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Re: Bug? flow_find_cross_jump deletes USE insns ...

Jakub Jelinek <> writes:

> On Mon, Jan 14, 2002 at 12:56:22PM -0800, Richard Henderson wrote:
> > On Mon, Jan 14, 2002 at 04:56:53PM +0100, Ulrich Weigand wrote:
> > > The prolog on S/390 generates a USE insn for the GOT register,
> > > because the GOT pointer must be loaded even if it isn't used
> > > in the routine (because the PLT stubs rely on the register).
> > 
> > This isn't going to work.  Bare USE insns aren't meaningful
> > after reload.  You need to add the USE to the call insn.  You
> > can do this either inside the call pattern itself, or by adding
> > it to the CALL_INSN_FUNCTION_USAGE expr_list.
> I have a similar problem on IA-64, unfortunately there is no call where to
> stick the USEs in.

If you don't have any calls, how can the function throw?

> where the use is trying to make sure the set before it is not deleted:
>           /* Even if we're not going to generate an epilogue, we still
>              need to save the register so that EH works.  */
>           if (! epilogue_p)
>             emit_insn (gen_rtx_USE (VOIDmode, alt_reg));

- Geoffrey Keating <> <>

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