PT800

.text
.type fun, @function
.global fun

#a - rdi
#b - rsi
#pcs - rdx
#count - rcx
fun:
    PUSH %rbx
    PUSH %rdx
    XOR %rbx, %rbx
    XOR %r9, %r9
    XOR %r10, %r10
    XOR %rax, %rax
    MOV $1, %rbx # (i+1)
    MOV $0, %r9 # how Many 1
    CMP $1, %rsi # which bit
    JE sum
    CMP $2, %rsi
    JE mul
    JMP nothing
loop:
    PUSH %rdi
    AND $1, %rdi
    JMP count
afterCount:
    CMP $0, %rsi
    JE afterOp
    PUSH %rax
    MOV %rdi, %rax
    XOR %rdx, %rdx
    MUL %rbx
    MOV %rax, %r8
    POP %rax
    CMP $1, %rsi
    JE sumOp
    CMP $2, %rsi
    JE mulOp
afterOp:
    POP %rdi
    INC %rbx
    SHR $1, %rdi
    CMP $64, %rbx
    JNE loop
afterLoop:
    POP %rdx
    POP %rbx
    MOVL %r9d, (%rcx)
    MOVL %r10d, (%rdx)
    RET

sum:
    MOV $0, %rax #starting value
    JMP loop

mul:
    MOV $1, %rax #starting value
    JMP loop

nothing:
    MOV $0, %rax
    JMP loop

sumOp:
    ADD %r8, %rax #xi in rax
    JMP afterOp

mulOp:
    CMP $0, %r8
    JE afterOp
    XOR %rdx, %rdx
    MUL %r8 #xi in rax
    JMP afterOp

count:
    CMP $0, %rdi
    JE afterCount
    INC %r9
    MOV %rbx, %r10
    JMP afterCount