Extract live range calculations from SplitKit.

[oota-llvm.git] / lib / CodeGen / SpillPlacement.h

diff --git a/lib/CodeGen/SpillPlacement.h b/lib/CodeGen/SpillPlacement.h
index d1c6ceb78575ec39c6ac3c5134c957165a00ccfc..fc412f817cdb490545129c4bfd9710558a4b0fd4 100644 (file)
--- a/lib/CodeGen/SpillPlacement.h
+++ b/lib/CodeGen/SpillPlacement.h
@@ -49,6 +49,13 @@ class SpillPlacement  : public MachineFunctionPass {
   // caller.
   BitVector *ActiveNodes;
 
+  // Nodes with active links. Populated by scanActiveBundles.
+  SmallVector<unsigned, 8> Linked;
+
+  // Nodes that went positive during the last call to scanActiveBundles or
+  // iterate.
+  SmallVector<unsigned, 8> RecentPositive;
+
   // Block frequencies are computed once. Indexed by block number.
   SmallVector<float, 4> BlockFrequency;
 
@@ -64,6 +71,7 @@ public:
     DontCare,  ///< Block doesn't care / variable not live.
     PrefReg,   ///< Block entry/exit prefers a register.
     PrefSpill, ///< Block entry/exit prefers a stack slot.
+    PrefBoth,  ///< Block entry prefers both register and stack.
     MustSpill  ///< A register is impossible, variable must be spilled.
   };
 
@@ -72,6 +80,11 @@ public:
     unsigned Number;            ///< Basic block number (from MBB::getNumber()).
     BorderConstraint Entry : 8; ///< Constraint on block entry.
     BorderConstraint Exit : 8;  ///< Constraint on block exit.
+
+    /// True when this block changes the value of the live range. This means
+    /// the block has a non-PHI def.  When this is false, a live-in value on
+    /// the stack can be live-out on the stack without inserting a spill.
+    bool ChangesValue;
   };
 
   /// prepare - Reset state and prepare for a new spill placement computation.
@@ -86,11 +99,35 @@ public:
   /// addConstraints - Add constraints and biases. This method may be called
   /// more than once to accumulate constraints.
   /// @param LiveBlocks Constraints for blocks that have the variable live in or
-  ///                   live out. DontCare/DontCare means the variable is live
-  ///                   through the block. DontCare/X means the variable is live
-  ///                   out, but not live in.
+  ///                   live out.
   void addConstraints(ArrayRef<BlockConstraint> LiveBlocks);
 
+  /// addPrefSpill - Add PrefSpill constraints to all blocks listed.  This is
+  /// equivalent to calling addConstraint with identical BlockConstraints with
+  /// Entry = Exit = PrefSpill, and ChangesValue = false.
+  ///
+  /// @param Blocks Array of block numbers that prefer to spill in and out.
+  /// @param Strong When true, double the negative bias for these blocks.
+  void addPrefSpill(ArrayRef<unsigned> Blocks, bool Strong);
+
+  /// addLinks - Add transparent blocks with the given numbers.
+  void addLinks(ArrayRef<unsigned> Links);
+
+  /// scanActiveBundles - Perform an initial scan of all bundles activated by
+  /// addConstraints and addLinks, updating their state. Add all the bundles
+  /// that now prefer a register to RecentPositive.
+  /// Prepare internal data structures for iterate.
+  /// Return true is there are any positive nodes.
+  bool scanActiveBundles();
+
+  /// iterate - Update the network iteratively until convergence, or new bundles
+  /// are found.
+  void iterate();
+
+  /// getRecentPositive - Return an array of bundles that became positive during
+  /// the previous call to scanActiveBundles or iterate.
+  ArrayRef<unsigned> getRecentPositive() { return RecentPositive; }
+
   /// finish - Compute the optimal spill code placement given the
   /// constraints. No MustSpill constraints will be violated, and the smallest
   /// possible number of PrefX constraints will be violated, weighted by
@@ -112,7 +149,6 @@ private:
   virtual void releaseMemory();
 
   void activate(unsigned);
-  void iterate(const SmallVectorImpl<unsigned>&);
 };
 
 } // end namespace llvm