[Interpreter] Optimize equality check with null/undefined with a check on the map.

src/interpreter/bytecode-peephole-optimizer.cc

Index: src/interpreter/bytecode-peephole-optimizer.cc
diff --git a/src/interpreter/bytecode-peephole-optimizer.cc b/src/interpreter/bytecode-peephole-optimizer.cc
index 40552943f75dcb3b07d196b910f00cfd321d2946..4c7512155bcc394b7d9620cd68ffbfe5fb1fae80 100644
--- a/src/interpreter/bytecode-peephole-optimizer.cc
+++ b/src/interpreter/bytecode-peephole-optimizer.cc
@@ -138,6 +138,16 @@ void TransformLdaZeroBinaryOpToBinaryOpWithZero(Bytecode new_bytecode,
   }
 }
 
+void TransformEqualityWithNullOrUndefinedToTestUndetectable(
+    BytecodeNode* const last, BytecodeNode* const current) {
+  DCHECK((last->bytecode() == Bytecode::kLdaNull) ||
+         (last->bytecode() == Bytecode::kLdaUndefined));

[rmcilroy, 2016/12/05 19:08:09]

Do you want to DCHECK that this current bytecode is a TestEqual here?

[mythria, 2016/12/06 10:13:27]

Done.

+  current->set_bytecode(Bytecode::kTestUndetectable, current->operand(0));
+  if (last->source_info().is_valid()) {
+    current->set_source_info(last->source_info());
+  }
+}
+
 }  // namespace
 
 void BytecodePeepholeOptimizer::DefaultAction(
@@ -251,6 +261,16 @@ void BytecodePeepholeOptimizer::
   }
 }
 
+void BytecodePeepholeOptimizer::
+    TransformEqualityWithNullOrUndefinedToTestUndetectableAction(
+        BytecodeNode* const node, const PeepholeActionAndData* action_data) {
+  DCHECK(LastIsValid());
+  DCHECK(!Bytecodes::IsJump(node->bytecode()));
+  // Fused last and current into current.
+  TransformEqualityWithNullOrUndefinedToTestUndetectable(last(), node);
+  SetLast(node);
+}
+
 void BytecodePeepholeOptimizer::DefaultJumpAction(
     BytecodeNode* const node, const PeepholeActionAndData* action_data) {
   DCHECK(LastIsValid());