path: root/lib/Transforms/ExprTypeConvert.cpp

//===- ExprTypeConvert.cpp - Code to change an LLVM Expr Type -------------===//
//
//                     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 part of level raising that checks to see if it is
// possible to coerce an entire expression tree into a different type.  If
// convertible, other routines from this file will do the conversion.
//
//===----------------------------------------------------------------------===//

#include "TransformInternals.h"
#include "llvm/Constants.h"
#include "llvm/Instructions.h"
#include "llvm/Analysis/Expressions.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Support/Debug.h"
#include <algorithm>
using namespace llvm;

static bool OperandConvertibleToType(User *U, Value *V, const Type *Ty,
                                     ValueTypeCache &ConvertedTypes,
                                     const TargetData &TD);

static void ConvertOperandToType(User *U, Value *OldVal, Value *NewVal,
                                 ValueMapCache &VMC, const TargetData &TD);

// Peephole Malloc instructions: we take a look at the use chain of the
// malloc instruction, and try to find out if the following conditions hold:
//   1. The malloc is of the form: 'malloc [sbyte], uint <constant>'
//   2. The only users of the malloc are cast & add instructions
//   3. Of the cast instructions, there is only one destination pointer type
//      [RTy] where the size of the pointed to object is equal to the number
//      of bytes allocated.
//
// If these conditions hold, we convert the malloc to allocate an [RTy]
// element.  TODO: This comment is out of date WRT arrays
//
static bool MallocConvertibleToType(MallocInst *MI, const Type *Ty,
                                    ValueTypeCache &CTMap,
                                    const TargetData &TD) {
  if (!isa<PointerType>(Ty)) return false;   // Malloc always returns pointers

  // Deal with the type to allocate, not the pointer type...
  Ty = cast<PointerType>(Ty)->getElementType();
  if (!Ty->isSized() || !MI->getType()->getElementType()->isSized())
    return false;      // Can only alloc something with a size

  // Analyze the number of bytes allocated...
  ExprType Expr = ClassifyExpr(MI->getArraySize());

  // Get information about the base datatype being allocated, before & after
  uint64_t ReqTypeSize = TD.getTypeSize(Ty);
  if (ReqTypeSize == 0) return false;
  uint64_t OldTypeSize = TD.getTypeSize(MI->getType()->getElementType());

  // Must have a scale or offset to analyze it...
  if (!Expr.Offset && !Expr.Scale && OldTypeSize == 1) return false;

  // Get the offset and scale of the allocation...
  int64_t OffsetVal = Expr.Offset ? getConstantValue(Expr.Offset) : 0;
  int64_t ScaleVal = Expr.Scale ? getConstantValue(Expr.Scale) :(Expr.Var != 0);

  // The old type might not be of unit size, take old size into consideration
  // here...
  uint64_t Offset = OffsetVal * OldTypeSize;
  uint64_t Scale  = ScaleVal  * OldTypeSize;

  // In order to be successful, both the scale and the offset must be a multiple
  // of the requested data type's size.
  //
  if (Offset/ReqTypeSize*ReqTypeSize != Offset ||
      Scale/ReqTypeSize*ReqTypeSize != Scale)
    return false;   // Nope.

  return true;
}

static Instruction *ConvertMallocToType(MallocInst *MI, const Type *Ty,
                                        const std::string &Name,
                                        ValueMapCache &VMC,
                                        const TargetData &TD){
  BasicBlock *BB = MI->getParent();
  BasicBlock::iterator It = BB->end();

  // Analyze the number of bytes allocated...
  ExprType Expr = ClassifyExpr(MI->getArraySize());

  const PointerType *AllocTy = cast<PointerType>(Ty);
  const Type *ElType = AllocTy->getElementType();

  uint64_t DataSize = TD.getTypeSize(ElType);
  uint64_t OldTypeSize = TD.getTypeSize(MI->getType()->getElementType());

  // Get the offset and scale coefficients that we are allocating...
  int64_t OffsetVal =<