Group switch cases in switch lowering (PR tree-optimization/87205).

2018-09-05  Martin Liska  <mliska@suse.cz>

	PR tree-optimization/87205
	* tree-switch-conversion.c (pass_lower_switch::execute):
	Group cases for switch statements.
2018-09-05  Martin Liska  <mliska@suse.cz>

	PR tree-optimization/87205
	* gcc.dg/tree-ssa/pr87205-2.c: New test.
	* gcc.dg/tree-ssa/pr87205.c: New test.

From-SVN: r264124

gcc/ChangeLog

+2018-09-05  Martin Liska  <mliska@suse.cz>
+
+	PR tree-optimization/87205
+	* tree-switch-conversion.c (pass_lower_switch::execute):
+	Group cases for switch statements.
+
 2018-09-05  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/87217

gcc/testsuite/ChangeLog

+2018-09-05  Martin Liska  <mliska@suse.cz>
+
+	PR tree-optimization/87205
+	* gcc.dg/tree-ssa/pr87205-2.c: New test.
+	* gcc.dg/tree-ssa/pr87205.c: New test.
+
 2018-09-05  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/87217

gcc/testsuite/gcc.dg/tree-ssa/pr87205-2.c

+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+void f(int);
+void h(unsigned i)
+{
+  switch (i) {
+    default: __builtin_unreachable();
+    case 0: f(42); break;
+    case 1: f(42); break;
+    case 2: f(42); break;
+    case 3: f(42); break;
+    case 4: f(42); break;
+    case 5: f(42); break;
+  }
+} 
+
+/* { dg-final { scan-tree-dump-not "if" "optimized" } } */
+/* { dg-final { scan-tree-dump-not "switch" "optimized" } } */

gcc/testsuite/gcc.dg/tree-ssa/pr87205.c

+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+void f( int x );
+
+void h( unsigned ix )
+{
+  switch( ix )
+  {
+    case 0: f(42); break;
+    case 1: f(42); break;
+    case 2: f(42); break;
+    case 3: f(42); break;
+    case 4: f(42); break;
+    case 5: f(42); break;
+    default: __builtin_unreachable();
+  }
+}
+
+
+/* { dg-final { scan-tree-dump-not "if" "optimized" } } */
+/* { dg-final { scan-tree-dump-not "switch" "optimized" } } */

gcc/tree-switch-conversion.c

@@ -2419,8 +2419,13 @@ pass_lower_switch<O0>::execute (function *fun)
   FOR_EACH_BB_FN (bb, fun)
     {
       gimple *stmt = last_stmt (bb);
-      if (stmt && gimple_code (stmt) == GIMPLE_SWITCH)
-	switch_statements.safe_push (stmt);
+      gswitch *swtch;
+      if (stmt && (swtch = dyn_cast<gswitch *> (stmt)))
+	{
+	  if (!O0)
+	    group_case_labels_stmt (swtch);
+	  switch_statements.safe_push (swtch);
+	}
     }
 
   for (unsigned i = 0; i < switch_statements.length (); i++)