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match.pd: Move cast into p+ operand for (ptr) (x p+ y) p+ z -> (ptr) (x p+ (y + z)) [PR124358]

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The following testcase is miscompiled since my r12-6382 change, because
it doesn't play well with the gimple_fold_indirect_ref function which uses
STRIP_NOPS and then has
  /* *(foo *)fooarrptr => (*fooarrptr)[0] */
  if (TREE_CODE (TREE_TYPE (subtype)) == ARRAY_TYPE
      && TREE_CODE (TYPE_SIZE (TREE_TYPE (TREE_TYPE (subtype)))) == INTEGER_CST
      && useless_type_conversion_p (type, TREE_TYPE (TREE_TYPE (subtype))))
    {
      tree type_domain;
      tree min_val = size_zero_node;
      tree osub = sub;
      sub = gimple_fold_indirect_ref (sub);
      if (! sub)
        sub = build1 (INDIRECT_REF, TREE_TYPE (subtype), osub);
      type_domain = TYPE_DOMAIN (TREE_TYPE (sub));
      if (type_domain && TYPE_MIN_VALUE (type_domain))
        min_val = TYPE_MIN_VALUE (type_domain);
      if (TREE_CODE (min_val) == INTEGER_CST)
        return build4 (ARRAY_REF, type, sub, min_val, NULL_TREE, NULL_TREE);
    }
Without the GENERIC
 #if GENERIC
 (simplify
   (pointer_plus (convert:s (pointer_plus:s @0 @1)) @3)
   (convert:type (pointer_plus @0 (plus @1 @3))))
 #endif
we have INDIRECT_REF of POINTER_PLUS_EXPR with int * type of NOP_EXPR
to that type of POINTER_PLUS_EXPR with pointer to int[4] ARRAY_TYPE, so
gimple_fold_indirect_ref doesn't create the ARRAY_REF.
But with it, it is simplified to NOP_EXPR to int * type from
POINTER_PLUS_EXPR with pointer to int[4] ARRAY_TYPE, the NOP_EXPR is
skipped over by STRIP_NOPS and the above code triggers.

The following patch fixes it by swapping the order, do NOP_EXPR
inside of POINTER_PLUS_EXPR first argument instead of NOP_EXPR with
POINTER_PLUS_EXPR.

2026-03-06  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/124358
	* match.pd ((ptr) (x p+ y) p+ z -> (ptr) (x p+ (y + z))): Simplify
	into (ptr) x p+ (y + z) instead.

	* gcc.c-torture/execute/pr124358.c: New test.
This commit is contained in:
Jakub Jelinek
2026-03-06 08:14:09 +01:00
committed by Jakub Jelinek
parent d2881c26c2
commit acf7028b79
2 changed files with 20 additions and 1 deletions
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2
gcc/match.pd
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@@ -3136,7 +3136,7 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
#if GENERIC
(simplify
(pointer_plus (convert:s (pointer_plus:s @0 @1)) @3)
(convert:type (pointer_plus @0 (plus @1 @3))))
(pointer_plus (convert:type @0) (plus @1 @3)))
#endif
/* Pattern match

19
gcc/testsuite/gcc.c-torture/execute/pr124358.c Normal file
View File

@@ -0,0 +1,19 @@
/* PR tree-optimization/124358 */
[[gnu::noipa]] void
foo (int d)
{
static int u = 11;
if (d != u++)
__builtin_abort ();
}
int
main ()
{
int a[1][4] = { 11, 12, 13, 14 };
int (*p)[4] = a;
for (int i = 0; i < 1; i++)
for (int j = 0; j < 4; j++)
foo (*(*(p + i) + j));
}