有问题的基准，令人困惑的装配
有问题的基准，令人困惑的装配
提问于 2022-03-25 13:53:06
这里的大会新手。我写了一个基准来测量机器在计算转置矩阵张量积时的浮点性能。
鉴于我的机器有32 Given (带宽~37 CPU /s)和Intel(R) Core(TM) i5-8400 CPU@ 2.80GHz (Turbo4.0GHz)处理器，我估计最大性能(有流水线和数据在寄存器中)为6核x 4.0GHz =24 24GFLOP/s。然而，当我运行基准时，我测量的是127 24GFLOP/s，这显然是错误的。
注:为了衡量FP的性能，我正在测量运算计数：n*n*n*n*6 (矩阵矩阵乘法的n^3，在复杂数据点的n片上执行)，即假设一个复复乘法有6次失败，除以每次运行所需的平均时间。
主函数中的代码片段
// benchmark runs
auto avg_dur = 0.0;
for (auto counter = std::size_t{}; counter < experiment_count; ++counter)
{
#pragma noinline
do_timed_run(n, avg_dur);
}
avg_dur /= static_cast<double>(experiment_count);代码片段: do_timed_run
void do_timed_run(const std::size_t& n, double& avg_dur)
{
// create the data and lay first touch
auto operand0 = matrix<double>(n, n);
auto operand1 = tensor<double>(n, n, n);
auto result = tensor<double>(n, n, n);
// first touch
#pragma omp parallel
{
set_first_touch(operand1);
set_first_touch(result);
}
// do the experiment
const auto dur1 = omp_get_wtime() * 1E+6;
#pragma omp parallel firstprivate(operand0)
{
#pragma noinline
transp_matrix_tensor_mult(operand0, operand1, result);
}
const auto dur2 = omp_get_wtime() * 1E+6;
avg_dur += dur2 - dur1;
}备注：
此时，我没有为函数relevant.
- the提供代码，因为我不认为它是一个调试工具，我用它来更好地理解disassembler.
的输出
现在用于函数do_timed_run的反汇编。
0000000000403a20 <_Z12do_timed_runRKmRd>:
403a20: 48 81 ec d8 00 00 00 sub $0xd8,%rsp
403a27: 48 89 ac 24 c8 00 00 mov %rbp,0xc8(%rsp)
403a2e: 00
403a2f: 48 89 fd mov %rdi,%rbp
403a32: 48 89 9c 24 c0 00 00 mov %rbx,0xc0(%rsp)
403a39: 00
403a3a: 48 89 f3 mov %rsi,%rbx
403a3d: 48 89 ee mov %rbp,%rsi
403a40: 48 8d 7c 24 78 lea 0x78(%rsp),%rdi
403a45: 48 89 ea mov %rbp,%rdx
403a48: 4c 89 bc 24 a0 00 00 mov %r15,0xa0(%rsp)
403a4f: 00
403a50: 4c 89 b4 24 a8 00 00 mov %r14,0xa8(%rsp)
403a57: 00
403a58: 4c 89 ac 24 b0 00 00 mov %r13,0xb0(%rsp)
403a5f: 00
403a60: 4c 89 a4 24 b8 00 00 mov %r12,0xb8(%rsp)
403a67: 00
403a68: e8 03 f8 ff ff callq 403270 <_ZN5s3dft6matrixIdEC1ERKmS3_@plt>
403a6d: 48 89 ee mov %rbp,%rsi
403a70: 48 8d 7c 24 08 lea 0x8(%rsp),%rdi
403a75: 48 89 ea mov %rbp,%rdx
403a78: 48 89 e9 mov %rbp,%rcx
403a7b: e8 80 f8 ff ff callq 403300 <_ZN5s3dft6tensorIdEC1ERKmS3_S3_@plt>
403a80: 48 89 ee mov %rbp,%rsi
403a83: 48 8d 7c 24 40 lea 0x40(%rsp),%rdi
403a88: 48 89 ea mov %rbp,%rdx
403a8b: 48 89 e9 mov %rbp,%rcx
