[compiler-rt] [msan] Dynamically grow kNumStackOriginDescrs (PR #92826)

[Evgenii Stepanov via llvm-commits]

eugenis wrote:

> > We could go with an array of pointers to exponentially increasing allocations (i.e. same as your case, but never deallocate, instead just allocate more and consider the container a logical concatenation of multiple buffers).
> 
> This is still tricky to implement in a thread-safe, lock-free manner, because there are two arrays to be grown (StackOriginDescrs, StackOriginPC).

I think it will actually work pretty well.

If subarrays are power of 2 sized (1, 2, 4, 8, 16, ...), then the subarray for index i is basically log2(i+1). Both arrays can be handled independently; once the index is acquired, the subarray pointer is initialized with a double-checked locking pattern.


https://github.com/llvm/llvm-project/pull/92826