Break the spill placement algorithm into three parts: prepare, addConstraints, and finish.
This will allow us to abort the algorithm early if it is determined to be futile.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@129020 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SpillPlacement.h b/lib/CodeGen/SpillPlacement.h
index b0135cb..d1c6ceb 100644
--- a/lib/CodeGen/SpillPlacement.h
+++ b/lib/CodeGen/SpillPlacement.h
@@ -10,8 +10,8 @@
// This analysis computes the optimal spill code placement between basic blocks.
//
// The runOnMachineFunction() method only precomputes some profiling information
-// about the CFG. The real work is done by placeSpills() which is called by the
-// register allocator.
+// about the CFG. The real work is done by prepare(), addConstraints(), and
+// finish() which are called by the register allocator.
//
// Given a variable that is live across multiple basic blocks, and given
// constraints on the basic blocks where the variable is live, determine which
@@ -27,6 +27,7 @@
#ifndef LLVM_CODEGEN_SPILLPLACEMENT_H
#define LLVM_CODEGEN_SPILLPLACEMENT_H
+#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
@@ -44,7 +45,7 @@
const MachineLoopInfo *loops;
Node *nodes;
- // Nodes that are active in the current computation. Owned by the placeSpills
+ // Nodes that are active in the current computation. Owned by the prepare()
// caller.
BitVector *ActiveNodes;
@@ -73,24 +74,31 @@
BorderConstraint Exit : 8; ///< Constraint on block exit.
};
- /// placeSpills - 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
- /// expected execution frequencies.
- /// @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.
+ /// prepare - Reset state and prepare for a new spill placement computation.
/// @param RegBundles Bit vector to receive the edge bundles where the
/// variable should be kept in a register. Each bit
/// corresponds to an edge bundle, a set bit means the
/// variable should be kept in a register through the
/// bundle. A clear bit means the variable should be
- /// spilled.
+ /// spilled. This vector is retained.
+ void prepare(BitVector &RegBundles);
+
+ /// 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.
+ void addConstraints(ArrayRef<BlockConstraint> LiveBlocks);
+
+ /// 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
+ /// expected execution frequencies.
+ /// The selected bundles are returned in the bitvector passed to prepare().
/// @return True if a perfect solution was found, allowing the variable to be
/// in a register through all relevant bundles.
- bool placeSpills(const SmallVectorImpl<BlockConstraint> &LiveBlocks,
- BitVector &RegBundles);
+ bool finish();
/// getBlockFrequency - Return the estimated block execution frequency per
/// function invocation.
@@ -104,7 +112,6 @@
virtual void releaseMemory();
void activate(unsigned);
- void prepareNodes(const SmallVectorImpl<BlockConstraint>&);
void iterate(const SmallVectorImpl<unsigned>&);
};