--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/gcc.dg/Wstringop-truncation.c	Thu Oct 25 07:37:49 2018 +0900
@@ -0,0 +1,131 @@
+/* PR tree-optimization/84468 - Inconsistent -Wstringop-truncation warnings
+   with -O2
+   { dg-do compile }
+   { dg-options "-O2 -Wstringop-truncation -ftrack-macro-expansion=0 -g" }  */
+
+#define strncpy __builtin_strncpy
+
+struct A
+{
+  char a[4];
+};
+
+void no_pred_succ_lit (struct A *p)
+{
+  /* The following is folded early on, before the strncpy statement
+     has a basic block.  Verify that the case is handled gracefully
+     (i.e., there's no assumption that the statement does have
+     a basic block).  */
+  strncpy (p->a, "1234", sizeof p->a - 1);    /* { dg-warning "\\\[-Wstringop-truncation" } */
+}
+
+/* Verify a strncpy call in a basic block with no predecessor or
+   successor.  */
+void no_pred_succ (struct A *p, const struct A *q)
+{
+  strncpy (p->a, q->a, sizeof p->a - 1);      /* { dg-warning "\\\[-Wstringop-truncation" } */
+}
+
+
+/* Verify a strncpy call in a basic block with no successor.  */
+void no_succ (struct A *p, const struct A *q)
+{
+  if (q->a)
+    strncpy (p->a, q->a, sizeof p->a - 1);    /* { dg-warning "\\\[-Wstringop-truncation" } */
+}
+
+/* Verify a strncpy call in a basic block with nul assignment in
+   a successor block.  */
+void succ (struct A *p, const struct A *q)
+{
+  /* Verify that the assignment suppresses the warning for the conditional
+     strcnpy call.  The conditional should be folded to true since the
+     address of an array can never be null (see bug 84470).  */
+  if (q->a)
+    strncpy (p->a, q->a, sizeof p->a - 1);    /* { dg-bogus "\\\[-Wstringop-truncation" } */
+
+  p->a[sizeof p->a - 1] = 0;
+}
+
+
+void succ_2 (struct A *p, const struct A *q, int i)
+{
+  /* Same as above but with a conditional that cannot be eliminated.  */
+  if (i < 0)
+    strncpy (p->a, q->a, sizeof p->a - 1);    /* { dg-bogus "\\\[-Wstringop-truncation" } */
+
+  p->a[sizeof p->a - 1] = 0;
+}
+
+
+/* Verify a strncpy call in a basic block with nul assignment in
+   the next successor block.  */
+int next_succ (struct A *p, const struct A *q, int i, int j)
+{
+  /* Same as above but with a nested conditionals with else clauses.  */
+  if (i < 0)
+    {
+      if (j < 0)
+	strncpy (p->a, q->a, sizeof p->a - 1);    /* { dg-bogus "\\\[-Wstringop-truncation" } */
+    }
+  else
+    __builtin_strcpy (p->a, q->a);
+
+  p->a[sizeof p->a - 1] = 0;
+  return 0;
+}
+
+
+int next_succ_1 (struct A *p, const struct A *q, int i, int j)
+{
+  /* Same as above but with a nested conditionals with else clauses.  */
+  if (i < 0)
+    {
+      if (j < 0)
+	strncpy (p->a, q->a, sizeof p->a - 1);    /* { dg-bogus "\\\[-Wstringop-truncation" } */
+      else
+	strncpy (p->a, q->a, sizeof p->a - 2);    /* { dg-bogus "\\\[-Wstringop-truncation" } */
+    }
+
+  p->a[sizeof p->a - 2] = 0;
+  return 1;
+}
+
+
+int next_succ_2 (struct A *p, const struct A *q, int i, int j)
+{
+  /* Same as above but with a nested conditionals with else clauses.  */
+  if (i < 0)
+    {
+      if (j < 0)
+	strncpy (p->a, q->a, sizeof p->a - 1);    /* { dg-bogus "\\\[-Wstringop-truncation" } */
+      else
+	strncpy (p->a, q->a, sizeof p->a - 2);    /* { dg-bogus "\\\[-Wstringop-truncation" } */
+    }
+  else
+    __builtin_strcpy (p->a, q->a);
+
+  p->a[sizeof p->a - 2] = 0;
+  return 2;
+}
+
+
+void cond_succ_warn (struct A *p, const struct A *q, int i)
+{
+  /* Verify that a conditional assignment doesn't suppress the warning.  */
+  strncpy (p->a, q->a, sizeof p->a - 1);      /* { dg-warning "\\\[-Wstringop-truncation" } */
+
+  if (i < 0)
+    p->a[sizeof p->a - 1] = 0;
+}
+
+void cond_succ_nowarn (struct A *p, const struct A *q)
+{
+  /* Verify that distinct but provably equivalent conditionals are
+     recognized and don't trigger the warning.  */
+  if (p != q)
+    strncpy (p->a, q->a, sizeof p->a - 1);
+
+  if (p->a != q->a)
+    p->a[sizeof p->a - 1] = 0;
+}