[all-commits] [llvm/llvm-project] 59d14b: [X86] combineLoad - try to reuse existing constant...

[Simon Pilgrim via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 59d14b623357d9b0514a9575e6d92474694b2f74
      https://github.com/llvm/llvm-project/commit/59d14b623357d9b0514a9575e6d92474694b2f74
  Author: Simon Pilgrim <llvm-dev at redking.me.uk>
  Date:   2023-11-20 (Mon, 20 Nov 2023)

  Changed paths:
    M llvm/lib/Target/X86/X86ISelLowering.cpp
    M llvm/test/CodeGen/X86/broadcast-elm-cross-splat-vec.ll
    M llvm/test/CodeGen/X86/vector-interleaved-load-i16-stride-7.ll
    M llvm/test/CodeGen/X86/vector-interleaved-load-i8-stride-5.ll
    M llvm/test/CodeGen/X86/vector-interleaved-store-i16-stride-3.ll
    M llvm/test/CodeGen/X86/vector-interleaved-store-i16-stride-5.ll
    M llvm/test/CodeGen/X86/vector-interleaved-store-i16-stride-7.ll
    M llvm/test/CodeGen/X86/vector-interleaved-store-i8-stride-5.ll
    M llvm/test/CodeGen/X86/vector-interleaved-store-i8-stride-7.ll

  Log Message:
  -----------
  [X86] combineLoad - try to reuse existing constant pool entries for smaller vector constant data (REAPPLIED)

If we already have a YMM/ZMM constant that a smaller XMM/YMM has matching lower bits, then ensure we reuse the same constant pool entry.

Extends the similar combines we already have to reuse VBROADCAST_LOAD/SUBV_BROADCAST_LOAD constant loads.

This is a mainly a canonicalization, but should make it easier for us to merge constant loads in a future commit (related to both #70947 and better X86FixupVectorConstantsPass usage for #71078).

Reapplied with fix to ensure we don't 'flip-flop' between multiple matching constants - only perform the fold if the new constant pool entry is larger than the current entry.