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80 lines
2.8 KiB
C++
80 lines
2.8 KiB
C++
//===- llvm/Transforms/HoistPHIConstants.h - Normalize PHI nodes ------------=//
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//
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// HoistPHIConstants - Remove literal constants that are arguments of PHI nodes
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// by inserting cast instructions in the preceeding basic blocks, and changing
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// constant references into references of the casted value.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/HoistPHIConstants.h"
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#include "llvm/iPHINode.h"
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#include "llvm/iOther.h"
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#include "llvm/BasicBlock.h"
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#include "llvm/Method.h"
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#include <map>
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#include <vector>
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typedef std::pair<BasicBlock *, Value*> BBConstTy;
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typedef std::map<BBConstTy, CastInst *> CachedCopyMap;
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static Value *NormalizePhiOperand(PHINode *PN, Value *CPV,
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BasicBlock *Pred, CachedCopyMap &CopyCache) {
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/* NOTE: CahedCopyMap was disabled to insert phi elimination code
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for all phi args -- Ruchira
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*/
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// Check if we've already inserted a copy for this constant in Pred
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// Note that `copyCache[Pred]' will create an empty vector the first time
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//
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CachedCopyMap::iterator CCI = CopyCache.find(BBConstTy(Pred, CPV));
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if (CCI != CopyCache.end()) return CCI->second;
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// Create a copy instruction and add it to the cache...
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CastInst *Inst = new CastInst(CPV, CPV->getType());
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CopyCache.insert(std::make_pair(BBConstTy(Pred, CPV), Inst));
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// Insert the copy just before the terminator inst of the predecessor BB
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assert(Pred->getTerminator() && "Degenerate BB encountered!");
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Pred->getInstList().insert(Pred->getInstList().end()-1, Inst);
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return Inst;
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}
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//---------------------------------------------------------------------------
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// Entry point for normalizing constant args in PHIs
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//---------------------------------------------------------------------------
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bool HoistPHIConstants::doHoistPHIConstants(Method *M) {
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CachedCopyMap Cache;
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bool Changed = false;
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for (Method::iterator BI = M->begin(), BE = M->end(); BI != BE; ++BI) {
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std::vector<PHINode*> phis; // normalizing invalidates BB iterator
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for (BasicBlock::iterator II = (*BI)->begin(); II != (*BI)->end(); ++II) {
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if (PHINode *PN = dyn_cast<PHINode>(*II))
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phis.push_back(PN);
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else
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break; // All PHIs occur at top of BB!
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}
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for (std::vector<PHINode*>::iterator PI=phis.begin(); PI != phis.end();++PI)
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for (unsigned i = 0; i < (*PI)->getNumIncomingValues(); ++i) {
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Value *Op = (*PI)->getIncomingValue(i);
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if (isa<Constant>(Op)) {
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(*PI)->setIncomingValue(i,
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NormalizePhiOperand((*PI),
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(*PI)->getIncomingValue(i),
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(*PI)->getIncomingBlock(i), Cache));
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Changed = true;
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}
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}
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}
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return Changed;
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}
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