gcc 编译为汇编代码
原始C++代码如下：
#include<atomic> using namespace std; atomic<int> a; int j; int main() { int n; a.store(1,memory_order_acquire); n = j; return 0; }
编译成汇编代码：
root@ubuntu:/data1# g++ -S -g -std=c++11 test10.cpp -o test10.s root@ubuntu:/data1# cat test10.s
root@ubuntu:/data1# cat test10.s | grep main -A 20 .global main .type main, %function main: .LFB331: .file 3 "test10.cpp" .loc 3 8 0 .cfi_startproc stp x29, x30, [sp, -32]! .cfi_def_cfa_offset 32 .cfi_offset 29, -32 .cfi_offset 30, -24 add x29, sp, 0 .cfi_def_cfa_register 29 mov w0, 1 str w0, [x29, 20] mov w0, 2 str w0, [x29, 24] .LBB5: .LBB6: .loc 1 369 0 mov w1, 65535 ldr w0, [x29, 24] bl _ZStanSt12memory_orderSt23__memory_order_modifier -- .size main, .-main .align 2 .type _Z41__static_initialization_and_destruction_0ii, %function _Z41__static_initialization_and_destruction_0ii: .LFB351: .loc 3 14 0 .cfi_startproc stp x29, x30, [sp, -32]! .cfi_def_cfa_offset 32 .cfi_offset 29, -32 .cfi_offset 30, -24 add x29, sp, 0 .cfi_def_cfa_register 29 str w0, [x29, 28] str w1, [x29, 24] .loc 3 14 0 ldr w0, [x29, 28] cmp w0, 1 bne .L9 .loc 3 14 0 is_stmt 0 discriminator 1 ldr w1, [x29, 24] -- .string "main" .LASF92: .string "~atomic" .LASF90: .string "atomic" .LASF98: .string "__gnu_cxx" .ident "GCC: (Ubuntu/Linaro 5.5.0-12ubuntu1) 5.5.0 20171010" .section .note.GNU-stack,"",@progbits
使用 as 展示汇编代码
另一种更好的做法是使用as：
编译成汇编代码：
root@ubuntu:/data1# g++ -S -fverbose-asm -g -std=c++11 test10.cpp -o test10.s root@ubuntu:/data1# cat test10.s | grep main -A 20 .global main .type main, %function main: .LFB331: .file 3 "test10.cpp" .loc 3 8 0 .cfi_startproc stp x29, x30, [sp, -32]! //,,, .cfi_def_cfa_offset 32 .cfi_offset 29, -32 .cfi_offset 30, -24 add x29, sp, 0 //,, .cfi_def_cfa_register 29 mov w0, 1 // tmp78, str w0, [x29, 20] // tmp78, __i mov w0, 2 // tmp79, str w0, [x29, 24] // tmp79, __m .LBB5: .LBB6: .loc 1 369 0 mov w1, 65535 //, ldr w0, [x29, 24] //, __m bl _ZStanSt12memory_orderSt23__memory_order_modifier // -- .size main, .-main .align 2 .type _Z41__static_initialization_and_destruction_0ii, %function _Z41__static_initialization_and_destruction_0ii: .LFB351: .loc 3 14 0 .cfi_startproc stp x29, x30, [sp, -32]! //,,, .cfi_def_cfa_offset 32 .cfi_offset 29, -32 .cfi_offset 30, -24 add x29, sp, 0 //,, .cfi_def_cfa_register 29 str w0, [x29, 28] // __initialize_p, __initialize_p str w1, [x29, 24] // __priority, __priority .loc 3 14 0 ldr w0, [x29, 28] // tmp73, __initialize_p cmp w0, 1 // tmp73, bne .L9 //, .loc 3 14 0 is_stmt 0 discriminator 1 ldr w1, [x29, 24] // tmp74, __priority -- .string "main" .LASF92: .string "~atomic" .LASF90: .string "atomic" .LASF98: .string "__gnu_cxx" .ident "GCC: (Ubuntu/Linaro 5.5.0-12ubuntu1) 5.5.0 20171010" .section .note.GNU-stack,"",@progbits
使用 objdump 进行反汇编
如果直接编成机器码，需要使用objdump进行反汇编：
root@ubuntu:/data1# g++ -save-temps -fverbose-asm -g -std=c++11 test10.cpp -o test10.s root@ubuntu:/data1# objdump -S --disassemble test10.s | grep main -A 20 0000000000000640 <__libc_start_main@plt>: 640: 90000090 adrp x16, 10000 <__FRAME_END__+0xf594> 644: f947d211 ldr x17, [x16, #4000] 648: 913e8210 add x16, x16, #0xfa0 64c: d61f0220 br x17 0000000000000650 <__gmon_start__@plt>: 650: 90000090 adrp x16, 10000 <__FRAME_END__+0xf594> 654: f947d611 ldr x17, [x16, #4008] 658: 913ea210 add x16, x16, #0xfa8 65c: d61f0220 br x17 0000000000000660 <abort@plt>: 660: 90000090 adrp x16, 10000 <__FRAME_END__+0xf594> 664: f947da11 ldr x17, [x16, #4016] 668: 913ec210 add x16, x16, #0xfb0 66c: d61f0220 br x17 Disassembly of section .text: 0000000000000670 <_start>: -- 6a0: 97ffffe8 bl 640 <__libc_start_main@plt> 6a4: 97ffffef bl 660 <abort@plt> 00000000000006a8 <call_weak_fn>: 6a8: 90000080 adrp x0, 10000 <__FRAME_END__+0xf594> 6ac: f947ec00 ldr x0, [x0, #4056] 6b0: b4000040 cbz x0, 6b8 <call_weak_fn+0x10> 6b4: 17ffffe7 b 650 <__gmon_start__@plt> 6b8: d65f03c0 ret 6bc: 00000000 .inst 0x00000000 ; undefined 00000000000006c0 <deregister_tm_clones>: 6c0: b0000081 adrp x1, 11000 <__data_start> 6c4: b0000080 adrp x0, 11000 <__data_start> 6c8: 91004021 add x1, x1, #0x10 6cc: 91004000 add x0, x0, #0x10 6d0: 91001c21 add x1, x1, #0x7 6d4: cb000021 sub x1, x1, x0 6d8: f100383f cmp x1, #0xe 6dc: 540000a9 b.ls 6f0 <deregister_tm_clones+0x30> // b.plast 6e0: 90000081 adrp x1, 10000 <__FRAME_END__+0xf594> -- 00000000000007b8 <main>: atomic<int> a; int j; int main() { 7b8: a9be7bfd stp x29, x30, [sp, #-32]! 7bc: 910003fd mov x29, sp 7c0: 52800020 mov w0, #0x1 // #1 7c4: b90017a0 str w0, [x29, #20] 7c8: 52800040 mov w0, #0x2 // #2 7cc: b9001ba0 str w0, [x29, #24] } _GLIBCXX_ALWAYS_INLINE void store(__int_type __i, memory_order __m = memory_order_seq_cst) noexcept { memory_order __b = __m & __memory_order_mask; 7d0: 529fffe1 mov w1, #0xffff // #65535 7d4: b9401ba0 ldr w0, [x29, #24] 7d8: 94000025 bl 86c <_ZStanSt12memory_orderSt23__memory_order_modifier> 7dc: b9001fa0 str w0, [x29, #28] __glibcxx_assert(__b != memory_order_acquire); __glibcxx_assert(__b != memory_order_acq_rel); __glibcxx_assert(__b != memory_order_consume);
使用 godbolt 可视化结果
这个网站： https://godbolt.org
真的非常好用，效果如下：