Crystals-Dilithium on ARMv8

Algorithm 4

Butterfly method on ARM processor.

(1)	Input:in1 (x8), in2 (x9)             ⊳ 4 (in1:2, int2:2) coefficient on ARM
(2)	Output: out1, out2             ⊳ 4 (out1:2, out2:2) coefficient on ARM
(3)	// Butterfly 1
(4)	⊳  = in2 ( : 1 coefficient ) zetas
(5)	⊳
(6)	⊳
(7)	⊳
(8)	⊳ Addition: in1
(9)	⊳ Subtraction: in1
(10)	// Masking
(11)	⊳ (in1: 1 coefficient ) =
(12)	⊳ (in2: 1 coefficient ) =
(13)	// Butterfly 2
(14)	⊳  = in2 ( : 1 coefficient ) zetas
(15)	⊳
(16)	⊳
(17)	⊳
(18)	⊳ Addition: in1
(19)	⊳ Subtraction: in1
(20)	// Concatenation
(21)	⊳
(22)	⊳