lib/Transforms/Utils/CloneTrace.cpp

//===- CloneTrace.cpp - Clone a trace -------------------------------------===//
// 
//                     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 CloneTrace interface, which is used when writing
// runtime optimizations. It takes a vector of basic blocks clones the basic
// blocks, removes internal phi nodes, adds it to the same function as the
// original (although there is no jump to it) and returns the new vector of
// basic blocks.
//
//===----------------------------------------------------------------------===//

#include "llvm/Analysis/Trace.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Instructions.h"
#include "llvm/Function.h"
#include "ValueMapper.h"
using namespace llvm;

//Clones the trace (a vector of basic blocks)
std::vector<BasicBlock *>
llvm::CloneTrace(const std::vector<BasicBlock*> &origTrace) {
  std::vector<BasicBlock *> clonedTrace;
  std::map<const Value*, Value*> ValueMap;
  
  //First, loop over all the Basic Blocks in the trace and copy
  //them using CloneBasicBlock. Also fix the phi nodes during
  //this loop. To fix the phi nodes, we delete incoming branches
  //that are not in the trace.
  for(std::vector<BasicBlock *>::const_iterator T = origTrace.begin(),
	End = origTrace.end(); T != End; ++T) {

    //Clone Basic Block
    BasicBlock *clonedBlock =
      CloneBasicBlock(*T, ValueMap, ".tr", (*T)->getParent());
    
    //Add it to our new trace
    clonedTrace.push_back(clonedBlock);

    //Add this new mapping to our Value Map
    ValueMap[*T] = clonedBlock;

    //Loop over the phi instructions and delete operands
    //that are from blocks not in the trace
    //only do this if we are NOT the first block
    if(T != origTrace.begin()) {
      for (BasicBlock::iterator I = clonedBlock->begin();
	   PHINode *PN = dyn_cast<PHINode>(I); ++I) {
	//get incoming value for the previous BB
	Value *V = PN->getIncomingValueForBlock(*(T-1));
	assert(V && "No incoming value from a BasicBlock in our trace!");
	
	//remap our phi node to point to incoming value
	ValueMap[*&I] = V;
	
	//remove phi node
	clonedBlock->getInstList().erase(PN);
      }
    }
  }

  //Second loop to do the remapping
  for(std::vector<BasicBlock *>::const_iterator BB = clonedTrace.begin(),
	BE = clonedTrace.end(); BB != BE; ++BB) {
    for(BasicBlock::iterator I = (*BB)->begin(); I != (*BB)->end(); ++I) {
      
      //Loop over all the operands of the instruction
      for(unsigned op=0, E = I->getNumOperands(); op != E; ++op) {
	const Value *Op = I->getOperand(op);
	
	//Get it out of the value map
	Value *V = ValueMap[Op];

	//If not in the value map, then its outside our trace so ignore
	if(V != 0)
	  I->setOperand(op,V);
      }
    }
  }
  
  //return new vector of basic blocks
  return clonedTrace;
}

/// CloneTraceInto - Clone T into NewFunc. Original<->clone mapping is
/// saved in ValueMap.
///
void llvm::CloneTraceInto(Function *NewFunc, Trace &T,
                          std::map<const Value*, Value*> &ValueMap,
                          const char *NameSuffix) {
  assert(NameSuffix && "NameSuffix cannot be null!");

  // Loop over all of the basic blocks in the trace, cloning them as
  // appropriate.
  //
  for (Trace::const_iterator BI = T.begin(), BE = T.end(); BI != BE; ++BI) {
    const BasicBlock *BB = *BI;

    // Create a new basic block and copy instructions into it!
    BasicBlock *CBB = CloneBasicBlock(BB, ValueMap, NameSuffix, NewFunc);
    ValueMap[BB] = CBB;                       // Add basic block mapping.
  }

  // Loop over all of the instructions in the new function, fixing up operand
  // references as we go.  This uses ValueMap to do all the hard work.
  //
  for (Function::iterator BB =
         cast<BasicBlock>(ValueMap[T.getEntryBasicBlock()]),
         BE = NewFunc->end(); BB != BE; ++BB)
    // Loop over all instructions, fixing each one as we find it...
    for (BasicBlock::iterator II = BB->begin(); II != BB->end(); ++II)
      RemapInstruction(II, ValueMap);
}