Skeleton for MachineInstr level SSA updater.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@90353 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/MachineSSAUpdater.h

@@ -0,0 +1,99 @@
+//===-- MachineSSAUpdater.h - Unstructured SSA Update Tool ------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file declares the MachineSSAUpdater class.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_MACHINESSAUPDATER_H
+#define LLVM_CODEGEN_MACHINESSAUPDATER_H
+
+namespace llvm {
+  class MachineBasicBlock;
+  class MachineInstr;
+  template<typename T> class SmallVectorImpl;
+
+/// SSAUpdater - This class updates SSA form for a set of values defined in
+/// multiple blocks.  This is used when code duplication or another unstructured
+/// transformation wants to rewrite a set of uses of one value with uses of a
+/// set of values.
+class MachineSSAUpdater {
+  /// AvailableVals - This keeps track of which value to use on a per-block
+  /// basis.  When we insert PHI nodes, we keep track of them here.
+  //typedef DenseMap<MachineBasicBlock*, unsigned > AvailableValsTy;
+  void *AV;
+
+  /// IncomingPredInfo - We use this as scratch space when doing our recursive
+  /// walk.  This should only be used in GetValueInBlockInternal, normally it
+  /// should be empty.
+  //std::vector<std::pair<MachineBasicBlock*, unsigned > > IncomingPredInfo;
+  void *IPI;
+
+  /// InsertedPHIs - If this is non-null, the MachineSSAUpdater adds all PHI
+  /// nodes that it creates to the vector.
+  SmallVectorImpl<MachineInstr*> *InsertedPHIs;
+public:
+  /// MachineSSAUpdater constructor.  If InsertedPHIs is specified, it will be
+  /// filled in with all PHI Nodes created by rewriting.
+  explicit MachineSSAUpdater(SmallVectorImpl<MachineInstr*> *InsertedPHIs = 0);
+  ~MachineSSAUpdater();
+
+  /// Initialize - Reset this object to get ready for a new set of SSA
+  /// updates.
+  void Initialize();
+
+  /// AddAvailableValue - Indicate that a rewritten value is available at the
+  /// end of the specified block with the specified value.
+  void AddAvailableValue(MachineBasicBlock *BB, unsigned V);
+
+  /// HasValueForBlock - Return true if the MachineSSAUpdater already has a
+  /// value for the specified block.
+  bool HasValueForBlock(MachineBasicBlock *BB) const;
+
+  /// GetValueAtEndOfBlock - Construct SSA form, materializing a value that is
+  /// live at the end of the specified block.
+  unsigned GetValueAtEndOfBlock(MachineBasicBlock *BB);
+
+  /// GetValueInMiddleOfBlock - Construct SSA form, materializing a value that
+  /// is live in the middle of the specified block.
+  ///
+  /// GetValueInMiddleOfBlock is the same as GetValueAtEndOfBlock except in one
+  /// important case: if there is a definition of the rewritten value after the
+  /// 'use' in BB.  Consider code like this:
+  ///
+  ///      X1 = ...
+  ///   SomeBB:
+  ///      use(X)
+  ///      X2 = ...
+  ///      br Cond, SomeBB, OutBB
+  ///
+  /// In this case, there are two values (X1 and X2) added to the AvailableVals
+  /// set by the client of the rewriter, and those values are both live out of
+  /// their respective blocks.  However, the use of X happens in the *middle* of
+  /// a block.  Because of this, we need to insert a new PHI node in SomeBB to
+  /// merge the appropriate values, and this value isn't live out of the block.
+  ///
+  unsigned GetValueInMiddleOfBlock(MachineBasicBlock *BB);
+
+  /// RewriteUse - Rewrite a use of the symbolic value.  This handles PHI nodes,
+  /// which use their value in the corresponding predecessor.  Note that this
+  /// will not work if the use is supposed to be rewritten to a value defined in
+  /// the same block as the use, but above it.  Any 'AddAvailableValue's added
+  /// for the use's block will be considered to be below it.
+  void RewriteUse(unsigned &U);
+
+private:
+  unsigned GetValueAtEndOfBlockInternal(MachineBasicBlock *BB);
+  void operator=(const MachineSSAUpdater&); // DO NOT IMPLEMENT
+  MachineSSAUpdater(const MachineSSAUpdater&);     // DO NOT IMPLEMENT
+};
+
+} // End llvm namespace
+
+#endif

