Generalize PostRAHazardRecognizer so it can be used in any pass for

both forward and backward scheduling. Rename it to
ScoreboardHazardRecognizer (Scoreboard is one word). Remove integer
division from the scoreboard's critical path.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@121274 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 105 insertions, 0 deletions

diff --git a/include/llvm/CodeGen/ScoreboardHazardRecognizer.h b/include/llvm/CodeGen/ScoreboardHazardRecognizer.h
new file mode 100644
index 0000000000..561bf0fecf
--- /dev/null
+++ b/include/llvm/CodeGen/ScoreboardHazardRecognizer.h
@@ -0,0 +1,105 @@
+//=- llvm/CodeGen/ScoreboardHazardRecognizer.h - Schedule Support -*- C++ -*-=//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the ScoreboardHazardRecognizer class, which
+// encapsulates hazard-avoidance heuristics for scheduling, based on the
+// scheduling itineraries specified for the target.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_SCOREBOARDHAZARDRECOGNIZER_H
+#define LLVM_CODEGEN_SCOREBOARDHAZARDRECOGNIZER_H
+
+#include "llvm/CodeGen/ScheduleHazardRecognizer.h"
+#include "llvm/Support/DataTypes.h"
+
+#include <cassert>
+#include <cstring>
+#include <string>
+
+namespace llvm {
+
+class InstrItineraryData;
+class SUnit;
+
+class ScoreboardHazardRecognizer : public ScheduleHazardRecognizer {
+  // Scoreboard to track function unit usage. Scoreboard[0] is a
+  // mask of the FUs in use in the cycle currently being
+  // schedule. Scoreboard[1] is a mask for the next cycle. The
+  // Scoreboard is used as a circular buffer with the current cycle
+  // indicated by Head.
+  //
+  // Scoreboard always counts cycles in forward execution order. If used by a
+  // bottom-up scheduler, then the scoreboard cycles are the inverse of the
+  // scheduler's cycles.
+  class Scoreboard {
+    unsigned *Data;
+
+    // The maximum number of cycles monitored by the Scoreboard. This
+    // value is determined based on the target itineraries to ensure
+    // that all hazards can be tracked.
+    size_t Depth;
+    // Indices into the Scoreboard that represent the current cycle.
+    size_t Head;
+  public:
+    Scoreboard():Data(NULL), Depth(0), Head(0) { }
+    ~Scoreboard() {
+      delete[] Data;
+    }
+
+    size_t getDepth() const { return Depth; }
+    unsigned& operator[](size_t idx) const {
+      // Depth is expected to be a power-of-2.
+      assert(Depth && !(Depth & (Depth - 1)) &&
+             "Scoreboard was not initialized properly!");
+
+      return Data[(Head + idx) & (Depth-1)];
+    }
+
+    void reset(size_t d = 1) {
+      if (Data == NULL) {
+        Depth = d;
+        Data = new unsigned[Depth];
+      }
+
+      memset(Data, 0, Depth * sizeof(Data[0]));
+      Head = 0;
+    }
+
+    void advance() {
+      Head = (Head + 1) & (Depth-1);
+    }
+
+    void recede() {
+      Head = (Head - 1) & (Depth-1);
+    }
+
+    // Print the scoreboard.
+    void dump() const;
+  };
+
+  // Itinerary data for the target.
+  const InstrItineraryData *ItinData;
+
+  Scoreboard ReservedScoreboard;
+  Scoreboard RequiredScoreboard;
+
+public:
+  ScoreboardHazardRecognizer(const InstrItineraryData *ItinData);
+
+  virtual HazardType getHazardType(SUnit *SU);
+  virtual void Reset();
+  virtual void EmitInstruction(SUnit *SU);
+  virtual void AdvanceCycle();
+  virtual void RecedeCycle();
+};
+
+}
+
+#endif //!LLVM_CODEGEN_SCOREBOARDHAZARDRECOGNIZER_H