403a8e: e8 6d f8 ff ff callq 403300 <_ZN5s3dft6tensorIdEC1ERKmS3_S3_@plt>
403a93: bf 88 f3 44 00 mov $0x44f388,%edi
403a98: e8 53 f7 ff ff callq 4031f0 <__kmpc_global_thread_num@plt>
403a9d: 89 84 24 d0 00 00 00 mov %eax,0xd0(%rsp)
403aa4: bf c0 f3 44 00 mov $0x44f3c0,%edi
403aa9: 33 c0 xor %eax,%eax
403aab: e8 20 f6 ff ff callq 4030d0 <__kmpc_ok_to_fork@plt>
403ab0: 85 c0 test %eax,%eax
403ab2: 74 21 je 403ad5 <_Z12do_timed_runRKmRd+0xb5>
403ab4: ba a5 3c 40 00 mov $0x403ca5,%edx
403ab9: bf c0 f3 44 00 mov $0x44f3c0,%edi
403abe: be 02 00 00 00 mov $0x2,%esi
403ac3: 48 8d 4c 24 08 lea 0x8(%rsp),%rcx
403ac8: 33 c0 xor %eax,%eax
403aca: 4c 8d 41 38 lea 0x38(%rcx),%r8
403ace: e8 cd f5 ff ff callq 4030a0 <__kmpc_fork_call@plt>
403ad3: eb 41 jmp 403b16 <_Z12do_timed_runRKmRd+0xf6>
403ad5: bf c0 f3 44 00 mov $0x44f3c0,%edi
403ada: 33 c0 xor %eax,%eax
403adc: 8b b4 24 d0 00 00 00 mov 0xd0(%rsp),%esi
403ae3: e8 58 f7 ff ff callq 403240 <__kmpc_serialized_parallel@plt>
403ae8: be 9c 13 47 00 mov $0x47139c,%esi
403aed: 48 8d bc 24 d0 00 00 lea 0xd0(%rsp),%rdi
403af4: 00
403af5: 48 8d 54 24 08 lea 0x8(%rsp),%rdx
403afa: 48 8d 4a 38 lea 0x38(%rdx),%rcx
403afe: e8 a2 01 00 00 callq 403ca5 <_Z12do_timed_runRKmRd+0x285>
403b03: bf c0 f3 44 00 mov $0x44f3c0,%edi
403b08: 33 c0 xor %eax,%eax
403b0a: 8b b4 24 d0 00 00 00 mov 0xd0(%rsp),%esi
403b11: e8 aa f7 ff ff callq 4032c0 <__kmpc_end_serialized_parallel@plt>
403b16: e8 85 f6 ff ff callq 4031a0 <omp_get_wtime@plt>
403b1b: c5 fb 11 04 24 vmovsd %xmm0,(%rsp)
403b20: bf f8 f3 44 00 mov $0x44f3f8,%edi
403b25: 33 c0 xor %eax,%eax
403b27: e8 a4 f5 ff ff callq 4030d0 <__kmpc_ok_to_fork@plt>
403b2c: 85 c0 test %eax,%eax
403b2e: 74 25 je 403b55 <_Z12do_timed_runRKmRd+0x135>
403b30: ba 0b 3c 40 00 mov $0x403c0b,%edx
403b35: bf f8 f3 44 00 mov $0x44f3f8,%edi
403b3a: be 03 00 00 00 mov $0x3,%esi
403b3f: 48 8d 4c 24 08 lea 0x8(%rsp),%rcx
403b44: 33 c0 xor %eax,%eax
403b46: 4c 8d 41 38 lea 0x38(%rcx),%r8
403b4a: 4c 8d 49 70 lea 0x70(%rcx),%r9
403b4e: e8 4d f5 ff ff callq 4030a0 <__kmpc_fork_call@plt>
403b53: eb 45 jmp 403b9a <_Z12do_timed_runRKmRd+0x17a>
403b55: bf f8 f3 44 00 mov $0x44f3f8,%edi
403b5a: 33 c0 xor %eax,%eax
403b5c: 8b b4 24 d0 00 00 00 mov 0xd0(%rsp),%esi
