path: root/lib/Transforms/LevelRaise.cpp

//===- LevelRaise.cpp - Code to change LLVM to higher level -----------------=//
//
// This file implements the 'raising' part of the LevelChange API.  This is
// useful because, in general, it makes the LLVM code terser and easier to
// analyze.
//
//===----------------------------------------------------------------------===//

#include "llvm/Transforms/LevelChange.h"
#include "TransformInternals.h"
#include "llvm/Method.h"
#include "llvm/iOther.h"
#include "llvm/iMemory.h"
#include "llvm/ConstantVals.h"
#include "llvm/Optimizations/ConstantHandling.h"
#include "llvm/Optimizations/DCE.h"
#include "llvm/Optimizations/ConstantProp.h"
#include "llvm/Analysis/Expressions.h"
#include "Support/STLExtras.h"
#include <algorithm>

#include "llvm/Assembly/Writer.h"

//#define DEBUG_PEEPHOLE_INSTS 1

#ifdef DEBUG_PEEPHOLE_INSTS
#define PRINT_PEEPHOLE(ID, NUM, I)            \
  cerr << "Inst P/H " << ID << "[" << NUM << "] " << I;
#else
#define PRINT_PEEPHOLE(ID, NUM, I)
#endif

#define PRINT_PEEPHOLE1(ID, I1) do { PRINT_PEEPHOLE(ID, 0, I1); } while (0)
#define PRINT_PEEPHOLE2(ID, I1, I2) \
  do { PRINT_PEEPHOLE(ID, 0, I1); PRINT_PEEPHOLE(ID, 1, I2); } while (0)
#define PRINT_PEEPHOLE3(ID, I1, I2, I3) \
  do { PRINT_PEEPHOLE(ID, 0, I1); PRINT_PEEPHOLE(ID, 1, I2); \
       PRINT_PEEPHOLE(ID, 2, I3); } while (0)
#define PRINT_PEEPHOLE4(ID, I1, I2, I3, I4) \
  do { PRINT_PEEPHOLE(ID, 0, I1); PRINT_PEEPHOLE(ID, 1, I2); \
       PRINT_PEEPHOLE(ID, 2, I3); PRINT_PEEPHOLE(ID, 3, I4); } while (0)


// isReinterpretingCast - Return true if the cast instruction specified will
// cause the operand to be "reinterpreted".  A value is reinterpreted if the
// cast instruction would cause the underlying bits to change.
//
static inline bool isReinterpretingCast(const CastInst *CI) {
  return!CI->getOperand(0)->getType()->isLosslesslyConvertableTo(CI->getType());
}



#if 0  // Unneccesary code, handled by convert exprs
// Peephole optimize the following instructions:
// %t1 = cast ? to x *
// %t2 = add x * %SP, %t1              ;; Constant must be 2nd operand
//
// Into: %t3 = getelementptr {<...>} * %SP, <element indices>
//       %t2 = cast <eltype> * %t3 to {<...>}*
//
static bool HandleCastToPointer(BasicBlock::iterator BI,
                                const PointerType *DestPTy) {
  CastInst *CI = cast<CastInst>(*BI);

  // Scan all of the uses, looking for any uses that are not add
  // instructions.  If we have non-adds, do not make this transformation.
  //
  for (Value::use_iterator I = CI->use_begin(), E = CI->use_end();
       I != E; ++I) {
    if (BinaryOperator *BO = dyn_cast<BinaryOperator>(*I)) {
      if (BO->getOpcode() != Instruction::Add)
        return false;
    } else {
      return false;
    }
  }

  vector<Value*> Indices;
  Value *Src = CI->getOperand(0);
  const Type *Result = ConvertableToGEP(DestPTy, Src, Indices, &BI);
  const PointerType *UsedType = DestPTy;

  // If we fail, check to see if we have an pointer source type that, if
  // converted to an unsized array type, would work.  In this case, we propogate
  // the cast forward to the input of the add instruction.
  //
  if (Result == 0 && getPointedToComposite(DestPTy) == 0) {
    // Make an unsized array and try again...
    UsedType = PointerType::get(ArrayType::get(DestPTy->getElementType()));
    Result = ConvertableToGEP(UsedType, Src, Indices, &BI);    
  }

  if (Result == 0) return false;  // Not convertable...

