New attempt: subword-based DCE, PR42575

[Peter Bergner]

On Thu, 2010-07-29 at 21:03 +0200, Bernd Schmidt wrote:
> On 07/29/2010 08:25 PM, David Edelsohn wrote:
> > This patch may have caused a new bootstrap ICE on PowerPC:
> > 
> > /farm/dje/src/src/gcc/cfg.c: In function 'scale_bbs_frequencies_gcov_type':
> > /farm/dje/src/src/gcc/cfg.c:1109:1: internal compiler error: in
> > delete_corresponding_reg_eq_notes, at dce.c:495
> > 
> > I see the error on powerpc-ibm-aix5.3 and I was told the error also
> > occurs on powerpc-darwin.
> 
> Can you test the following patch?  This makes sure we clear some DF
> flags during DCE, and while I was there I also made the whole thing
> conditional on flag_dce for consistency.

I tested this on powerpc64-linux and it does fix the bootstrap failure.

Peter