zcfh commented on PR #2156:
URL: https://github.com/apache/brpc/pull/2156#issuecomment-1976430923
目前从clang11 切换 到clang16 遇到了一些新的问题。和 #1776
提到的问题应该是一样的，不过我看**1776对应的代码并没有合入**, 是有做了其他修复吗。
对比了汇编，这样差异在于326-331 行这段代码（version 0.96）
```c++
// Clean tls variables, must be done before changing version_butex
// otherwise another thread just joined this thread may not see side
// effects of destructing tls variables.
KeyTable* kt = tls_bls.keytable;
if (kt != NULL) {
return_keytable(m->attr.keytable_pool, kt);
// After deletion: tls may be set during deletion.
tls_bls.keytable = NULL;
m->local_storage.keytable = NULL; // optional
}
```
clang11 对于 tls_bls 成员变量的读写，每次都会经过一次call。而clang16会在`do`循环外缓存`tls_bls`的地址。
具体汇编差异如下
clang11
``` as
;third_party/brpc-0.9.6/src/bthread/task_group.cpp:325
# KeyTable* kt = tls_bls.keytable;
a9e: 66 48 8d 3d 00 00 00 data16 lea 0x0(%rip),%rdi # aa6
<bthread::TaskGroup::task_runner(long)+0x196>
aa5: 00
aa6: 66 66 48 e8 00 00 00 data16 data16 callq aae
<bthread::TaskGroup::task_runner(long)+0x19e>
aad: 00
aae: 48 8b 30 mov (%rax),%rsi
third_party/brpc-0.9.6/src/bthread/task_group.cpp:326
ab1: 48 85 f6 test %rsi,%rsi
ab4: 74 28 je ade
<bthread::TaskGroup::task_runner(long)+0x1ce>
...
third_party/brpc-0.9.6/src/bthread/task_group.cpp:329
# tls_bls.keytable = NULL;
abf: 66 48 8d 3d 00 00 00 data16 lea 0x0(%rip),%rdi # ac7
<bthread::TaskGroup::task_runner(long)+0x1b7>
ac6: 00
ac7: 66 66 48 e8 00 00 00 data16 data16 callq acf
<bthread::TaskGroup::task_runner(long)+0x1bf>
ace: 00
acf: 48 c7 00 00 00 00 00 movq $0x0,(%rax)
```
clang16
```
;third_party/brpc-0.9.6/src/bthread/task_group.cpp:265
838: 48 8b 40 30 mov 0x30(%rax),%rax
83c: 48 85 c0 test %rax,%rax
83f: 75 df jne 820
<bthread::TaskGroup::task_runner(long)+0x30>
841: 4c 89 65 d0 mov %r12,-0x30(%rbp)
845: 66 48 8d 3d 00 00 00 data16 lea 0x0(%rip),%rdi # 84d
<bthread::TaskGroup::task_runner(long)+0x5d>
84c: 00
84d: 66 66 48 e8 00 00 00 data16 data16 callq 855
<bthread::TaskGroup::task_runner(long)+0x65>
854: 00
855: 48 89 c3 mov %rax,%rbx # do 循环外保存 tls_bls
的地址到rbx
...
;third_party/brpc-0.9.6/src/bthread/task_group.cpp:325
# KeyTable* kt = tls_bls.keytable;
96e: 48 8b 33 mov (%rbx),%rsi
;third_party/brpc-0.9.6/src/bthread/task_group.cpp:326
971: 48 85 f6 test %rsi,%rsi
974: 74 18 je 98e
<bthread::TaskGroup::task_runner(long)+0x19e>
...
;third_party/brpc-0.9.6/src/bthread/task_group.cpp:329
# tls_bls.keytable = NULL;
97f: 48 c7 03 00 00 00 00 movq $0x0,(%rbx)
```
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