https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113478
Bug ID: 113478
Summary: -Os does not inline single instruction function
Product: gcc
Version: 13.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: jari.helaakoski at qt dot io
Target Milestone: ---
GCC -Os option does not inline single instruction std::atomic function when
accessed via template class. Inlining works ok with -O2. Inlining is also
working if std::atomic is used directly.
Test case and compilation result found from godbolt:
https://godbolt.org/z/nh758aT3K
Problem reproduces all GCC versions with x86 and aarch64 target and with and
without specific -march and -mtune options.
And here's test case pasted in case of godbolt is not accessable:
template <typename T>
class D {
public:
#if 1
inline T test() { return i.load(std::memory_order_relaxed); }
#else
__attribute__((always_inline)) T test() { return
i.load(std::memory_order_relaxed); }
#endif
std::atomic<T> i {0};
};
D<char> a1;
D<long> a2;
D<int> a3;
D<short> a4;
D<long long> a5;
D<wchar_t> a6;
extern void mod();
int main()
{
int ret = 0;
mod();
ret |= a1.test();
ret |= a1.test();
ret |= a1.test();
ret |= a1.test();
ret |= a1.test();
ret |= a1.test();
ret |= a1.test();
ret |= a1.test();
ret |= a1.test();
ret |= a1.test();
ret |= a2.test();
ret |= a3.test();
ret |= a4.test();
ret |= a5.test();
ret |= a6.test();
return ret;
}
Function that should be inlined
D<char>::test():
ldrb w0, [x0]
ret
