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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206142 91177308-0d34-0410-b5e6-96231b3b80d8
178 lines
6.1 KiB
C++
178 lines
6.1 KiB
C++
//===-- SSAUpdater.h - Unstructured SSA Update Tool -------------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file declares the SSAUpdater class.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_TRANSFORMS_UTILS_SSAUPDATER_H
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#define LLVM_TRANSFORMS_UTILS_SSAUPDATER_H
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#include "llvm/ADT/StringRef.h"
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#include "llvm/Support/Compiler.h"
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namespace llvm {
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class BasicBlock;
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class Instruction;
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class LoadInst;
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template<typename T> class SmallVectorImpl;
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template<typename T> class SSAUpdaterTraits;
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class PHINode;
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class Type;
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class Use;
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class Value;
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/// \brief Helper class for SSA formation on a set of values defined in
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/// multiple blocks.
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///
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/// This is used when code duplication or another unstructured
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/// transformation wants to rewrite a set of uses of one value with uses of a
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/// set of values.
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class SSAUpdater {
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friend class SSAUpdaterTraits<SSAUpdater>;
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private:
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/// This keeps track of which value to use on a per-block basis. When we
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/// insert PHI nodes, we keep track of them here.
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//typedef DenseMap<BasicBlock*, Value*> AvailableValsTy;
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void *AV;
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/// ProtoType holds the type of the values being rewritten.
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Type *ProtoType;
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/// PHI nodes are given a name based on ProtoName.
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std::string ProtoName;
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/// If this is non-null, the SSAUpdater adds all PHI nodes that it creates to
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/// the vector.
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SmallVectorImpl<PHINode*> *InsertedPHIs;
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public:
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/// If InsertedPHIs is specified, it will be filled
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/// in with all PHI Nodes created by rewriting.
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explicit SSAUpdater(SmallVectorImpl<PHINode*> *InsertedPHIs = nullptr);
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~SSAUpdater();
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/// \brief Reset this object to get ready for a new set of SSA updates with
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/// type 'Ty'.
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///
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/// PHI nodes get a name based on 'Name'.
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void Initialize(Type *Ty, StringRef Name);
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/// \brief Indicate that a rewritten value is available in the specified block
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/// with the specified value.
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void AddAvailableValue(BasicBlock *BB, Value *V);
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/// \brief Return true if the SSAUpdater already has a value for the specified
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/// block.
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bool HasValueForBlock(BasicBlock *BB) const;
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/// \brief Construct SSA form, materializing a value that is live at the end
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/// of the specified block.
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Value *GetValueAtEndOfBlock(BasicBlock *BB);
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/// \brief Construct SSA form, materializing a value that is live in the
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/// middle of the specified block.
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///
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/// \c GetValueInMiddleOfBlock is the same as \c GetValueAtEndOfBlock except
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/// in one important case: if there is a definition of the rewritten value
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/// after the 'use' in BB. Consider code like this:
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///
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/// \code
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/// X1 = ...
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/// SomeBB:
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/// use(X)
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/// X2 = ...
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/// br Cond, SomeBB, OutBB
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/// \endcode
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///
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/// In this case, there are two values (X1 and X2) added to the AvailableVals
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/// set by the client of the rewriter, and those values are both live out of
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/// their respective blocks. However, the use of X happens in the *middle* of
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/// a block. Because of this, we need to insert a new PHI node in SomeBB to
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/// merge the appropriate values, and this value isn't live out of the block.
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Value *GetValueInMiddleOfBlock(BasicBlock *BB);
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/// \brief Rewrite a use of the symbolic value.
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///
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/// This handles PHI nodes, which use their value in the corresponding
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/// predecessor. Note that this will not work if the use is supposed to be
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/// rewritten to a value defined in the same block as the use, but above it.
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/// Any 'AddAvailableValue's added for the use's block will be considered to
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/// be below it.
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void RewriteUse(Use &U);
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/// \brief Rewrite a use like \c RewriteUse but handling in-block definitions.
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///
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/// This version of the method can rewrite uses in the same block as
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/// a definition, because it assumes that all uses of a value are below any
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/// inserted values.
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void RewriteUseAfterInsertions(Use &U);
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private:
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Value *GetValueAtEndOfBlockInternal(BasicBlock *BB);
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void operator=(const SSAUpdater&) LLVM_DELETED_FUNCTION;
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SSAUpdater(const SSAUpdater&) LLVM_DELETED_FUNCTION;
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};
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/// \brief Helper class for promoting a collection of loads and stores into SSA
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/// Form using the SSAUpdater.
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///
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/// This handles complexities that SSAUpdater doesn't, such as multiple loads
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/// and stores in one block.
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///
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/// Clients of this class are expected to subclass this and implement the
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/// virtual methods.
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class LoadAndStorePromoter {
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protected:
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SSAUpdater &SSA;
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public:
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LoadAndStorePromoter(const SmallVectorImpl<Instruction*> &Insts,
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SSAUpdater &S, StringRef Name = StringRef());
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virtual ~LoadAndStorePromoter() {}
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/// \brief This does the promotion.
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///
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/// Insts is a list of loads and stores to promote, and Name is the basename
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/// for the PHIs to insert. After this is complete, the loads and stores are
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/// removed from the code.
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void run(const SmallVectorImpl<Instruction*> &Insts) const;
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/// \brief Return true if the specified instruction is in the Inst list.
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///
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/// The Insts list is the one passed into the constructor. Clients should
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/// implement this with a more efficient version if possible.
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virtual bool isInstInList(Instruction *I,
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const SmallVectorImpl<Instruction*> &Insts) const;
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/// \brief This hook is invoked after all the stores are found and inserted as
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/// available values.
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virtual void doExtraRewritesBeforeFinalDeletion() const {
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}
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/// \brief Clients can choose to implement this to get notified right before
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/// a load is RAUW'd another value.
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virtual void replaceLoadWithValue(LoadInst *LI, Value *V) const {
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}
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/// \brief Called before each instruction is deleted.
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virtual void instructionDeleted(Instruction *I) const {
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}
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/// \brief Called to update debug info associated with the instruction.
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virtual void updateDebugInfo(Instruction *I) const {
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}
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};
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} // End llvm namespace
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#endif
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