Reapply r91392, it was only unmasking the bug, and since TOT is still broken having it reverted does no good.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@91560 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp

@@ -20,10 +20,16 @@
 #include "llvm/Target/TargetInstrInfo.h"
 #include "llvm/Target/TargetRegisterInfo.h"
 #include "llvm/Target/TargetSubtarget.h"
+#include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
 using namespace llvm;
 
+cl::opt<bool>
+DisableInstScheduling("disable-inst-scheduling",
+                      cl::init(false),
+                      cl::desc("Disable instruction scheduling"));
+
 ScheduleDAGSDNodes::ScheduleDAGSDNodes(MachineFunction &mf)
   : ScheduleDAG(mf) {
 }