Question

Consider the following high-level recursive procedure: long long int flong long int n, long long int k long long int b b k+2; if (n=-O) b = 8; else b = b + 4 * n + f(n-1 ,k+1); return b + k; Translate the high-level procedure f into ARMv8 assembly language. · Pay particular attention to properly saving and restoring registers across procedure calls; Use the ARMv8 preserved register convention Clearly comment your code; . Assume that the procedure starts at address 0x00400100; . Keep local variable b in X19; Assume n and k are passed in XO and X1 respectively and that the result is returned in X2

Answer 1

Answer:

f(long long, long long):

push rbp

mov rbp, rsp

push rbx

sub rsp, 40

mov QWORD PTR [rbp-40], rdi

mov QWORD PTR [rbp-48], rsi

mov rax, QWORD PTR [rbp-48]

add rax, 2

mov QWORD PTR [rbp-24], rax

cmp QWORD PTR [rbp-40], 0

jne .L2

mov QWORD PTR [rbp-24], 8

jmp .L3

.L2:

mov rax, QWORD PTR [rbp-40]

lea rdx, [0+rax*4]

mov rax, QWORD PTR [rbp-24]

lea rbx, [rdx+rax]

mov rax, QWORD PTR [rbp-48]

lea rdx, [rax+1]

mov rax, QWORD PTR [rbp-40]

sub rax, 1

mov rsi, rdx

mov rdi, rax

call f(long long, long long)

add rax, rbx

mov QWORD PTR [rbp-24], rax

.L3:

mov rdx, QWORD PTR [rbp-24]

mov rax, QWORD PTR [rbp-48]

add rax, rdx

add rsp, 40

pop rbx

pop rbp

ret

Explanation: