Add an InterferenceCache class for caching per-block interference ranges.

When the greedy register allocator is splitting multiple global live ranges, it
tends to look at the same interference data many times. The InterferenceCache
class caches queries for unaltered LiveIntervalUnions.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@128764 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 159 insertions, 0 deletions

diff --git a/lib/CodeGen/InterferenceCache.h b/lib/CodeGen/InterferenceCache.h
new file mode 100644
index 000000000000..2e613ae09593
--- /dev/null
+++ b/lib/CodeGen/InterferenceCache.h
@@ -0,0 +1,159 @@
+//===-- InterferenceCache.h - Caching per-block interference ---*- C++ -*--===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// InterferenceCache remembers per-block interference in LiveIntervalUnions.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_INTERFERENCECACHE
+#define LLVM_CODEGEN_INTERFERENCECACHE
+
+#include "LiveIntervalUnion.h"
+
+namespace llvm {
+
+class InterferenceCache {
+  const TargetRegisterInfo *TRI;
+  LiveIntervalUnion *LIUArray;
+  SlotIndexes *Indexes;
+  MachineFunction *MF;
+
+  /// BlockInterference - information about the interference in a single basic
+  /// block.
+  struct BlockInterference {
+    BlockInterference() : Tag(0) {}
+    unsigned Tag;
+    SlotIndex First;
+    SlotIndex Last;
+  };
+
+  /// Entry - A cache entry containing interference information for all aliases
+  /// of PhysReg in all basic blocks.
+  class Entry {
+    /// PhysReg - The register currently represented.
+    unsigned PhysReg;
+
+    /// Tag - Cache tag is changed when any of the underlying LiveIntervalUnions
+    /// change.
+    unsigned Tag;
+
+    /// Indexes - Mapping block numbers to SlotIndex ranges.
+    SlotIndexes *Indexes;
+
+    /// PrevPos - The previous position the iterators were moved to.
+    SlotIndex PrevPos;
+
+    /// AliasTags - A LiveIntervalUnion pointer and tag for each alias of
+    /// PhysReg.
+    SmallVector<std::pair<LiveIntervalUnion*, unsigned>, 8> Aliases;
+
+    typedef LiveIntervalUnion::SegmentIter Iter;
+
+    /// Iters - an iterator for each alias
+    SmallVector<Iter, 8> Iters;
+
+    /// Blocks - Interference for each block in the function.
+    SmallVector<BlockInterference, 8> Blocks;
+
+    /// update - Recompute Blocks[MBBNum]
+    void update(unsigned MBBNum);
+
+  public:
+    Entry() : PhysReg(0), Tag(0), Indexes(0) {}
+
+    void clear(SlotIndexes *indexes) {
+      PhysReg = 0;
+      Indexes = indexes;
+    }
+
+    unsigned getPhysReg() const { return PhysReg; }
+
+    void revalidate();
+
+    /// valid - Return true if this is a valid entry for physReg.
+    bool valid(LiveIntervalUnion *LIUArray, const TargetRegisterInfo *TRI);
+
+    /// reset - Initialize entry to represent physReg's aliases.
+    void reset(unsigned physReg,
+               LiveIntervalUnion *LIUArray,
+               const TargetRegisterInfo *TRI,
+               const MachineFunction *MF);
+
+    /// get - Return an up to date BlockInterference.
+    BlockInterference *get(unsigned MBBNum) {
+      if (Blocks[MBBNum].Tag != Tag)
+        update(MBBNum);
+      return &Blocks[MBBNum];
+    }
+  };
+
+  // We don't keep a cache entry for every physical register, that would use too
+  // much memory. Instead, a fixed number of cache entries are used in a round-
+  // robin manner.
+  enum { CacheEntries = 32 };
+
+  // Point to an entry for each physreg. The entry pointed to may not be up to
+  // date, and it may have been reused for a different physreg.
+  SmallVector<unsigned char, 2> PhysRegEntries;
+
+  // Next round-robin entry to be picked.
+  unsigned RoundRobin;
+
+  // The actual cache entries.
+  Entry Entries[CacheEntries];
+
+  // get - Get a valid entry for PhysReg.
+  Entry *get(unsigned PhysReg);
+
+public:
+  InterferenceCache() : TRI(0), LIUArray(0), Indexes(0), MF(0), RoundRobin(0) {}
+
+  /// init - Prepare cache for a new function.
+  void init(MachineFunction*, LiveIntervalUnion*, SlotIndexes*,
+            const TargetRegisterInfo *);
+
+  /// Cursor - The primary query interface for the block interference cache.
+  class Cursor {
+    Entry *CacheEntry;
+    BlockInterference *Current;
+  public:
+    /// Cursor - Create a cursor for the interference allocated to PhysReg and
+    /// all its aliases.
+    Cursor(InterferenceCache &Cache, unsigned PhysReg)
+      : CacheEntry(Cache.get(PhysReg)), Current(0) {}
+
+    /// moveTo - Move cursor to basic block MBBNum.
+    void moveToBlock(unsigned MBBNum) {
+      Current = CacheEntry->get(MBBNum);
+    }
+
+    /// hasInterference - Return true if the current block has any interference.
+    bool hasInterference() {
+      return Current->First.isValid();
+    }
+
+    /// first - Return the starting index of the first interfering range in the
+    /// current block.
+    SlotIndex first() {
+      return Current->First;
+    }
+
+    /// last - Return the ending index of the last interfering range in the
+    /// current block.
+    SlotIndex last() {
+      return Current->Last;
+    }
+  };
+
+  friend class Cursor;
+};
+
+} // namespace llvm
+
+#endif