Initial support for count-based profiling

src/ia32/builtins-ia32.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1641 matching lines @@
     __ CallRuntime(Runtime::kCompileForOnStackReplacement, 1);
   }
 
   // If the result was -1 it means that we couldn't optimize the
   // function. Just return and continue in the unoptimized version.
   Label skip;
   __ cmp(eax, Immediate(Smi::FromInt(-1)));
   __ j(not_equal, &skip, Label::kNear);
   __ ret(0);
 
-  // If we decide not to perform on-stack replacement we perform a
-  // stack guard check to enable interrupts.
+  // Insert a stack guard check so that if we decide not to perform
+  // on-stack replacement right away, the function calling this stub can
+  // still be interrupted.
   __ bind(&stack_check);
   Label ok;
   ExternalReference stack_limit =
       ExternalReference::address_of_stack_limit(masm->isolate());
   __ cmp(esp, Operand::StaticVariable(stack_limit));
   __ j(above_equal, &ok, Label::kNear);
   StackCheckStub stub;
   __ TailCallStub(&stub);
   if (FLAG_debug_code) {
     __ Abort("Unreachable code: returned from tail call.");
@@ skipping 11 matching lines @@
   Deoptimizer::EntryGenerator generator(masm, Deoptimizer::OSR);
   generator.Generate();
 }
 
 
 #undef __
 }
 }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32