re PR c++/91024 (-Wimplicit-fallthrough is confused by likely/unlikely attributes)

	PR c++/91024
	* gimplify.c (collect_fallthrough_labels): Ignore GIMPLE_PREDICT
	statements.

	* g++.dg/warn/Wimplicit-fallthrough-4.C: New test.

From-SVN: r272764

gcc/ChangeLog

 2019-06-27  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c++/91024
+	* gimplify.c (collect_fallthrough_labels): Ignore GIMPLE_PREDICT
+	statements.
+
 	PR tree-optimization/91010
 	* tree-vect-stmts.c (scan_operand_equal_p): If offset1 == offset2,
 	return true.  Otherwise, don't call operand_equal_p if offset1 or

gcc/gimplify.c

@@ -2120,6 +2120,8 @@ collect_fallthrough_labels (gimple_stmt_iterator *gsi_p,
 	}
       else if (gimple_call_internal_p (gsi_stmt (*gsi_p), IFN_ASAN_MARK))
 	;
+      else if (gimple_code (gsi_stmt (*gsi_p)) == GIMPLE_PREDICT)
+	;
       else if (!is_gimple_debug (gsi_stmt (*gsi_p)))
 	prev = gsi_stmt (*gsi_p);
       gsi_next (gsi_p);

gcc/testsuite/ChangeLog

 2019-06-27  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c++/91024
+	* g++.dg/warn/Wimplicit-fallthrough-4.C: New test.
+
 	PR tree-optimization/91010
 	* g++.dg/vect/simd-10.cc: New test.
 

gcc/testsuite/g++.dg/warn/Wimplicit-fallthrough-4.C

+// PR c++/91024
+// { dg-do compile { target c++11 } }
+// { dg-options "-Wimplicit-fallthrough" }
+
+int
+foo (char c)
+{
+  int result = 0;
+
+  switch (c)
+    {
+    case 'O':
+    case 'K':
+      return result;
+    [[unlikely]] case 'X':	// { dg-bogus "this statement may fall through" }
+    case 'x':			// { dg-bogus "here" }
+      return result;
+    default:
+      break;
+    }
+  return result;
+}