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

runtime/vm/stub_code_mips.cc

Index: runtime/vm/stub_code_mips.cc
diff --git a/runtime/vm/stub_code_mips.cc b/runtime/vm/stub_code_mips.cc
index 62d3b6787c1daca2e6dd1abbb488751d7bfab1a2..db6ca354a5e4e9106bc97f6a75f2a34e1d0151a3 100644
--- a/runtime/vm/stub_code_mips.cc
+++ b/runtime/vm/stub_code_mips.cc
@@ -1929,6 +1929,7 @@ void StubCode::GenerateGetStackPointerStub(Assembler* assembler) {
 // A2: frame_pointer.
 // A3: error object.
 // SP + 4*kWordSize: address of stacktrace object.
+// SP + 5*kWordSize: address of isolate.
 // Does not return.
 void StubCode::GenerateJumpToExceptionHandlerStub(Assembler* assembler) {
   ASSERT(kExceptionObjectReg == V0);
@@ -1938,6 +1939,13 @@ void StubCode::GenerateJumpToExceptionHandlerStub(Assembler* assembler) {
   // the last of five arguments, so it is first pushed on the stack.
   __ lw(V1, Address(SP, 4 * kWordSize));  // StackTrace object.
   __ mov(FP, A2);  // Frame_pointer.
+  __ lw(A3, Address(SP, 5 * kWordSize));  // Isolate.
+  // Set tag.
+  __ LoadImmediate(A2, VMTag::kScriptTagId);
+  __ sw(A2, Address(A3, Isolate::vm_tag_offset()));
+  // Clear top exit frame.
+  __ sw(ZR, Address(A3, Isolate::top_exit_frame_info_offset()));
+
   __ jr(A0);  // Jump to the exception handler code.
   __ delay_slot()->mov(SP, A1);  // Stack pointer.
 }