  PRINT_PEEPHOLE2("cast-add-to-gep:in", Src, CI);

  // If we have a getelementptr capability... transform all of the 
  // add instruction uses into getelementptr's.
  for (Value::use_iterator UI = CI->use_begin(), E = CI->use_end();
       UI != E; ++UI) {
    Instruction *I = cast<Instruction>(*UI);
    assert(I->getOpcode() == Instruction::Add && I->getNumOperands() == 2 &&
           "Use is not a valid add instruction!");
    
    // Get the value added to the cast result pointer...
    Value *OtherPtr = I->getOperand((I->getOperand(0) == CI) ? 1 : 0);

    BasicBlock *BB = I->getParent();
    BasicBlock::iterator AddIt = find(BB->getInstList().begin(),
                                      BB->getInstList().end(), I);

    if (UsedType != DestPTy) {
      // Insert a cast of the incoming value to something addressable...
      CastInst *C = new CastInst(OtherPtr, UsedType, OtherPtr->getName());
      AddIt = BB->getInstList().insert(AddIt, C)+1;
      OtherPtr = C;
    }

    GetElementPtrInst *GEP = new GetElementPtrInst(OtherPtr, Indices,
                                                   I->getName());

    PRINT_PEEPHOLE1("cast-add-to-gep:i", I);
    
    // Replace the old add instruction with the shiny new GEP inst
    ReplaceInstWithInst(BB->getInstList(), AddIt, GEP);
    PRINT_PEEPHOLE1("cast-add-to-gep:o", GEP);
  }
  return true;
}
#endif

// Peephole optimize the following instructions:
// %t1 = cast ulong <const int> to {<...>} *
// %t2 = add {<...>} * %SP, %t1              ;; Constant must be 2nd operand
//
//    or
// %t1 = cast {<...>}* %SP to int*
// %t5 = cast ulong <const int> to int*
// %t2 = add int* %t1, %t5                   ;; int is same size as field
//
// Into: %t3 = getelementptr {<...>} * %SP, <element indices>
//       %t2 = cast <eltype> * %t3 to {<...>}*
//
static bool PeepholeOptimizeAddCast(BasicBlock *BB, BasicBlock::iterator &BI,
                                    Value *AddOp1, CastInst *AddOp2) {
  const CompositeType *CompTy;
  Value *OffsetVal = AddOp2->getOperand(0);
  Value *SrcPtr;  // Of type pointer to struct...

  if ((CompTy = getPointedToComposite(AddOp1->getType()))) {
    SrcPtr = AddOp1;                      // Handle the first case...
  } else if (CastInst *AddOp1c = dyn_cast<CastInst>(AddOp1)) {
    SrcPtr = AddOp1c->getOperand(0);      // Handle the second case...
    CompTy = getPointedToComposite(SrcPtr->getType());
  }

  // Only proceed if we have detected all of our conditions successfully...
  if (!CompTy || !SrcPtr || !OffsetVal->getType()->isIntegral())
    return false;

  vector<Value*> Indices;
  if (!ConvertableToGEP(SrcPtr->getType(), OffsetVal, Indices, &BI))
    return false;  // Not convertable... perhaps next time

  if (getPointedToComposite(AddOp1->getType())) {  // case 1
    PRINT_PEEPHOLE2("add-to-gep1:in", AddOp2, *BI);
  } else {
    PRINT_PEEPHOLE3("add-to-gep2:in", AddOp1, AddOp2, *BI);
  }

