Exponential Series in ARM Cortex M4 Assembly

e^x = 1 + (x/1!)+((x^2)/2!)+((x^3)/3!)+......

The below ARM assembly code will be used to find the value of e^x  based on the above definition for any value of x using the Floating point unit of ARM Cortex-M4 Processor.

Code:

 PRESERVE8
        THUMB
        AREA    |.text|,CODE,READONLY
        EXPORT __main
        ENTRY
__main    FUNCTION
        MOV R0,#10;Holding the Number of Terms in Series 'n'
        MOV R1,#1;Counting Variable 'i'
        VLDR.F32 S0,=1;Holding the sum of series elements 's'
        VLDR.F32 S1,=1;Temp Variable to hold the intermediate series elements 't'
        VLDR.F32 S2,=3;Holding 'x' Value
LOOP1    CMP R1,R0;Compare 'i' and 'n' 
        BLE LOOP;if i < n goto LOOP
        B stop;else goto stop
LOOP      VMUL.F32 S1,S1,S2; t = t*x
        VMOV.F32 S5,R1;Moving the bit stream in R1('i') to S5(floating point register)
        VCVT.F32.U32 S5, S5;Converting the bitstream into unsigned fp Number 32 bit
        VDIV.F32 S1,S1,S5;Divide t by 'i' and store it back in 't'
        VADD.F32 S0,S0,S1;Finally add 's' to 't' and store it in 's'
        ADD R1,R1,#1;Increment the counter variable 'i'
        B LOOP1;Again goto comparision
stop    B stop
        ENDFUNC
        END