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Re: [PATCH] Fix emit_library_call_value to not use virtual stack regs after expand

> On Wed, Jun 24, 2009 at 2:11 PM, Maxim Kuvyrkov<> wrote:
> > Hello,
> >
> > The following simple patch [which is just a duplication of a hunk from
> > within emit_library_call_value_1] fixes ICE when compiling for m68k/ColdFire
> > machines without hardware divide.
> >
> > The ICE occurs in reload on gcc.c-torture/execute/loop-3b.c test due to
> > occurrence of virtual_outgoing_args_rtx in the instruction stream. ?This
> > virtual register is used within expand and then is substituted with
> > (stack_pointer_rtx + STACK_POINTER_OFFSET) at the end of expand.
> >
> > Evidently, there still remains a way to generate virtual_outgoing_args by
> > the loop optimizer. ?The loop optimizer emits a divide instruction which,
> > due to target not having hwdiv, expands into a library call.
> >
> > emit_library_call_value_1 deals with virtual_outgoing_args_rtx in two
> > places: the first already handles case when virtuals are instantiated; this
> > patch fixes the second.
> >
> > Tested by bootstrapping on x86_64. ?OK for trunk?
> It was my understanding that the expanders should never be used after
> 'expand', but to get this libcall you have to go through an expander,
> right?
> So maybe the bug is in the loop optimizer -- it shouldn't try to do
> its transformations if it has to do them via expanders.

Loop optimizer always did call back to expanders to produce simple
arithmetic and loop test conditions.  It is hackish, but I hardly see
way around when you need to invent brand new hunk of code for i.e.
preconditioning in unroller so rewriting existing RTL instructions won't

This always sort-of worked because the code it produces tends to be very
simple.  I guess it should just give up when libcall results when doing
the desired transform.

> Thoughs?
> Ciao!
> Steven

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