1 //===- llvm/Transforms/HoistPHIConstants.h - Normalize PHI nodes ------------=//
3 // HoistPHIConstants - Remove literal constants that are arguments of PHI nodes
4 // by inserting cast instructions in the preceeding basic blocks, and changing
5 // constant references into references of the casted value.
7 //===----------------------------------------------------------------------===//
12 #include "llvm/Transforms/HoistPHIConstants.h"
13 #include "llvm/iOther.h"
14 #include "llvm/BasicBlock.h"
15 #include "llvm/Method.h"
18 typedef pair<BasicBlock *, Value*> BBConstTy;
19 typedef map<BBConstTy, CastInst *> CachedCopyMap;
21 static Value *NormalizePhiOperand(PHINode *PN, Value *CPV,
22 BasicBlock *Pred, CachedCopyMap &CopyCache) {
24 /* NOTE: CahedCopyMap was disabled to insert phi elimination code
25 for all phi args -- Ruchira
29 // Check if we've already inserted a copy for this constant in Pred
30 // Note that `copyCache[Pred]' will create an empty vector the first time
32 //CachedCopyMap::iterator CCI = CopyCache.find(BBConstTy(Pred, CPV));
33 //if (CCI != CopyCache.end()) return CCI->second;
35 // Create a copy instruction and add it to the cache...
36 CastInst *Inst = new CastInst(CPV, CPV->getType());
37 //CopyCache.insert(make_pair(BBConstTy(Pred, CPV), Inst));
39 // Insert the copy just before the terminator inst of the predecessor BB
40 assert(Pred->getTerminator() && "Degenerate BB encountered!");
41 Pred->getInstList().insert(Pred->getInstList().end()-1, Inst);
47 //---------------------------------------------------------------------------
48 // Entry point for normalizing constant args in PHIs
49 //---------------------------------------------------------------------------
51 bool HoistPHIConstants::doHoistPHIConstants(Method *M) {
55 for (Method::iterator BI = M->begin(), BE = M->end(); BI != BE; ++BI)
56 for (BasicBlock::iterator II = (*BI)->begin(); II != (*BI)->end(); ++II) {
57 Instruction *Inst = *II;
58 if (!isa<PHINode>(Inst)) break; // All PHIs occur at top of BB!
60 PHINode *PN = cast<PHINode>(Inst);
61 for (unsigned i = 0; i < PN->getNumIncomingValues(); ++i) {
62 Value *Op = PN->getIncomingValue(i);
64 //if (isa<ConstPoolVal>(Op)) { --- Do for all phi args -- Ruchira
66 PN->setIncomingValue(i,
67 NormalizePhiOperand(PN, Op, PN->getIncomingBlock(i), Cache));