Re: How does FJit::compileCEE_NEWOBJ work?

Thanks for the replies. I have a related question. For a new piece of
memory allocated by GC, can I always assume that its content is zero?

-Yuan

>Rotor always uses JIT_NewFast to allocate objects. There is a mechanism
>to allow for use of highly tuned per platforms allocators via use of
>getNewHelper(...), but it is not used in Rotor for portability reasons.
>
>Here is x86 dissasembly for the following IL:
>
>IL_0000:  newobj     instance void MainApp::.ctor()
>IL_0005:  stloc.0
>
>03457bb1 b8b844d700       mov     eax,0xd744b8   // MT for MainApp
>03457bb6 50               push    eax
>03457bb7 b83a4c9500       mov     eax,0x954c3a   // Address of
>JIT_NewFast
>03457bbc ffd0             call    eax
>03457bbe 83c404           add     esp,0x4
>
>03457bc1 8bf0             mov     esi,eax        // Save the pointer to
>the
>03457bc3 8bc8             mov     ecx,eax        // blank object in esi
>03457bc5 51               push    ecx
>03457bc6 b8fc44d700       mov     eax,0xd744fc
>03457bcb ff10             call    dword ptr [eax]// Call the constructor
>03457bcd 83c404           add     esp,0x4
>03457bd0 8bc6             mov     eax,esi        // Get the object ref
>from
>03457bd2 be00000000       mov     esi,0x0        // esi and store it in
>a
>03457bd7 8945f0           mov     [ebp-0x10],eax // local
>
>(Note esi is set to NULL because it is in the root set for the GC)
>
>The code paths for allocating valuetypes and arrays are different. Let
>me know which one you are interested in.
>
>Thanks,
>
>Vladimir
>
>This posting is provided "AS IS" with no warranties, and confers no
>rights.
>
>-----Original Message-----
>From: Discussion of the Rotor Shared Source CLI implementation
>[mailto:[email protected]] On Behalf Of Yuan Yu
>Sent: Friday, August 01, 2003 6:12 PM
>To: [email protected]
>Subject: [DOTNET-ROTOR] How does FJit::compileCEE_NEWOBJ work?
>
>I have been trying to understand how the newobj instruction is jitted.
>For
>a simple class like
>
>   class Foo { int x = 5; }
>
>and an instruction
>
>   newobj     instance void Foo
>
>Rotor calls FJit::compileCEE_NEWOBJ, and goes to the "allocate normal
>object" case where the first line is
>
>  helper_ftn = jitInfo->getHelperFtn(jitInfo->getNewHelper(targetClass,
>methodHandle));
>
>The value of jitInfo->getNewHelper(targetClass, methodHandle) appears to
>be CORINFO_HELP_NEWSFAST, and, according to the table hlpFuncTable, it
>seems to map to JIT_NewFast. So, I thought the helper function
>helper_ftn
>must have been JIT_NewFast. However, it does not seem to be the case.
>So,
>what is the value of helper_ftn?
>
>Thanks,
>-Yuan