[llvm] [AArch64] Fix post-inc stores of floating-point conversions (PR #151372)

[Paul Walker via llvm-commits]

paulwalker-arm wrote:

You cannot fix it like this because the patterns are not really missing.  It is a design decision for element types smaller than i32 to use i32 as their container type.  This is common across element extracts, inserts, splats and likely elsewhere.

It might be worth going the isel route you tried before but either restricting the pattern to the zero index case or implement a way to ensure the index is scaled appropriately for the target instruction.

https://github.com/llvm/llvm-project/pull/151372