[llvm-branch-commits] [InstCombine][asan] Don't speculate loads before `select ptr` (PR #100773)

[Vitaly Buka via llvm-branch-commits]

https://github.com/vitalybuka created https://github.com/llvm/llvm-project/pull/100773

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.