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Chris Lattner1bffea02001-10-15 17:31:51 +00001//===- llvm/Transforms/HoistPHIConstants.h - Normalize PHI nodes ------------=//
2//
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.
6//
7//===----------------------------------------------------------------------===//
8
9#include "llvm/Transforms/HoistPHIConstants.h"
10#include "llvm/iOther.h"
11#include "llvm/BasicBlock.h"
12#include "llvm/Method.h"
13#include <map>
14
15typedef pair<BasicBlock *, Value*> BBConstTy;
16typedef map<BBConstTy, CastInst *> CachedCopyMap;
17
18static Value *NormalizePhiOperand(PHINode *PN, Value *CPV,
19 BasicBlock *Pred, CachedCopyMap &CopyCache) {
20
21 // Check if we've already inserted a copy for this constant in Pred
22 // Note that `copyCache[Pred]' will create an empty vector the first time
23 //
24 CachedCopyMap::iterator CCI = CopyCache.find(BBConstTy(Pred, CPV));
25 if (CCI != CopyCache.end()) return CCI->second;
26
27 // Create a copy instruction and add it to the cache...
28 CastInst *Inst = new CastInst(CPV, CPV->getType());
29 CopyCache.insert(make_pair(BBConstTy(Pred, CPV), Inst));
30
31 // Insert the copy just before the terminator inst of the predecessor BB
32 assert(Pred->getTerminator() && "Degenerate BB encountered!");
33 Pred->getInstList().insert(Pred->getInstList().end()-1, Inst);
34
35 return Inst;
36}
37
38
39//---------------------------------------------------------------------------
40// Entry point for normalizing constant args in PHIs
41//---------------------------------------------------------------------------
42
Chris Lattner42c9c2c2001-10-18 05:27:33 +000043bool HoistPHIConstants::doHoistPHIConstants(Method *M) {
Chris Lattner1bffea02001-10-15 17:31:51 +000044 CachedCopyMap Cache;
Chris Lattner42c9c2c2001-10-18 05:27:33 +000045 bool Changed = false;
Chris Lattner1bffea02001-10-15 17:31:51 +000046
47 for (Method::iterator BI = M->begin(), BE = M->end(); BI != BE; ++BI)
48 for (BasicBlock::iterator II = (*BI)->begin(); II != (*BI)->end(); ++II) {
49 Instruction *Inst = *II;
50 if (!isa<PHINode>(Inst)) break; // All PHIs occur at top of BB!
51
52 PHINode *PN = cast<PHINode>(Inst);
53 for (unsigned i = 0; i < PN->getNumIncomingValues(); ++i) {
54 Value *Op = PN->getIncomingValue(i);
Chris Lattner42c9c2c2001-10-18 05:27:33 +000055 if (isa<ConstPoolVal>(Op)) {
Chris Lattner1bffea02001-10-15 17:31:51 +000056 PN->setIncomingValue(i,
57 NormalizePhiOperand(PN, Op, PN->getIncomingBlock(i), Cache));
Chris Lattner42c9c2c2001-10-18 05:27:33 +000058 Changed = true;
59 }
Chris Lattner1bffea02001-10-15 17:31:51 +000060 }
61 }
62
Chris Lattner42c9c2c2001-10-18 05:27:33 +000063 return Changed;
Chris Lattner1bffea02001-10-15 17:31:51 +000064}