Now, in terms of not issuing an "mfence" instruction in asm volatile but using "memory" in the clobber list. From what I've been able to read If your assembler instructions access memory in an unpredictable fashion, add `memory' to the list of clobbered registers. This will cause GCC to...
__volatile__("":::"memory"),而这行代码就是内存屏障。 2)__asm__用于指示编译器在此插入汇编语句 3)__volatile__用于告诉编译器,严禁将此处的汇编语句与其它的语 句重组合优化。即:原原本本按原来的样子处理这这里的汇编。 4)memory强制gcc编译器假设RAM所有内存单元均被汇编指令修改, ...
注意这里的mfence指令,它强制执行CPU端的屏障,以及volatile块中的"memory"说明符,它强制执行编译时屏障。在现代CPU上,您可以将mfence:rdtsc替换为更高效的rdtscp。 - Cory Nelson 那么,使用空块,它就像是一种指令屏障? - Bryan Chen 2 请注意,编译器只能控制它生成的静态代码顺序,并避免在编译时将内容移动到此...
Another problem you're bound to run into, for some reason Intel dropped pushad and popad. So I wrote macros to replace them; seems most useful to include only the volatile registers. Often I don't want rax included since it sends back info (like error code) so made it optional: Code ...
static inline void mfence() { asm volatile("mfence" ::: "memory"); } static inline void lfence() { asm volatile("lfence" ::: "memory"); } static inline void sfence() { asm volatile("sfence" ::: "memory"); } 对于你的汇编代码,我不太清楚存在什么缓存。 movl $0, -4(%rbp) //...
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