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113 lines
4.3 KiB
C++
113 lines
4.3 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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namespace llvm {
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class Value;
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class BasicBlock;
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class Use;
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class PHINode;
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template<typename T> class SmallVectorImpl;
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template<typename T> class SSAUpdaterTraits;
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class BumpPtrAllocator;
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/// SSAUpdater - This class updates SSA form for a set of values defined in
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/// multiple blocks. 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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/// AvailableVals - This keeps track of which value to use on a per-block
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/// basis. When we 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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/// PrototypeValue is an arbitrary representative value, which we derive names
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/// and a type for PHI nodes.
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Value *PrototypeValue;
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/// InsertedPHIs - If this is non-null, the SSAUpdater adds all PHI nodes that
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/// it creates to the vector.
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SmallVectorImpl<PHINode*> *InsertedPHIs;
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public:
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/// SSAUpdater constructor. 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 = 0);
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~SSAUpdater();
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/// Initialize - Reset this object to get ready for a new set of SSA
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/// updates. ProtoValue is the value used to name PHI nodes.
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void Initialize(Value *ProtoValue);
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/// AddAvailableValue - Indicate that a rewritten value is available at the
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/// end of the specified block with the specified value.
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void AddAvailableValue(BasicBlock *BB, Value *V);
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/// HasValueForBlock - Return true if the SSAUpdater already has a value for
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/// the specified block.
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bool HasValueForBlock(BasicBlock *BB) const;
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/// GetValueAtEndOfBlock - Construct SSA form, materializing a value that is
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/// live at the end of the specified block.
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Value *GetValueAtEndOfBlock(BasicBlock *BB);
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/// GetValueInMiddleOfBlock - Construct SSA form, materializing a value that
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/// is live in the middle of the specified block.
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///
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/// GetValueInMiddleOfBlock is the same as GetValueAtEndOfBlock except in one
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/// important case: if there is a definition of the rewritten value after the
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/// 'use' in BB. Consider code like this:
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///
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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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///
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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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///
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Value *GetValueInMiddleOfBlock(BasicBlock *BB);
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/// RewriteUse - Rewrite a use of the symbolic value. This handles PHI nodes,
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/// which use their value in the corresponding predecessor. Note that this
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/// will not work if the use is supposed to be rewritten to a value defined in
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/// the same block as the use, but above it. Any 'AddAvailableValue's added
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/// for the use's block will be considered to be below it.
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void RewriteUse(Use &U);
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/// RewriteUseAfterInsertions - Rewrite a use, just like RewriteUse. However,
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/// this version of the method can rewrite uses in the same block as a
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/// 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&); // DO NOT IMPLEMENT
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SSAUpdater(const SSAUpdater&); // DO NOT IMPLEMENT
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};
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} // End llvm namespace
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#endif
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