Detect leaf optimized methods and skip stack check overflow test in those, unless it is in a loop (…

runtime/vm/flow_graph_compiler.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_XXX.
 
 #include "vm/flow_graph_compiler.h"
 
 #include "vm/cha.h"
 #include "vm/dart_entry.h"
@@ skipping 111 matching lines @@
   const DeoptInfo& deopt_info = DeoptInfo::Handle(builder->CreateDeoptInfo());
   return deopt_info.raw();
 }
 
 
 FlowGraphCompiler::FlowGraphCompiler(Assembler* assembler,
                                      const FlowGraph& flow_graph,
                                      bool is_optimizing)
     : assembler_(assembler),
       parsed_function_(flow_graph.parsed_function()),
+      flow_graph_(flow_graph),
       block_order_(flow_graph.reverse_postorder()),
       current_block_(NULL),
       exception_handlers_list_(NULL),
       pc_descriptors_list_(NULL),
       stackmap_table_builder_(
           is_optimizing ? new StackmapTableBuilder() : NULL),
       block_info_(block_order_.length()),
       deopt_infos_(),
       static_calls_target_table_(GrowableObjectArray::ZoneHandle(
           GrowableObjectArray::New())),
@@ skipping 11 matching lines @@
 
 bool FlowGraphCompiler::HasFinally() const {
   return parsed_function().function().has_finally();
 }
 
 
 void FlowGraphCompiler::InitCompiler() {
   pc_descriptors_list_ = new DescriptorList(64);
   exception_handlers_list_ = new ExceptionHandlerList();
   block_info_.Clear();
+  bool is_leaf = !parsed_function().function().IsClosureFunction() &&
+                 is_optimizing();
   for (int i = 0; i < block_order_.length(); ++i) {
     block_info_.Add(new BlockInfo());
     if (is_optimizing()) {
       BlockEntryInstr* entry = block_order_[i];
       for (ForwardInstructionIterator it(entry); !it.Done(); it.Advance()) {
         Instruction* current = it.Current();
         const ICData* ic_data = NULL;
         if (current->IsBranch()) {
           current = current->AsBranch()->comparison();
         }
         // In optimized code, ICData is always set in the instructions.
         if (current->IsInstanceCall()) {
           ic_data = current->AsInstanceCall()->ic_data();
           ASSERT(ic_data != NULL);
         } else if (current->IsRelationalOp()) {
           ic_data = current->AsRelationalOp()->ic_data();
           ASSERT(ic_data != NULL);
         } else if (current->IsEqualityCompare()) {
           ic_data = current->AsEqualityCompare()->ic_data();
           ASSERT(ic_data != NULL);
         }
         if ((ic_data != NULL) && (ic_data->NumberOfChecks() == 0)) {
           may_reoptimize_ = true;
           break;
         }
+        if (is_leaf && !current->IsCheckStackOverflow()) {
+          // Note that we do no care if the code contains instructions that
+          // can deoptimize.
+          LocationSummary* locs = current->locs();
+          if ((locs != NULL) && locs->can_call()) {
+            is_leaf = false;
+          }
+        }
       }
     }
   }
+  if (is_leaf) {
+    // Remove check stack overflow at entry.
+    CheckStackOverflowInstr* check = flow_graph_.graph_entry()->normal_entry()
+        ->next()->AsCheckStackOverflow();
+    ASSERT(check != NULL);
+    check->RemoveFromGraph();
+  }
 }
 
 
 bool FlowGraphCompiler::CanOptimize() {
   return !FLAG_report_usage_count &&
          (FLAG_optimization_counter_threshold >= 0);
 }
 
 
 bool FlowGraphCompiler::CanOptimizeFunction() const {
@@ skipping 927 matching lines @@
     if (i != largest_ix) {
       // Swap.
       CidTarget temp = (*sorted)[i];
       (*sorted)[i] = (*sorted)[largest_ix];
       (*sorted)[largest_ix] = temp;
     }
   }
 }
 
 }  // namespace dart