403b63: e8 d8 f6 ff ff callq 403240 <__kmpc_serialized_parallel@plt>
403b68: be a0 13 47 00 mov $0x4713a0,%esi
403b6d: 48 8d bc 24 d0 00 00 lea 0xd0(%rsp),%rdi
403b74: 00
403b75: 48 8d 54 24 08 lea 0x8(%rsp),%rdx
403b7a: 48 8d 4a 38 lea 0x38(%rdx),%rcx
403b7e: 4c 8d 42 70 lea 0x70(%rdx),%r8
403b82: e8 84 00 00 00 callq 403c0b <_Z12do_timed_runRKmRd+0x1eb>
403b87: bf f8 f3 44 00 mov $0x44f3f8,%edi
403b8c: 33 c0 xor %eax,%eax
403b8e: 8b b4 24 d0 00 00 00 mov 0xd0(%rsp),%esi
403b95: e8 26 f7 ff ff callq 4032c0 <__kmpc_end_serialized_parallel@plt>
403b9a: e8 01 f6 ff ff callq 4031a0 <omp_get_wtime@plt>
403b9f: c5 fb 5c 0c 24 vsubsd (%rsp),%xmm0,%xmm1
403ba4: c5 fb 10 05 cc c4 01 vmovsd 0x1c4cc(%rip),%xmm0 # 420078 <alpha_beta.61562.0.0.28+0x28>
403bab: 00
403bac: 48 8d 7c 24 40 lea 0x40(%rsp),%rdi
403bb1: c4 e2 f9 a9 0b vfmadd213sd (%rbx),%xmm0,%xmm1
403bb6: c5 fb 11 0b vmovsd %xmm1,(%rbx)
403bba: e8 71 f5 ff ff callq 403130 <_ZN5s3dft9data_packIdED1Ev@plt>
403bbf: 48 8d 7c 24 08 lea 0x8(%rsp),%rdi
403bc4: e8 67 f5 ff ff callq 403130 <_ZN5s3dft9data_packIdED1Ev@plt>
403bc9: 48 8d 7c 24 78 lea 0x78(%rsp),%rdi
403bce: e8 5d f5 ff ff callq 403130 <_ZN5s3dft9data_packIdED1Ev@plt>
403bd3: 4c 8b bc 24 a0 00 00 mov 0xa0(%rsp),%r15
403bda: 00
403bdb: 4c 8b b4 24 a8 00 00 mov 0xa8(%rsp),%r14
403be2: 00
403be3: 4c 8b ac 24 b0 00 00 mov 0xb0(%rsp),%r13
403bea: 00
403beb: 4c 8b a4 24 b8 00 00 mov 0xb8(%rsp),%r12
403bf2: 00
403bf3: 48 8b 9c 24 c0 00 00 mov 0xc0(%rsp),%rbx
403bfa: 00
403bfb: 48 8b ac 24 c8 00 00 mov 0xc8(%rsp),%rbp
403c02: 00
403c03: 48 81 c4 d8 00 00 00 add $0xd8,%rsp
403c0a: c3 retq
403c0b: 48 81 ec d8 00 00 00 sub $0xd8,%rsp
403c12: 4c 89 c6 mov %r8,%rsi
403c15: 4c 89 a4 24 b8 00 00 mov %r12,0xb8(%rsp)
403c1c: 00
403c1d: 4c 8d 24 24 lea (%rsp),%r12
403c21: 4c 89 e7 mov %r12,%rdi
403c24: 48 89 ac 24 c8 00 00 mov %rbp,0xc8(%rsp)
403c2b: 00
403c2c: 48 89 cd mov %rcx,%rbp
403c2f: 48 89 9c 24 c0 00 00 mov %rbx,0xc0(%rsp)
403c36: 00
403c37: 48 89 d3 mov %rdx,%rbx
403c3a: 4c 89 bc 24 a0 00 00 mov %r15,0xa0(%rsp)
403c41: 00
403c42: 4c 89 b4 24 a8 00 00 mov %r14,0xa8(%rsp)
403c49: 00
403c4a: 4c 89 ac 24 b0 00 00 mov %r13,0xb0(%rsp)
403c51: 00
403c52: e8 49 03 00 00 callq 403fa0 <_ZN5s3dft6matrixIdEC1ERKS1_> # <--- Here starts the part with the function call...
