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Re: [PATCH] Fix DCE REG_LIBCALL note moving from noop move insns (PR rtl-optimization/33644)
- From: Jakub Jelinek <jakub at redhat dot com>
- To: Kenneth Zadeck <Kenneth dot Zadeck at NaturalBridge dot com>
- Cc: gcc-patches at gcc dot gnu dot org, Eric Botcazou <ebotcazou at libertysurf dot fr>
- Date: Sun, 14 Oct 2007 17:45:21 -0400
- Subject: Re: [PATCH] Fix DCE REG_LIBCALL note moving from noop move insns (PR rtl-optimization/33644)
- References: <firstname.lastname@example.org> <email@example.com>
- Reply-to: Jakub Jelinek <jakub at redhat dot com>
On Sun, Oct 14, 2007 at 12:29:44PM -0400, Kenneth Zadeck wrote:
> I have not looked at this bug. I am happy to if you want. I am sure
> that it will be trivial to modify the pass that moved/created the insn
> in the middle of the libcall to inherit the LIB_CALL_ID from the
> previous insn.
That is not desirable, if anything in this case the insn should be
added before the whole libcall sequence rather than before the insn
that actually needs it. Otherwise, useless insns added to the libcall
sequences wouldn't be ever DCEd.
While it might be easy to modify the instantiate_virtual_regs, there
are dozens of other passes that do similar things, so at least for 4.3 it is
highly unlikely they will be all modified.