Please Solve the following problem by using ARMv8 2.26 [10] <§2.7> Translate the

Question

Please Solve the following problem by using ARMv8

2.26 [10] <§2.7> Translate the following C code to LEGv8 assembly code. Use a minimum number of instructions. Assume that the values of a, b, i, and j are in registers X0,X1,X10, and X11, respectively. Also, assume that register X2 holds the base address of the array D.

2.27 [5] <§2.7> How many LEGv8 instructions does it take to implement the C code from Exercise 2.26? If the variables a and b are initialized to 10 and 1 and all elements of D are initially 0, what is the total number of LEGv8 instructions executed to complete the loop?

Explanation / Answer

2.26 solution:

given c code

For (i = 0; i < a; i++)
For (j = 0; j < b; j++)
D[4*i] = i + j;

translated legv8 code

Instruction *

SUBI X10,XZR,1

ADD X10, X10, 1

SUB X3, X10, X0 CBZ X3,

exit

SUBI X11, XZR, 1 L2:

ADD X11, X11, 1

SUB X4, X11, X1 CBZ X4, L1

ADD X5, X10, X10 ADD X6, X11, X11

ADD X6, X6, X11

ADD X5, X5, X6 LSL X6, X10, #3

ADD X6, X6, X2 STUR X5, [X6, #0] B L2

exit

L1: Comment * i = -1

L1: i = i + 1

temp1 = i - a

if temp1==0,

exit

j=-1 L2:

j = j+1

temp2 = j - b

if temp2==0,

L1 temp3 = i + i

temp4 = j + j

temp4 = temp4 + j

temp3 = temp3 + temp4 lsl temp4, i, #3

temp4 = temp4 + X2 stur temp3,

[temp4, #0] goto L2

exit

2.27 solution:

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