Add utility to clone loops.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@40997 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 149 insertions, 0 deletions

diff --git a/lib/Transforms/Utils/CloneLoop.cpp b/lib/Transforms/Utils/CloneLoop.cpp
new file mode 100644
index 0000000..02278b6
--- /dev/null
+++ b/lib/Transforms/Utils/CloneLoop.cpp
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+//===- CloneLoop.cpp - Clone loop nest ------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by Devang Patel and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the CloneLoop interface which makes a copy of a loop.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Utils/Cloning.h"
+#include "llvm/BasicBlock.h"
+#include "llvm/Analysis/LoopPass.h"
+#include "llvm/Analysis/Dominators.h"
+#include "llvm/ADT/DenseMap.h"
+
+
+using namespace llvm;
+
+/// CloneDominatorInfo - Clone basicblock's dominator tree and, if available,
+/// dominance info. It is expected that basic block is already cloned.
+static void CloneDominatorInfo(BasicBlock *BB, 
+                               DenseMap<const Value *, Value *> &ValueMap,
+                               DominatorTree *DT,
+                               DominanceFrontier *DF) {
+
+  assert (DT && "DominatorTree is not available");
+  DenseMap<const Value *, Value*>::iterator BI = ValueMap.find(BB);
+  assert (BI != ValueMap.end() && "BasicBlock clone is missing");
+  BasicBlock *NewBB = cast<BasicBlock>(BI->second);
+
+  // NewBB already got dominator info.
+  if (DT->getNode(NewBB))
+    return;
+
+  assert (DT->getNode(BB) && "BasicBlock does not have dominator info");
+  // Entry block is not expected here. Infinite loops are not to cloned.
+  assert (DT->getNode(BB)->getIDom() && "BasicBlock does not have immediate dominator");
+  BasicBlock *BBDom = DT->getNode(BB)->getIDom()->getBlock();
+
+  // NewBB's dominator is either BB's dominator or BB's dominator's clone.
+  BasicBlock *NewBBDom = BBDom;
+  DenseMap<const Value *, Value*>::iterator BBDomI = ValueMap.find(BBDom);
+  if (BBDomI != ValueMap.end()) {
+    NewBBDom = cast<BasicBlock>(BBDomI->second);
+    if (!DT->getNode(NewBBDom))
+      CloneDominatorInfo(BBDom, ValueMap, DT, DF);
+  }
+  DT->addNewBlock(NewBB, NewBBDom);
+
+  // Copy cloned dominance frontiner set
+  if (DF) {
+    DominanceFrontier::DomSetType NewDFSet;
+    DominanceFrontier::iterator DFI = DF->find(BB);
+    if ( DFI != DF->end()) {
+      DominanceFrontier::DomSetType S = DFI->second;
+        for (DominanceFrontier::DomSetType::iterator I = S.begin(), E = S.end();
+             I != E; ++I) {
+          BasicBlock *DB = *I;
+          DenseMap<const Value*, Value*>::iterator IDM = ValueMap.find(DB);
+          if (IDM != ValueMap.end())
+            NewDFSet.insert(cast<BasicBlock>(IDM->second));
+          else
+            NewDFSet.insert(DB);
+        }
+    }
+    DF->addBasicBlock(NewBB, NewDFSet);
+  }
+}
+
+/// CloneLoop - Clone Loop. Clone dominator info. Populate ValueMap
+/// using old blocks to new blocks mapping.
+Loop *llvm::CloneLoop(Loop *OrigL, LPPassManager  *LPM, LoopInfo *LI,
+                      DenseMap<const Value *, Value *> &ValueMap, Pass *P) {
+  
+  DominatorTree *DT = NULL;
+  DominanceFrontier *DF = NULL;
+  if (P) {
+    DT = P->getAnalysisToUpdate<DominatorTree>();
+    DF = P->getAnalysisToUpdate<DominanceFrontier>();
+  }
+
+  SmallVector<BasicBlock *, 16> NewBlocks;
+  SmallVector<std::pair<Loop *, Loop::iterator>, 8> LoopNest;
+  LoopNest.push_back(std::make_pair(OrigL, OrigL->begin()));
+  
+  Loop *NewLoop = NULL;
+  while (!LoopNest.empty()) {
+    Loop *L = LoopNest.back().first;
+    Loop::iterator SubLoop = LoopNest.back().second;
+    
+    // Handle sub loops.
+    if (SubLoop != L->end()) {
+      Loop *SL  = *SubLoop;
+      LoopNest.push_back(std::make_pair(SL, SL->begin()));
+    } 
+
+    LoopNest.pop_back();
+    NewLoop = new Loop();
+    LPM->insertLoop(NewLoop, L->getParentLoop());
+
+    // Clone Basic Blocks.
+    for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
+         I != E; ++I) {
+      BasicBlock *BB = *I;
+      BasicBlock *NewBB = CloneBasicBlock(BB, ValueMap, ".clone");
+      ValueMap[BB] = NewBB;
+      if (P)
+        LPM->cloneBasicBlockSimpleAnalysis(BB, NewBB, L);
+      NewLoop->addBasicBlockToLoop(NewBB, *LI);
+      NewBlocks.push_back(NewBB);
+    }
+
+    // Clone dominator info.
+    if (DT)
+      for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
+           I != E; ++I) {
+        BasicBlock *BB = *I;
+        CloneDominatorInfo(BB, ValueMap, DT, DF);
+      }
+
+  }
+
+  // Remap instructions to reference operands from ValueMap.
+  for(SmallVector<BasicBlock *, 16>::iterator NBItr = NewBlocks.begin(), 
+        NBE = NewBlocks.end();  NBItr != NBE; ++NBItr) {
+    BasicBlock *NB = *NBItr;
+    for(BasicBlock::iterator BI = NB->begin(), BE = NB->end(); 
+        BI != BE; ++BI) {
+      Instruction *Insn = BI;
+      for (unsigned index = 0, num_ops = Insn->getNumOperands(); 
+           index != num_ops; ++index) {
+        Value *Op = Insn->getOperand(index);
+        DenseMap<const Value *, Value *>::iterator OpItr = ValueMap.find(Op);
+        if (OpItr != ValueMap.end())
+          Insn->setOperand(index, OpItr->second);
+      }
+    }
+  }
+
+  BasicBlock *Latch = OrigL->getLoopLatch();
+  Function *F = Latch->getParent();
+  F->getBasicBlockList().insert(Latch, NewBlocks.begin(), NewBlocks.end());
+
+  return NewLoop;
+}