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

[Erik Eckstein]

yes. When omitting the call to PassRegistry::lock() I experience the 5% increased compile time.

> On 02 Mar 2015, at 10:33, Mehdi Amini <mehdi.amini at apple.com> wrote:
> 
> 
>> 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
>