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

[Martin Liška]

Hi.

The function c_getstr returns string and length of the string.
In inline_expand_builtin_string_cmp, we should consider situations
where a string constant contains a zero character. In that case
we have to shorten len[12].

Patch can bootstrap on x86_64-linux-gnu and survives regression tests.

Ready to be installed?
Thanks,
Martin

gcc/ChangeLog:

2019-06-17  Martin Liska  <mli...@suse.cz>

        PR tree-optimization/90892
        * builtins.c (inline_expand_builtin_string_cmp): Handle '\0'
        in string constants.

gcc/testsuite/ChangeLog:

2019-06-17  Martin Liska  <mli...@suse.cz>

        PR tree-optimization/90892
        * gcc.dg/pr90892.c: New test.
---
 gcc/builtins.c                 | 14 ++++++++++++++
 gcc/testsuite/gcc.dg/pr90892.c | 14 ++++++++++++++
 2 files changed, 28 insertions(+)
 create mode 100644 gcc/testsuite/gcc.dg/pr90892.c



diff --git a/gcc/builtins.c b/gcc/builtins.c
index 3463ffb1539..917852071b9 100644
--- a/gcc/builtins.c
+++ b/gcc/builtins.c
@@ -7142,6 +7142,20 @@ inline_expand_builtin_string_cmp (tree exp, rtx target)
   const char *src_str1 = c_getstr (arg1, &len1);
   const char *src_str2 = c_getstr (arg2, &len2);
 
+  if (src_str1 != NULL)
+    {
+      unsigned HOST_WIDE_INT str_str1_strlen = strlen (src_str1);
+      if (str_str1_strlen + 1 < len1)
+	len1 = str_str1_strlen + 1;
+    }
+
+  if (src_str2 != NULL)
+    {
+      unsigned HOST_WIDE_INT str_str2_strlen = strlen (src_str2);
+      if (str_str2_strlen + 1 < len2)
+	len2 = str_str2_strlen + 1;
+    }
+
   /* If neither strings is constant string, the call is not qualify.  */
   if (!src_str1 && !src_str2)
     return NULL_RTX;
diff --git a/gcc/testsuite/gcc.dg/pr90892.c b/gcc/testsuite/gcc.dg/pr90892.c
new file mode 100644
index 00000000000..e4b5310807a
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr90892.c
@@ -0,0 +1,14 @@
+/* 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;
+}