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Preview File Edit View Go Tools Window Help Dygsl Design and Comguter Achesture At xtion ty Sara arh (rago 30 of 12- Exercise 6.20 Consider the following high-level code snippet. Assume that the base addresses of array1 and array2 are held in R1 and R2 and that array2 s initialized before it is used. inti: int array11100] int array20100]: for (i0: 1100: i-i+1) (a) Write the code snippet in ARM assembly without using pre- or post-indexing (b) Write the code snippet in ARM assembly with pre- or post-indexing and a (c) Compare the difference in code density (i.e., number of instructions) between array1[i] = array2[i]; or a scaled register. Use as few instructions as possible (given the constraints), scaled register available. Use as few instructions as possible. (a) and (b). Discuss any advantages or disadvantages. 20 4

Explanation / Answer

@R1 contains initial address of array1

@R2 contains initial address of array2, Array 2 is already initialized with values

@For count and offset value in Solution with pre or post indexing--> R3

@For Count in Solution without pre or post indexing--> R3

@Q.1.

@Without pre or post indexing

MOV R3, #0;

.loop

ADD R2, R2, #4

LDR R4, [R2];

ADD R1, R1, #4

STR R4, [R1];

ADD R3, R3, #4;

CMP R3, #400;

BL loop;

@Q.2.

@With pre or post indexing

MOV R3, #0;

.loop

LDR R4, [R2, R3];

STR R4, [R1, R3];

ADD R3, R3, #4;

CMP R3, #400;

BL loop;

Total number of lines in Q.1. -> 8

Total number of lines in Q.2 -> 6

Difference of lines: 2 (Lesser in solution with pre or post indexing)

Advantages of pre or post indexing: Number of lines of code reduces

Disadvantages of pre or post indexing: Internally the process becomes more complicated. Moreover assembler has to convert pre or post indexing into normal internally which takes some more computational cycles of CPU.

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