re PR tree-optimization/78819 (Wrong code with VRP caused by register assertions along default switch labels)

PR tree-optimization/78819
	* tree-vrp.c (find_switch_asserts): Return if the insertion limit is 0.
	Don't register an assertion if the default case shares a label with
	another case.

	* gcc.dg/tree-ssa/vrp112.c: New test.

From-SVN: r243746

gcc/ChangeLog

@@ -1,3 +1,10 @@
+2016-12-16  Marek Polacek  <polacek@redhat.com>
+
+	PR tree-optimization/78819
+	* tree-vrp.c (find_switch_asserts): Return if the insertion limit is 0.
+	Don't register an assertion if the default case shares a label with
+	another case.
+
 2016-12-16  Wilco Dijkstra  <wdijkstr@arm.com>
 
 	* config/arm/arm.md (subsi3_carryin): Add Thumb-2 RSC #0.

gcc/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2016-12-16  Marek Polacek  <polacek@redhat.com>
+
+	PR tree-optimization/78819
+	* gcc.dg/tree-ssa/vrp112.c: New test.
+
 2016-12-16  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* gnat.dg/opt61.adb: New test.

gcc/testsuite/gcc.dg/tree-ssa/vrp112.c

@@ -0,0 +1,31 @@
+/* PR tree-optimization/78819 */
+/* { dg-do run } */
+/* { dg-options "-O2" } */
+
+__attribute__((noinline, noclone)) void
+foo (int argc)
+{
+  if (argc <= 0 || argc > 3)
+    return;
+
+  switch (argc)
+    {
+    case 1:
+    case 3:
+      if (argc != 3)
+	__builtin_abort ();
+      break;
+    case 2:
+      asm ("");
+      break;
+    default:
+      __builtin_abort ();
+    }
+}
+
+int
+main (void)
+{
+  foo (3);
+  return 0;
+}

gcc/tree-vrp.c

@@ -6051,10 +6051,17 @@ find_switch_asserts (basic_block bb, gswitch *last)
   /* Now register along the default label assertions that correspond to the
      anti-range of each label.  */
   int insertion_limit = PARAM_VALUE (PARAM_MAX_VRP_SWITCH_ASSERTIONS);
+  if (insertion_limit == 0)
+    return;
+
+  /* We can't do this if the default case shares a label with another case.  */
+  tree default_cl = gimple_switch_default_label (last);
   for (idx = 1; idx < n; idx++)
     {
       tree min, max;
       tree cl = gimple_switch_label (last, idx);
+      if (CASE_LABEL (cl) == CASE_LABEL (default_cl))
+	continue;
 
       min = CASE_LOW (cl);
       max = CASE_HIGH (cl);
@@ -6065,6 +6072,8 @@ find_switch_asserts (basic_block bb, gswitch *last)
 	{
 	  tree next_min, next_max;
 	  tree next_cl = gimple_switch_label (last, idx);
+	  if (CASE_LABEL (next_cl) == CASE_LABEL (default_cl))
+	    break;
 
 	  next_min = CASE_LOW (next_cl);
 	  next_max = CASE_HIGH (next_cl);