403c57: 4c 89 e7 mov %r12,%rdi
403c5a: 48 89 de mov %rbx,%rsi
403c5d: 48 89 ea mov %rbp,%rdx
403c60: e8 8b 01 00 00 callq 403df0 <_Z25transp_matrix_tensor_multIdEvRKN5s3dft6matrixIT_EERKNS0_6tensorIS2_EERS7_>
403c65: 4c 89 e7 mov %r12,%rdi
403c68: e8 63 01 00 00 callq 403dd0 <_ZN5s3dft6matrixIdED1Ev> # <--- ...and here it ends
403c6d: 4c 8b bc 24 a0 00 00 mov 0xa0(%rsp),%r15
403c74: 00
403c75: 4c 8b b4 24 a8 00 00 mov 0xa8(%rsp),%r14
403c7c: 00
403c7d: 4c 8b ac 24 b0 00 00 mov 0xb0(%rsp),%r13
403c84: 00
403c85: 4c 8b a4 24 b8 00 00 mov 0xb8(%rsp),%r12
403c8c: 00
403c8d: 48 8b 9c 24 c0 00 00 mov 0xc0(%rsp),%rbx
403c94: 00
403c95: 48 8b ac 24 c8 00 00 mov 0xc8(%rsp),%rbp
403c9c: 00
403c9d: 48 81 c4 d8 00 00 00 add $0xd8,%rsp
403ca4: c3 retq
403ca5: 48 81 ec d8 00 00 00 sub $0xd8,%rsp
403cac: 48 89 d7 mov %rdx,%rdi
403caf: 48 89 ac 24 c8 00 00 mov %rbp,0xc8(%rsp)
403cb6: 00
403cb7: 48 89 9c 24 c0 00 00 mov %rbx,0xc0(%rsp)
403cbe: 00
403cbf: 48 89 cb mov %rcx,%rbx
403cc2: 4c 89 bc 24 a0 00 00 mov %r15,0xa0(%rsp)
403cc9: 00
403cca: 4c 89 b4 24 a8 00 00 mov %r14,0xa8(%rsp)
403cd1: 00
403cd2: 4c 89 ac 24 b0 00 00 mov %r13,0xb0(%rsp)
403cd9: 00
403cda: 4c 89 a4 24 b8 00 00 mov %r12,0xb8(%rsp)
403ce1: 00
403ce2: e8 99 f4 ff ff callq 403180 <_Z15set_first_touchIdEvRN5s3dft6tensorIT_EE@plt> # <--- here are the calls to set-first-touch
403ce7: 48 89 df mov %rbx,%rdi
403cea: e8 91 f4 ff ff callq 403180 <_Z15set_first_touchIdEvRN5s3dft6tensorIT_EE@plt>
403cef: 4c 8b bc 24 a0 00 00 mov 0xa0(%rsp),%r15
403cf6: 00
403cf7: 4c 8b b4 24 a8 00 00 mov 0xa8(%rsp),%r14
403cfe: 00
403cff: 4c 8b ac 24 b0 00 00 mov 0xb0(%rsp),%r13
403d06: 00
403d07: 4c 8b a4 24 b8 00 00 mov 0xb8(%rsp),%r12
403d0e: 00
403d0f: 48 8b 9c 24 c0 00 00 mov 0xc0(%rsp),%rbx
403d16: 00
403d17: 48 8b ac 24 c8 00 00 mov 0xc8(%rsp),%rbp
403d1e: 00
403d1f: 48 81 c4 d8 00 00 00 add $0xd8,%rsp
403d26: c3 retq
403d27: 48 89 04 24 mov %rax,(%rsp)
403d2b: bf 30 f4 44 00 mov $0x44f430,%edi
403d30: e8 bb f4 ff ff callq 4031f0 <__kmpc_global_thread_num@plt>
403d35: 89 84 24 d0 00 00 00 mov %eax,0xd0(%rsp)
403d3c: 48 8d 7c 24 40 lea 0x40(%rsp),%rdi
403d41: e8 9a 00 00 00 callq 403de0 <_ZN5s3dft6tensorIdED1Ev>
403d46: 48 8d 7c 24 08 lea 0x8(%rsp),%rdi
403d4b: e8 90 00 00 00 callq 403de0 <_ZN5s3dft6tensorIdED1Ev>
403d50: 48 8d 7c 24 78 lea 0x78(%rsp),%rdi
403d55: e8 76 00 00 00 callq 403dd0 <_ZN5s3dft6matrixIdED1Ev>
403d5a: 48 8b 3c 24 mov (%rsp),%rdi
403d5e: e8 5d f3 ff ff callq 4030c0 <_Unwind_Resume@plt>
403d63: 48 89 04 24 mov %rax,(%rsp)
403d67: bf 68 f4 44 00 mov $0x44f468,%edi
403d6c: e8 7f f4 ff ff callq 4031f0 <__kmpc_global_thread_num@plt>
403d71: 89 84 24 d0 00 00 00 mov %eax,0xd0(%rsp)
403d78: eb cc jmp 403d46 <_Z12do_timed_runRKmRd+0x326>
403d7a: 48 89 04 24 mov %rax,(%rsp)
403d7e: bf a0 f4 44 00 mov $0x44f4a0,%edi
403d83: e8 68 f4 ff ff callq 4031f0 <__kmpc_global_thread_num@plt>
403d88: 89 84 24 d0 00 00 00 mov %eax,0xd0(%rsp)
403d8f: eb bf jmp 403d50 <_Z12do_timed_runRKmRd+0x330>
403d91: 0f 1f 84 00 00 00 00 nopl 0x0(%rax,%rax,1)
403d98: 00
403d99: 0f 1f 80 00 00 00 00 nopl 0x0(%rax)初级问题
假设函数是在时间区域之外调用的，这是正确的吗?如果上面的happening?
