[all-commits] [llvm/llvm-project] ba818c: [DAG] replaceStoreOfInsertLoad - don't fold if the...

[Simon Pilgrim via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: ba818c4019c550e1a413e1563a05b241b508defd
      https://github.com/llvm/llvm-project/commit/ba818c4019c550e1a413e1563a05b241b508defd
  Author: Simon Pilgrim <llvm-dev at redking.me.uk>
  Date:   2023-08-21 (Mon, 21 Aug 2023)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    M llvm/test/CodeGen/X86/pr64655.ll

  Log Message:
  -----------
  [DAG] replaceStoreOfInsertLoad - don't fold if the inserted element is implicitly truncated

D152276 wasn't handling the case where the inserted element is implicitly truncated into the vector - resulting in a i1 element (implicitly truncated from i8) overwriting 8 bits instead of 1 bit.

This patch is intended to be merged into 17.x so I've just disallowed any vector element vs inserted element type mismatch - technically we could be more elegant and permit truncated stores (as long as the store is still byte sized), but the use cases for that are so limited I'd prefer to play it safe for now.

Candidate patch for #64655 17.x merge

Differential Revision: https://reviews.llvm.org/D158366