[llvm-dev] thread safety ExecutionEngine::getFunctionAddress

[Mehdi Amini via llvm-dev]

> On Dec 20, 2016, at 9:13 AM, koffie drinker via llvm-dev <llvm-dev at lists.llvm.org> wrote:
> 
> Hi,
> 
> I'm trying to speed up the JIT time with llvm (3.9.1).
> So far i've implemented the object cache, used FastISel and disabled optimizations.

I can’t help with the rest, but just wanted to mention that totally disabling the IR optimizations is not necessarily a good idea depending on what does the input IR looks like: some of the optimizations can be “lightweight” and simplify the IR / delete dead core, making the compile-time actually faster.

— 
Mehdi


> Jit time is still too slow for my purpose (I do have a lot of code to Jit).
> 
> http://llvm.org/docs/ProgrammersManual.html#threads-and-the-jit <http://llvm.org/docs/ProgrammersManual.html#threads-and-the-jit> states that we can invoke ExecutionEngine::getPointerToFunction() concurrently. This function was replaced by ExecutionEngine::getFunctionAddress(). Is this function also thread safe?
> 
> I want to speed up codegen by invoking parallel calls to getfunctionaddress(). Currently  due the the large amount of code that has to be Jitted, the getfunctionaddress() takes around 40% of my load time.
> 
> What is meant with "he user must still ensure that only one thread accesses IR in a given LLVMContext while another thread might be modifying it" ?
> 
> If I pre-generate all IR, and before execution, invoke the parallel getfunctionaddress() I should be fine right ? Since IR won't be modified anymore.
> 
> Cheers,
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