Optimize AOT's switchable calls for the monomorphic case.

runtime/vm/debugger_dbc.cc

 // Copyright (c) 2016, 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"
 #if defined(TARGET_ARCH_DBC)
 
 #include "vm/code_patcher.h"
 #include "vm/cpu.h"
 #include "vm/debugger.h"
@@ skipping 17 matching lines @@
 static Instr* FastSmiInstructionFromReturnAddress(uword pc) {
   return reinterpret_cast<Instr*>(pc) - 2;
 }
 
 
 void CodeBreakpoint::PatchCode() {
   ASSERT(!is_enabled_);
   const Code& code = Code::Handle(code_);
   const Instructions& instrs = Instructions::Handle(code.instructions());
   {
-    WritableInstructionsScope writable(instrs.EntryPoint(), instrs.size());
+    WritableInstructionsScope writable(instrs.PayloadStart(), instrs.size());
     saved_value_ = *CallInstructionFromReturnAddress(pc_);
     switch (breakpoint_kind_) {
       case RawPcDescriptors::kIcCall:
       case RawPcDescriptors::kUnoptStaticCall: {
         // DebugBreak has an A operand matching the call it replaces.
         // This ensures that Return instructions continue to work - as they
         // look at calls to figure out how many arguments to drop.
         *CallInstructionFromReturnAddress(pc_) =
             Bytecode::Encode(Bytecode::kDebugBreak,
                              Bytecode::DecodeArgc(saved_value_),
@@ skipping 24 matching lines @@
   }
   is_enabled_ = true;
 }
 
 
 void CodeBreakpoint::RestoreCode() {
   ASSERT(is_enabled_);
   const Code& code = Code::Handle(code_);
   const Instructions& instrs = Instructions::Handle(code.instructions());
   {
-    WritableInstructionsScope writable(instrs.EntryPoint(), instrs.size());
+    WritableInstructionsScope writable(instrs.PayloadStart(), instrs.size());
     switch (breakpoint_kind_) {
       case RawPcDescriptors::kIcCall:
       case RawPcDescriptors::kUnoptStaticCall:
       case RawPcDescriptors::kRuntimeCall: {
         *CallInstructionFromReturnAddress(pc_) = saved_value_;
         break;
       }
       default:
         UNREACHABLE();
     }
 
     if (saved_value_fastsmi_ != Bytecode::kTrap) {
       Instr current_instr = *FastSmiInstructionFromReturnAddress(pc_);
       ASSERT(Bytecode::DecodeOpcode(current_instr) == Bytecode::kNop);
       *FastSmiInstructionFromReturnAddress(pc_) = saved_value_fastsmi_;
     }
   }
   is_enabled_ = false;
 }
 
 #endif  // !PRODUCT
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_DBC