fix scheduling antideps

[Mike Stump]

On Dec 11, 2015, at 6:09 AM, Jeff Law <law@redhat.com> wrote:
> On 12/11/2015 02:22 AM, Eric Botcazou wrote:
>>> This patch allows a target to increase the cost of anti-deps to better
>>> reflect the actual cost on the machine.
>> 
>> But it can already do it via the TARGET_SCHED_ADJUST_COST hook, can't it?
> And can't this be done with define_bypass as well?

          if (dep_type == REG_DEP_ANTI)
            cost = 0;
          else if (dep_type == REG_DEP_OUTPUT)
            {
              cost = (insn_default_latency (insn)
                      - insn_default_latency (used));
              if (cost <= 0)
                cost = 1;
            }
          else if (bypass_p (insn))
            cost = insn_latency (insn, used);

I don’t see how if the first case is true, one gets into the third without code mods.  I opted for the adjust_cost_2 hook.