Adds debugger patching to arm64.

runtime/vm/debugger_arm64.cc

Index: runtime/vm/debugger_arm64.cc
===================================================================
--- runtime/vm/debugger_arm64.cc	(revision 35975)
+++ runtime/vm/debugger_arm64.cc	(working copy)
@@ -15,30 +15,85 @@
 
 RawInstance* ActivationFrame::GetInstanceCallReceiver(
                  intptr_t num_actual_args) {
-  UNIMPLEMENTED();
-  return NULL;
+  ASSERT(num_actual_args > 0);  // At minimum we have a receiver on the stack.
+  // Stack pointer points to last argument that was pushed on the stack.
+  const uword receiver_addr = sp() + ((num_actual_args - 1) * kWordSize);
+  const uword receiver = *reinterpret_cast<uword*>(receiver_addr);
+  return reinterpret_cast<RawInstance*>(receiver);
 }
 
 
 RawObject* ActivationFrame::GetClosureObject(intptr_t num_actual_args) {
-  UNIMPLEMENTED();
-  return NULL;
+  // At a minimum we have the closure object on the stack.
+  ASSERT(num_actual_args > 0);
+  // Stack pointer points to last argument that was pushed on the stack.
+  const uword closure_addr = sp() + ((num_actual_args - 1) * kWordSize);
+  const uword closure = *reinterpret_cast<uword*>(closure_addr);
+  return reinterpret_cast<RawObject*>(closure);
 }
 
 
 uword CodeBreakpoint::OrigStubAddress() const {
-  UNIMPLEMENTED();
-  return 0;
+  const Code& code = Code::Handle(code_);
+  const Array& object_pool = Array::Handle(code.ObjectPool());
+  const uword offset = saved_value_;
+  ASSERT((offset % kWordSize) == 0);
+  const intptr_t index = (offset - Array::data_offset()) / kWordSize;
+  const uword stub_address = reinterpret_cast<uword>(object_pool.At(index));
+  ASSERT(stub_address % kWordSize == 0);
+  return stub_address;
 }
 
 
 void CodeBreakpoint::PatchCode() {
-  UNIMPLEMENTED();
+  ASSERT(!is_enabled_);
+  const Code& code = Code::Handle(code_);
+  const Instructions& instrs = Instructions::Handle(code.instructions());
+  {
+    WritableInstructionsScope writable(instrs.EntryPoint(), instrs.size());
+    switch (breakpoint_kind_) {
+      case PcDescriptors::kIcCall:
+      case PcDescriptors::kUnoptStaticCall:
+      case PcDescriptors::kRuntimeCall:
+      case PcDescriptors::kClosureCall:
+      case PcDescriptors::kReturn: {
+        int32_t offset = CodePatcher::GetPoolOffsetAt(pc_);
+        ASSERT((offset > 0) && ((offset & 0x7) == 0));
+        saved_value_ = static_cast<uword>(offset);
+        const uint32_t stub_offset =
+            InstructionPattern::OffsetFromPPIndex(
+                Assembler::kBreakpointRuntimeCPIndex);
+        CodePatcher::SetPoolOffsetAt(pc_, stub_offset);
+        break;
+      }
+      default:
+        UNREACHABLE();
+    }
+  }
+  is_enabled_ = true;
 }
 
 
 void CodeBreakpoint::RestoreCode() {
-  UNIMPLEMENTED();
+  ASSERT(is_enabled_);
+  const Code& code = Code::Handle(code_);
+  const Instructions& instrs = Instructions::Handle(code.instructions());
+  {
+    WritableInstructionsScope writable(instrs.EntryPoint(), instrs.size());
+    switch (breakpoint_kind_) {
+      case PcDescriptors::kIcCall:
+      case PcDescriptors::kUnoptStaticCall:
+      case PcDescriptors::kClosureCall:
+      case PcDescriptors::kRuntimeCall:
+      case PcDescriptors::kReturn: {
+        CodePatcher::SetPoolOffsetAt(pc_, static_cast<int32_t>(saved_value_));
+        break;
+      }
+      default:
+        UNREACHABLE();
+    }
+  }
+  is_enabled_ = false;
 }
 
 }  // namespace dart