Unify the handling of comparinsons against null and undefined.

src/hydrogen.cc

Index: src/hydrogen.cc
===================================================================
--- src/hydrogen.cc	(revision 9305)
+++ src/hydrogen.cc	(working copy)
@@ -5668,26 +5668,36 @@
 }
 
 
-void HGraphBuilder::HandleLiteralCompareTypeof(CompareOperation* compare_expr,
-                                               Expression* expr,
+void HGraphBuilder::HandleLiteralCompareTypeof(CompareOperation* expr,
+                                               Expression* sub_expr,
                                                Handle<String> check) {
-  CHECK_ALIVE(VisitForTypeOf(expr));
-  HValue* expr_value = Pop();
-  HTypeofIsAndBranch* instr = new(zone()) HTypeofIsAndBranch(expr_value, check);
-  instr->set_position(compare_expr->position());
-  return ast_context()->ReturnControl(instr, compare_expr->id());
+  CHECK_ALIVE(VisitForTypeOf(sub_expr));
+  HValue* value = Pop();
+  HTypeofIsAndBranch* instr = new(zone()) HTypeofIsAndBranch(value, check);
+  instr->set_position(expr->position());
+  return ast_context()->ReturnControl(instr, expr->id());
 }
 
 
-void HGraphBuilder::HandleLiteralCompareUndefined(
-    CompareOperation* compare_expr, Expression* expr) {
-  CHECK_ALIVE(VisitForValue(expr));
-  HValue* lhs = Pop();
-  HValue* rhs = graph()->GetConstantUndefined();
-  HCompareObjectEqAndBranch* instr =
-      new(zone()) HCompareObjectEqAndBranch(lhs, rhs);
-  instr->set_position(compare_expr->position());
-  return ast_context()->ReturnControl(instr, compare_expr->id());
+bool HGraphBuilder::TryLiteralCompare(CompareOperation* expr) {
+  Expression *sub_expr;
+  Handle<String> check;
+  if (expr->IsLiteralCompareTypeof(&sub_expr, &check)) {
+    HandleLiteralCompareTypeof(expr, sub_expr, check);
+    return true;
+  }
+
+  if (expr->IsLiteralCompareUndefined(&sub_expr)) {
+    HandleLiteralCompareNil(expr, sub_expr, kUndefinedValue);
+    return true;
+  }
+
+  if (expr->IsLiteralCompareNull(&sub_expr)) {
+    HandleLiteralCompareNil(expr, sub_expr, kNullValue);
+    return true;
+  }
+
+  return false;
 }
 
 
@@ -5709,23 +5719,8 @@
   }
 
   // Check for special cases that compare against literals.
-  Expression *sub_expr;
-  Handle<String> check;
-  if (expr->IsLiteralCompareTypeof(&sub_expr, &check)) {
-    HandleLiteralCompareTypeof(expr, sub_expr, check);
-    return;
-  }
+  if (TryLiteralCompare(expr)) return;
 
-  if (expr->IsLiteralCompareUndefined(&sub_expr)) {
-    HandleLiteralCompareUndefined(expr, sub_expr);
-    return;
-  }
-
-  if (expr->IsLiteralCompareNull(&sub_expr)) {
-    HandleLiteralCompareNull(expr, sub_expr);
-    return;
-  }
-
   TypeInfo type_info = oracle()->CompareType(expr);
   // Check if this expression was ever executed according to type feedback.
   if (type_info.IsUninitialized()) {
@@ -5829,16 +5824,19 @@
 }
 
 
-void HGraphBuilder::HandleLiteralCompareNull(CompareOperation* compare_expr,
-                                             Expression* expr) {
+void HGraphBuilder::HandleLiteralCompareNil(CompareOperation* expr,
+                                            Expression* sub_expr,
+                                            NilValue nil) {
   ASSERT(!HasStackOverflow());
   ASSERT(current_block() != NULL);
   ASSERT(current_block()->HasPredecessor());
-  CHECK_ALIVE(VisitForValue(expr));
+  CHECK_ALIVE(VisitForValue(sub_expr));
   HValue* value = Pop();
-  bool is_strict = compare_expr->op() == Token::EQ_STRICT;
-  HIsNullAndBranch* instr = new(zone()) HIsNullAndBranch(value, is_strict);
-  return ast_context()->ReturnControl(instr, compare_expr->id());
+  EqualityKind kind =
+      expr->op() == Token::EQ_STRICT ? kStrictEquality : kNonStrictEquality;
+  HIsNilAndBranch* instr = new(zone()) HIsNilAndBranch(value, kind, nil);
+  instr->set_position(expr->position());
+  return ast_context()->ReturnControl(instr, expr->id());
 }