[llvm-branch-commits] [llvm] [RISCV] Add initial support of memcmp expansion (PR #107548)

[Philip Reames via llvm-branch-commits]

preames wrote:

At a macro level, it looks like ExpandMemCmp is making some problematic choices around unaligned loads and stores.  As I commented before, ExpandMemCmp appears to be blindly emitting unaligned accesses (counted as one against budget) without accounting for the fact that such loads are going to be scalarized again (i.e. resulting in N x loads, where N is the type size).  I think we need to fix this.  In particular, the discussion around Zbb and Zbkb in this review seem to mostly come from cases where unaligned load.store are being expanded implicitly,

I don't believe this change should move forward until the underlying issue in ExpandMemCmp has been addressed.

https://github.com/llvm/llvm-project/pull/107548