The asm in a naked function may reasonably expect the argument registers and the
return address register (if present) to be live.
When using -pg and -finstrument-functions, functions are instrumented by adding
a function call to `_mcount/__cyg_profile_func_enter/__cyg_profile_func_enter_bare`/etc,
which will clobber these registers. If the return address register is clobbered,
the function will be unable to return to the caller, possibly causing an
infinite loop.
```
__attribute__((naked)) void g() {
#if defined(__arm__)
__asm__("bx lr");
#else
__asm__("ret");
#endif
}
int main() { g(); }
```
It seems that the only one reasonable way to handle the combination is to
disable instrumenting for naked functions.
GCC PR: https://gcc.gnu.org/PR109707
Close https://github.com/llvm/llvm-project/issues/62504
Reviewed By: hans
Differential Revision: https://reviews.llvm.org/D149721
3460f727ea