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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;
template<typename T> class SSAUpdaterTraits;
class BumpPtrAllocator;
/// 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 {
friend class SSAUpdaterTraits<SSAUpdater>;
private:
/// 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<BasicBlock*, Value*> AvailableValsTy;
void *AV;
/// ProtoType holds the type of the values being rewritten.
const Type *ProtoType;
// PHI nodes are given a name based on ProtoName.
std::string ProtoName;
/// 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.
explicit SSAUpdater(SmallVectorImpl<PHINode*> *InsertedPHIs = 0);
~SSAUpdater();
/// Initialize - Reset this object to get ready for a new set of SSA
/// updates with type 'Ty'. PHI nodes get a name based on 'Name'.
void Initialize(const Type *Ty, StringRef Name);
/// 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);
/// RewriteUseAfterInsertions - Rewrite a use, just like RewriteUse. However,
/// this version of the method can rewrite uses in the same block as a
/// definition, because it assumes that all uses of a value are below any
/// inserted values.
void RewriteUseAfterInsertions(Use &U);
private:
Value *GetValueAtEndOfBlockInternal(BasicBlock *BB);
void operator=(const SSAUpdater&); // DO NOT IMPLEMENT
SSAUpdater(const SSAUpdater&); // DO NOT IMPLEMENT
};
/// LoadAndStorePromoter - This little helper class provides a convenient way to
/// promote a collection of loads and stores into SSA Form using the SSAUpdater.
/// This handles complexities that SSAUpdater doesn't, such as multiple loads
/// and stores in one block.
///
/// Clients of this class are expected to subclass this and implement the
/// virtual methods.
///
class LoadAndStorePromoter {
protected:
SSAUpdater &SSA;
public:
LoadAndStorePromoter(const SmallVectorImpl<Instruction*> &Insts,
SSAUpdater &S, StringRef Name = StringRef());
virtual ~LoadAndStorePromoter() {}
/// run - This does the promotion. Insts is a list of loads and stores to
/// promote, and Name is the basename for the PHIs to insert. After this is
/// complete, the loads and stores are removed from the code.
void run(const SmallVectorImpl<Instruction*> &Insts) const;
/// Return true if the specified instruction is in the Inst list (which was
/// passed into the run method). Clients should implement this with a more
/// efficient version if possible.
virtual bool isInstInList(Instruction *I,
const SmallVectorImpl<Instruction*> &Insts) const {
for (unsigned i = 0, e = Insts.size(); i != e; ++i)
if (Insts[i] == I)
return true;
return false;
}
/// doExtraRewritesBeforeFinalDeletion - This hook is invoked after all the
/// stores are found and inserted as available values, but
virtual void doExtraRewritesBeforeFinalDeletion() const {
}
/// replaceLoadWithValue - Clients can choose to implement this to get
/// notified right before a load is RAUW'd another value.
virtual void replaceLoadWithValue(LoadInst *LI, Value *V) const {
}
/// This is called before each instruction is deleted.
virtual void instructionDeleted(Instruction *I) const {
}
};
} // End llvm namespace
#endif
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