[PATCH] D102767: [RISCV] Ensure small mask BUILD_VECTORs aren't expanded

[Fraser Cormack via Phabricator via llvm-commits]

frasercrmck created this revision.
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The default expansion for BUILD_VECTORs -- save for going through
shuffles -- is to go through the stack. This method only works when the
type is at least byte-sized, so for v2i1 and v4i1 we would crash.

This patch ensures that small mask-type BUILD_VECTORs are always handled
without crashing. We lower to a SETCC of the equivalent i8 type.

This also exposes some pre-existing issues where the lowering when
optimizing for size results in larger code than without. Those will be
tackled in future patches.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D102767

Files:
  llvm/lib/Target/RISCV/RISCVISelLowering.cpp
  llvm/test/CodeGen/RISCV/rvv/fixed-vectors-mask-buildvec.ll

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