- If是正确的，为什么上面的是不正确的，我如何才能找出为什么我的基准测试是错误的？
二级问题
- 为什么代码中存在无条件跳转(在403 ad3、403 b53、403 d78和403 d8f)？
- 为什么在同一个函数中有3个
retq实例，只有一个返回路径(403 c0a、403 ca4和403 d26)？
。
请考虑我只提供了我认为有关的资料。如有要求，我们会乐意提供更多资料。提前谢谢你抽出时间。
编辑
@PeterCordes，我确实是在启用调试符号的情况下构建的。上面张贴的程序集是使用objdump获得的，它不知何故没有检索到所需的符号。下面是(使用icpc获得的程序集的片段)
# omp_get_wtime()
call omp_get_wtime #122.23
..___tag_value__Z12do_timed_runRKmRd.267:
..LN419:
# LOE rbx xmm0
..B4.12: # Preds ..B4.11
# Execution count [1.00e+00]
..LN420:
vmovsd %xmm0, (%rsp) #122.23[spill]
..LN421:
# LOE rbx
..B4.13: # Preds ..B4.12
# Execution count [1.00e+00]
..LN422:
.loc 1 123 is_stmt 1
movl $.2.40_2_kmpc_loc_struct_pack.65, %edi #123.5
..LN423:
xorl %eax, %eax #123.5
..___tag_value__Z12do_timed_runRKmRd.269:
..LN424:
call __kmpc_ok_to_fork #123.5
..___tag_value__Z12do_timed_runRKmRd.270:
..LN425:
# LOE rbx eax
..B4.14: # Preds ..B4.13
# Execution count [1.00e+00]
..LN426:
testl %eax, %eax #123.5
..LN427:
je ..B4.17 # Prob 50% #123.5
..LN428:
# LOE rbx
..B4.15: # Preds ..B4.14
# Execution count [0.00e+00]
..LN429:
movl $.2.40_2_kmpc_loc_struct_pack.65, %edi #123.5
..LN430:
xorl %edx, %edx #123.5
..LN431:
incq %rdx #123.5
..LN432:
xorl %eax, %eax #123.5
..LN433:
movl 208(%rsp), %esi #123.5
..___tag_value__Z12do_timed_runRKmRd.271:
..LN434:
call __kmpc_push_num_threads #123.5
..___tag_value__Z12do_timed_runRKmRd.272:
..LN435:
# LOE rbx
..B4.16: # Preds ..B4.15
# Execution count [0.00e+00]
..LN436:
movl $L__Z12do_timed_runRKmRd_123__par_region1_2.5, %edx #123.5
..LN437:
movl $.2.40_2_kmpc_loc_struct_pack.65, %edi #123.5
..LN438:
movl $3, %esi #123.5
..LN439:
lea 8(%rsp), %rcx #123.5
..LN440:
xorl %eax, %eax #123.5
..LN441:
lea 56(%rcx), %r8 #123.5
..LN442:
lea 112(%rcx), %r9 #123.5
..___tag_value__Z12do_timed_runRKmRd.273:
..LN443:
call __kmpc_fork_call #123.5
..___tag_value__Z12do_timed_runRKmRd.274:
..LN444:
jmp ..B4.20 # Prob 100% #123.5
..LN445:
# LOE rbx
..B4.17: # Preds ..B4.14
# Execution count [0.00e+00]
..LN446:
movl $.2.40_2_kmpc_loc_struct_pack.65, %edi #123.5
..LN447:
xorl %eax, %eax #123.5
..LN448:
movl 208(%rsp), %esi #123.5
..___tag_value__Z12do_timed_runRKmRd.275:
..LN449:
call __kmpc_serialized_parallel #123.5
