[PATCH] D103246: [SelectionDAG] Extend FoldConstantVectorArithmetic to SPLAT_VECTOR

[Fraser Cormack via Phabricator via llvm-commits]

frasercrmck created this revision.
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This patch extends the SelectionDAG's ability to constant-fold vector
arithmetic to include support for SPLAT_VECTOR. This is not only for
scalable-vector types but also for fixed-length vector types, which
helps Hexagon in a couple of cases.

The original RISC-V test case was in fact an infinite DAGCombine loop.
The pattern `and (truncate v1), (truncate v2)` can be combined to
`truncate (and v1, v2)` but the truncate can similarly be combined back
to `truncate (and v1, v2)` (but, crucially, only when one of `v1` or
`v2` is a constant vector).

It wasn't exposed in on fixed-length types because a TRUNCATE of a
constant BUILD_VECTOR was folded into the BUILD_VECTOR itself, whereas
this did not happen for the equivalent (scalable-vector) SPLAT_VECTOR.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D103246

Files:
  llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
  llvm/test/CodeGen/AArch64/sve-expand-div.ll
  llvm/test/CodeGen/Hexagon/isel-memory-vNi1.ll
  llvm/test/CodeGen/RISCV/rvv/constant-folding.ll
  llvm/test/CodeGen/RISCV/rvv/setcc-integer-rv32.ll
  llvm/test/CodeGen/RISCV/rvv/vdivu-sdnode-rv32.ll
  llvm/test/CodeGen/RISCV/rvv/vdivu-sdnode-rv64.ll
  llvm/test/CodeGen/RISCV/rvv/vremu-sdnode-rv32.ll
  llvm/test/CodeGen/RISCV/rvv/vremu-sdnode-rv64.ll

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