VM: Explicitly load function and context before calling a closure.

runtime/vm/intermediate_language_x64.cc

Index: runtime/vm/intermediate_language_x64.cc
===================================================================
--- runtime/vm/intermediate_language_x64.cc	(revision 35546)
+++ runtime/vm/intermediate_language_x64.cc	(working copy)
@@ -5487,28 +5487,26 @@
 
 
 LocationSummary* ClosureCallInstr::MakeLocationSummary(bool opt) const {
-  return MakeCallSummary();
+  const intptr_t kNumInputs = 1;
+  const intptr_t kNumTemps = 0;
+  LocationSummary* summary =
+      new LocationSummary(kNumInputs, kNumTemps, LocationSummary::kCall);
+  summary->set_in(0, Location::RegisterLocation(RAX));  // Function.
+  summary->set_out(0, Location::RegisterLocation(RAX));
+  return summary;
 }
 
 
 void ClosureCallInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
-  // Load closure object (first argument) in R13.
-  intptr_t argument_count = ArgumentCount();
-  __ movq(R13, Address(RSP, (argument_count - 1) * kWordSize));
-
   // Arguments descriptor is expected in R10.
+  intptr_t argument_count = ArgumentCount();
   const Array& arguments_descriptor =
       Array::ZoneHandle(ArgumentsDescriptor::New(argument_count,
                                                  argument_names()));
   __ LoadObject(R10, arguments_descriptor, PP);
 
-  // Load the actual closure function.
-  __ movq(RAX, FieldAddress(R13, Closure::function_offset()));
-
-  // Load closure context in CTX; note that CTX has already been preserved.
-  __ movq(CTX, FieldAddress(R13, Closure::context_offset()));
-
-  // Load closure function code in RAX.
+  // Function in RAX.
+  ASSERT(locs()->in(0).reg() == RAX);
   __ movq(RCX, FieldAddress(RAX, Function::code_offset()));
 
   // RAX: Function.
@@ -5526,7 +5524,7 @@
   // deoptimization point in optimized code, after call.
   const intptr_t deopt_id_after = Isolate::ToDeoptAfter(deopt_id());
   if (compiler->is_optimizing()) {
-    compiler->AddDeoptIndexAtCall(deopt_id_after, token_pos());
+    compiler->AddDeoptIndexAtCall(deopt_id_after, token_pos(), InputCount());
   } else {
     // Add deoptimization continuation point after the call and before the
     // arguments are removed.