[PATCH] D17763: AVX512: Remove VSHRI kmask patterns from TD file

[Igor Breger via llvm-commits]

igorb created this revision.
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AVX512:  Remove VSHRI kmask patterns from TD file. It is incorrect to use kshiftw to implement VSHRI v4i1 , bits 15-4 is undef so the upper bits of v4i1 may not be zeroed. v4i1  should be zero_extend to v16i1 ( or any natively supported vector).
The only use of removed patterns i identified  was in Insert1BitVector() , update it implementation to use natively supported shift .
Fix 2 additional bugs in Insert1BitVector implementation
    IdxVal == 0 case  -- SubVec should be zero extend ,  
    IdxVal + SubVecNumElems == NumElems  - Vec was used instead SubVec
 I failed to create test case for IdxVal == 0 ,  may be you can suggest one.

Most probably in many cases insert kmask sub-vector into zero-vector don't require any instructions ( shiftl + shiftr ) to zero upper part - it already zero.
I think only exstruct_subvec (low part)  in current implementation doesn't zero upper part, but i am not sure. In any case i believe this performance improvement ( if it is possible ) should be implemented as separate patch.   
Thanks.

Repository:
  rL LLVM

http://reviews.llvm.org/D17763

Files:
  lib/Target/X86/X86ISelLowering.cpp
  lib/Target/X86/X86InstrAVX512.td
  test/CodeGen/X86/avx512-skx-insert-subvec.ll
  test/CodeGen/X86/masked_gather_scatter.ll
  test/CodeGen/X86/masked_memop.ll

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