..___tag_value__Z12do_timed_runRKmRd.276:
..LN450:
# LOE rbx
..B4.18: # Preds ..B4.17
# Execution count [0.00e+00]
..LN451:
movl $___kmpv_zero_Z12do_timed_runRKmRd_1, %esi #123.5
..LN452:
lea 208(%rsp), %rdi #123.5
..LN453:
lea 8(%rsp), %rdx #123.5
..LN454:
lea 56(%rdx), %rcx #123.5
..LN455:
lea 112(%rdx), %r8 #123.5
..___tag_value__Z12do_timed_runRKmRd.277:
..LN456:
call L__Z12do_timed_runRKmRd_123__par_region1_2.5 #123.5
..___tag_value__Z12do_timed_runRKmRd.278:
..LN457:
# LOE rbx
..B4.19: # Preds ..B4.18
# Execution count [0.00e+00]
..LN458:
movl $.2.40_2_kmpc_loc_struct_pack.65, %edi #123.5
..LN459:
xorl %eax, %eax #123.5
..LN460:
movl 208(%rsp), %esi #123.5
..___tag_value__Z12do_timed_runRKmRd.279:
..LN461:
call __kmpc_end_serialized_parallel #123.5
..___tag_value__Z12do_timed_runRKmRd.280:
..LN462:
# LOE rbx
..B4.20: # Preds ..B4.16 ..B4.19
# Execution count [1.00e+00]
..___tag_value__Z12do_timed_runRKmRd.281:
..LN463:
.loc 1 128 is_stmt 1
# omp_get_wtime()
call omp_get_wtime #128.23正如您所看到的，输出非常冗长，很难阅读。
回答 1
Stack Overflow用户
回答已采纳
发布于 2022-03-25 19:33:27
对于现代超标量CPU来说，每个核心时钟周期1 FP操作将是可悲的。您的Skylake派生CPU实际上可以完成2x4宽的SIMD双精度FMA操作，每个核心时钟每个FMA计算为两个触发器，因此理论max =16个双精度触发器，因此24 * 16 = 384 GFLOP/S (使用4 doubles的向量，即256位宽AVX)。请参阅FLOPS per cycle for sandy-bridge and haswell SSE2/AVX/AVX2
在赋时区域callq 403c0b <_Z12do_timed_runRKmRd+0x1eb> (以及__kmpc_end_serialized_parallel )中有一个函数调用。
没有与这个调用目标相关的符号，所以我想您没有在启用调试信息的情况下编译。(这与优化级别是分开的，例如，gcc -g -O3 -march=native -fopenmp应该运行相同的asm，只是有更多的调试元数据。)即使是OpenMP发明的函数，也应该有一个符号名在某个点上关联。
就基准有效性而言，一个好的试金石是它是否与问题的大小相称。除非您超出了L3缓存大小，或者没有出现更小或更大的问题，否则时间应该以某种合理的方式改变。如果不是，那么您就会担心它优化掉了，或者时钟速度热身效应(Idiomatic way of performance evaluation?用于这一点和更多，比如页面错误)。
- 为什么代码中存在无条件跳转(在403 ad3,403 b53,403 d78和403 d8f)？
一旦您已经在if块中，您就无条件地知道不应该运行else块，所以您可以在它上运行jmp而不是jcc (即使仍然设置了FLAGS，所以您不必再次测试条件)。或者将一个或另一个块放置在行(比如函数的末尾，或入口点之前)，然后将jcc放到它，然后它将jmp返回到另一侧。这样，快速路径就可以与不被占用的分支相连。
- 为什么同一个函数中只有一个返回路径(在403 c0a、403 ca4和403 d26处)有3个retq实例？
重复的ret来自“尾复制”优化，其中所有返回的多条执行路径都可以得到自己的ret，而不是跳转到ret。(以及任何必要的清理的副本，比如还原regs和堆栈指针。)
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/71618068
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