[PATCH] D130895: [RISCV] Make VL choosing for a splat-like VMV based on its users

[Craig Topper via Phabricator via llvm-commits]

craig.topper added inline comments.


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Comment at: llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp:2490
+  if (!Node->isMachineOpcode())
+    return SDValue{};
+  const MCInstrDesc &MCID = TII.get(Node->getMachineOpcode());
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Can we use `SDValue()` for consistency with the vast majority of SelectionDAG code


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Comment at: llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp:2548
+  // Check whether VL operands are the same. Return common non-constant VL.
+  SDValue VL = getVLOperand(*Range.begin(), TII);
+  if (all_of(drop_begin(Range),
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I don't think you can assume the using instruction VL is relative to the same SEW/LMUL as the splat. There could have been a bitcast between them that changed the element size. Bitcasts don't generate code. I think insert_subvector/extract_subvector can also change the type without creating any code. Mainly for fractional LMULs.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D130895/new/

https://reviews.llvm.org/D130895