[Interpreter] Add conditional expressions.

src/interpreter/bytecode-generator.cc

 // 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.
 
 #include "src/interpreter/bytecode-generator.h"
 
 #include "src/compiler.h"
 #include "src/interpreter/control-flow-builders.h"
 #include "src/objects.h"
 #include "src/parser.h"
@@ skipping 638 matching lines @@
     NativeFunctionLiteral* expr) {
   UNIMPLEMENTED();
 }
 
 
 void BytecodeGenerator::VisitDoExpression(DoExpression* expr) {
   UNIMPLEMENTED();
 }
 
 
-void BytecodeGenerator::VisitConditional(Conditional* expr) { UNIMPLEMENTED(); }
+void BytecodeGenerator::VisitConditional(Conditional* expr) {
+  // TODO(rmcilroy): Spot easy cases where there code would not need to
+  // emit the then block or the else block, e.g. condition is
+  // obviously true/1/false/0.

[oth, 2015/10/23 15:24:29]

We should use ToBooleanIsFalse/True for the easy cases like
VisitLogicalAndExpression.

[rmcilroy, 2015/10/27 12:03:35]

Ack, I'll do this in a followup CL.

+
+  BytecodeLabel else_label, end_label;
+
+  VisitForAccumulatorValue(expr->condition());
+  builder()->CastAccumulatorToBoolean();
+  builder()->JumpIfFalse(&else_label);
+
+  VisitForAccumulatorValue(expr->then_expression());
+  builder()->Jump(&end_label);
+
+  builder()->Bind(&else_label);
+  VisitForAccumulatorValue(expr->else_expression());
+  builder()->Bind(&end_label);
+
+  execution_result()->SetResultInAccumulator();
+}
 
 
 void BytecodeGenerator::VisitLiteral(Literal* expr) {
   if (!execution_result()->IsEffect()) {
     Handle<Object> value = expr->value();
     if (value->IsSmi()) {
       builder()->LoadLiteral(Smi::cast(*value));
     } else if (value->IsUndefined()) {
       builder()->LoadUndefined();
     } else if (value->IsTrue()) {
@@ skipping 1146 matching lines @@
 }
 
 
 int BytecodeGenerator::feedback_index(FeedbackVectorSlot slot) const {
   return info()->feedback_vector()->GetIndex(slot);
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8