Generalize the HazardRecognizer interface so that it can be used

to support MachineInstr-based scheduling in addition to
SDNode-based scheduling.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@62284 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 63 insertions, 0 deletions

diff --git a/include/llvm/CodeGen/ScheduleHazardRecognizer.h b/include/llvm/CodeGen/ScheduleHazardRecognizer.h
new file mode 100644
index 0000000..5cf45f7
--- /dev/null
+++ b/include/llvm/CodeGen/ScheduleHazardRecognizer.h
@@ -0,0 +1,63 @@
+//=- llvm/CodeGen/ScheduleHazardRecognizer.h - Scheduling 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 implements the ScheduleHazardRecognizer class, which implements
+// hazard-avoidance heuristics for scheduling.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_SCHEDULEHAZARDRECOGNIZER_H
+#define LLVM_CODEGEN_SCHEDULEHAZARDRECOGNIZER_H
+
+namespace llvm {
+
+class SUnit;
+
+/// HazardRecognizer - This determines whether or not an instruction can be
+/// issued this cycle, and whether or not a noop needs to be inserted to handle
+/// the hazard.
+class ScheduleHazardRecognizer {
+public:
+  virtual ~ScheduleHazardRecognizer();
+
+  enum HazardType {
+    NoHazard,      // This instruction can be emitted at this cycle.
+    Hazard,        // This instruction can't be emitted at this cycle.
+    NoopHazard     // This instruction can't be emitted, and needs noops.
+  };
+
+  /// getHazardType - Return the hazard type of emitting this node.  There are
+  /// three possible results.  Either:
+  ///  * NoHazard: it is legal to issue this instruction on this cycle.
+  ///  * Hazard: issuing this instruction would stall the machine.  If some
+  ///     other instruction is available, issue it first.
+  ///  * NoopHazard: issuing this instruction would break the program.  If
+  ///     some other instruction can be issued, do so, otherwise issue a noop.
+  virtual HazardType getHazardType(SUnit *) {
+    return NoHazard;
+  }
+
+  /// EmitInstruction - This callback is invoked when an instruction is
+  /// emitted, to advance the hazard state.
+  virtual void EmitInstruction(SUnit *) {}
+
+  /// AdvanceCycle - This callback is invoked when no instructions can be
+  /// issued on this cycle without a hazard.  This should increment the
+  /// internal state of the hazard recognizer so that previously "Hazard"
+  /// instructions will now not be hazards.
+  virtual void AdvanceCycle() {}
+
+  /// EmitNoop - This callback is invoked when a noop was added to the
+  /// instruction stream.
+  virtual void EmitNoop() {}
+};
+
+}
+
+#endif