[PATCH] D99682: [SelectionDAG] Teach SelectionDAG::FoldConstantArithmetic to handle SPLAT_VECTOR

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.
craig.topper added reviewers: RKSimon, spatel, frasercrmck, sdesmalen.
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This allows FoldConstantArithmetic to handle SPLAT_VECTOR in
addition to BUILD_VECTOR. This allows it to support scalable
vectors. I'm also allowing fixed length SPLAT_VECTOR which is
used by some targets, but I'm not familiar enough to write tests
for those targets.

I had to block this function from running on CONCAT_VECTORS to
avoid calling getNode for a CONCAT_VECTORS of 2 scalars.
This can happen because the 2 operand getNode calls this
function for any opcode. Previously we were protected because
CONCAT_VECTORs of BUILD_VECTOR is folded to a larger BUILD_VECTOR
before that call. But it's not always possible to fold a CONCAT_VECTORS
of SPLAT_VECTORs, and we don't even try.

This fixes PR49781 where DAG combine thought constant folding
should be possible, but FoldConstantArithmetic couldn't do it.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D99682

Files:
  llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
  llvm/test/CodeGen/AArch64/pr49781.ll
  llvm/test/CodeGen/RISCV/rvv/vadd-sdnode-rv32.ll
  llvm/test/CodeGen/RISCV/rvv/vadd-sdnode-rv64.ll
  llvm/test/CodeGen/RISCV/rvv/vsub-sdnode-rv32.ll
  llvm/test/CodeGen/RISCV/rvv/vsub-sdnode-rv64.ll

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