[PATCH] D48963: [X86][SSE] Combine v16i8 SHL by constants to multiplies

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon created this revision.
RKSimon added reviewers: spatel, craig.topper, efriedma, lebedev.ri, andreadb.

Pre-AVX512 (which can perform a quick extend/shift/truncate), extending to 2 v8i16 for the PMULLW and then truncating  is more performant than relying on the generic PBLENDVB vXi8 shift path and uses a similar amount of mask constant pool data.


Repository:
  rL LLVM

https://reviews.llvm.org/D48963

Files:
  lib/Target/X86/X86ISelLowering.cpp
  test/CodeGen/X86/vector-mul.ll
  test/CodeGen/X86/vector-shift-shl-128.ll
  test/CodeGen/X86/vector-shift-shl-256.ll

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