[Interpreter] Basic flow control.

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 e40a5b3513eeeb97b9e8c7cda8299136cd427cb5..3ccc83d6880c077005f40f569ece4f235759c5a7 100644
--- a/src/interpreter/bytecode-generator.cc
+++ b/src/interpreter/bytecode-generator.cc
@@ -45,13 +45,6 @@ Handle<BytecodeArray> BytecodeGenerator::MakeBytecode(CompilationInfo* info) {
   // Visit statements in the function body.
   VisitStatements(info->literal()->body());
 
-  // If the last bytecode wasn't a return, then return 'undefined' to avoid
-  // falling off the end.
-  if (!builder_.HasExplicitReturn()) {
-    builder_.LoadUndefined();
-    builder_.Return();
-  }
-
   set_scope(nullptr);
   set_info(nullptr);
   return builder_.ToBytecodeArray();
@@ -59,6 +52,7 @@ Handle<BytecodeArray> BytecodeGenerator::MakeBytecode(CompilationInfo* info) {
 
 
 void BytecodeGenerator::VisitBlock(Block* node) {
+  builder().EnterBlock();
   if (node->scope() == NULL) {
     // Visit statements in the same scope, no declarations.
     VisitStatements(node->statements());
@@ -71,6 +65,7 @@ void BytecodeGenerator::VisitBlock(Block* node) {
       VisitStatements(node->statements());
     }
   }
+  builder().LeaveBlock();
 }
 
 
@@ -114,11 +109,22 @@ void BytecodeGenerator::VisitExpressionStatement(ExpressionStatement* stmt) {
 
 
 void BytecodeGenerator::VisitEmptyStatement(EmptyStatement* stmt) {
-  UNIMPLEMENTED();
+  // For control-flow it could be useful to signal empty paths here.

[rmcilroy, 2015/09/23 14:00:29]

nit - TODO(oth): 

[oth, 2015/09/24 11:15:27]

Done.

 }
 
 
-void BytecodeGenerator::VisitIfStatement(IfStatement* stmt) { UNIMPLEMENTED(); }
+void BytecodeGenerator::VisitIfStatement(IfStatement* stmt) {
+  // TODO(oth): spot easy cases if (true/1/false/0)?

[rmcilroy, 2015/09/23 14:00:29]

nit - clarify comment please - e.g.: spot easy cases where we wouldn't need to
emit the then or else block, e.g., if (true/1/false/0).

[oth, 2015/09/24 11:15:27]

Done.

+  BytecodeLabel else_start, else_end;
+  Visit(stmt->condition());
+  builder().CastAccumulatorToBoolean();
+  builder().JumpIfFalse(&else_start);
+  Visit(stmt->then_statement());
+  builder().Jump(&else_end);
+  builder().Bind(&else_start);
+  Visit(stmt->else_statement());
+  builder().Bind(&else_end);

[rmcilroy, 2015/09/23 14:00:29]

nit - maybe some whitespace between condition, then, else, etc.

[oth, 2015/09/24 11:15:27]

Done.

+}
 
 
 void BytecodeGenerator::VisitSloppyBlockFunctionStatement(
@@ -458,7 +464,17 @@ void BytecodeGenerator::VisitBinaryOperation(BinaryOperation* binop) {
 
 
 void BytecodeGenerator::VisitCompareOperation(CompareOperation* expr) {
-  UNIMPLEMENTED();
+  Token::Value op = expr->op();
+  Expression* left = expr->left();
+  Expression* right = expr->right();
+
+  TemporaryRegisterScope temporary_register_scope(&builder_);
+  Register temporary = temporary_register_scope.NewRegister();
+
+  Visit(left);
+  builder().StoreAccumulatorInRegister(temporary);
+  Visit(right);
+  builder().CompareOperation(op, temporary, language_mode());
 }