Rewrite the SDep class, and simplify some of the related code.

The Cost field is removed. It was only being used in a very limited way,
to indicate when the scheduler should attempt to protect a live register,
and it isn't really needed to do that. If we ever want the scheduler to
start inserting copies in non-prohibitive situations, we'll have to
rethink some things anyway.

A Latency field is added. Instead of giving each node a single
fixed latency, each edge can have its own latency. This will eventually
be used to model various micro-architecture properties more accurately.

The PointerIntPair class and an internal union are now used, which
reduce the overall size.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60806 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp

@@ -176,7 +176,10 @@ void ScheduleDAGSDNodes::BuildSchedUnits() {
         int Cost = 1;
         // Determine if this is a physical register dependency.
         CheckForPhysRegDependency(OpN, N, i, TRI, TII, PhysReg, Cost);
-        SU->addPred(OpSU, isChain, false, PhysReg, Cost);
+        assert((PhysReg == 0 || !isChain) &&
+               "Chain dependence via physreg data?");
+        SU->addPred(SDep(OpSU, isChain ? SDep::Order : SDep::Data,
+                         OpSU->Latency, PhysReg));
       }
     }
   }