On Fri, Nov 20, 2009 at 4:18 PM, David Edelsohn <dje....@gmail.com> wrote: > On Fri, Nov 20, 2009 at 10:05 AM, Ian Bolton <bol...@icerasemi.com> wrote: >> From some simple experiments (see below), it appears as though GCC aims >> to >> create a lop-sided tree when there are constants involved (func1 below), >> but a balanced tree when there aren't (func2 below). >> >> Our assumption is that GCC likes having constants all near to each other >> to >> aid with tree-based optimisations, but I'm fairly sure that, when it >> comes >> to scheduling, it would be better to have a balanced tree, so sched has >> more >> choices about what to schedule next? > > I think this would depend on the target architecture and instruction > set: CISC vs RISC, many registers vs few registers, etc. I do not > believe that GCC intentionally is trying to optimize for either, but I > do not think there is a single, right answer.
Indeed. I think the scheduler should maybe learn about re-association possibilities - do existing papers cover that? Richard. > David >
