[llvm] r251904 - [X86] Generate .cfi_adjust_cfa_offset correctly when pushing arguments

[Rafael Espíndola via llvm-commits]

On 3 November 2015 at 10:55, Kuperstein, Michael M
<michael.m.kuperstein at intel.com> wrote:
> GCC is always precise, but that seems unnecessary when we only care about performing unwinding for synchronous EH (since in this case, we only need to be right at call sites), and inflates the module size.
>
> It's actually a bit hard to compare apples-to-apples here, since for -O2, there's no definitely harm in emitting extra CFI, but clang doesn't use pushes, and for -Os, GCC defaults to -no-omit-frame-pointer, so the issue does not arise.

-Os -fomit-frame-pointers?

I think it is incorrect to say that we don't care about asynchronous
unwinding (not exceptions). The .eh_frame is part of the ABI and any
tool wanting to unwind can depend on it being precise.

Cheers,
Rafael