Correct handling of constant representations containing embedded nuls.

Resolves:
PR middle-end/95189 - memcmp being wrongly stripped like strcm
PR middle-end/95886 - suboptimal memcpy with embedded zero bytes

gcc/ChangeLog:

	PR middle-end/95189
	PR middle-end/95886
	* builtins.c (inline_expand_builtin_string_cmp): Rename...
	(inline_expand_builtin_bytecmp): ...to this.
	(builtin_memcpy_read_str): Don't expect data to be nul-terminated.
	(expand_builtin_memory_copy_args): Handle object representations
	with embedded nul bytes.
	(expand_builtin_memcmp): Same.
	(expand_builtin_strcmp): Adjust call to naming change.
	(expand_builtin_strncmp): Same.
	* expr.c (string_constant): Create empty strings with nonzero size.
	* fold-const.c (c_getstr): Rename locals and update comments.
	* tree.c (build_string): Accept null pointer argument.
	(build_string_literal): Same.
	* tree.h (build_string): Provide a default.
	(build_string_literal): Same.

gcc/testsuite/ChangeLog:

	PR middle-end/95189
	PR middle-end/95886
	* gcc.dg/memcmp-pr95189.c: New test.
	* gcc.dg/strncmp-3.c: New test.
	* gcc.target/i386/memcpy-pr95886.c: New test.

1 files changed, 2 insertions, 2 deletions

diff --git a/gcc/expr.c b/gcc/expr.c
index edc5571..b4bbeff 100644
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -11829,12 +11829,12 @@ string_constant (tree arg, tree *ptr_offset, tree *mem_size, tree *decl)
       while (TREE_CODE (chartype) == ARRAY_TYPE)
 	chartype = TREE_TYPE (chartype);
       /* Convert a char array to an empty STRING_CST having an array
-	 of the expected type.  */
+	 of the expected type and size.  */
       if (!initsize)
 	  initsize = integer_zero_node;
 
       unsigned HOST_WIDE_INT size = tree_to_uhwi (initsize);
-      init = build_string_literal (size ? 1 : 0, "", chartype, size);
+      init = build_string_literal (size, NULL, chartype, size);
       init = TREE_OPERAND (init, 0);
       init = TREE_OPERAND (init, 0);