[compiler-rt] [TSan] Ignore reads if not stored early (PR #74575)

[Dmitry Vyukov via llvm-commits]

dvyukov wrote:

> Should this be a runtime option, so that is can actively be en/disabled?

This looks like a property of region of memory, rather than property of a program. Think of e.g. ML model serving server that does both matmult and lots of generic server logic.

I am also concerned about performance overhead of a global flag check in handling of every memory access.

I am thinking is we could check that all existing accesses access the same byte range as the current read, then skipping the read looks more reasonable. This is still subject to some potential false negatives, which are extremely hard to discover later in real life (much worse than fixable false positives). So I thinking if we could also skip using some pseudo-random check. All of this needs benchmarking on real programs to estimate effects.

https://github.com/llvm/llvm-project/pull/74575