[all-commits] [llvm/llvm-project] b107db: [X86] Reuse X86ISD::SUBV_BROADCAST_LOAD for subvec...

[Simon Pilgrim via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: b107dbb46769ace9ee6b2bf116e8168fc4fb56eb
      https://github.com/llvm/llvm-project/commit/b107dbb46769ace9ee6b2bf116e8168fc4fb56eb
  Author: Simon Pilgrim <llvm-dev at redking.me.uk>
  Date:   2025-06-03 (Tue, 03 Jun 2025)

  Changed paths:
    M llvm/lib/Target/X86/X86ISelLowering.cpp
    M llvm/test/CodeGen/X86/any_extend_vector_inreg_of_broadcast_from_memory.ll
    M llvm/test/CodeGen/X86/oddshuffles.ll
    M llvm/test/CodeGen/X86/vector-interleave.ll
    M llvm/test/CodeGen/X86/vector-interleaved-store-i32-stride-3.ll
    M llvm/test/CodeGen/X86/vector-interleaved-store-i32-stride-5.ll
    M llvm/test/CodeGen/X86/vector-interleaved-store-i32-stride-6.ll
    M llvm/test/CodeGen/X86/vector-interleaved-store-i32-stride-7.ll
    M llvm/test/CodeGen/X86/vector-interleaved-store-i64-stride-2.ll
    M llvm/test/CodeGen/X86/vector-interleaved-store-i8-stride-6.ll
    M llvm/test/CodeGen/X86/vector-interleaved-store-i8-stride-7.ll
    M llvm/test/CodeGen/X86/x86-interleaved-access.ll
    M llvm/test/CodeGen/X86/zero_extend_vector_inreg_of_broadcast_from_memory.ll

  Log Message:
  -----------
  [X86] Reuse X86ISD::SUBV_BROADCAST_LOAD for subvector loads across chains (#142381)

Improve handling of folding a (small) vector load that is also loaded as a X86ISD::SUBV_BROADCAST_LOAD node to just (freely) extract the bottom subvector - similar to #139575 we should be checking the SUBV_BROADCAST_LOAD has uses of the loaded value, and not that the out chain isn't empty to ensure its actually used, we must also call makeEquivalentMemoryOrdering to ensure the out chains are correctly merged to handle any aliasing with later load/stores.

This PR is a little messy as it has 2 other inter-dependent changes to avoid regressions - now that we're properly merging subvector loads, we can drop the oneuse limit on the "vperm2x128(load(p),undef) -> broadcast128(p+offset)" and "insert_subvector(load256(p),load128(p),0) -> broadcast128(p)" folds.



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