[turbofan] Implement tail calls with differing stack parameter counts

src/compiler/ast-graph-builder.cc

Index: src/compiler/ast-graph-builder.cc
diff --git a/src/compiler/ast-graph-builder.cc b/src/compiler/ast-graph-builder.cc
index 7ccb8aa320d18044f9bdf1ab77f9d37f371f9eed..cca187c81a24e6ddf4d44fcb2ca01c366eb02af3 100644
--- a/src/compiler/ast-graph-builder.cc
+++ b/src/compiler/ast-graph-builder.cc
@@ -2601,7 +2601,12 @@ void AstGraphBuilder::VisitCallRuntime(CallRuntime* expr) {
 
   // Create node to perform the runtime call.
   Runtime::FunctionId functionId = function->function_id;
-  const Operator* call = javascript()->CallRuntime(functionId, args->length());
+  // Outer-most frame of calls into native function chains must have a frame in
+  // the stack crawl.
+  TailCallMode mode =

[Benedikt Meurer, 2015/07/30 06:47:24]

IMHO this will be highly confusing and might be a source of weird bugs in the
future. By just looking at a tail call site in a .js file you will be mostly
unable to tell whether it is actually a tailcall to the runtime or a regular
call. I'd really prefer to have this explicit at the tail call site so people
are aware of what they are doing, just like we do in the native code stubs,
where we have __ TailCallRuntime and __ CallRuntime.

+      info()->shared_info()->native() ? NO_TAIL_CALLS : ALLOW_TAIL_CALLS;
+  const Operator* call =
+      javascript()->CallRuntime(functionId, args->length(), mode);
   FrameStateBeforeAndAfter states(this, expr->CallId());
   Node* value = ProcessArguments(call, args->length());
   states.AddToNode(value, expr->id(), ast_context()->GetStateCombine());