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TransformInternals.cpp

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00001 //===- TransformInternals.cpp - Implement shared functions for transforms -===//
00002 // 
00003 //                     The LLVM Compiler Infrastructure
00004 //
00005 // This file was developed by the LLVM research group and is distributed under
00006 // the University of Illinois Open Source License. See LICENSE.TXT for details.
00007 // 
00008 //===----------------------------------------------------------------------===//
00009 //
00010 //  This file defines shared functions used by the different components of the
00011 //  Transforms library.
00012 //
00013 //===----------------------------------------------------------------------===//
00014 
00015 #include "TransformInternals.h"
00016 #include "llvm/Type.h"
00017 #include "llvm/Analysis/Expressions.h"
00018 #include "llvm/Function.h"
00019 #include "llvm/Instructions.h"
00020 using namespace llvm;
00021 
00022 static const Type *getStructOffsetStep(const StructType *STy, uint64_t &Offset,
00023                                        std::vector<Value*> &Indices,
00024                                        const TargetData &TD) {
00025   assert(Offset < TD.getTypeSize(STy) && "Offset not in composite!");
00026   const StructLayout *SL = TD.getStructLayout(STy);
00027 
00028   // This loop terminates always on a 0 <= i < MemberOffsets.size()
00029   unsigned i;
00030   for (i = 0; i < SL->MemberOffsets.size()-1; ++i)
00031     if (Offset >= SL->MemberOffsets[i] && Offset < SL->MemberOffsets[i+1])
00032       break;
00033   
00034   assert(Offset >= SL->MemberOffsets[i] &&
00035          (i == SL->MemberOffsets.size()-1 || Offset < SL->MemberOffsets[i+1]));
00036   
00037   // Make sure to save the current index...
00038   Indices.push_back(ConstantUInt::get(Type::UIntTy, i));
00039   Offset = SL->MemberOffsets[i];
00040   return STy->getContainedType(i);
00041 }
00042 
00043 
00044 // getStructOffsetType - Return a vector of offsets that are to be used to index
00045 // into the specified struct type to get as close as possible to index as we
00046 // can.  Note that it is possible that we cannot get exactly to Offset, in which
00047 // case we update offset to be the offset we actually obtained.  The resultant
00048 // leaf type is returned.
00049 //
00050 // If StopEarly is set to true (the default), the first object with the
00051 // specified type is returned, even if it is a struct type itself.  In this
00052 // case, this routine will not drill down to the leaf type.  Set StopEarly to
00053 // false if you want a leaf
00054 //
00055 const Type *llvm::getStructOffsetType(const Type *Ty, unsigned &Offset,
00056                                       std::vector<Value*> &Indices,
00057                                       const TargetData &TD, bool StopEarly) {
00058   if (Offset == 0 && StopEarly && !Indices.empty())
00059     return Ty;    // Return the leaf type
00060 
00061   uint64_t ThisOffset;
00062   const Type *NextType;
00063   if (const StructType *STy = dyn_cast<StructType>(Ty)) {
00064     if (STy->getNumElements()) {
00065       Offset = 0;
00066       return STy;
00067     }
00068 
00069     ThisOffset = Offset;
00070     NextType = getStructOffsetStep(STy, ThisOffset, Indices, TD);
00071   } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
00072     assert(Offset == 0 || Offset < TD.getTypeSize(ATy) &&
00073            "Offset not in composite!");
00074 
00075     NextType = ATy->getElementType();
00076     unsigned ChildSize = TD.getTypeSize(NextType);
00077     if (ConstantSInt::isValueValidForType(Type::IntTy, Offset/ChildSize))
00078       Indices.push_back(ConstantSInt::get(Type::IntTy, Offset/ChildSize));
00079     else
00080       Indices.push_back(ConstantSInt::get(Type::LongTy, Offset/ChildSize));
00081     ThisOffset = (Offset/ChildSize)*ChildSize;
00082   } else {
00083     Offset = 0;   // Return the offset that we were able to achieve
00084     return Ty;    // Return the leaf type
00085   }
00086 
00087   unsigned SubOffs = Offset - ThisOffset;
00088   const Type *LeafTy = getStructOffsetType(NextType, SubOffs,
00089                                            Indices, TD, StopEarly);
00090   Offset = ThisOffset + SubOffs;
00091   return LeafTy;
00092 }
00093 
00094 // ConvertibleToGEP - This function returns true if the specified value V is
00095 // a valid index into a pointer of type Ty.  If it is valid, Idx is filled in
00096 // with the values that would be appropriate to make this a getelementptr
00097 // instruction.  The type returned is the root type that the GEP would point to
00098 //
00099 const Type *llvm::ConvertibleToGEP(const Type *Ty, Value *OffsetVal,
00100                                    std::vector<Value*> &Indices,
00101                                    const TargetData &TD,
00102                                    BasicBlock::iterator *BI) {
00103   return 0;
00104 }
00105