Modify BoundsSan to improve debuggability (#65972)

BoundsSanitizer is a mitigation that is part of UBSAN. It can be enabled
in "trap" mode to crash on OOB array accesses.

BoundsSan has zero false positives meaning every crash is a OOB array
access, unfortunately optimizations cause these crashes in production
builds to be a bit useless because we only know which function is
crashing but not which line of code.

Godbolt example of the optimization:

This Diff
I wanted to provide a way to know exactly which LOC is responsible for
the crash. What we do here is use the size of the basic block as an
iterator to an immediate value for the ubsan trap.

Previous discussion:

GitOrigin-RevId: 832b3b2462c1bb8e2b41ef96fe0ffd3791df0e12
3 files changed