Skeleton for MachineInstr level SSA updater.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@90353 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/MachineSSAUpdater.cpp b/lib/CodeGen/MachineSSAUpdater.cpp
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+++ b/lib/CodeGen/MachineSSAUpdater.cpp
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+//===- 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;
+}