LoopVectorize: Emit reductions as log2(vectorsize) shuffles + vector ops...
LoopVectorize: Emit reductions as log2(vectorsize) shuffles + vector ops instead of scalar operations. For example on x86 with SSE4.2 a <8 x i8> add reduction becomes movdqa %xmm0, %xmm1 movhlps %xmm1, %xmm1 ## xmm1 = xmm1[1,1] paddw %xmm0, %xmm1 pshufd $1, %xmm1, %xmm0 ## xmm0 = xmm1[1,0,0,0] paddw %xmm1, %xmm0 phaddw %xmm0, %xmm0 pextrb $0, %xmm0, %edx instead of pextrb $2, %xmm0, %esi pextrb $0, %xmm0, %edx addb %sil, %dl pextrb $4, %xmm0, %esi addb %dl, %sil pextrb $6, %xmm0, %edx addb %sil, %dl pextrb $8, %xmm0, %esi addb %dl, %sil pextrb $10, %xmm0, %edi pextrb $14, %xmm0, %edx addb %sil, %dil pextrb $12, %xmm0, %esi addb %dil, %sil addb %sil, %dl llvm-svn: 170439
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