[llvm] [AMDGPU] Limit promoting allocas that have users with dynamic index above a threshold on number of elements (PR #170327)

[via llvm-commits]

ruiling wrote:

Have you checked whether in the original case, the gep result pointer is aligned to 16 for the <16 x i8> access? If aligned, we can still bitcast the <128 x i8> to <8 x i128> and do insert/extract of i128 without expansion. For the unaligned case, abort promotion maybe a reasonable comprise.

https://github.com/llvm/llvm-project/pull/170327