Add a really faster pre-RA scheduler (-pre-RA-sched=linearize). It doesn't use
any scheduling heuristics nor does it build up any scheduling data structure
that other heuristics use. It essentially linearize by doing a DFA walk but
it does handle glues correctly.

IMPORTANT: it probably can't handle all the physical register dependencies so
it's not suitable for x86. It also doesn't deal with dbg_value nodes right now
so it's definitely is still WIP.

rdar://12474515


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@166122 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.h b/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.h
index 8e7bd82..907356f 100644
--- a/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.h
+++ b/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.h
@@ -114,7 +114,8 @@
     /// EmitSchedule - Insert MachineInstrs into the MachineBasicBlock
     /// according to the order specified in Sequence.
     ///
-    MachineBasicBlock *EmitSchedule(MachineBasicBlock::iterator &InsertPos);
+    virtual MachineBasicBlock*
+    EmitSchedule(MachineBasicBlock::iterator &InsertPos);
 
     virtual void dumpNode(const SUnit *SU) const;