[turbofan] Fix OSR entry in case label.

With do-expressions any expression used as a case label can turn into an
OSR entry-point. This means the value being switched over is renamed to
an OSR value and needs to be reloaded from the environment at each case.

R=rossberg@chromium.org
TEST=mjsunit/regress/regress-osr-in-case-label

Review URL: https://codereview.chromium.org/1438123007

Cr-Commit-Position: refs/heads/master@{#31986}

src/compiler/ast-graph-builder.cc

@@ -1204,7 +1204,6 @@ void AstGraphBuilder::VisitSwitchStatement(SwitchStatement* stmt) {
 
   // Keep the switch value on the stack until a case matches.
   VisitForValue(stmt->tag());
-  Node* tag = environment()->Top();
 
   // Iterate over all cases and create nodes for label comparison.
   for (int i = 0; i < clauses->length(); i++) {
@@ -1220,6 +1219,7 @@ void AstGraphBuilder::VisitSwitchStatement(SwitchStatement* stmt) {
     // value is still on the operand stack while the label is evaluated.
     VisitForValue(clause->label());
     Node* label = environment()->Pop();
+    Node* tag = environment()->Top();
     const Operator* op = javascript()->StrictEqual();
     Node* condition = NewNode(op, tag, label);
     compare_switch.BeginLabel(i, condition);

test/mjsunit/mjsunit.status

@@ -1005,6 +1005,7 @@
   'regress/regress-lazy-deopt-reloc': [SKIP],
   'regress/regress-map-invalidation-2': [SKIP],
   'regress/regress-opt-after-debug-deopt': [SKIP],
+  'regress/regress-osr-in-case-label': [SKIP],
   'regress/regress-param-local-type': [SKIP],
   'regress/regress-prepare-break-while-recompile': [SKIP],
   'regress/regress-put-prototype-transition': [SKIP],

test/mjsunit/regress/regress-osr-in-case-label.js

+// Copyright 2015 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --allow-natives-syntax --harmony-do-expressions
+
+function f(x) {
+  switch (x) {
+    case 1: return "one";
+    case 2: return "two";
+    case do { for (var i = 0; i < 10; i++) { if (i == 5) %OptimizeOsr(); } }:
+    case 3: return "WAT";
+  }
+}
+
+assertEquals("one", f(1));
+assertEquals("two", f(2));
+assertEquals("WAT", f(3));