[llvm] [Instrumentation][nsan] Add support for Freeze instruction (PR #100490)

[Alexander Shaposhnikov via llvm-commits]

alexander-shaposhnikov wrote:

P.S. The freeze instructions in the reproducer follow vector instructions (e.g. `insertelement` (see https://llvm.org/docs/LangRef.html#id186 for the cases where it may return `poison`). In the current PR we try to keep the instruction sequences for original/shadow ~close, but generally it's a bit of a "grey" area, maybe I'm missing something here.

https://github.com/llvm/llvm-project/pull/100490