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//===-- SSAUpdater.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 SSAUpdater class.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_TRANSFORMS_UTILS_SSAUPDATER_H
#define LLVM_TRANSFORMS_UTILS_SSAUPDATER_H
namespace llvm {
class Value;
class BasicBlock;
class Use;
class PHINode;
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 SSAUpdater {
/// 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. We use
/// WeakVH's for the value of the map because we RAUW PHI nodes when we
/// eliminate them, and want the WeakVH to track this.
//typedef DenseMap<BasicBlock*, TrackingVH<Value> > AvailableValsTy;
void *AV;
/// PrototypeValue is an arbitrary representative value, which we derive names
/// and a type for PHI nodes.
Value *PrototypeValue;
/// 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<BasicBlock*, TrackingVH<Value> > > IncomingPredInfo;
void *IPI;
/// InsertedPHIs - If this is non-null, the SSAUpdater adds all PHI nodes that
/// it creates to the vector.
SmallVectorImpl<PHINode*> *InsertedPHIs;
public:
/// SSAUpdater constructor. If InsertedPHIs is specified, it will be filled
/// in with all PHI Nodes created by rewriting.
SSAUpdater(SmallVectorImpl<PHINode*> *InsertedPHIs = 0);
~SSAUpdater();
/// Initialize - Reset this object to get ready for a new set of SSA
/// updates. ProtoValue is the value used to name PHI nodes.
void Initialize(Value *ProtoValue);
/// AddAvailableValue - Indicate that a rewritten value is available at the
/// end of the specified block with the specified value.
void AddAvailableValue(BasicBlock *BB, Value *V);
/// HasValueForBlock - Return true if the SSAUpdater already has a value for
/// the specified block.
bool HasValueForBlock(BasicBlock *BB) const;
/// GetValueAtEndOfBlock - Construct SSA form, materializing a value that is
/// live at the end of the specified block.
Value *GetValueAtEndOfBlock(BasicBlock *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.
///
Value *GetValueInMiddleOfBlock(BasicBlock *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(Use &U);
private:
Value *GetValueAtEndOfBlockInternal(BasicBlock *BB);
void operator=(const SSAUpdater&); // DO NOT IMPLEMENT
SSAUpdater(const SSAUpdater&); // DO NOT IMPLEMENT
};
} // End llvm namespace
#endif
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