Added temp flag -misched-bench for staging in default changes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191423 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/TargetSubtargetInfo.cpp

@@ -11,6 +11,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "llvm/Support/CommandLine.h"
 #include "llvm/Target/TargetSubtargetInfo.h"
 #include "llvm/ADT/SmallVector.h"
 using namespace llvm;
@@ -22,6 +23,21 @@ TargetSubtargetInfo::TargetSubtargetInfo() {}
 
 TargetSubtargetInfo::~TargetSubtargetInfo() {}
 
+// Temporary option to compare overall performance change when moving from the
+// SD scheduler to the MachineScheduler pass pipeline. It should be removed
+// before 3.4. The normal way to enable/disable the MachineScheduling pass
+// itself is by using -enable-misched. For targets that already use MI sched
+// (via MySubTarget::enableMachineScheduler()) -misched-bench=false negates the
+// subtarget hook.
+static cl::opt<bool> BenchMachineSched("misched-bench", cl::Hidden,
+    cl::desc("Migrate from the target's default SD scheduler to MI scheduler"));
+
+bool TargetSubtargetInfo::useMachineScheduler() const {
+  if (BenchMachineSched.getNumOccurrences())
+    return BenchMachineSched;
+  return enableMachineScheduler();
+}
+
 bool TargetSubtargetInfo::enableMachineScheduler() const {
   return false;
 }
@@ -38,4 +54,3 @@ bool TargetSubtargetInfo::enablePostRAScheduler(
 bool TargetSubtargetInfo::useAA() const {
   return false;
 }
-