1 files changed, 289 insertions, 0 deletions
diff --git a/lib/VMCore/BasicBlock.cpp b/lib/VMCore/BasicBlock.cpp
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+++ b/lib/VMCore/BasicBlock.cpp
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+//===-- BasicBlock.cpp - Implement BasicBlock related methods -------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by the LLVM research group and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the BasicBlock class for the VMCore library.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/BasicBlock.h"
+#include "llvm/Constants.h"
+#include "llvm/Instructions.h"
+#include "llvm/Type.h"
+#include "llvm/Support/CFG.h"
+#include "llvm/Support/LeakDetector.h"
+#include "llvm/Support/Compiler.h"
+#include "SymbolTableListTraitsImpl.h"
+#include <algorithm>
+using namespace llvm;
+
+inline ValueSymbolTable *
+ilist_traits<Instruction>::getSymTab(BasicBlock *BB) {
+  if (BB)
+    if (Function *F = BB->getParent())
+      return &F->getValueSymbolTable();
+  return 0;
+}
+
+
+namespace {
+  /// DummyInst - An instance of this class is used to mark the end of the
+  /// instruction list.  This is not a real instruction.
+  struct VISIBILITY_HIDDEN DummyInst : public Instruction {
+    DummyInst() : Instruction(Type::VoidTy, OtherOpsEnd, 0, 0) {
+      // This should not be garbage monitored.
+      LeakDetector::removeGarbageObject(this);
+    }
+
+    virtual Instruction *clone() const {
+      assert(0 && "Cannot clone EOL");abort();
+      return 0;
+    }
+    virtual const char *getOpcodeName() const { return "*end-of-list-inst*"; }
+
+    // Methods for support type inquiry through isa, cast, and dyn_cast...
+    static inline bool classof(const DummyInst *) { return true; }
+    static inline bool classof(const Instruction *I) {
+      return I->getOpcode() == OtherOpsEnd;
+    }
+    static inline bool classof(const Value *V) {
+      return isa<Instruction>(V) && classof(cast<Instruction>(V));
+    }
+  };
+}
+
+Instruction *ilist_traits<Instruction>::createSentinel() {
+  return new DummyInst();
+}
+iplist<Instruction> &ilist_traits<Instruction>::getList(BasicBlock *BB) {
+  return BB->getInstList();
+}
+
+// Explicit instantiation of SymbolTableListTraits since some of the methods
+// are not in the public header file...
+template class SymbolTableListTraits<Instruction, BasicBlock>;
+
+
+BasicBlock::BasicBlock(const std::string &Name, Function *NewParent,
+                       BasicBlock *InsertBefore)
+  : Value(Type::LabelTy, Value::BasicBlockVal), Parent(0) {
+
+  // Make sure that we get added to a function
+  LeakDetector::addGarbageObject(this);
+
+  if (InsertBefore) {
+    assert(NewParent &&
+           "Cannot insert block before another block with no function!");
+    NewParent->getBasicBlockList().insert(InsertBefore, this);
+  } else if (NewParent) {
+    NewParent->getBasicBlockList().push_back(this);
+  }
+  
+  setName(Name);
+}
+
+
+BasicBlock::~BasicBlock() {
+  assert(getParent() == 0 && "BasicBlock still linked into the program!");
+  dropAllReferences();
+  InstList.clear();
+}
+
+void BasicBlock::setParent(Function *parent) {
+  if (getParent())
+    LeakDetector::addGarbageObject(this);
+
+  // Set Parent=parent, updating instruction symtab entries as appropriate.
+  InstList.setSymTabObject(&Parent, parent);
+
+  if (getParent())
+    LeakDetector::removeGarbageObject(this);
+}
+
+void BasicBlock::removeFromParent() {
+  getParent()->getBasicBlockList().remove(this);
+}
+
+void BasicBlock::eraseFromParent() {
+  getParent()->getBasicBlockList().erase(this);
+}
+
+/// moveBefore - Unlink this basic block from its current function and
+/// insert it into the function that MovePos lives in, right before MovePos.
+void BasicBlock::moveBefore(BasicBlock *MovePos) {
+  MovePos->getParent()->getBasicBlockList().splice(MovePos,
+                       getParent()->getBasicBlockList(), this);
+}
+
+/// moveAfter - Unlink this basic block from its current function and
+/// insert it into the function that MovePos lives in, right after MovePos.
+void BasicBlock::moveAfter(BasicBlock *MovePos) {
+  Function::iterator I = MovePos;
+  MovePos->getParent()->getBasicBlockList().splice(++I,
+                                       getParent()->getBasicBlockList(), this);
+}
+
+
+TerminatorInst *BasicBlock::getTerminator() {
+  if (InstList.empty()) return 0;
+  return dyn_cast<TerminatorInst>(&InstList.back());
+}
+
+const TerminatorInst *const BasicBlock::getTerminator() const {
+  if (InstList.empty()) return 0;
+  return dyn_cast<TerminatorInst>(&InstList.back());
+}
+
+Instruction* BasicBlock::getFirstNonPHI()
+{
+    BasicBlock::iterator i = begin();
+    // All valid basic blocks should have a terminator,
+    // which is not a PHINode. If we have invalid basic
+    // block we'll get assert when dereferencing past-the-end
+    // iterator.
+    while (isa<PHINode>(i)) ++i;
+    return &*i;
+}
+
+void BasicBlock::dropAllReferences() {
+  for(iterator I = begin(), E = end(); I != E; ++I)
+    I->dropAllReferences();
+}
+
+/// getSinglePredecessor - If this basic block has a single predecessor block,
+/// return the block, otherwise return a null pointer.
