[LLVMdev] Dynamic (JIT) type resolution

[Nicolas Geoffray]

Hi Chris,

Chris Lattner wrote:
> On Wed, 7 Nov 2007, Nicolas Geoffray wrote:
>   
>> Thanks BGB, but at this point I can handle it ;-). The problem is not
>> how in theory (patch the caller), but how in the LLVM code generation
>> process. There are three steps for that:
>>
>> 1) How to represent the stub in the IR? An intrinsic? An external field
>> with a ghost linkage?
>>     
>
> Probably an intrinsic.  The trick is making it general purpose, not 
> language specific.
>
>   

I'm not sure actually how can I do that language specific ;). OK
currently only Java does that (from what I know), but intrinsics like
getElementDouble or setElementDouble do look general purpose. Unless,
I'm too Java-minded?

>> 2) At which point in LLVM do we know we won't have any optimization, so
>> that the field operation is next to the stub call?
>>     
>
> You'll probably want to do this late in the code generator.
>   

Therefore when instructions are lowered to target-specific instructions?

>   
>> 3) Make LLVM think the stub call is not a real call, so that
>> callee-saved registers do not get clobbered.
>>     
>
> LLVM supports calling convetions like "coldcc".  The idea of coldcc is 
> that the function is compiled to not clobber callee-save registers. 
> However, in practice, no current code generators do anything special with 
> it, it's compiled like fastcc or ccc.
>
>   

As long as there is room for it, and obviously coldcc is here for that,
it works fine for me :)

Thanks,
Nicolas

> -Chris
>
>