[llvm] r190974 - Encapsulate PassManager debug flags to avoid static init and cxa_exit.

[Andrew Trick]

On Sep 18, 2013, at 5:51 PM, Chris Lattner <clattner at apple.com> wrote:

> On Sep 18, 2013, at 4:54 PM, Chandler Carruth <chandlerc at google.com> wrote:
>> Andy, this really feels like a hack, and a bad hack at that.
>> 
>> Where is the requirement for the core library to have no static initializers coming from? What is the support plan here? What problem are you actually trying to fix?
>> 
>> Just for clarity, I have read the llvmdev thread, and I understand the *general* goal, but this patch itself doesn't seem like a clean incremental step toward that goal, doesn't reference any of the constructs under discussion in that thread.
> 
> I totally agree.  This seems like a hack that would be resolved by making cl::opt's get compiled out in non-assert builds, which you already described.

I'll coalesce my responses to Chris and Chandler here:

This fixes a particularly horrible bug where LLVM crashes during PassRegistry::removeRegistrationListener when a multi-threaded process exits while compiler threads are running.

This patch was meant to
(a) fix a bug
(b) handle one of the handful of special cl::opt cases that won't be covered by the general approach I outlined in the RFC.

The proposal talked about handling the majority of options incrementally without enormous churn. This case is an exception that I wanted to get out of the way first.

This case is special because we want the PassManager options to be availabe in non-assert builds, or so I thought. These are clearly "tool" options that need to be exported to a number of LLVM-based tools.

What about this patch is a hack, other than being a special case? Having tools call initializePassManager()? I can't think of any long-term solution where that can be avoided.

I thought this fix would be general all-around goodness, but I'd be happy to revert this patch and wrap the whole thing in #ifndef LLVM_NO_STATICINIT if Chris and Chandler prefer.

-Andy

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