[all-commits] [llvm/llvm-project] f99580: [DAGCombine] Fix bug in load scalarization

[Fraser Cormack via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: f99580c1e57885c8337a7deb08459095f4c16422
      https://github.com/llvm/llvm-project/commit/f99580c1e57885c8337a7deb08459095f4c16422
  Author: Fraser Cormack <fraser at codeplay.com>
  Date:   2020-11-04 (Wed, 04 Nov 2020)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    M llvm/test/CodeGen/AMDGPU/extract-load-i1.ll

  Log Message:
  -----------
  [DAGCombine] Fix bug in load scalarization

Summary:
For vector element types which are not byte-sized, we would generate
incorrect scalar offsets and produce incorrect codegen.

This optimization could potentially be supported in the future, e.g. by
loading in bytes, then shifting and masking out the remaining bits of
the vector element. However, without an upstream target to test against
it's best to avoid the bad codegen in the simplest possible way.

Related to this bug:

  https://bugs.llvm.org/show_bug.cgi?id=27600

Reviewed by: foad

Differential Revision: https://reviews.llvm.org/D78568