[generators] Perform state dispatch in loop header.

src/interpreter/bytecode-array-builder.cc

Index: src/interpreter/bytecode-array-builder.cc
diff --git a/src/interpreter/bytecode-array-builder.cc b/src/interpreter/bytecode-array-builder.cc
index f664349dd44b9952326bef8d8688a5297337bebe..23bf7548aaf5c2bca7f36f7225bc7c34582d2db5 100644
--- a/src/interpreter/bytecode-array-builder.cc
+++ b/src/interpreter/bytecode-array-builder.cc
@@ -96,7 +96,8 @@ BytecodeArrayBuilder::BytecodeArrayBuilder(Isolate* isolate, Zone* zone,
                                            int parameter_count,
                                            int context_count, int locals_count,
                                            FunctionLiteral* literal)
-    : isolate_(isolate),
+    : generator_resume_points(0, zone),
+      isolate_(isolate),
       zone_(zone),
       bytecodes_(zone),
       bytecode_generated_(false),
@@ -110,7 +111,8 @@ BytecodeArrayBuilder::BytecodeArrayBuilder(Isolate* isolate, Zone* zone,
       parameter_count_(parameter_count),
       local_register_count_(locals_count),
       context_register_count_(context_count),
-      temporary_allocator_(zone, fixed_register_count()) {
+      temporary_allocator_(zone, fixed_register_count()),
+      generator_yields_seen_(0) {
   DCHECK_GE(parameter_count_, 0);
   DCHECK_GE(context_register_count_, 0);
   DCHECK_GE(local_register_count_, 0);
@@ -875,6 +877,21 @@ BytecodeArrayBuilder& BytecodeArrayBuilder::JumpIfNotHole(
   return OutputJump(Bytecode::kJumpIfNotHole, label);
 }
 
+
+BytecodeArrayBuilder& BytecodeArrayBuilder::IndexedJump(

[rmcilroy, 2016/04/19 09:30:03]

As mentioned in a comment below, I think this should also live in the
BytecodeGenerator (along with the resume points and yields seen). Doing this
here breaks the abstraction between BytecodeGenerator (which is meant to be
where the logic of turning JS into bytecode lives) and BytecodeArrayBuilder
(which is meant to simply abstract over bytecode creation and output).

[neis, 2016/04/19 11:02:15]

Ack.  I thought my IndexedJump would fit well next to the JumpIfFoo functions
but I didn't realize that those all have their own bytecode.

+    Register index, int min, size_t size, ZoneVector<BytecodeLabel>& targets) {
+  // TODO(neis): Optimize this by using a proper jump table.
+  for (int i = min; i < min + size; i++) {
+    DCHECK(0 <= i && i < targets.size());
+    LoadLiteral(Smi::FromInt(static_cast<int>(i)));
+    CompareOperation(Token::Value::EQ_STRICT, index);
+    JumpIfTrue(&(targets[i]));
+  }
+  Illegal();  // Should never get here.
+  return *this;
+}
+
+
 BytecodeArrayBuilder& BytecodeArrayBuilder::Throw() {
   Output(Bytecode::kThrow);
   exit_seen_in_block_ = true;