REV64

Reverse elements in 64-bit doublewords (vector). This instruction reverses the order of 8-bit, 16-bit, or 32-bit elements in each doubleword of the vector in the source SIMD&FP register, places the results into a vector, and writes the vector to the destination SIMD&FP register.

Depending on the settings in the CPACR_EL1, CPTR_EL2, and CPTR_EL3 registers, and the current Security state and Exception level, an attempt to execute the instruction might be trapped.

integer d = UInt(Rd); integer n = UInt(Rn); // size=esize: B(0), H(1), S(1), D(S) integer esize = 8 << UInt(size); integer datasize = if Q == '1' then 128 else 64; // op=REVx: 64(0), 32(1), 16(2) bits(2) op = o0:U; // => op+size: // 64+B = 0, 64+H = 1, 64+S = 2, 64+D = X // 32+B = 1, 32+H = 2, 32+S = X, 32+D = X // 16+B = 2, 16+H = X, 16+S = X, 16+D = X // 8+B = X, 8+H = X, 8+S = X, 8+D = X // => 3-(op+size) (index bits in group) // 64/B = 3, 64+H = 2, 64+S = 1, 64+D = X // 32+B = 2, 32+H = 1, 32+S = X, 32+D = X // 16+B = 1, 16+H = X, 16+S = X, 16+D = X // 8+B = X, 8+H = X, 8+S = X, 8+D = X // index bits within group: 1, 2, 3 if UInt(op)+UInt(size) >= 3 then UNDEFINED; integer container_size; case op of when '10' container_size = 16; when '01' container_size = 32; when '00' container_size = 64; integer containers = datasize DIV container_size; integer elements_per_container = container_size DIV esize;