[Bug ipa/70646] [4.9/5/6 Regression] Corrupt truncated function

[jpoimboe at redhat dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70646

--- Comment #17 from Josh Poimboeuf <jpoimboe at redhat dot com> ---
(In reply to Richard Biener from comment #14)
> (In reply to Josh Poimboeuf from comment #13)
> > Interestingly, the function's epilogue (frame pointer restore) and return
> > instruction are also getting discarded.  Can you tell if that will always be
> > the case when this bug triggers?
> 
> I don't think we can rely on that.  The path could simply fall thru to
> a random instruction which is still inside the function.  Say, if it was
> 
>   if (x)
>     ...
>   else
>     ...
>   foo ();
> 
> then the arm marked unreachable would simply disappear.

I tried doing that by putting the offending wwn_to_u64() call in an if
statement, but then the bug disappeared.

In fact, adding *any* code before the call seems to make the bug disappear.