Fix llvm::BumpPtrAllocatorImpl::Reset()

[Hans Wennborg]

On Mon, May 11, 2015 at 10:37 AM, Kal <b17c0de at gmail.com> wrote:
> BumpPtrAllocator's Reset doesn't act as documented if Slaps.size() == 0 but
> CustomSizedSlabs.size() != 0.

Nice find!

>      DeallocateCustomSizedSlabs();
>      CustomSizedSlabs.clear();

How about just moving these to the top of the function, before the "if
(Slabs.empty()" check?

Could we also add a test in unittests/Support/AllocatorTest.cpp?

Cheers,
Hans