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

runtime/vm/stub_code_ia32.cc

 // Copyright (c) 2013, 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_IA32)
 
 #include "vm/assembler.h"
 #include "vm/compiler.h"
 #include "vm/dart_entry.h"
@@ skipping 1735 matching lines @@
 }
 
 
 // Jump to the exception or error handler.
 // TOS + 0: return address
 // TOS + 1: program_counter
 // TOS + 2: stack_pointer
 // TOS + 3: frame_pointer
 // TOS + 4: exception object
 // TOS + 5: stacktrace object
+// TOS + 6: isolate
 // No Result.
 void StubCode::GenerateJumpToExceptionHandlerStub(Assembler* assembler) {
   ASSERT(kExceptionObjectReg == EAX);
   ASSERT(kStackTraceObjectReg == EDX);
+  __ movl(CTX, Address(ESP, 6 * kWordSize));  // Load target isolate.

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

You could use EAX instead of CTX.

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

Can't use EAX because it is the same askExceptionObjectReg. Switched to EDI.

   __ movl(kStackTraceObjectReg, Address(ESP, 5 * kWordSize));
   __ movl(kExceptionObjectReg, Address(ESP, 4 * kWordSize));
   __ movl(EBP, Address(ESP, 3 * kWordSize));  // Load target frame_pointer.
   __ movl(EBX, Address(ESP, 1 * kWordSize));  // Load target PC into EBX.
   __ movl(ESP, Address(ESP, 2 * kWordSize));  // Load target stack_pointer.
+  // Set tag.
+  __ movl(Address(CTX, Isolate::vm_tag_offset()),
+          Immediate(VMTag::kScriptTagId));
+  // Clear top exit frame.
+  __ movl(Address(CTX, Isolate::top_exit_frame_info_offset()), Immediate(0));
   __ jmp(EBX);  // Jump to the exception handler code.
 }
 
 
 // Calls to the runtime to optimize the given function.
 // EDI: function to be reoptimized.
 // EDX: argument descriptor (preserved).
 void StubCode::GenerateOptimizeFunctionStub(Assembler* assembler) {
   const Immediate& raw_null =
       Immediate(reinterpret_cast<intptr_t>(Object::null()));
@@ skipping 126 matching lines @@
   const Register temp = ECX;
   __ movl(left, Address(ESP, 2 * kWordSize));
   __ movl(right, Address(ESP, 1 * kWordSize));
   GenerateIdenticalWithNumberCheckStub(assembler, left, right, temp);
   __ ret();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_IA32