This is the mail archive of the gcc-patches@gcc.gnu.org mailing list for the GCC project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: RFA: Fix rtl-optimization/58021


On 07/29/2013 02:24 PM, Joern Rennecke wrote:
The interesting case where we encounter a basic block head is when
the check of return_copy for BB_HEAD check succeeds with return_copy
being a label; then last_insn is a NOTE_INSN_BASIC_BLOCK, and we must
not try to split off a part of the basic block before that note. That
can be properly tested for by changing the !INSN_P (last_insn) check
into a NOTE_INSN_BASIC_BLOCK_P (last_insn) check.

last_insn == BB_HEAD (src_bb) can't actually be true, because we
don't copy return_copy to last_insn when we've bit BB_HEAD, so I
removed that test.

bootstrapped / regtested on i686-pc-linux-gnu .
OK for the trunk.




AFAICT, the second block split is useless, and could be replaced
with pre_exit = src_bb; , and then the slack space allocated for
post_entry / pre_exit blocks reduced to two.  However, I didn't want
to tie a bugfix with a potentialy destabilizing cleanup - maybe
there's some target port code (in the context of likely spilled
classes?) that relies on the MODE_EXIT switch note only before, but
in a block separate from the return value copy?
Well, the mode switching code is only used on sh (which you obviously know quite well) x86 and the epiphany ports. I trust your judgement on this since you've probably dealt more with the optimize_switching code than anyone.

jeff


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]