lib/CodeGen/MachineSSAUpdater.cpp

@@ -0,0 +1,108 @@
+//===- MachineSSAUpdater.cpp - Unstructured SSA Update Tool ---------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the MachineSSAUpdater class.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/MachineSSAUpdater.h"
+#include "llvm/CodeGen/MachineInstr.h"
+#include "llvm/ADT/DenseMap.h"
+using namespace llvm;
+
+typedef DenseMap<MachineBasicBlock*, unsigned > AvailableValsTy;
+typedef std::vector<std::pair<MachineBasicBlock*, unsigned> >
+                IncomingPredInfoTy;
+
+static AvailableValsTy &getAvailableVals(void *AV) {
+  return *static_cast<AvailableValsTy*>(AV);
+}
+
+static IncomingPredInfoTy &getIncomingPredInfo(void *IPI) {
+  return *static_cast<IncomingPredInfoTy*>(IPI);
+}
+
+
+MachineSSAUpdater::MachineSSAUpdater(SmallVectorImpl<MachineInstr*> *NewPHI)
+  : AV(0), IPI(0), InsertedPHIs(NewPHI) {}
+
+MachineSSAUpdater::~MachineSSAUpdater() {
+  delete &getAvailableVals(AV);
+  delete &getIncomingPredInfo(IPI);
+}
+
+/// Initialize - Reset this object to get ready for a new set of SSA
+/// updates.  ProtoValue is the value used to name PHI nodes.
+void MachineSSAUpdater::Initialize() {
+  if (AV == 0)
+    AV = new AvailableValsTy();
+  else
+    getAvailableVals(AV).clear();
+
+  if (IPI == 0)
+    IPI = new IncomingPredInfoTy();
+  else
+    getIncomingPredInfo(IPI).clear();
+}
+
+/// HasValueForBlock - Return true if the MachineSSAUpdater already has a value for
+/// the specified block.
+bool MachineSSAUpdater::HasValueForBlock(MachineBasicBlock *BB) const {
+  return getAvailableVals(AV).count(BB);
+}
+
+/// AddAvailableValue - Indicate that a rewritten value is available in the
+/// specified block with the specified value.
+void MachineSSAUpdater::AddAvailableValue(MachineBasicBlock *BB, unsigned V) {
+  getAvailableVals(AV)[BB] = V;
+}
+
+/// GetValueAtEndOfBlock - Construct SSA form, materializing a value that is
+/// live at the end of the specified block.
+unsigned MachineSSAUpdater::GetValueAtEndOfBlock(MachineBasicBlock *BB) {
+  return GetValueAtEndOfBlockInternal(BB);
+}
+
+/// GetValueInMiddleOfBlock - Construct SSA form, materializing a value that
+/// is live in the middle of the specified block.
+///
+/// GetValueInMiddleOfBlock is the same as GetValueAtEndOfBlock except in one
+/// important case: if there is a definition of the rewritten value after the
+/// 'use' in BB.  Consider code like this:
+///
+///      X1 = ...
+///   SomeBB:
+///      use(X)
+///      X2 = ...
+///      br Cond, SomeBB, OutBB
+///
+/// In this case, there are two values (X1 and X2) added to the AvailableVals
+/// set by the client of the rewriter, and those values are both live out of
+/// their respective blocks.  However, the use of X happens in the *middle* of
+/// a block.  Because of this, we need to insert a new PHI node in SomeBB to
+/// merge the appropriate values, and this value isn't live out of the block.
+///
+unsigned MachineSSAUpdater::GetValueInMiddleOfBlock(MachineBasicBlock *BB) {
+  return 0;
+}
+
+/// RewriteUse - Rewrite a use of the symbolic value.  This handles PHI nodes,
+/// which use their value in the corresponding predecessor.
+void MachineSSAUpdater::RewriteUse(unsigned &U) {
+}
+
+
+/// GetValueAtEndOfBlockInternal - Check to see if AvailableVals has an entry
+/// for the specified BB and if so, return it.  If not, construct SSA form by
+/// walking predecessors inserting PHI nodes as needed until we get to a block
+/// where the value is available.
+///
+unsigned MachineSSAUpdater::GetValueAtEndOfBlockInternal(MachineBasicBlock *BB){
+  return 0;
+}