Move some isolate state setup from C++ code to JumpToExceptionHandler stub

runtime/vm/stub_code_arm64.cc

Index: runtime/vm/stub_code_arm64.cc
diff --git a/runtime/vm/stub_code_arm64.cc b/runtime/vm/stub_code_arm64.cc
index d6c165ff3de002cfe4784dcf2b369ef414b1b328..ace945e080d4f231b05f73519bd2233667df0975 100644
--- a/runtime/vm/stub_code_arm64.cc
+++ b/runtime/vm/stub_code_arm64.cc
@@ -1795,6 +1795,7 @@ void StubCode::GenerateGetStackPointerStub(Assembler* assembler) {
 // R2: frame_pointer.
 // R3: error object.
 // R4: address of stacktrace object.
+// R5: isolate.
 // Does not return.
 void StubCode::GenerateJumpToExceptionHandlerStub(Assembler* assembler) {
   ASSERT(kExceptionObjectReg == R0);
@@ -1804,6 +1805,12 @@ void StubCode::GenerateJumpToExceptionHandlerStub(Assembler* assembler) {
   __ mov(FP, R2);  // Frame_pointer.
   __ mov(R0, R3);  // Exception object.
   __ mov(R1, R4);  // StackTrace object.
+  __ mov(CTX, R5);  // Isolate.

[regis, 2014/07/14 20:00:34]

Why not use R5 below?

[Cutch, 2014/07/14 21:32:07]

Done.

+  // Set the tag.
+  __ LoadImmediate(R2, VMTag::kScriptTagId, kNoPP);
+  __ StoreToOffset(R2, CTX, Isolate::vm_tag_offset(), kNoPP);
+  // Clear top exit frame.
+  __ StoreToOffset(ZR, CTX, Isolate::top_exit_frame_info_offset(), kNoPP);
   __ ret();  // Jump to the exception handler code.
 }