--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/gcc.dg/strlenopt-66.c	Thu Feb 13 11:34:05 2020 +0900
@@ -0,0 +1,114 @@
+/* PRE tree-optimization/90626 - fold strcmp(a, b) == 0 to zero when
+   one string length is exact and the other is unequal
+   { dg-do run }
+   { dg-options "-O2 -Wall" } */
+
+#include "strlenopt.h"
+
+#define A(expr)                                                 \
+  ((expr)                                                       \
+   ? (void)0                                                    \
+   : (__builtin_printf ("assertion failed on line %i: %s\n",    \
+                        __LINE__, #expr),                       \
+      __builtin_abort ()))
+
+
+__attribute__ ((noclone, noinline, noipa)) void
+clobber (void *p, int x, size_t n)
+{
+  for (volatile unsigned char *q = p; n--; )
+    *q = x;
+}
+
+__attribute__ ((noclone, noinline, noipa)) void
+test_strcmp (void)
+{
+  char a[8], b[8];
+  strcpy (a, "1235");
+  strcpy (b, "1234");
+
+  A (strcmp (a, b));
+
+  clobber (a, 0, sizeof a);
+  clobber (b, 0, sizeof b);
+  clobber (b + 4, '5', 1);
+
+  memcpy (a, "1234", 4);
+  memcpy (b, "1234", 4);
+
+  A (0 > strcmp (a, b));
+  A (0 < strcmp (b, a));
+}
+
+__attribute__ ((noclone, noinline, noipa)) void
+test_strncmp (void)
+{
+  char a[8], b[8];
+  strcpy (a, "1235");
+  strcpy (b, "1234");
+
+  A (0 == strncmp (a, b, 1));
+  A (0 == strncmp (a, b, 2));
+  A (0 == strncmp (a, b, 3));
+  A (0 <  strncmp (a, b, 4));
+  A (0 >  strncmp (b, a, 4));
+
+  clobber (a, 0, sizeof a);
+  clobber (b, 0, sizeof b);
+  clobber (b + 4, '5', 1);
+
+  memcpy (a, "1234", 4);
+  memcpy (b, "1234", 4);
+
+  A (0 == strncmp (a, b, 4));
+  A (0 >  strncmp (a, b, 5));
+  A (0 <  strncmp (b, a, 5));
+}
+
+
+__attribute__ ((noclone, noinline, noipa)) void
+test_strncmp_a4_cond_s5_s2_2 (const char *s, int i)
+{
+  char a4[4];
+  strcpy (a4, s);
+  A (0 == strncmp (a4, i ? "12345" : "12", 2));
+}
+
+
+__attribute__ ((noclone, noinline, noipa)) void
+test_strncmp_a4_cond_a5_s2_5 (const char *s, const char *t, int i)
+{
+  char a4[4], a5[5];
+  strcpy (a4, s);
+  strcpy (a5, t);
+  A (0 == strncmp (a4, i ? a5 : "12", 5));
+}
+
+__attribute__ ((noclone, noinline, noipa)) void
+test_strncmp_a4_cond_a5_a3_n (const char *s1, const char *s2, const char *s3,
+			      int i, unsigned n)
+{
+  char a3[3], a4[4], a5[5];
+  strcpy (a3, s1);
+  strcpy (a4, s2);
+  strcpy (a5, s3);
+  A (0 == strncmp (a4, i ? a5 : a3, n));
+}
+
+
+int main (void)
+{
+  test_strcmp ();
+  test_strncmp ();
+  test_strncmp_a4_cond_s5_s2_2 ("12", 0);
+  test_strncmp_a4_cond_a5_s2_5 ("12", "1234", 0);
+
+  test_strncmp_a4_cond_a5_a3_n ("12", "1", "1",    0, 1);
+  test_strncmp_a4_cond_a5_a3_n ("",   "1", "1234", 1, 1);
+
+  test_strncmp_a4_cond_a5_a3_n ("12", "12", "1",    0, 2);
+  test_strncmp_a4_cond_a5_a3_n ("",   "12", "1234", 1, 2);
+
+  test_strncmp_a4_cond_a5_a3_n ("12", "123", "1",    0, 2);
+  test_strncmp_a4_cond_a5_a3_n ("",   "123", "1234", 1, 3);
+}