This is a non-C++ related part from the PR89074 address_compare changes.
For "foo" == "foo" we already optimize this from the (cmp @0 @0)
simplification, because we use operand_equal_p in that case
and operand_equal_p also compares the STRING_CSTs bytes rather than
just addresses.
2022-01-19 Jakub Jelinek <jakub@redhat.com>
PR c++/89074
* fold-const.cc (address_compare): Consider different STRING_CSTs
with the same lengths that memcmp the same as equal, not different.
* gcc.dg/tree-ssa/pr89074.c: New test.
|| TREE_CODE (base1) == SSA_NAME
|| TREE_CODE (base1) == STRING_CST))
equal = (base0 == base1);
+ /* Assume different STRING_CSTs with the same content will be
+ merged. */
+ if (equal == 0
+ && TREE_CODE (base0) == STRING_CST
+ && TREE_CODE (base1) == STRING_CST
+ && TREE_STRING_LENGTH (base0) == TREE_STRING_LENGTH (base1)
+ && memcmp (TREE_STRING_POINTER (base0), TREE_STRING_POINTER (base1),
+ TREE_STRING_LENGTH (base0)) == 0)
+ equal = 1;
if (equal == 1)
{
if (code == EQ_EXPR
--- /dev/null
+/* PR c++/89074 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+/* { dg-final { scan-tree-dump "return 1;" "optimized" } } */
+
+int
+foo (void)
+{
+ const char *a = &"foo"[0];
+ const char *b = "foo";
+ return a == b;
+}