[PATCH] Add a lock() function in PassRegistry to speed up multi-thread synchronization.

[Mehdi Amini]

> On Mar 2, 2015, at 1:32 AM, Erik Eckstein <eeckstein at apple.com> wrote:
> 
>> You are mentioning 5% perf improvement in single-threaded release build, can you tell how to reproduce?
> 
> 
> It is reproducible in following scenario:
> 
> 4 threads on a 3,2 GHz Intel Core i5
> 
> A shared working queue contains ~100 independent llvm modules  (each llvm module has its own LLVMContext).
> Each thread runs following loop:
> 
> while queue is not empty {
> 
>  fetch an llvm module from the working queue
>  create llvm passes
>  call PassRegistry::lock()
>  run the llvm passes
> 
> }

This is the multi-threaded scenario isn’t it?

Thanks,

— 
Mehdi