VM: Reduce the number of edge counters in generated code.

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"
 #include "vm/debugger.h"
 #include "vm/deopt_instructions.h"
 #include "vm/exceptions.h"
 #include "vm/flow_graph_allocator.h"
 #include "vm/il_printer.h"
 #include "vm/intrinsifier.h"
 #include "vm/locations.h"
 #include "vm/longjump.h"
 #include "vm/object_store.h"
 #include "vm/parser.h"
 #include "vm/stack_frame.h"
 #include "vm/stub_code.h"
 #include "vm/symbols.h"
 
 namespace dart {
 
 DECLARE_FLAG(bool, code_comments);
 DECLARE_FLAG(bool, disassemble);
 DECLARE_FLAG(bool, disassemble_optimized);
+DECLARE_FLAG(bool, emit_edge_counters);
 DECLARE_FLAG(bool, enable_type_checks);
 DECLARE_FLAG(bool, intrinsify);
 DECLARE_FLAG(bool, propagate_ic_data);
 DECLARE_FLAG(int, optimization_counter_threshold);
 DECLARE_FLAG(bool, use_cha);
 DECLARE_FLAG(bool, use_osr);
 DECLARE_FLAG(int, stacktrace_every);
 DECLARE_FLAG(charp, stacktrace_filter);
 DECLARE_FLAG(int, deoptimize_every);
 DECLARE_FLAG(charp, deoptimize_filter);
@@ skipping 914 matching lines @@
 
 
 void FlowGraphCompiler::EmitComment(Instruction* instr) {
   char buffer[256];
   BufferFormatter f(buffer, sizeof(buffer));
   instr->PrintTo(&f);
   assembler()->Comment("%s", buffer);
 }
 
 
+bool FlowGraphCompiler::NeedsEdgeCounter(TargetEntryInstr* block) {
+  // Only emit an edge counter if there is not goto at the end of the block,
+  // except for the entry block.
+  return (FLAG_emit_edge_counters
+      && (!block->last_instruction()->IsGoto()
+          || (block == flow_graph().graph_entry()->normal_entry())));
+}
+
+
 // Allocate a register that is not explicitly blocked.
 static Register AllocateFreeRegister(bool* blocked_registers) {
   for (intptr_t regno = 0; regno < kNumberOfCpuRegisters; regno++) {
     if (!blocked_registers[regno]) {
       blocked_registers[regno] = true;
       return static_cast<Register>(regno);
     }
   }
   UNREACHABLE();
   return kNoRegister;
@@ skipping 334 matching lines @@
 
   for (int i = 0; i < len; i++) {
     sorted->Add(CidTarget(ic_data.GetReceiverClassIdAt(i),
                           &Function::ZoneHandle(ic_data.GetTargetAt(i)),
                           ic_data.GetCountAt(i)));
   }
   sorted->Sort(HighestCountFirst);
 }
 
 }  // namespace dart