[LLVMdev] LLVM JIT Questions

[Dmitri Rubinstein]

Hi Andrew,

Am 23.04.2013 19:41 schrieb "Kaylor, Andrew" <andrew.kaylor at intel.com>:
>
> Hi Dmitri,
>
> Regarding your first question, if you can use the MCJIT engine a caching
mechanism will be available very soon.  I'm preparing to commit a patch
today to add this capability.  I'm not sure what it would take to get
something similar working with the older JIT engine.  I expect it would
take a fair amount of work because the older JIT engine isn't designed
around object loading as the MCJIT engine is.
>
> Regarding your second question, there might be more than one way to do
this, but once you have an llvm::Function (but before you JIT the code) you
should be able to use llvm::Function::setCallingConv().

SetCallingConv is not enough. For example consider following C code:

typedef struct S { int a, b, c; } S;

void doS(S s) { ... }

Is compled on Linux x86 32bit as

%struct.S = type { i32, i32, i32 }

define void @doS(i32 %s.0, i32 %s.1, i32 %s.2) nounwind { ... }

And on Linux x86 64bit as

%0 = type { i64, i32 }
%struct.S = type { i32, i32, i32 }

define void @doS(i64 %s.coerce0, i32 %s.coerce1) nounwind { ... }

Dmitri

>
> -Andy
>
> -----Original Message-----
> From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On
Behalf Of Dmitri Rubinstein
> Sent: Tuesday, April 23, 2013 5:25 AM
> To: LLVM Dev
> Subject: [LLVMdev] LLVM JIT Questions
>
> Hi all,
>
> For my current project I need a couple of informations about JIT. I seen
similar questions already, but the answers are a bit older and I hope
somebody can provide me a recent information.
>
> 1. In my project I frequently construct LLVM IR, compile it and execute
with JIT. Because the constructed IR is often the same (but can vary
depending on input data) I would like to cache produced machine code on the
disk. There is no JIT API for dumping and loading of compiled code.
>
> Are there any plans to add this feature in the near future ?
>
> How complex would it be to implement this for somebody who has only
experience with LLVM code generation, but no deep knowledge of JIT
internals ?
>
> 2. I also need to interface with C-libraries which are either loaded as a
shared library or pre-compiled with clang and loaded as BC file.
> However, LLVM does not provide a way how to construct function signature
compatible with the C-ABI of the specific platform. I know that clang
library has internally this information, but I need this functionality
without clang.
>
> Is there any documentation which describes how to do generate C-ABI
compatible LLVM functions or code that implements this functionality ?
>
> Thanks,
>
> Dmitri
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