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

Chris Lattner clattner at apple.com
Wed Sep 18 21:56:29 PDT 2013


On Sep 18, 2013, at 9:03 PM, Andrew Trick <atrick at apple.com> wrote:
>>> 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.

Ok, the juxtaposition of the two discussions made this confusing.

> 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.

Ok.  In that case, I'd still rather you solve this a different way.  How about hoisting these options up to the opt tool (the only one that they make sense?  or do they also belong in llc)?

-Chris
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