[PATCH] D117377: [RISCV] Legalize fixed length (insert_subvector undef, X, 0) to a scalable insert.

[Craig Topper via Phabricator via llvm-commits]

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We were considering this legal, but later the undef would become an all
zeros vector. This would cause us to need to re-legalize the insert later
into a vslideup with zero vector.

This patch catches the case and directly legalizes it to a scalable
insert.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D117377

Files:
  llvm/lib/Target/RISCV/RISCVISelLowering.cpp
  llvm/test/CodeGen/RISCV/rvv/fixed-vectors-extload-truncstore.ll
  llvm/test/CodeGen/RISCV/rvv/fixed-vectors-fp-conv.ll
  llvm/test/CodeGen/RISCV/rvv/fixed-vectors-fp2i.ll
  llvm/test/CodeGen/RISCV/rvv/fixed-vectors-i2fp.ll
  llvm/test/CodeGen/RISCV/rvv/fixed-vectors-insert-subvector.ll
  llvm/test/CodeGen/RISCV/rvv/fixed-vectors-insert.ll
  llvm/test/CodeGen/RISCV/rvv/fixed-vectors-int-exttrunc.ll
  llvm/test/CodeGen/RISCV/rvv/fixed-vectors-masked-gather.ll

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