[all-commits] [llvm/llvm-project] 528e6f: [AArch64] Avoid creating a new generic constant in...

[Benjamin Maxwell via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 528e6f9a030c4b3bf760807c22c98f17fb582f5f
      https://github.com/llvm/llvm-project/commit/528e6f9a030c4b3bf760807c22c98f17fb582f5f
  Author: Benjamin Maxwell <benjamin.maxwell at arm.com>
  Date:   2026-06-12 (Fri, 12 Jun 2026)

  Changed paths:
    M llvm/lib/Target/AArch64/AArch64ISelDAGToDAG.cpp
    M llvm/test/CodeGen/AArch64/sme-intrinsics-mova-insert.ll

  Log Message:
  -----------
  [AArch64] Avoid creating a new generic constant in SelectSMETileSlice (#203344)

This was creating a new ISD::Constant node during instruction selection,
which may also need lowering (e.g., to a `mov gpr, wzr`). The issue with
this is the new constant node will not end up on the instruction
selection worklist, as the complex pattern executes after the worklist
has been prepared. This means the constant will lower directly to an
immediate. This issue was hidden in some cases by `getConstant()`
returning a pre-existing `ISD::Constant` node already within the
instruction selection worklist.

This patch works around this by directly emitting a `CopyFromReg WZR`
within SelectSMETileSlice, which does not need further instruction
selection.

Fixes #203295



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