+BasicBlock *BasicBlock::getSinglePredecessor() {
+  pred_iterator PI = pred_begin(this), E = pred_end(this);
+  if (PI == E) return 0;         // No preds.
+  BasicBlock *ThePred = *PI;
+  ++PI;
+  return (PI == E) ? ThePred : 0 /*multiple preds*/;
+}
+
+/// removePredecessor - This method is used to notify a BasicBlock that the
+/// specified Predecessor of the block is no longer able to reach it.  This is
+/// actually not used to update the Predecessor list, but is actually used to
+/// update the PHI nodes that reside in the block.  Note that this should be
+/// called while the predecessor still refers to this block.
+///
+void BasicBlock::removePredecessor(BasicBlock *Pred,
+                                   bool DontDeleteUselessPHIs) {
+  assert((hasNUsesOrMore(16)||// Reduce cost of this assertion for complex CFGs.
+          find(pred_begin(this), pred_end(this), Pred) != pred_end(this)) &&
+         "removePredecessor: BB is not a predecessor!");
+
+  if (InstList.empty()) return;
+  PHINode *APN = dyn_cast<PHINode>(&front());
+  if (!APN) return;   // Quick exit.
+
+  // If there are exactly two predecessors, then we want to nuke the PHI nodes
+  // altogether.  However, we cannot do this, if this in this case:
+  //
+  //  Loop:
+  //    %x = phi [X, Loop]
+  //    %x2 = add %x, 1         ;; This would become %x2 = add %x2, 1
+  //    br Loop                 ;; %x2 does not dominate all uses
+  //
+  // This is because the PHI node input is actually taken from the predecessor
+  // basic block.  The only case this can happen is with a self loop, so we
+  // check for this case explicitly now.
+  //
+  unsigned max_idx = APN->getNumIncomingValues();
+  assert(max_idx != 0 && "PHI Node in block with 0 predecessors!?!?!");
+  if (max_idx == 2) {
+    BasicBlock *Other = APN->getIncomingBlock(APN->getIncomingBlock(0) == Pred);
+
+    // Disable PHI elimination!
+    if (this == Other) max_idx = 3;
+  }
+
+  // <= Two predecessors BEFORE I remove one?
+  if (max_idx <= 2 && !DontDeleteUselessPHIs) {
+    // Yup, loop through and nuke the PHI nodes
+    while (PHINode *PN = dyn_cast<PHINode>(&front())) {
+      // Remove the predecessor first.
+      PN->removeIncomingValue(Pred, !DontDeleteUselessPHIs);
+
+      // If the PHI _HAD_ two uses, replace PHI node with its now *single* value
+      if (max_idx == 2) {
+        if (PN->getOperand(0) != PN)
+          PN->replaceAllUsesWith(PN->getOperand(0));
+        else
+          // We are left with an infinite loop with no entries: kill the PHI.
+          PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
+        getInstList().pop_front();    // Remove the PHI node
+      }
+
+      // If the PHI node already only had one entry, it got deleted by
+      // removeIncomingValue.
+    }
+  } else {
+    // Okay, now we know that we need to remove predecessor #pred_idx from all
+    // PHI nodes.  Iterate over each PHI node fixing them up
+    PHINode *PN;
+    for (iterator II = begin(); (PN = dyn_cast<PHINode>(II)); ) {
+      ++II;
+      PN->removeIncomingValue(Pred, false);
+      // If all incoming values to the Phi are the same, we can replace the Phi
+      // with that value.
+      Value* PNV = 0;
+      if (!DontDeleteUselessPHIs && (PNV = PN->hasConstantValue())) {
+        PN->replaceAllUsesWith(PNV);
+        PN->eraseFromParent();
+      }
+    }
+  }
+}
+
+
+/// splitBasicBlock - This splits a basic block into two at the specified
+/// instruction.  Note that all instructions BEFORE the specified iterator stay
+/// as part of the original basic block, an unconditional branch is added to
+/// the new BB, and the rest of the instructions in the BB are moved to the new
+/// BB, including the old terminator.  This invalidates the iterator.
+///
+/// Note that this only works on well formed basic blocks (must have a
+/// terminator), and 'I' must not be the end of instruction list (which would
+/// cause a degenerate basic block to be formed, having a terminator inside of
+/// the basic block).
+///
+BasicBlock *BasicBlock::splitBasicBlock(iterator I, const std::string &BBName) {
+  assert(getTerminator() && "Can't use splitBasicBlock on degenerate BB!");
+  assert(I != InstList.end() &&
+         "Trying to get me to create degenerate basic block!");
+
+  BasicBlock *New = new BasicBlock(BBName, getParent(), getNext());
+
+  // Move all of the specified instructions from the original basic block into
+  // the new basic block.
+  New->getInstList().splice(New->end(), this->getInstList(), I, end());
+
+  // Add a branch instruction to the newly formed basic block.
+  new BranchInst(New, this);
+
+  // Now we must loop through all of the successors of the New block (which
+  // _were_ the successors of the 'this' block), and update any PHI nodes in
+  // successors.  If there were PHI nodes in the successors, then they need to
+  // know that incoming branches will be from New, not from Old.
+  //
+  for (succ_iterator I = succ_begin(New), E = succ_end(New); I != E; ++I) {
+    // Loop over any phi nodes in the basic block, updating the BB field of
+    // incoming values...
+    BasicBlock *Successor = *I;
+    PHINode *PN;
+    for (BasicBlock::iterator II = Successor->begin();
+         (PN = dyn_cast<PHINode>(II)); ++II) {
+      int IDX = PN->getBasicBlockIndex(this);
+      while (IDX != -1) {
+        PN->setIncomingBlock((unsigned)IDX, New);
+        IDX = PN->getBasicBlockIndex(this);
+      }
+    }
+  }
+  return New;
+}