re PR c/52769 (Unspecified designated initializer might not set to zero in some cases)

[thirdparty/gcc.git] / gcc / match.pd

/* Match-and-simplify patterns for shared GENERIC and GIMPLE folding.
   This file is consumed by genmatch which produces gimple-match.c
   and generic-match.c from it.

   Copyright (C) 2014 Free Software Foundation, Inc.
   Contributed by Richard Biener <rguenther@suse.de>
   and Prathamesh Kulkarni  <bilbotheelffriend@gmail.com>

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 3, or (at your option) any later
version.

GCC is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING3.  If not see
<http://www.gnu.org/licenses/>.  */


/* Generic tree predicates we inherit.  */
(define_predicates
   integer_onep integer_zerop integer_all_onesp
   real_zerop real_onep
   CONSTANT_CLASS_P)


/* Simplifications of operations with one constant operand and
   simplifications to constants or single values.  */

(for op (plus pointer_plus minus bit_ior bit_xor)
  (simplify
    (op @0 integer_zerop)
    (non_lvalue @0)))

/* Simplify x - x.
   This is unsafe for certain floats even in non-IEEE formats.
   In IEEE, it is unsafe because it does wrong for NaNs.
   Also note that operand_equal_p is always false if an operand
   is volatile.  */
(simplify
  (minus @0 @0)
  (if (!FLOAT_TYPE_P (type) || !HONOR_NANS (TYPE_MODE (type)))
   { build_zero_cst (type); }))

(simplify
  (mult @0 integer_zerop@1)
  @1)

/* Make sure to preserve divisions by zero.  This is the reason why
   we don't simplify x / x to 1 or 0 / x to 0.  */
(for op (mult trunc_div ceil_div floor_div round_div exact_div)
  (simplify
    (op @0 integer_onep)
    (non_lvalue @0)))

/* Same applies to modulo operations, but fold is inconsistent here
   and simplifies 0 % x to 0, only preserving literal 0 % 0.  */
(for op (ceil_mod floor_mod round_mod trunc_mod)
 /* 0 % X is always zero.  */
 (simplify
  (op integer_zerop@0 @1)
  /* But not for 0 % 0 so that we can get the proper warnings and errors.  */
  (if (!integer_zerop (@1))
   @0))
 /* X % 1 is always zero.  */
 (simplify
  (op @0 integer_onep)
  { build_zero_cst (type); }))

/* x | ~0 -> ~0  */
(simplify
  (bit_ior @0 integer_all_onesp@1)
  @1)

/* x & 0 -> 0  */
(simplify
  (bit_and @0 integer_zerop@1)
  @1)

/* x ^ x -> 0 */
(simplify
  (bit_xor @0 @0)
  { build_zero_cst (type); })

/* Canonicalize X ^ ~0 to ~X.  */
(simplify
  (bit_xor @0 integer_all_onesp@1)
  (bit_not @0))

/* x & ~0 -> x  */
(simplify
 (bit_and @0 integer_all_onesp)
  (non_lvalue @0))

/* x & x -> x,  x | x -> x  */
(for bitop (bit_and bit_ior)
 (simplify
  (bitop @0 @0)
  (non_lvalue @0)))


/* Simplifications of conversions.  */

/* Basic strip-useless-type-conversions / strip_nops.  */
(for cvt (convert view_convert)
 (simplify
  (cvt @0)
  (if ((GIMPLE && useless_type_conversion_p (type, TREE_TYPE (@0)))
       || (GENERIC && type == TREE_TYPE (@0)))
   @0)))

/* Contract view-conversions.  */
(simplify
  (view_convert (view_convert @0))
  (view_convert @0))

/* For integral conversions with the same precision or pointer
   conversions use a NOP_EXPR instead.  */
(simplify
  (view_convert @0)
  (if ((INTEGRAL_TYPE_P (type) || POINTER_TYPE_P (type))
       && (INTEGRAL_TYPE_P (TREE_TYPE (@0)) || POINTER_TYPE_P (TREE_TYPE (@0)))
       && TYPE_PRECISION (type) == TYPE_PRECISION (TREE_TYPE (@0)))
   (convert @0)))

/* Strip inner integral conversions that do not change precision or size.  */
(simplify
  (view_convert (convert@0 @1))
  (if ((INTEGRAL_TYPE_P (TREE_TYPE (@0)) || POINTER_TYPE_P (TREE_TYPE (@0)))
       && (INTEGRAL_TYPE_P (TREE_TYPE (@1)) || POINTER_TYPE_P (TREE_TYPE (@1)))
       && (TYPE_PRECISION (TREE_TYPE (@0)) == TYPE_PRECISION (TREE_TYPE (@1)))
       && (TYPE_SIZE (TREE_TYPE (@0)) == TYPE_SIZE (TREE_TYPE (@1))))
   (view_convert @1)))

/* Re-association barriers around constants and other re-association
   barriers can be removed.  */
(simplify
 (paren CONSTANT_CLASS_P@0)
 @0)
(simplify
 (paren (paren@1 @0))
 @1)