Add the beginnings of an implementatation of lazy liveness analysis, based on "Fast Liveness Checking for SSA-form Programs" by Boissinot, et al.

This is still very early, hasn't been tested, and is not yet well documented.  More to come soon.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@73141 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 62 insertions, 0 deletions

diff --git a/include/llvm/CodeGen/LazyLiveness.h b/include/llvm/CodeGen/LazyLiveness.h
new file mode 100644
index 0000000000..702ba142c5
--- /dev/null
+++ b/include/llvm/CodeGen/LazyLiveness.h
@@ -0,0 +1,62 @@
+//===- LazyLiveness.h - Lazy, CFG-invariant liveness information ----------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass implements a lazy liveness analysis as per "Fast Liveness Checking
+// for SSA-form Programs," by Boissinot, et al.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_LAZYLIVENESS_H
+#define LLVM_CODEGEN_LAZYLIVENESS_H
+
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineDominators.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/DenseSet.h"
+#include "llvm/ADT/SparseBitVector.h"
+#include <vector>
+
+namespace llvm {
+
+class MachineRegisterInfo;
+
+class LazyLiveness : public MachineFunctionPass {
+public:
+  static char ID; // Pass identification, replacement for typeid
+  LazyLiveness() : MachineFunctionPass(&ID) { }
+  
+  void getAnalysisUsage(AnalysisUsage &AU) const {
+    AU.setPreservesAll();
+    AU.addRequired<MachineDominatorTree>();
+  }
+  
+  bool runOnMachineFunction(MachineFunction &mf);
+
+  bool vregLiveIntoMBB(unsigned vreg, MachineBasicBlock* MBB);
+  
+private:
+  void computeBackedgeChain(MachineFunction& mf, MachineBasicBlock* MBB);
+  
+  typedef std::pair<MachineBasicBlock*, MachineBasicBlock*> edge_t;
+  
+  MachineRegisterInfo* MRI;
+  
+  DenseMap<MachineBasicBlock*, unsigned> preorder;
+  std::vector<MachineBasicBlock*> rev_preorder;
+  DenseMap<MachineBasicBlock*, SparseBitVector<128> > rv;
+  DenseMap<MachineBasicBlock*, SparseBitVector<128> > tv;
+  DenseSet<edge_t> backedges;
+  SparseBitVector<128> backedge_source;
+  SparseBitVector<128> backedge_target;
+  SparseBitVector<128> calculated;
+};
+
+}
+
+#endif
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