Add a subtarget hook: enablePostMachineScheduler.

As requested by AArch64 subtargets.

Note that this will have no effect until the
AArch64 target actually enables the pass like this:
substitutePass(&PostRASchedulerID, &PostMachineSchedulerID);

As soon as armv7 switches over, PostMachineScheduler will become the
default postRA scheduler, so this won't be necessary any more.
Targets using the old postRA schedule would then do:
substitutePass(&PostMachineSchedulerID, &PostRASchedulerID);

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210167 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Target/TargetSubtargetInfo.h

@@ -66,6 +66,13 @@ public:
   /// scheduler. It does not yet disable the postRA scheduler.
   virtual bool enableMachineScheduler() const;
 
+  /// \brief True if the subtarget should run PostMachineScheduler.
+  ///
+  /// This only takes effect if the target has configured the
+  /// PostMachineScheduler pass to run, or if the global cl::opt flag,
+  /// MISchedPostRA, is set.
+  virtual bool enablePostMachineScheduler() const;
+
   /// \brief Override generic scheduling policy within a region.
   ///
   /// This is a convenient way for targets that don't provide any custom

lib/CodeGen/MachineScheduler.cpp

@@ -333,6 +333,12 @@ bool PostMachineScheduler::runOnMachineFunction(MachineFunction &mf) {
   if (skipOptnoneFunction(*mf.getFunction()))
     return false;
 
+  const TargetSubtargetInfo &ST =
+    mf.getTarget().getSubtarget<TargetSubtargetInfo>();
+  if (!ST.enablePostMachineScheduler()) {
+    DEBUG(dbgs() << "Subtarget disables post-MI-sched.\n");
+    return false;
+  }
   DEBUG(dbgs() << "Before post-MI-sched:\n"; mf.print(dbgs()));
 
   // Initialize the context of the pass.

lib/CodeGen/Passes.cpp

@@ -92,9 +92,9 @@ PrintMachineInstrs("print-machineinstrs", cl::ValueOptional,
 
 // Temporary option to allow experimenting with MachineScheduler as a post-RA
 // scheduler. Targets can "properly" enable this with
-// substitutePass(&PostRASchedulerID, &MachineSchedulerID); Ideally it wouldn't
-// be part of the standard pass pipeline, and the target would just add a PostRA
-// scheduling pass wherever it wants.
+// substitutePass(&PostRASchedulerID, &PostMachineSchedulerID); Ideally it
+// wouldn't be part of the standard pass pipeline, and the target would just add
+// a PostRA scheduling pass wherever it wants.
 static cl::opt<bool> MISchedPostRA("misched-postra", cl::Hidden,
   cl::desc("Run MachineScheduler post regalloc (independent of preRA sched)"));
 

lib/Target/ARM/ARMSubtarget.cpp

@@ -352,6 +352,13 @@ bool ARMSubtarget::hasSinCos() const {
     !getTargetTriple().isOSVersionLT(7, 0);
 }
 
+// Enable the PostMachineScheduler if the target selects it instead of
+// PostRAScheduler. Currently only available on the command line via
+// -misched-postra.
+bool ARMSubtarget::enablePostMachineScheduler() const {
+  return PostRAScheduler;
+}
+
 bool ARMSubtarget::enablePostRAScheduler(
            CodeGenOpt::Level OptLevel,
            TargetSubtargetInfo::AntiDepBreakMode& Mode,

lib/Target/ARM/ARMSubtarget.h

@@ -396,6 +396,9 @@ public:
   /// compiler runtime or math libraries.
   bool hasSinCos() const;
 
+  /// True for some subtargets at > -O0.
+  bool enablePostMachineScheduler() const;
+
   /// enablePostRAScheduler - True at 'More' optimization.
   bool enablePostRAScheduler(CodeGenOpt::Level OptLevel,
                              TargetSubtargetInfo::AntiDepBreakMode& Mode,

lib/Target/TargetSubtargetInfo.cpp

@@ -43,6 +43,10 @@ bool TargetSubtargetInfo::enableMachineScheduler() const {
   return false;
 }
 
+bool TargetSubtargetInfo::enablePostMachineScheduler() const {
+  return false;
+}
+
 bool TargetSubtargetInfo::enablePostRAScheduler(
           CodeGenOpt::Level OptLevel,
           AntiDepBreakMode& Mode,