNED (TREE_TYPE (@0)) == TYPE_UNSIGNED (type))
> - (trunc_mod (convert @0) (convert @1))))
> + (minus (convert1? @2) (convert2? (mult:c (trunc_div @0 @1) @1)))
> + (if (operand_equal_p (@0, @2, 0)
> + && (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,
> to A & ((C << N) - 1). */
> (match (power_of_two_cand @1)
> INTEGER_CST@1)
> (match (power_of_two_cand @1)
> (lshift INTEGER_CST@1 @2))
> (for mod (trunc_mod floor_mod)
>