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<base href="https://bugs.llvm.org/">
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<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Common code between acquire-release not sunk"
href="https://bugs.llvm.org/show_bug.cgi?id=47215">47215</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Common code between acquire-release not sunk
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</td>
</tr>
<tr>
<th>Version</th>
<td>unspecified
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>All
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>new bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>hiraditya@msn.com
</td>
</tr>
<tr>
<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>$ cat test.cpp
```
struct foo {
[[gnu::weak]] foo() noexcept;
[[gnu::weak]] ~foo();
foo* begin() { return this; }
foo* end() { return this; }
};
__attribute__((noinline))
void bar(foo* i, foo* j) {}
foo* go_leaky() { static foo *f = new foo(); return f; }
int main() {
bar(go_leaky()->begin(), go_leaky()->end());
return 0;
}
```
Interesting disassembly code: with clang++ -O3 -std=c++17 -fno-exceptions
```
main:
push rbx
mov al,BYTE PTR [rip+0x2e81] # 404058 <guard variable for
go_leaky()::f>
test al,al
je 4011e9 <main+0x19>
mov al,BYTE PTR [rip+0x2e77] # 404058 <guard variable for
go_leaky()::f>
test al,al
je 40121f <main+0x4f>
xor eax,eax
pop rbx
ret
mov edi,0x404058
call 401060 <__cxa_guard_acquire@plt> /// < -------start of acquire-release
test eax,eax
je 4011db <main+0xb>
mov edi,0x1
call 401050 <operator new(unsigned long)@plt>
mov rbx,rax
mov rdi,rax
call 401030 <foo::foo()@plt>
mov QWORD PTR [rip+0x2e3d],rbx # 404050 <go_leaky()::f>
mov edi,0x404058
call 401040 <__cxa_guard_release@plt> /// < -------end of acquire-release
jmp 4011db <main+0xb>
mov edi,0x404058
call 401060 <__cxa_guard_acquire@plt> /// < -------start of acquire-release
test eax,eax
je 4011e5 <main+0x15>
mov edi,0x1
call 401050 <operator new(unsigned long)@plt>
mov rbx,rax
mov rdi,rax
call 401030 <foo::foo()@plt>
mov QWORD PTR [rip+0x2e07],rbx # 404050 <go_leaky()::f>
mov edi,0x404058
call 401040 <__cxa_guard_release@plt> /// < -------end of acquire-release
xor eax,eax
pop rbx
ret
nop WORD PTR [rax+rax*1+0x0]```
The compiler should be able to fold/sink the common code to a common successor.
Even -gvn-sink didn't seem to help.</pre>
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