[Interpreter] Add conditional expressions.

src/interpreter/bytecode-generator.cc

Index: src/interpreter/bytecode-generator.cc
diff --git a/src/interpreter/bytecode-generator.cc b/src/interpreter/bytecode-generator.cc
index 8c791db5e3d9ddbab25e65145c45bccffcb413e1..150439091610e14cbd58d8e09a2cecc3ccfc9e88 100644
--- a/src/interpreter/bytecode-generator.cc
+++ b/src/interpreter/bytecode-generator.cc
@@ -656,7 +656,26 @@ void BytecodeGenerator::VisitDoExpression(DoExpression* expr) {
 }
 
 
-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) {