PR19038 causes regression of 3.9% in SPEC int

[Jeffrey A Law]

On Wed, 2004-12-29 at 20:40 +0100, Steven Bosscher wrote:
> On Wednesday 29 December 2004 20:19, Jeffrey A Law wrote:
> > Well, this ought to fix the poor placement of the copy instruction.
> 
> Cool.  One question, don't you need a call to mark_dfs_back_edges()
> somewhere?
They should have been marked much earlier in the tree-ssa path.

They can get slightly out-of-date which would at worst cause us to
not apply this optimization when it was appropriate or apply it
when it was not necessary -- neither of which should generate
incorrect code.

Jeff