[llvm][Hexagon] Generalize VLIWResourceModel, VLIWMachineScheduler, and ConvergingVLIWScheduler

The Pre-RA VLIWMachineScheduler used by Hexagon is a relatively generic
implementation that would make sense to use on other VLIW targets.

This commit lifts those classes into their own header/source file with the
root VLIWMachineScheduler. I chose this path rather than adding the
strategy et al. into MachineScheduler to avoid bloating the file with other
implementations.

Target-specific behaviors have been captured and replicated through
function overloads.

- Added an overloadable DFAPacketizer creation member function. This is
  mainly done for our downstream, which has the capability to override
  the DFAPacketizer with custom implementations. This is an upstreamable
  TODO on our end. Currently, it always returns the result of
  TargetInstrInfo::CreateTargetScheduleState
- Added an extra helper which returns the number of instructions in the
  current packet. This is used in our downstream, and may be useful
  elsewhere.
- Placed the priority heuristic values into the ConvergingVLIWscheduler
  class instead of defining them as local statics in the implementation
- Added a overridable helper in ConvergingVLIWScheduler so that targets
  can create their own VLIWResourceModel

Differential Revision: https://reviews.llvm.org/D113150

1 files changed, 8 insertions, 4 deletions

diff --git a/llvm/lib/CodeGen/MachineScheduler.cpp b/llvm/lib/CodeGen/MachineScheduler.cpp
index 5f7181c..b043d4c 100644
--- a/llvm/lib/CodeGen/MachineScheduler.cpp
+++ b/llvm/lib/CodeGen/MachineScheduler.cpp
@@ -90,12 +90,17 @@ cl::opt<bool> VerifyScheduling(
     "verify-misched", cl::Hidden,
     cl::desc("Verify machine instrs before and after machine scheduling"));
 
+#ifndef NDEBUG
+cl::opt<bool> ViewMISchedDAGs(
+    "view-misched-dags", cl::Hidden,
+    cl::desc("Pop up a window to show MISched dags after they are processed"));
+#else
+const bool ViewMISchedDAGs = false;
+#endif // NDEBUG
+
 } // end namespace llvm
 
 #ifndef NDEBUG
-static cl::opt<bool> ViewMISchedDAGs("view-misched-dags", cl::Hidden,
-  cl::desc("Pop up a window to show MISched dags after they are processed"));
-
 /// In some situations a few uninteresting nodes depend on nearly all other
 /// nodes in the graph, provide a cutoff to hide them.
 static cl::opt<unsigned> ViewMISchedCutoff("view-misched-cutoff", cl::Hidden,
@@ -111,7 +116,6 @@ static cl::opt<unsigned> SchedOnlyBlock("misched-only-block", cl::Hidden,
 static cl::opt<bool> PrintDAGs("misched-print-dags", cl::Hidden,
                               cl::desc("Print schedule DAGs"));
 #else
-static const bool ViewMISchedDAGs = false;
 static const bool PrintDAGs = false;
 #endif // NDEBUG