The architecture of the arm 7 is quite unique & is optimized for speed and area. To talk about its bus structure which is patented by Arm called the Amba bus is completely designed by the company itself. Tough its a difficult task to code and design for the entire ARM here is a small module of ARM called the Barrel Shifter as circled in the figure below. The task of the Barrel sifter is to do simple shift & roate operation on the second operands . Shifting a bit to right by one position means the same as to dive the number bu the base 2 . Conversely left shift by one position implies multiplying by 2. So this Shifter reduces the task of the ALU in total. Here is the Verilog code for the Barrel Shifter
module barrel_shifter(d,out,q,c); // Main
module of 8-Bit Barrel shifter
input [7:0]d;
output [7:0]out,q;
input[2:0]c;
mux m1(q[0],d,c);
mux m2(q[1],{d[0],d[7:1]},c);
mux m3(q[2],{d[1:0],d[7:2]},c);
mux m4(q[3],{d[2:0],d[7:3]},c);
mux m5(q[4],{d[3:0],d[7:4]},c);
mux m6(q[5],{d[4:0],d[7:5]},c);
mux m7(q[6],{d[5:0],d[7:6]},c);
mux m8(q[7],{d[6:0],d[7:7]},c);
assign out=q;
endmodule
module mux(y,d,c); // Sub module of 8-Bit
barrel shifter
input[7:0]d;
output y;
reg y;
input [2:0]c;
always @ (c)
begin
if (c==3'b000)
y = d[0];
else if (c==3'b001)
y = d[1];
else if
(c==3'b010)
y = d[2];
else if
(c==3'b011)
y = d[3];
else if
(c==3'b100)
y = d[4];
else if
(c==3'b101)
y = d[5];
else if
(c==3'b110)
y = d[6];
else if
(c==3'b111)
y = d[7];
end
endmodule
