[Inliner] Should we inline callee containing llvm.frameaddress?

[bzEq]

For code

#include <iostream>

void foo() {
  std::cout << __builtin_frame_address(0) << std::endl;
}

int main() {
  std::cout << __builtin_frame_address(0) << std::endl;
  foo();
  return 0;
}

Using trunk's clang, with -O2, the output is

0x7ffd0501a2c0
0x7ffd0501a2a0

With -O3, the output is

0x7ffd97138270
0x7ffd97138270

We have InlinerPass enabled at O3, which inlines callee(foo)'s llvm.frameaddress. The different behaviors at O2 and O3 affects IBM OpenXL C/C++ compiler when compiling and running compiler-rt/test/asan/TestCases/Posix/stack-overflow.cpp.

[anematode]

GCC will give the address for the caller function if the callee gets inlined. Maybe emit a warning if the function isn't marked noinline?

[nickdesaulniers]

Maybe emit a warning if the function isn't marked noinline?

Maybe noinline or always_inline?