On 12/20/2016 10:33 AM, Richard Biener wrote:
but for loops we can just continue and ignore this use. And
bitmap_set_bit
returns whether it set a bit, thus
if (bitmap_set_bit (visited_ssa, SSA_NAME_VERSION
(name)))
worklist.safe_push (name);
should work?
What if we're in an irreducible region?
Handling all back edges by deferring to their defs should work. At least I
can't see how it would not.
I'll take your word for it -- I haven't thought deeply about this.
In principle the thing is sound but I'd like to be able to pass in a
bitmap of
known maybe-undefined/must-defined SSA names to have a cache for
multiple invocations from within a pass (like this unswitching case).
So that means keeping another bitmap for things positively identified
as
defined, then saving it for later invocations.
We eventually need a tristate here for maximum caching. And as the result
depends on the dominating BB of the postdom region the savings might be
questionable.
Possibly.
Jeff
