misched: Allow subtargets to enable misched and dependent options.

This allows me to begin enabling (or backing out) misched by default
for one subtarget at a time. To run misched we typically want to:
- Disable SelectionDAG scheduling (use the source order scheduler)
- Enable more aggressive coalescing (until we decide to always run the coalescer this way)
- Enable MachineScheduler pass itself.

Disabling PostRA sched may follow for some subtargets.

llvm-svn: 167826

1 files changed, 4 insertions, 0 deletions

diff --git a/llvm/lib/Target/TargetSubtargetInfo.cpp b/llvm/lib/Target/TargetSubtargetInfo.cpp
index 59ffdea..af0cef6 100644
--- a/llvm/lib/Target/TargetSubtargetInfo.cpp
+++ b/llvm/lib/Target/TargetSubtargetInfo.cpp
@@ -22,6 +22,10 @@ TargetSubtargetInfo::TargetSubtargetInfo() {}
 
 TargetSubtargetInfo::~TargetSubtargetInfo() {}
 
+bool TargetSubtargetInfo::enableMachineScheduler() const {
+  return false;
+}
+
 bool TargetSubtargetInfo::enablePostRAScheduler(
           CodeGenOpt::Level OptLevel,
           AntiDepBreakMode& Mode,