[PATCH] Remove support for enabling / disabling multi-threading at runtime.

[David Blaikie]

On Mon, Jun 9, 2014 at 4:07 PM, Reid Kleckner <rnk at google.com> wrote:
> Nice!  I want to get a little more support for this direction before committing.  Let me try to rope in some appropriate people.  In the meantime, I had some comments.
>
> ================
> Comment at: include/llvm-c/Core.h:2856
> @@ -2855,3 @@
> -    @see llvm::llvm_start_multithreaded */
> -LLVMBool LLVMStartMultithreaded(void);
> -
> ----------------
> The C API is one of the few places where we have hard ABI stability guarantees.  These should become no-op stubs.
>
> ================
> Comment at: include/llvm/Support/Threading.h:38
> @@ +37,3 @@
> +  /// llvm_get_global_lock() - returns the llvm global lock object.
> +  llvm::recursive_mutex& llvm_get_global_lock();
> +
> ----------------
> nit: LLVM is in the 'star-on-the-right' camp.

clang-format can handle this sort of thing for you. There are scripts
to run it over your current diff or git revision, etc.

>
> ================
> Comment at: lib/Support/Threading.cpp:28-32
> @@ -27,13 +27,7 @@
> +bool llvm::llvm_is_multithreaded() {
>  #if LLVM_ENABLE_THREADS != 0
> -  assert(!multithreaded_mode && "Already multithreaded!");
> -  multithreaded_mode = true;
> -  global_lock = new sys::Mutex(true);
> -
> -  // We fence here to ensure that all initialization is complete BEFORE we
> -  // return from llvm_start_multithreaded().
> -  sys::MemoryFence();
>    return true;
>  #else
>    return false;
>  #endif
>  }
> ----------------
> return bool(LLVM_ENABLE_THREADS) ?
>
> http://reviews.llvm.org/D4076
>
>