Page 284 - ARM 64 Bit Assembly Language

Non-integral mathematics 273

sine and cosine function can be implemented in ARM assembly using fixed point computa-
tion, and Listing 8.8 shows a main program which prints a table of values and their sine and
cosines.

Listing 8.6 C implementation of sinx and cosx using fixed point calculations.
1 #include <stdio.h>
2 //*************************************************************
3 // Name: sincos.c
4 // Author: Larry Pyeatt
5 // Date: 2/22/2018
6 //*************************************************************
7 // This file provides functions for calculating sine and
8 // cosine using fixed-point arithmetic. It uses the first
9 // nine terms in the Taylor series.
10
11 #define pi 0x3243F6A8 // pi as an S(3,28)
12 #define pi_2 0x1921FB54 // pi/2 as an S(3,28)
13 #define pi_x2 0x6487ED51 // 2*pi as an S(3,28)
14
15 // Define a structure that holds coefficient and shift.
16 struct tabentry{
17 int coeff;
18 int shift;
19 };
20
21 // create a table of coefficients and shift amounts.
22 #define TABSIZE 8
23 static struct tabentry sintab[]={
24 {0xAAAAAAAA, 0}, // term 2
25 {0x44444445, 2}, // term 3
26 {0x97F97F97, 6}, // term 4
27 {0x5C778E96, 10}, // term 5
28 {0x9466EA60, 15}, // term 6
29 {0x5849184F, 20}, // term 7
30 {0x94603063, 26}, // term 8
31 {0x654B1DC1, 32} // term 9
32 };
33
34 //*************************************************************
35 // sinq is used internally by the sine and cosine functions
36 // input: x as an S(1,30) s.t. 0 <= x <= pi/2
37 // returns sin(x) as an S(3,28)
38 static int sinq(int x)
39 {
40 long long sum;
41 long long tmp;
42 long long curpower = x;
43 long long xsq;