Write an ARM Assembly code subroutine to approximate the square root of an argum

Question

Write an ARM Assembly code subroutine to approximate the square root of an argument using the bisection method. Your code must approximate the square root of an integer between 0 and 2^(31) -1. Using integer maths is sufficient (no floating point or fractions are required); your code will return the truncated (integer portion) of the square root.

Base your software on the following pseudocode:

Explanation / Answer

#include "stdint.h" /** @cond DO_NOT_INCLUDE_WITH_DOXYGEN */ #include "string.h" /** @endcond */ /** * @brief 5863 Write a brief description of the function here * * Detailed description of the function after one line gap * * @note You can also add a note this way * * @param[in] * You can also start writing on a new line. * And continue on the next line. This is how you describe an input parameter * * @return * This is how you describe the return value * */ __asm int my_sqrt(int x){ PUSH {R4-R7} ; LDR R1, =0 ;done = 0 LDR R7, =0 ;a=0 LDR R2, =0xFFFF ;b=2^31 -1 LDR R3, =0xFFFFFFFF ;c=-1 DO_WHILE MOV R4, R3 ;c_old = c HERE R4 is being considered as c_old ADDS R5, R2, R7 ;R5 = a+b ASRS R5, R5, #1 ;R5 >> 1 which is nothing but (a+b/2) MOV R3, R5 ;c = (a+b)/2 MOV R6,R3 MULS R6, R3, R6 ;R6 = c*c CMP R6,R0 ;compare c*c and x (input integer) BEQ DONE BLT LESS_THAN MOV R2, R3 ;setting b=c B FINAL LESS_THAN MOV R7,R3 ;setting a=c B FINAL DONE LDR R1, =1 ;setting done = 1 B FINAL ;return C FINAL CMP R1, #1 ;compare done = 1 BEQ END BNE COMPARE COMPARE CMP R4, R3 ;compare c_old and c BNE DO_WHILE BEQ END END MOV R0, R3 POP {R4-R7} BX LR } void printCpuCycles(double readValue, int number, int sqrt) { double cpuCycles = 0; cpuCycles = (readValue * 48000000); // read value * frequqncy of clock pc.printf("Sqrt of %d using bisection menthod is %d ", number, sqrt); pc.printf("Total time of execution for sqrt of(%d)is %f ", number, readValue); pc.printf("Number of CPU cycles for sqrt(%d): %d ", number, (int)cpuCycles); } MAIN function *----------------------------------------------------------------------------*/ /** * @brief Main function * * Detailed description of the main */ int main(void){ volatile int r, j=0; double timer_read = 0.0; double sum = 0; pc.printf("/*----------------------------------------------------------------------------*/ "); pc.printf("Frequency of KL25Z (ARM Cortex M0+): 48 MHZ "); timer.start(); timer.reset(); r = my_sqrt(2); // should be 1 timer_read = timer.read(); printCpuCycles(timer_read, 2, r); sum = sum + timer_read; timer.reset(); r = my_sqrt(4); // should be 2 timer_read = timer.read(); printCpuCycles(timer_read, 4, r); sum = sum + timer_read; timer.reset(); r = my_sqrt(22); // should be 4 timer_read = timer.read(); printCpuCycles(timer_read, 22, r); sum = sum + timer_read; timer.reset(); r = my_sqrt(121); // should be 11 timer_read = timer.read(); printCpuCycles(timer_read, 121, r); sum = sum + timer_read; pc.printf("Total time of operation: %f ", sum); sum = sum * 48000000; pc.printf("CPU cycles: %d ", (int)(sum)); pc.printf("/*----------------------------------------------------------------------------*/ "); }

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