Handle '\0' in strcmp in RTL expansion (PR tree-optimization/90892).

2019-07-03  Martin Liska  <mliska@suse.cz>

	PR tree-optimization/90892
	* builtins.c (inline_expand_builtin_string_cmp): Handle '\0'
	in string constants.
2019-07-03  Martin Liska  <mliska@suse.cz>

	PR tree-optimization/90892
	* gcc.dg/pr90892.c: New test.

From-SVN: r272993

gcc/ChangeLog

 2019-07-03  Martin Liska  <mliska@suse.cz>
 
+	PR tree-optimization/90892
+	* builtins.c (inline_expand_builtin_string_cmp): Handle '\0'
+	in string constants.
+
+2019-07-03  Martin Liska  <mliska@suse.cz>
+
 	PR middle-end/90899
 	* multiple_target.c (create_dispatcher_calls): Add to comdat
 	group only if set for ifunc.

gcc/builtins.c

@@ -7118,8 +7118,19 @@ inline_expand_builtin_string_cmp (tree exp, rtx target)
     return NULL_RTX;
 
   /* For strncmp, if the length is not a const, not qualify.  */
-  if (is_ncmp && !tree_fits_uhwi_p (len3_tree))
-    return NULL_RTX;
+  if (is_ncmp)
+    {
+      if (!tree_fits_uhwi_p (len3_tree))
+	return NULL_RTX;
+      else
+	len3 = tree_to_uhwi (len3_tree);
+    }
+
+  if (src_str1 != NULL)
+    len1 = strnlen (src_str1, len1) + 1;
+
+  if (src_str2 != NULL)
+    len2 = strnlen (src_str2, len2) + 1;
 
   int const_str_n = 0;
   if (!len1)
@@ -7134,7 +7145,7 @@ inline_expand_builtin_string_cmp (tree exp, rtx target)
   gcc_checking_assert (const_str_n > 0);
   length = (const_str_n == 1) ? len1 : len2;
 
-  if (is_ncmp && (len3 = tree_to_uhwi (len3_tree)) < length)
+  if (is_ncmp && len3 < length)
     length = len3;
 
   /* If the length of the comparision is larger than the threshold,

gcc/testsuite/ChangeLog

 2019-07-03  Martin Liska  <mliska@suse.cz>
 
+	PR tree-optimization/90892
+	* gcc.dg/pr90892.c: New test.
+
+2019-07-03  Martin Liska  <mliska@suse.cz>
+
 	PR middle-end/90899
 	* gcc.target/i386/pr90899.c: New test.
 

gcc/testsuite/gcc.dg/pr90892.c

+/* PR tree-optimization/90892 */
+/* { dg-do run } */
+/* { dg-options "-O2" } */
+
+const char *a = "A\0b";
+
+int
+main()
+{
+  if (__builtin_strncmp(a, "A\0", 2) != 0)
+    __builtin_abort ();
+
+  return 0;
+}