Add Function based profile tree

runtime/vm/instructions_arm64.cc

 // Copyright (c) 2014, 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_ARM64.
 #if defined(TARGET_ARCH_ARM64)
 
 #include "vm/assembler.h"
 #include "vm/constants_arm64.h"
 #include "vm/cpu.h"
@@ skipping 347 matching lines @@
   const uint16_t h2 = Utils::Low16Bits(w1);
   const uint16_t h3 = Utils::High16Bits(w1);
 
   movz0->SetInstructionBits((movz0_bits & ~kImm16Mask) | (h0 << kImm16Shift));
   movk1->SetInstructionBits((movk1_bits & ~kImm16Mask) | (h1 << kImm16Shift));
   movk2->SetInstructionBits((movk2_bits & ~kImm16Mask) | (h2 << kImm16Shift));
   movk3->SetInstructionBits((movk3_bits & ~kImm16Mask) | (h3 << kImm16Shift));
   CPU::FlushICache(pc_, 4 * Instr::kInstrSize);
 }
 
+
+ReturnPattern::ReturnPattern(uword pc)
+    : pc_(pc) {
+}
+
+
+bool ReturnPattern::IsValid() const {
+  Instr* bx_lr = Instr::At(pc_);
+  const Register crn = ConcreteRegister(LR);
+  const int32_t instruction = RET | (static_cast<int32_t>(crn) << kRnShift);
+  return bx_lr->InstructionBits() == instruction;
+}
+
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM64