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[Bug rtl-optimization/24762] [killloop-branch] code motion of non-invariant expressions with hard registers.
- From: "rakdver at atrey dot karlin dot mff dot cuni dot cz" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 9 Nov 2005 23:15:53 -0000
- Subject: [Bug rtl-optimization/24762] [killloop-branch] code motion of non-invariant expressions with hard registers.
- References: <firstname.lastname@example.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #8 from rakdver at atrey dot karlin dot mff dot cuni dot cz 2005-11-09 23:15 -------
Subject: Re: [killloop-branch] code motion of non-invariant expressions with
> ------- Comment #6 from dberlin at gcc dot gnu dot org 2005-11-09 22:53 -------
> 1. Call clobbers aren't definitions. They are clobbers (IE kills). They do not
> generate a new value, they simply specify the old value is dead. Thus, you
> don't mean to say "df.c assumes call clobbers ...", because it's not an
> 2. The patch is actually an incorrect workaround. The real problem is that
> df.c on mainline doesn't get reaching definitions right for a number of
> For example, explicit clobbers in CALL_INSN_FUNCTION_USAGE but *not* in
> regs_invalidated_by_call will be treated as gen's, because they don't fall into
> the special case in df_bb_rd_local_compute. But they are not gen's.
> Have you tried making sure CLOBBER's don't get into the rd_gen set?
> I imagine that will fix your bug.
I am fairly sure you are wrong, in this case. The code is like
reg = r15
where r15 is set by exception handling. The problem is that there
currently simply is no insn that defines r15.