https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105862
Bug ID: 105862
Summary: missed inlining opportunity of
_Sp_counted_deleter::_M_destroy
Product: gcc
Version: 12.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: vanyacpp at gmail dot com
Target Milestone: ---
This sample is reduced from a real usage of shared_ptr.
#include <cstddef>
#include <new>
struct sp_counted_base
{
sp_counted_base() noexcept
: use_count(1)
{}
virtual void destroy() noexcept
{}
void release() noexcept
{
if (--use_count == 0)
destroy();
}
private:
sp_counted_base(sp_counted_base const&) = delete;
sp_counted_base& operator=(sp_counted_base const&) = delete;
int use_count;
};
struct sp_counted_deleter final : sp_counted_base
{
virtual void destroy() noexcept
{
::operator delete(this);
}
};
void test()
{
sp_counted_deleter* mem = static_cast<sp_counted_deleter*>(::operator
new(sizeof(sp_counted_deleter)));
::new (mem) sp_counted_deleter();
sp_counted_base* pi = mem;
pi->release();
}
https://godbolt.org/z/dG8h7f1Kn
sp_counted_deleter::destroy():
jmp operator delete(void*)
test():
sub rsp, 8
mov edi, 16
call operator new(unsigned long)
mov QWORD PTR [rax], OFFSET FLAT:vtable for sp_counted_deleter+16
mov rdi, rax
mov DWORD PTR [rax+8], 0
add rsp, 8
jmp sp_counted_deleter::destroy()
In the output assembly the call to sp_counted_deleter::destroy is left
uninlined. I tested the same sample on Clang and it somehow manages to inline
this function. It would be great if GCC was able to inline it too.
