循环控制语句for while do-while if switch

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1：For 语句循环控制

L3执行完后直接执行L2的代码

int main(){ int a=0; for(int i=0;i<100;i=i+2){ a=a+10;}}/************************/.file"b01.cpp".text.globlmain.typemain, @functionmain:.LFB0:.cfi_startprocpushq%rbp.cfi_def_cfa_offset 16.cfi_offset 6, -16movq%rsp, %rbp.cfi_def_cfa_register 6movl$0, -4(%rbp) //a addressmovl$0, -8(%rbp) //i addressjmp.L2.L3:addl$10, -4(%rbp) //a=a+10addl$2, -8(%rbp)  //i=i+2.L2:cmpl$99, -8(%rbp) //i-99jle.L3movl$0, %eaxpopq%rbp.cfi_def_cfa 7, 8ret.cfi_endproc.LFE0:.sizemain, .-main.ident"GCC: (GNU) 4.8.5 20150623 (Red Hat 4.8.5-11)".section.note.GNU-stack,"",@progbits

2：while 语句

int main(){ int a=0; while(a<2){  a++;}}//**************************.file"b01.cpp".text.globlmain.typemain, @functionmain:.LFB0:.cfi_startprocpushq%rbp.cfi_def_cfa_offset 16.cfi_offset 6, -16movq%rsp, %rbp.cfi_def_cfa_register 6movl$0, -4(%rbp)  //a=0jmp.L2.L3:addl$1, -4(%rbp) //a++.L2:cmpl$1, -4(%rbp) //a-1jle.L3movl$0, %eaxpopq%rbp.cfi_def_cfa 7, 8ret.cfi_endproc.LFE0:.sizemain, .-main.ident"GCC: (GNU) 4.8.5 20150623 (Red Hat 4.8.5-11)".section.note.GNU-stack,"",@progbits

3: Do-while

先执行后判断

int main(){ int a=20; do{  a++;}while(a>100);}//**********************.file"b01.cpp".text.globlmain.typemain, @functionmain:.LFB0:.cfi_startprocpushq%rbp.cfi_def_cfa_offset 16.cfi_offset 6, -16movq%rsp, %rbp.cfi_def_cfa_register 6movl$20, -4(%rbp)   //a=20.L2:addl$1, -4(%rbp) //a++cmpl$100, -4(%rbp)   // a-100jg.L2          大于 jg跳转movl$0, %eaxpopq%rbp.cfi_def_cfa 7, 8ret.cfi_endproc.LFE0:.sizemain, .-main.ident"GCC: (GNU) 4.8.5 20150623 (Red Hat 4.8.5-11)".section.note.GNU-stack,"",@progbits

4：IF语句

int main(){ int a;a=20;if(a<30){a=66;}else if(a==30){a=99;}else{ a=89;}}//**********************.file"b01.cpp".text.globlmain.typemain, @functionmain:.LFB0:.cfi_startprocpushq%rbp.cfi_def_cfa_offset 16.cfi_offset 6, -16movq%rsp, %rbp.cfi_def_cfa_register 6movl$20, -4(%rbp)  //a=20cmpl$29, -4(%rbp)  //a-29jg.L2            //a-29>0  跳L2movl$66, -4(%rbp)  //a<=29 a=66jmp.L3.L2:cmpl$30, -4(%rbp)  //a-30 jne.L4            ZF标志位为0时跳转 zf=1时a==30movl$99, -4(%rbp)  jmp.L3.L4:movl$89, -4(%rbp)  //a=89;.L3:movl$0, %eax  //return 0popq%rbp.cfi_def_cfa 7, 8ret.cfi_endproc.LFE0:.sizemain, .-main.ident"GCC: (GNU) 4.8.5 20150623 (Red Hat 4.8.5-11)".section.note.GNU-stack,"",@progbits

5:swith

int main(){ int a;a=20;int b;switch(a){case 100: b=100; break;case 20: b=20;break;default : b=0;}}//*********************.file"b01.cpp".text.globlmain.typemain, @functionmain:.LFB0:.cfi_startprocpushq%rbp.cfi_def_cfa_offset 16.cfi_offset 6, -16movq%rsp, %rbp.cfi_def_cfa_register 6movl$20, -4(%rbp)    //a=20movl-4(%rbp), %eax   //eax=20cmpl$20, %eax        //20-20je.L3             //相等jmp .L3cmpl$100, %eax      //20-100jne.L7             // 不等 jmp .L7movl$100, -8(%rbp)  //相等 b=100jmp.L5.L3:movl$20, -8(%rbp)  //b=20jmp.L5            //跳出.L7:movl$0, -8(%rbp)  //b=0.L5:movl$0, %eaxpopq%rbp.cfi_def_cfa 7, 8ret.cfi_endproc.LFE0:.sizemain, .-main.ident"GCC: (GNU) 4.8.5 20150623 (Red Hat 4.8.5-11)".section.note.GNU-stack,"",@progbits

6:continue break

continue 结束当下，继续下一个循环

break 结束循环

int main(){ int a;a=20;int b;for(int i=0;i<100;i++){if(a==50){b=50;continue;}if(a==60){b=60;break;}a++;}}//**************************.file"b01.cpp".text.globlmain.typemain, @functionmain:.LFB0:.cfi_startprocpushq%rbp.cfi_def_cfa_offset 16.cfi_offset 6, -16movq%rsp, %rbp.cfi_def_cfa_register 6movl$20, -4(%rbp) //a=20movl$0, -8(%rbp)  //i=0;jmp.L2.L7:cmpl$50, -4(%rbp) //a-50jne.L3           //a!=50 jmp .L3movl$50, -12(%rbp) //if a==50 b=50jmp.L4            //continue.L3:cmpl$60, -4(%rbp)jne.L5movl$60, -12(%rbp)jmp.L6             //break.L5:addl$1, -4(%rbp)    //a++.L4:addl$1, -8(%rbp) //i++.L2:cmpl$99, -8(%rbp) //i-99jle.L7    //i<=99 jmp .L7.L6:movl$0, %eaxpopq%rbp.cfi_def_cfa 7, 8ret.cfi_endproc.LFE0:.sizemain, .-main.ident"GCC: (GNU) 4.8.5 20150623 (Red Hat 4.8.5-11)".section.note.GNU-stack,"",@progbits

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