Recognize leaf functions: skip stack check and populating the pc slot, store the pc slot lazily in …

runtime/vm/flow_graph_compiler.cc

Index: runtime/vm/flow_graph_compiler.cc
===================================================================
--- runtime/vm/flow_graph_compiler.cc	(revision 9089)
+++ runtime/vm/flow_graph_compiler.cc	(working copy)
@@ -31,7 +31,8 @@
     Assembler* assembler,
     const ParsedFunction& parsed_function,
     const GrowableArray<BlockEntryInstr*>& block_order,
-    bool is_optimizing)
+    bool is_optimizing,
+    bool is_leaf)
     : assembler_(assembler),
       parsed_function_(parsed_function),
       block_order_(block_order),
@@ -42,6 +43,7 @@
       block_info_(block_order.length()),
       deopt_stubs_(),
       is_optimizing_(is_optimizing),
+      is_dart_leaf_(is_leaf),
       bool_true_(Bool::ZoneHandle(Bool::True())),
       bool_false_(Bool::ZoneHandle(Bool::False())),
       double_class_(Class::ZoneHandle(
@@ -61,6 +63,13 @@
 }
 
 
+bool FlowGraphCompiler::IsLeaf() const {
+  return is_dart_leaf_ &&
+         !parsed_function_.function().IsClosureFunction() &&
+         (parsed_function().copied_parameter_count() == 0);
+}
+
+
 void FlowGraphCompiler::InitCompiler() {
   pc_descriptors_list_ = new DescriptorList();
   exception_handlers_list_ = new ExceptionHandlerList();
@@ -278,6 +287,7 @@
     intptr_t argument_count,
     const Array& argument_names,
     intptr_t checked_argument_count) {
+  ASSERT(!IsLeaf());
   ASSERT(frame_register_allocator()->IsSpilled());
   ICData& ic_data =
       ICData::ZoneHandle(ICData::New(parsed_function().function(),