  GetElementPtrInst *GEP = new GetElementPtrInst(SrcPtr, Indices,
                                                 AddOp2->getName());
  BI = BB->getInstList().insert(BI, GEP)+1;

  Instruction *NCI = new CastInst(GEP, AddOp1->getType());
  ReplaceInstWithInst(BB->getInstList(), BI, NCI);
  PRINT_PEEPHOLE2("add-to-gep:out", GEP, NCI);
  return true;
}

static bool PeepholeOptimize(BasicBlock *BB, BasicBlock::iterator &BI) {
  Instruction *I = *BI;

  if (CastInst *CI = dyn_cast<CastInst>(I)) {
    Value       *Src    = CI->getOperand(0);
    Instruction *SrcI   = dyn_cast<Instruction>(Src); // Nonnull if instr source
    const Type  *DestTy = CI->getType();

    // Peephole optimize the following instruction:
    // %V2 = cast <ty> %V to <ty>
    //
    // Into: <nothing>
    //
    if (DestTy == Src->getType()) {   // Check for a cast to same type as src!!
      PRINT_PEEPHOLE1("cast-of-self-ty", CI);
      CI->replaceAllUsesWith(Src);
      if (!Src->hasName() && CI->hasName()) {
        string Name = CI->getName();
        CI->setName("");
        Src->setName(Name, BB->getParent()->getSymbolTable());
      }
      return true;
    }

    // Peephole optimize the following instructions:
    // %tmp = cast <ty> %V to <ty2>
    // %V   = cast <ty2> %tmp to <ty3>     ; Where ty & ty2 are same size
    //
    // Into: cast <ty> %V to <ty3>
    //
    if (SrcI)
      if (CastInst *CSrc = dyn_cast<CastInst>(SrcI))
        if (isReinterpretingCast(CI) + isReinterpretingCast(CSrc) < 2) {
          // We can only do c-c elimination if, at most, one cast does a
          // reinterpretation of the input data.
          //
          // If legal, make this cast refer the the original casts argument!
          //
          PRINT_PEEPHOLE2("cast-cast:in ", CI, CSrc);
          CI->setOperand(0, CSrc->getOperand(0));
          PRINT_PEEPHOLE1("cast-cast:out", CI);
          return true;
        }

    // Check to see if it's a cast of an instruction that does not depend on the
    // specific type of the operands to do it's job.
    if (!isReinterpretingCast(CI)) {
      // Check to see if we can convert the source of the cast to match the
      // destination type of the cast...
      //
      ValueTypeCache ConvertedTypes;
      if (ValueConvertableToType(CI, Src->getType(), ConvertedTypes)) {
        PRINT_PEEPHOLE2("CAST-DEST-EXPR-CONV:in ", Src, CI);

#ifdef DEBUG_PEEPHOLE_INSTS
        cerr << "\nCONVERTING EXPR TYPE:\n";
#endif
        ValueMapCache ValueMap;
        ConvertValueToNewType(CI, Src, ValueMap);  // This will delete CI!

        BI = BB->begin();  // Rescan basic block.  BI might be invalidated.
        PRINT_PEEPHOLE1("CAST-DEST-EXPR-CONV:out", Src);
#ifdef DEBUG_PEEPHOLE_INSTS
        cerr << "DONE CONVERTING EXPR TYPE: \n\n";// << BB->getParent();
#endif
        return true;
      }

      // Check to see if we can convert the users of the cast value to match the
      // source type of the cast...
      //
      ConvertedTypes.clear();
      if (ExpressionConvertableToType(Src, DestTy, ConvertedTypes)) {
        PRINT_PEEPHOLE2("CAST-SRC-EXPR-CONV:in ", Src, CI);
          
#ifdef DEBUG_PEEPHOLE_INSTS
        cerr << "\nCONVERTING SRC EXPR TYPE:\n";
#endif
        ValueMapCache ValueMap;
        Value *E =