[NFC][Regalloc] Factor types that would be used by the eviction advisor

This is in prepartion of pulling the eviction decision-making into an
analysis pass, which would then allow swapping that decision making
process.

RFC: https://lists.llvm.org/pipermail/llvm-dev/2021-November/153639.html

Differential Revision: https://reviews.llvm.org/D113929

llvm/lib/CodeGen/RegAllocEvictionAdvisor.h

@@ -0,0 +1,90 @@
+//===- RegAllocEvictionAdvisor.h - Interference resolution ------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_REGALLOCEVICTIONADVISOR_H
+#define LLVM_CODEGEN_REGALLOCEVICTIONADVISOR_H
+
+#include "AllocationOrder.h"
+#include "llvm/ADT/IndexedMap.h"
+#include "llvm/ADT/SmallSet.h"
+#include "llvm/CodeGen/LiveInterval.h"
+#include "llvm/CodeGen/LiveIntervals.h"
+#include "llvm/CodeGen/LiveRegMatrix.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/Register.h"
+#include "llvm/CodeGen/TargetRegisterInfo.h"
+#include "llvm/Pass.h"
+
+namespace llvm {
+
+using SmallVirtRegSet = SmallSet<Register, 16>;
+
+// Live ranges pass through a number of stages as we try to allocate them.
+// Some of the stages may also create new live ranges:
+//
+// - Region splitting.
+// - Per-block splitting.
+// - Local splitting.
+// - Spilling.
+//
+// Ranges produced by one of the stages skip the previous stages when they are
+// dequeued. This improves performance because we can skip interference checks
+// that are unlikely to give any results. It also guarantees that the live
+// range splitting algorithm terminates, something that is otherwise hard to
+// ensure.
+enum LiveRangeStage {
+  /// Newly created live range that has never been queued.
+  RS_New,
+
+  /// Only attempt assignment and eviction. Then requeue as RS_Split.
+  RS_Assign,
+
+  /// Attempt live range splitting if assignment is impossible.
+  RS_Split,
+
+  /// Attempt more aggressive live range splitting that is guaranteed to make
+  /// progress.  This is used for split products that may not be making
+  /// progress.
+  RS_Split2,
+
+  /// Live range will be spilled.  No more splitting will be attempted.
+  RS_Spill,
+
+  /// Live range is in memory. Because of other evictions, it might get moved
+  /// in a register in the end.
+  RS_Memory,
+
+  /// There is nothing more we can do to this live range.  Abort compilation
+  /// if it can't be assigned.
+  RS_Done
+};
+
+/// Cost of evicting interference - used by default advisor, and the eviction
+/// chain heuristic in RegAllocGreedy.
+// FIXME: this can be probably made an implementation detail of the default
+// advisor, if the eviction chain logic can be refactored.
+struct EvictionCost {
+  unsigned BrokenHints = 0; ///< Total number of broken hints.
+  float MaxWeight = 0;      ///< Maximum spill weight evicted.
+
+  EvictionCost() = default;
+
+  bool isMax() const { return BrokenHints == ~0u; }
+
+  void setMax() { BrokenHints = ~0u; }
+
+  void setBrokenHints(unsigned NHints) { BrokenHints = NHints; }
+
+  bool operator<(const EvictionCost &O) const {
+    return std::tie(BrokenHints, MaxWeight) <
+           std::tie(O.BrokenHints, O.MaxWeight);
+  }
+};
+} // namespace llvm
+
+#endif // LLVM_CODEGEN_REGALLOCEVICTIONADVISOR_H

llvm/lib/CodeGen/RegAllocGreedy.cpp

@@ -15,6 +15,7 @@
 #include "InterferenceCache.h"
 #include "LiveDebugVariables.h"
 #include "RegAllocBase.h"
+#include "RegAllocEvictionAdvisor.h"
 #include "SpillPlacement.h"
 #include "SplitKit.h"
 #include "llvm/ADT/ArrayRef.h"
@@ -57,6 +58,7 @@
 #include "llvm/CodeGen/TargetRegisterInfo.h"
 #include "llvm/CodeGen/TargetSubtargetInfo.h"
 #include "llvm/CodeGen/VirtRegMap.h"
+#include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/MC/MCRegisterInfo.h"
@@ -69,7 +71,6 @@
 #include "llvm/Support/Timer.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Target/TargetMachine.h"
-#include "llvm/IR/DebugInfoMetadata.h"
 #include <algorithm>
 #include <cassert>
 #include <cstdint>
@@ -148,7 +149,6 @@ class RAGreedy : public MachineFunctionPass,
   // Convenient shortcuts.
   using PQueue = std::priority_queue<std::pair<unsigned, unsigned>>;
   using SmallLISet = SmallPtrSet<LiveInterval *, 4>;
-  using SmallVirtRegSet = SmallSet<Register, 16>;
 
   // context
   MachineFunction *MF;
@@ -175,47 +175,6 @@ class RAGreedy : public MachineFunctionPass,
   unsigned NextCascade;
   std::unique_ptr<VirtRegAuxInfo> VRAI;
 
-  // Live ranges pass through a number of stages as we try to allocate them.
-  // Some of the stages may also create new live ranges:
-  //
-  // - Region splitting.
-  // - Per-block splitting.
-  // - Local splitting.
-  // - Spilling.
-  //
-  // Ranges produced by one of the stages skip the previous stages when they are
-  // dequeued. This improves performance because we can skip interference checks
-  // that are unlikely to give any results. It also guarantees that the live
-  // range splitting algorithm terminates, something that is otherwise hard to
-  // ensure.
-  enum LiveRangeStage {
-    /// Newly created live range that has never been queued.
-    RS_New,
-
-    /// Only attempt assignment and eviction. Then requeue as RS_Split.
-    RS_Assign,
-
-    /// Attempt live range splitting if assignment is impossible.
-    RS_Split,
-
-    /// Attempt more aggressive live range splitting that is guaranteed to make
-    /// progress.  This is used for split products that may not be making
-    /// progress.
-    RS_Split2,
-
-    /// Live range will be spilled.  No more splitting will be attempted.
-    RS_Spill,
-
-
-    /// Live range is in memory. Because of other evictions, it might get moved
-    /// in a register in the end.
-    RS_Memory,
-
-    /// There is nothing more we can do to this live range.  Abort compilation
-    /// if it can't be assigned.
-    RS_Done
-  };
-
   // Enum CutOffStage to keep a track whether the register allocation failed
   // because of the cutoffs encountered in last chance recoloring.
   // Note: This is used as bitmask. New value should be next power of 2.
@@ -267,25 +226,6 @@ class RAGreedy : public MachineFunctionPass,
     }
   }
 
-  /// Cost of evicting interference.
-  struct EvictionCost {
-    unsigned BrokenHints = 0; ///< Total number of broken hints.
-    float MaxWeight = 0;      ///< Maximum spill weight evicted.
-
-    EvictionCost() = default;
-
-    bool isMax() const { return BrokenHints == ~0u; }
-
-    void setMax() { BrokenHints = ~0u; }
-
-    void setBrokenHints(unsigned NHints) { BrokenHints = NHints; }
-
-    bool operator<(const EvictionCost &O) const {
-      return std::tie(BrokenHints, MaxWeight) <
-             std::tie(O.BrokenHints, O.MaxWeight);
-    }
-  };
-
   /// EvictionTrack - Keeps track of past evictions in order to optimize region
   /// split decision.
   class EvictionTrack {