Reapply "Deoptimization support in inlined code."

runtime/vm/stub_code_x64.cc

 // Copyright (c) 2012, 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_X64)
 
 #include "vm/assembler.h"
 #include "vm/assembler_macros.h"
 #include "vm/compiler.h"
@@ skipping 526 matching lines @@
   __ movq(Address(RSP, 0), RCX);
 
   __ EnterFrame(0);
   __ movq(RCX, RSP);  // Get last FP address.
   if (preserve_rax) {
     __ pushq(RBX);  // Preserve result.
   }
   __ ReserveAlignedFrameSpace(0);
   __ movq(RDI, RCX);  // Set up argument 1 last_fp.
   __ CallRuntime(kDeoptimizeFillFrameRuntimeEntry);
+  // Result (RAX) is our FP.
   if (preserve_rax) {
-    // Restore result into RAX.
-    __ movq(RAX, Address(RBP, -1 * kWordSize));
+    // Restore result into RBX.
+    __ movq(RBX, Address(RBP, -1 * kWordSize));
   }
   // Code above cannot cause GC.
   __ LeaveFrame();
+  __ movq(RBP, RAX);
 
   // Frame is fully rewritten at this point and it is safe to perform a GC.
   // Materialize any objects that were deferred by FillFrame because they
   // require allocation.
   __ EnterFrame(0);
   if (preserve_rax) {
-    __ pushq(RAX);  // Preserve result, it will be GC-d here.
+    __ pushq(RBX);  // Preserve result, it will be GC-d here.
   }
   __ CallRuntime(kDeoptimizeMaterializeDoublesRuntimeEntry);
   if (preserve_rax) {
     __ popq(RAX);  // Restore result.
   }
   __ LeaveFrame();
 
   __ ret();
 }
 
@@ skipping 1353 matching lines @@
 void StubCode::GenerateJumpToErrorHandlerStub(Assembler* assembler) {
   __ movq(RAX, RCX);  // error object.
   __ movq(RBP, RDX);  // target frame_pointer.
   __ movq(RSP, RSI);  // target stack_pointer.
   __ jmp(RDI);  // Jump to the exception handler code.
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64