[Bug ipa/119012] [riscv] Bootstrap comparison failure: gcc/rust/rust-lex.o differs

[rsworktech at outlook dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119012

--- Comment #21 from Levi Zim <rsworktech at outlook dot com> ---
(In reply to Sam James from comment #18)
> (In reply to Levi Zim from comment #17)
> > (In reply to Sam James from comment #16)
> > > (In reply to Levi Zim from comment #15)
> > > 
> > > As long as the flag is passed correctly and applied to both the stage2 +
> > > stage3 builds, then the flag can't be to blame (just a trigger for it,
> > > rather than some problem with the flag itself).
> > 
> > It is passed through BOOT_CFLAGS so I suppose it is passed correctly.
> 
> Yeah, that should be fine.
> 
> > I don't know why the comparison failure occur as I am not familiar with the
> > GCC internals. But building some of the commits yields a crash in RTL
> > pass(https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119012#c10). Would it be
> > related to the bisected commit?
> 
> It means the compiler itself got miscompiled. That's why it's really helpful
> to know precisely how to reproduce it manually (minimal set of commands and
> flags set), outside of any package manager.
> 
> Then we can compare the built objects, one built just before that commit,
> and one at that commit.

Could you share the steps to do it? I think doing it directly in the packaging
environment would be feasible.