[PATCH] D45736: [SimplifyLibcalls] Replace locked IO with unlocked IO

[Dávid Bolvanský via Phabricator via llvm-commits]

xbolva00 added a comment.

In https://reviews.llvm.org/D45736#1070249, @lebedev.ri wrote:

> > to gain better speed
>
> Out of curiosity, what are the motivational cases, benchmarks?
>
> > if we know, that there is no fork or pthread_create calls in the current module.
>
> I'm not sure this is sufficient.
>  I'll be super surprised if this could be done outside of a LTO build with no dynamic linking.


Motivation? I tried to "getchar and putchar" 2 MB file and using unlocked variants I got time difference around 0,1 s.

I believe there are more reasons to apply such optimizations, if possible. If we can have faster IO code, why not?

Why not sufficient?
Can you explain it more? Static function can be called only from module and if there is no fork or pthread_create, why we cant say that all static functions are not called from multiple threads/processes?


Repository:
  rL LLVM

https://reviews.llvm.org/D45736