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123 lines
4.2 KiB
C++
123 lines
4.2 KiB
C++
/* Title: FunctionLiveVarInfo.h -*- C++ -*-
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Author: Ruchira Sasanka
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Date: Jun 30, 01
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Purpose:
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This is the interface for live variable info of a function that is required
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by any other part of the compiler
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It must be called like:
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FunctionLiveVarInfo FLVI(Function *); // initializes data structures
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FLVI.analyze(); // do the actural live variable anal
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After the analysis, getInSetOfBB or getOutSetofBB can be called to get
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live var info of a BB.
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The live var set before an instruction can be obtained in 2 ways:
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1. Use the method getLiveVarSetAfterInst(Instruction *) to get the LV Info
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just after an instruction. (also exists getLiveVarSetBeforeInst(..))
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This function caluclates the LV info for a BB only once and caches that
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info. If the cache does not contain the LV info of the instruction, it
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calculates the LV info for the whole BB and caches them.
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Getting liveVar info this way uses more memory since, LV info should be
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cached. However, if you need LV info of nearly all the instructions of a
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BB, this is the best and simplest interfrace.
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2. Use the OutSet and applyTranferFuncForInst(const Instruction *const Inst)
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declared in LiveVarSet and traverse the instructions of a basic block in
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reverse (using const_reverse_iterator in the BB class).
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This is the most memory efficient method if you need LV info for
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only several instructions in a BasicBlock. An example is given below:
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LiveVarSet LVSet; // this will be the set used to traverse through each BB
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// Initialize LVSet so that it is the same as OutSet of the BB
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LVSet.setUnion( LVI->getOutSetOfBB( *BBI ) );
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BasicBlock::InstListType::const_reverse_iterator
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InstIterator = InstListInBB.rbegin(); // get the rev iter for inst in BB
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// iterate over all the instructions in BB in reverse
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for( ; InstIterator != InstListInBB.rend(); InstIterator++) {
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//...... all code here which uses LVSet ........
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LVSet.applyTranferFuncForInst(*InstIterator);
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// Now LVSet contains live vars ABOVE the current instrution
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}
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See buildInterferenceGraph() for the above example.
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*/
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#ifndef FUNCTION_LIVE_VAR_INFO_H
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#define FUNCTION_LIVE_VAR_INFO_H
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#include "llvm/Pass.h"
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#include "llvm/CodeGen/ValueSet.h"
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class BBLiveVar;
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class MachineInstr;
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class FunctionLiveVarInfo : public FunctionPass {
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// Machine Instr to LiveVarSet Map for providing LVset BEFORE each inst
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std::map<const MachineInstr *, const ValueSet *> MInst2LVSetBI;
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// Machine Instr to LiveVarSet Map for providing LVset AFTER each inst
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std::map<const MachineInstr *, const ValueSet *> MInst2LVSetAI;
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// Stored Function that the data is computed with respect to
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const Function *M;
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// --------- private methods -----------------------------------------
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// constructs BBLiveVars and init Def and In sets
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void constructBBs(const Function *F);
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// do one backward pass over the CFG
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bool doSingleBackwardPass(const Function *F, unsigned int iter);
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// calculates live var sets for instructions in a BB
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void calcLiveVarSetsForBB(const BasicBlock *BB);
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public:
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// --------- Implement the FunctionPass interface ----------------------
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// runOnFunction - Perform analysis, update internal data structures.
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virtual bool runOnFunction(Function &F);
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// releaseMemory - After LiveVariable analysis has been used, forget!
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virtual void releaseMemory();
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// getAnalysisUsage - Provide self!
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.setPreservesAll();
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}
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// --------- Functions to access analysis results -------------------
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// gets OutSet of a BB
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const ValueSet &getOutSetOfBB(const BasicBlock *BB) const;
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// gets InSet of a BB
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const ValueSet &getInSetOfBB(const BasicBlock *BB) const;
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// gets the Live var set BEFORE an instruction
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const ValueSet &getLiveVarSetBeforeMInst(const MachineInstr *MI,
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const BasicBlock *BB);
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// gets the Live var set AFTER an instruction
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const ValueSet &getLiveVarSetAfterMInst(const MachineInstr *MI,
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const BasicBlock *BB);
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};
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#endif
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