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