;long rsum(long *start, long count)
; start in %rdi, count in %rsi
rsum:
xorq %rax, %rax
andq %rsi, %rsi
jle .L2
pushq %rbx
mrmovq (%rdi), %rbx
irmovq $1, %r8
irmovq $8, %r9
subq %r8, %rsi ; count--
addq %r9, %rdi ; start++
call rsum
addq %rbx, %rax
popq %rbx
.L2:
ret