- leaq _end_before_pgt(%rip), %r8
- leaq _end_before_pgt(%rbx), %r9
- movq $_end_before_pgt /* - $startup_32 */, %rcx
-1: subq $8, %r8
- subq $8, %r9
- movq 0(%r8), %rax
- movq %rax, 0(%r9)
- subq $8, %rcx
- jnz 1b
+ pushq %rsi
+ leaq (_bss-8)(%rip), %rsi
+ leaq (_bss-8)(%rbx), %rdi
+ movq $_bss /* - $startup_32 */, %rcx
+ shrq $3, %rcx
+ std
+ rep movsq
+ cld
+ popq %rsi