[PATCH] D68527: [WebAssembly] v8x16.swizzle and rewrite BUILD_VECTOR lowering

[Thomas Lively via Phabricator via llvm-commits]

tlively created this revision.
tlively added reviewers: aheejin, dschuff.
Herald added subscribers: llvm-commits, sunfish, hiraditya, jgravelle-google, sbc100.
Herald added a project: LLVM.

Adds the new v8x16.swizzle SIMD instruction as specified at
https://github.com/WebAssembly/simd/blob/master/proposals/simd/SIMD.md#swizzling-using-variable-indices.
In addition to adding swizzles as a candidate lowering in
LowerBUILD_VECTOR, also rewrites and simplifies the lowering to
minimize the number of replace_lanes necessary rather than trying to
minimize code size. This leads to more uses of v128.const instead of
splats, which is expected to increase performance.

The new code will be easier to tune once V8 implements all the vector
construction operations, and it will also be easier to add new
candidate instructions in the future if necessary.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D68527

Files:
  llvm/lib/Target/WebAssembly/WebAssemblyISD.def
  llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
  llvm/lib/Target/WebAssembly/WebAssemblyInstrSIMD.td
  llvm/test/CodeGen/WebAssembly/simd-build-vector.ll
  llvm/test/MC/WebAssembly/simd-encodings.s

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