Allow subtarget selection of the default MachineScheduler and document the interface.

The global registry is used to allow command line override of the
scheduler selection, but does not work well as the normal selection
API. For example, the same LLVM process should be able to target
multiple targets or subtargets.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191071 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 22 insertions, 12 deletions

diff --git a/lib/CodeGen/MachineScheduler.cpp b/lib/CodeGen/MachineScheduler.cpp
index e7a0e6e..8dcb58e 100644
--- a/lib/CodeGen/MachineScheduler.cpp
+++ b/lib/CodeGen/MachineScheduler.cpp
@@ -101,6 +101,9 @@ public:
   virtual void print(raw_ostream &O, const Module* = 0) const;
 
   static char ID; // Class identification, replacement for typeinfo
+
+protected:
+  ScheduleDAGInstrs *createMachineScheduler();
 };
 } // namespace
 
@@ -202,6 +205,22 @@ nextIfDebug(MachineBasicBlock::iterator I,
       &*nextIfDebug(MachineBasicBlock::const_iterator(I), End)));
 }
 
+/// Instantiate a ScheduleDAGInstrs that will be owned by the called.
+ScheduleDAGInstrs *MachineScheduler::createMachineScheduler() {
+  // Select the scheduler, or set the default.
+  MachineSchedRegistry::ScheduleDAGCtor Ctor = MachineSchedOpt;
+  if (Ctor != useDefaultMachineSched)
+    return Ctor(this);
+
+  // Get the default scheduler set by the target for this function.
+  ScheduleDAGInstrs *Scheduler = PassConfig->createMachineScheduler(this);
+  if (Scheduler)
+    return Scheduler;
+
+  // Default to GenericScheduler.
+  return createGenericSched(this);
+}
+
 /// Top-level MachineScheduler pass driver.
 ///
 /// Visit blocks in function order. Divide each block into scheduling regions
@@ -237,18 +256,9 @@ bool MachineScheduler::runOnMachineFunction(MachineFunction &mf) {
   }
   RegClassInfo->runOnMachineFunction(*MF);
 
-  // Select the scheduler, or set the default.
-  MachineSchedRegistry::ScheduleDAGCtor Ctor = MachineSchedOpt;
-  if (Ctor == useDefaultMachineSched) {
-    // Get the default scheduler set by the target.
-    Ctor = MachineSchedRegistry::getDefault();
-    if (!Ctor) {
-      Ctor = createGenericSched;
-      MachineSchedRegistry::setDefault(Ctor);
-    }
-  }
-  // Instantiate the selected scheduler.
-  OwningPtr<ScheduleDAGInstrs> Scheduler(Ctor(this));
+  // Instantiate the selected scheduler for this target, function, and
+  // optimization level.
+  OwningPtr<ScheduleDAGInstrs> Scheduler(createMachineScheduler());
 
   // Visit all machine basic blocks.
   //