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749e8fee34
This patch teaches the backend how to efficiently lower logical and arithmetic packed shifts on both SSE and AVX/AVX2 machines. When possible, instead of scalarizing a vector shift, the backend should try to expand the shift into a sequence of two packed shifts by immedate count followed by a MOVSS/MOVSD. Example (v4i32 (srl A, (build_vector < X, Y, Y, Y>))) Can be rewritten as: (v4i32 (MOVSS (srl A, <Y,Y,Y,Y>), (srl A, <X,X,X,X>))) [with X and Y ConstantInt] The advantage is that the two new shifts from the example would be lowered into X86ISD::VSRLI nodes. This is always cheaper than scalarizing the vector into four scalar shifts plus four pairs of vector insert/extract. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206316 91177308-0d34-0410-b5e6-96231b3b80d8
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