Some optimization need to be undone with
sanitizers by #100773.

Pull Request: #100844

And extract `suppressSpeculativeLoadForSanitizers`.

Pull Request: #100794

In #100773 we will go conservative for sanitizers,
so it's better to pinpoint location consciously.

Pull Request: #100789

Even if memory is valid from `llvm` point of view,
e.g. local alloca, sanitizers have API for user
specific memory annotations.

This annotations can be used to track size of the
local object, e.g. inline vector like may prevent
accessed beyond the current vector size.

So valid programs should not access those parts of
alloca before checking preconditions.

Fixes #100639.

Pull Request: #100773

Created using spr 1.3.4