LUTI4 Lookup table read with 4-bit indices This instruction copies indexed 8-bit or 16-bit elements from the one or two table vectors to the destination vector using packed 4-bit indices from a segment of the source vector. A segment corresponds to a portion of the source vector that is consumed in order to fill the destination vector. The segment is selected by the vector segment index. If PSTATE.DIT is 1: The execution time of this instruction is independent of: The values of the data supplied in any of its registers. The values of the NZCV flags. The response of this instruction to asynchronous exceptions does not vary based on: The values of the data supplied in any of its registers. The values of the NZCV flags. 0 1 0 0 1 1 1 0 0 1 0 0 0 0 1 0 LUTI4 <Vd>.16B, { <Vn>.16B }, <Vm>[<index>] 1 LUTI4 <Vd>.8H, { <Vn1>.8H, <Vn2>.8H }, <Vm>[<index>] if !IsFeatureImplemented(FEAT_LUT) then UNDEFINED; if len<0> == '0' && op == '0' then UNDEFINED; constant integer d = UInt(Rd); constant integer n = UInt(Rn); constant integer m = UInt(Rm); constant integer isize = 4; constant integer esize = 8 << UInt(op); constant integer ntblr = 1 << UInt(op); constant integer part = if op == '0' then UInt(len<1>) else UInt(len); <Vd> Is the name of the SIMD&FP destination register, encoded in the "Rd" field. <Vn> Is the name of the SIMD&FP table register, encoded in the "Rn" field. <Vm> Is the name of the SIMD&FP source register, encoded in the "Rm" field. <index> For the byte variant: is the vector segment index, in the range 0 to 1, encoded in the "len<1>" field. <index> For the halfword variant: is the vector segment index, in the range 0 to 3, encoded in the "len" field. <Vn1> Is the name of the first SIMD&FP table register, encoded in the "Rn" field. <Vn2> Is the name of the second SIMD&FP table register, encoded as "Rn" plus 1 modulo 32. CheckFPAdvSIMDEnabled64(); constant integer elements = 128 DIV esize; constant integer ibase = elements * part; constant bits(128) indices = V[m, 128]; constant bits(128) table1 = V[n+0, 128]; constant bits(128) table2 = if ntblr == 2 then V[(n+1) MOD 32, 128] else Zeros(128); bits(128) result; bits(esize) res; for e = 0 to elements-1 constant integer index = UInt(Elem[indices, ibase + e, isize]); if index < elements then res = Elem[table1, index, esize]; else assert ntblr == 2; res = Elem[table2, index - elements, esize]; Elem[result, e, esize] = res; V[d, 128] = result;