Hi All, Does someone knows about the x86_64 instruction scheduling, and tell me why we see some various nop in function prologs. This is just general culture, curiosity. I see prolog like this in some linux kernel functions 0xffffffff8102fba0 pushq %rbp 0xffffffff8102fba1 movq %rsp,%rbp 0xffffffff8102fba4 nopl 0x0(%rax,%rax,1) <== 0xffffffff8102fba9 movl %edi,%edi <== 0xffffffff8102fbab movl %esi,-0xa05000(%rdi) 0xffffffff81176db0 pushq %rbp 0xffffffff81176db1 movq %rsp,%rbp 0xffffffff81176db4 subq $0x40,%rsp 0xffffffff81176db8 movq %rbx,-0x18(%rbp) 0xffffffff81176dbc movq %r12,-0x10(%rbp) 0xffffffff81176dc0 movq %r13,-0x8(%rbp) 0xffffffff81176dc4 nopl 0x0(%rax,%rax,1) <== 0xffffffff81176dc9 movq %rsi,%r12 At first I thought this NOP could be to fill some NULL instruction to reach some cache line boundaries, but the addrs here sugest this is not for that reason. (I am a newbe in the x86 architecture) Thanx in advance. Cheers, Phi
