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[avr-gcc-list] Re: bugfix for cselib_invalidate_regno
From: |
Richard Earnshaw |
Subject: |
[avr-gcc-list] Re: bugfix for cselib_invalidate_regno |
Date: |
Fri, 23 May 2003 10:45:28 +0100 |
> Richard Earnshaw <address@hidden> writes:
>
> > > Denis Chertykov <address@hidden> writes:
> > >
> > > > I have founded a bug in cselib.c:cselib_invalidate_regno.
> > > > The avr port triggers this bug.
> > > > Current version of cselib_invalidate_regno didn't invalidate lower
> > > > register numbers if they contain values that overlap REGNO in case
> > > > that (regno < FIRST_PSEUDO_REGISTER && mode == VOIDmode). This happens
> > > > if cselib_invalidate_regno called from cselib_process_insn which
> > > > handle CALL_INSN.
> > > > IE
> > > >
> > > > /* If this is a call instruction, forget anything stored in a
> > > > call clobbered register, or, if this is not a const call, in
> > > > memory. */
> > > > if (GET_CODE (insn) == CALL_INSN)
> > > > {
> > > > for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
> > > > if (call_used_regs[i])
> > > > cselib_invalidate_regno (i, VOIDmode);
> > > >
> >
> > Why not change the caller to pass reg_raw_mode[regno]. That seems much
> > cleaner to me than pretending a hard register can have no mode.
>
> Because my patch make cselib_invalidate_regno more universal.
> Your example will work with my patch too.
>
No it doesn't. At least, not unless we agree that we want this meaning to
exist everywhere. There's nothing in the documentation that says that a
hard register in mode VOIDmode has its natural size. So all you are doing
here is adding an undocumented local convention. I dislike that strongly.
> cselib_invalidate_regno have only two callers, are you sure that the
> second always pass the mode != VOIDmode ?
IMO cselib_invalidate_regno should abort if passed VOIDmode for a hard
register. As things stand at present it's meaningless.
R.