[bugs] Another ICE

[Graham Stott]

Jan Hubicka wrote:
> 
> Content-Description: message body text
> >
> > Hi Honza,
> >
> > I got another ICE with yesterday evenings version of gcc :-((
> >
> > Egbert.
> >
> Hi,
> the bug is caused by gcse, that emits result of gen_move_insn and then update
> basic block info for last insn. In case gen_move_insn used sequence of insns,
> others are kept w/o any info.
> 
> (hmm, ugly - perhaps we can avoid gcse from using the BASIC_BLOCK_FOR_INSN
> completely? I can't imagince case gcse is doing transformation and don't know
> basic block information and keeping that array up-to-date is expensive)
> 
> Honza
> 
I'm puzzled why doesn't set_block_for_new_insns DTRT because it is supposed to
handle a sequence. I think your change is just papering over a bug.

Looking at set_block_for_new_insns I see that it stop scanning backwards if it
finds a NOTE.

  /* Scan the previous instructions setting the block number until we find
     an instruction that has the block number set, or we find a note
     of any kind.  */
  for (insn = PREV_INSN (insn); insn != NULL_RTX; insn = PREV_INSN (insn))
    {
      if (GET_CODE (insn) == NOTE)
        break;

      ....
    }

Would the generated sequence by any chance of had a NOTE?

Graham