[builtins] support exception handling in TFJ builtins

src/compiler/code-assembler.cc

Index: src/compiler/code-assembler.cc
diff --git a/src/compiler/code-assembler.cc b/src/compiler/code-assembler.cc
index 6fd143b4dd9dd494e7e0485d9472896535c05e93..58a46944ae6eb9989f5775195bb006fd00d45576 100644
--- a/src/compiler/code-assembler.cc
+++ b/src/compiler/code-assembler.cc
@@ -312,6 +312,32 @@ void CodeAssembler::BranchIf(Node* condition, Label* if_true, Label* if_false) {
   Goto(if_false);
 }
 
+void CodeAssembler::BranchIfSuccess(Node* node, Label* if_success,
+                                    Label* if_exception,
+                                    Variable* exception_var) {
+  Label exception(this);

[Michael Starzinger, 2016/08/19 08:53:56]

Let's mark this label as deferred, to move the handler block out of the
instruction stream.

[caitp, 2016/08/19 15:38:53]

Done.

+  if_success->MergeVariables();
+  exception.MergeVariables();
+  DCHECK(!node->op()->HasProperty(Operator::kNoThrow));
+
+  raw_assembler_->BranchIfSuccess(node, if_success->label_, exception.label_);
+
+  Bind(&exception);
+  const Operator* op = raw_assembler_->common()->IfException();
+  raw_assembler_->AddNode(op, node, node);
+  if (exception_var != nullptr) {
+    exception_var->Bind(node);
+  }
+  Goto(if_exception);
+}
+
+void CodeAssembler::GotoIfException(Node* node, Label* if_exception,

[Michael Starzinger, 2016/08/19 08:53:56]

It seems that users of the CodeAssembler will be mostly interested in this
method (i.e. fall-through on success and goto on exception). Is there any
use-case for the BranchIfSuccess method above?

If no then I would vote for merging BranchIfSuccess into this method completely
(or alternatively making it a private method).

[caitp, 2016/08/19 15:38:53]

I've merged them into just GotoIfException --- I just figured it would be good
to follow the apparent convention of Goto and Branch being available

+                                    Variable* exception_var) {
+  Label if_success(this);
+  BranchIfSuccess(node, &if_success, if_exception, exception_var);
+  Bind(&if_success);
+}
+
 Node* CodeAssembler::CallN(CallDescriptor* descriptor, Node* code_target,
                            Node** args) {
   CallPrologue();