[all-commits] [llvm/llvm-project] d2057a: [X86][AVX] Lower v16i8/v8i16 binary shuffles using...

[Simon Pilgrim via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: d2057a8015e97b5e212f3963923dbdcce9356a8f
      https://github.com/llvm/llvm-project/commit/d2057a8015e97b5e212f3963923dbdcce9356a8f
  Author: Simon Pilgrim <llvm-dev at redking.me.uk>
  Date:   2020-08-18 (Tue, 18 Aug 2020)

  Changed paths:
    M llvm/lib/Target/X86/X86ISelLowering.cpp
    M llvm/test/CodeGen/X86/shuffle-vs-trunc-256.ll
    M llvm/test/CodeGen/X86/shuffle-vs-trunc-512.ll
    M llvm/test/CodeGen/X86/vector-trunc.ll
    M llvm/test/CodeGen/X86/x86-interleaved-access.ll

  Log Message:
  -----------
  [X86][AVX] Lower v16i8/v8i16 binary shuffles using VTRUNC/TRUNCATE

This patch adds lowerShuffleWithVTRUNC to handle basic binary shuffles that can be lowered either as a pure ISD::TRUNCATE or a X86ISD::VTRUNC (with undef/zero values in the remaining upper elements).

We concat the binary sources together into a single 256-bit source vector. To avoid regressions we perform this after we've tried to lower with PACKS/PACKUS which typically does a cleaner job than a concat.

For non-AVX512VL cases we have to canonicalize VTRUNC cases to use a 512-bit source vectors (inserting undefs/zeros in the upper elements as necessary), truncate and then (possibly) extract the 128-bit result.

This should address the last regressions in D66004

Differential Revision: https://reviews.llvm.org/D86093