Optimize function at its entry instead of at exit.

runtime/vm/stub_code_ia32.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_IA32)
 
 #include "vm/assembler.h"
 #include "vm/assembler_macros.h"
 #include "vm/compiler.h"
@@ skipping 2002 matching lines @@
   __ pushl(ECX);  // ICData
   __ CallRuntime(kUpdateICDataTwoArgsRuntimeEntry);
   __ Drop(4);
   __ LeaveFrame();
 
   __ jmp(&compute_result, Assembler::kNearJump);
 }
 
 
 // Calls to runtime to ooptimized give function
-// EDX: function to be reoptimized.
-// EAX: result of function being optimized (preserved).
+// 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()));
   AssemblerMacros::EnterStubFrame(assembler);
-  __ pushl(EAX);
   __ pushl(EDX);
+  __ pushl(raw_null);  // Setup space on stack for return value.
+  __ pushl(EDI);
   __ CallRuntime(kOptimizeInvokedFunctionRuntimeEntry);
-  __ popl(EDX);
-  __ popl(EAX);
+  __ popl(EAX);  // Discard argument.
+  __ popl(EAX);  // Get Code object
+  __ popl(EDX);  // Restore argument descriptor.
+  __ movl(EAX, FieldAddress(EAX, Code::instructions_offset()));
+  __ addl(EAX, Immediate(Instructions::HeaderSize() - kHeapObjectTag));
   __ LeaveFrame();
-  __ ret();
+  __ jmp(EAX);
+  __ int3();
 }
 
 
 DECLARE_LEAF_RUNTIME_ENTRY(intptr_t,
                            BigintCompare,
                            RawBigint* left,
                            RawBigint* right);
 
 
 // Does identical check (object references are equal or not equal) with special
@@ skipping 71 matching lines @@
   __ Bind(&done);
   __ popl(temp);
   __ popl(right);
   __ popl(left);
   __ ret();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_IA32