[sanitizer] Cache SizeClassForTransferBatch in the 32-bit local cache

Summary:
`SizeClassForTransferBatch` is expensive and is called for every `CreateBatch`
and `DestroyBatch`. Caching it means `kNumClasses` calls in `InitCache`
instead. This should be a performance gain if more than `kNumClasses / 2`
batches are created and destroyed during the lifetime of the local cache.

I have chosen to fully remove the function and putting the code in `InitCache`,
which is a debatable choice.

In single threaded benchmarks leveraging primary backed allocations, this turns
out to be a sizeable gain in performances (greater than 5%). In multithreaded
benchmarks leveraging everything, it is less significant but still an
improvement (about 1%).

Reviewers: kcc, dvyukov, alekseyshl

Reviewed By: dvyukov

Subscribers: kubamracek, llvm-commits

Differential Revision: https://reviews.llvm.org/D32365

llvm-svn: 301184

0 files changed, 0 insertions, 0 deletions