llvm-project

bc8302d5 - Reapply "[MemCpyOpt] support offset slices for performStackMoveOptzn and processMemCpy" (#180002)

Reapply "[MemCpyOpt] support offset slices for performStackMoveOptzn and processMemCpy" (#180002) In particular, support offset of src, since offset of dest will be a followup change when dest is allowed to be not full-sized with copy. Extracted from https://github.com/llvm/llvm-project/pull/150792 The miscomputation in the original version was due to incorrect checking for ModRef, causing incorrect elimination of temporary buffers: When checking for clobbering stores in performStackMoveOptzn, use SrcPtr instead of SrcAlloca for the MemoryLocation. When SrcPtr is offset into the alloca, but DstPtr is still not offset, we need to check the actual copied region [SrcPtr, SrcPtr+Size) rather than [SrcAlloca, SrcAlloca+Size) for ModRef. This check can become more complex once DstOffset is non-zero or not-full-sized, as indicated in the code comments. Fixes https://github.com/llvm/llvm-project/issues/177185 Reverts https://github.com/llvm/llvm-project/pull/177482 Relands https://github.com/llvm/llvm-project/pull/176436 Co-authored-by: Gabriel Baraldi <baraldigabriel@gmail.com>