lib/Transforms/Utils/BasicBlockUtils.cpp

//===-- BasicBlockUtils.cpp - BasicBlock Utilities -------------------------==//
//
// This family of functions perform manipulations on basic blocks, and
// instructions contained within basic blocks.
//
//===----------------------------------------------------------------------===//

#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Function.h"
#include "llvm/Instruction.h"
#include <algorithm>

// ReplaceInstWithValue - Replace all uses of an instruction (specified by BI)
// with a value, then remove and delete the original instruction.
//
void ReplaceInstWithValue(BasicBlock::InstListType &BIL,
                          BasicBlock::iterator &BI, Value *V) {
  Instruction &I = *BI;
  // Replaces all of the uses of the instruction with uses of the value
  I.replaceAllUsesWith(V);

  std::string OldName = I.getName();
  
  // Delete the unneccesary instruction now...
  BI = BIL.erase(BI);

  // Make sure to propogate a name if there is one already...
  if (OldName.size() && !V->hasName())
    V->setName(OldName, BIL.getParent()->getSymbolTable());
}


// ReplaceInstWithInst - Replace the instruction specified by BI with the
// instruction specified by I.  The original instruction is deleted and BI is
// updated to point to the new instruction.
//
void ReplaceInstWithInst(BasicBlock::InstListType &BIL,
                         BasicBlock::iterator &BI, Instruction *I) {
  assert(I->getParent() == 0 &&
         "ReplaceInstWithInst: Instruction already inserted into basic block!");

  // Insert the new instruction into the basic block...
  BasicBlock::iterator New = BIL.insert(BI, I);

  // Replace all uses of the old instruction, and delete it.
  ReplaceInstWithValue(BIL, BI, I);

  // Move BI back to point to the newly inserted instruction
  BI = New;
}

// ReplaceInstWithInst - Replace the instruction specified by From with the
// instruction specified by To.  Note that this is slower than providing an
// iterator directly, because the basic block containing From must be searched
// for the instruction.
//
void ReplaceInstWithInst(Instruction *From, Instruction *To) {
  BasicBlock::iterator BI(From);
  ReplaceInstWithInst(From->getParent()->getInstList(), BI, To);
}