1 //===-- TransformInternals.cpp - Implement shared functions for transforms --=//
3 // This file defines shared functions used by the different components of the
6 //===----------------------------------------------------------------------===//
8 #include "TransformInternals.h"
10 #include "llvm/Analysis/Expressions.h"
11 #include "llvm/Function.h"
12 #include "llvm/iOther.h"
14 static const Type *getStructOffsetStep(const StructType *STy, uint64_t &Offset,
15 std::vector<Value*> &Indices,
16 const TargetData &TD) {
17 assert(Offset < TD.getTypeSize(STy) && "Offset not in composite!");
18 const StructLayout *SL = TD.getStructLayout(STy);
20 // This loop terminates always on a 0 <= i < MemberOffsets.size()
22 for (i = 0; i < SL->MemberOffsets.size()-1; ++i)
23 if (Offset >= SL->MemberOffsets[i] && Offset < SL->MemberOffsets[i+1])
26 assert(Offset >= SL->MemberOffsets[i] &&
27 (i == SL->MemberOffsets.size()-1 || Offset < SL->MemberOffsets[i+1]));
29 // Make sure to save the current index...
30 Indices.push_back(ConstantUInt::get(Type::UByteTy, i));
31 Offset = SL->MemberOffsets[i];
32 return STy->getContainedType(i);
36 // getStructOffsetType - Return a vector of offsets that are to be used to index
37 // into the specified struct type to get as close as possible to index as we
38 // can. Note that it is possible that we cannot get exactly to Offset, in which
39 // case we update offset to be the offset we actually obtained. The resultant
40 // leaf type is returned.
42 // If StopEarly is set to true (the default), the first object with the
43 // specified type is returned, even if it is a struct type itself. In this
44 // case, this routine will not drill down to the leaf type. Set StopEarly to
45 // false if you want a leaf
47 const Type *getStructOffsetType(const Type *Ty, unsigned &Offset,
48 std::vector<Value*> &Indices,
49 const TargetData &TD, bool StopEarly) {
50 if (Offset == 0 && StopEarly && !Indices.empty())
51 return Ty; // Return the leaf type
55 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
57 NextType = getStructOffsetStep(STy, ThisOffset, Indices, TD);
58 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
59 assert(Offset == 0 || Offset < TD.getTypeSize(ATy) &&
60 "Offset not in composite!");
62 NextType = ATy->getElementType();
63 unsigned ChildSize = TD.getTypeSize(NextType);
64 Indices.push_back(ConstantSInt::get(Type::LongTy, Offset/ChildSize));
65 ThisOffset = (Offset/ChildSize)*ChildSize;
67 Offset = 0; // Return the offset that we were able to achieve
68 return Ty; // Return the leaf type
71 unsigned SubOffs = Offset - ThisOffset;
72 const Type *LeafTy = getStructOffsetType(NextType, SubOffs,
73 Indices, TD, StopEarly);
74 Offset = ThisOffset + SubOffs;
78 // ConvertibleToGEP - This function returns true if the specified value V is
79 // a valid index into a pointer of type Ty. If it is valid, Idx is filled in
80 // with the values that would be appropriate to make this a getelementptr
81 // instruction. The type returned is the root type that the GEP would point to
83 const Type *ConvertibleToGEP(const Type *Ty, Value *OffsetVal,
84 std::vector<Value*> &Indices,
86 BasicBlock::iterator *BI) {
87 const CompositeType *CompTy = dyn_cast<CompositeType>(Ty);
88 if (CompTy == 0) return 0;
90 // See if the cast is of an integer expression that is either a constant,
91 // or a value scaled by some amount with a possible offset.
93 ExprType Expr = ClassifyExpression(OffsetVal);
95 // Get the offset and scale values if they exists...
96 // A scale of zero with Expr.Var != 0 means a scale of 1.
98 int64_t Offset = Expr.Offset ? getConstantValue(Expr.Offset) : 0;
99 int64_t Scale = Expr.Scale ? getConstantValue(Expr.Scale) : 0;
101 if (Expr.Var && Scale == 0) Scale = 1; // Scale != 0 if Expr.Var != 0
103 // Loop over the Scale and Offset values, filling in the Indices vector for
104 // our final getelementptr instruction.
106 const Type *NextTy = CompTy;
108 if (!isa<CompositeType>(NextTy))
109 return 0; // Type must not be ready for processing...
110 CompTy = cast<CompositeType>(NextTy);
112 if (const StructType *StructTy = dyn_cast<StructType>(CompTy)) {
113 // Step into the appropriate element of the structure...
114 uint64_t ActualOffset = (Offset < 0) ? 0 : (uint64_t)Offset;
115 NextTy = getStructOffsetStep(StructTy, ActualOffset, Indices, TD);
116 Offset -= ActualOffset;
118 const Type *ElTy = cast<SequentialType>(CompTy)->getElementType();
119 if (!ElTy->isSized() || (isa<PointerType>(CompTy) && !Indices.empty()))
120 return 0; // Type is unreasonable... escape!
121 unsigned ElSize = TD.getTypeSize(ElTy);
122 if (ElSize == 0) return 0; // Avoid division by zero...
123 int64_t ElSizeS = ElSize;
125 // See if the user is indexing into a different cell of this array...
126 if (Scale && (Scale >= ElSizeS || -Scale >= ElSizeS)) {
127 // A scale n*ElSize might occur if we are not stepping through
128 // array by one. In this case, we will have to insert math to munge
131 int64_t ScaleAmt = Scale/ElSizeS;
132 if (Scale-ScaleAmt*ElSizeS)
133 return 0; // Didn't scale by a multiple of element size, bail out
134 Scale = 0; // Scale is consumed
136 int64_t Index = Offset/ElSize; // is zero unless Offset > ElSize
137 Offset -= Index*ElSize; // Consume part of the offset
139 if (BI) { // Generate code?
140 BasicBlock *BB = (*BI)->getParent();
141 if (Expr.Var->getType() != Type::LongTy)
142 Expr.Var = new CastInst(Expr.Var, Type::LongTy,
143 Expr.Var->getName()+"-idxcast", *BI);
145 if (ScaleAmt && ScaleAmt != 1) {
146 // If we have to scale up our index, do so now
147 Value *ScaleAmtVal = ConstantSInt::get(Type::LongTy, ScaleAmt);
148 Expr.Var = BinaryOperator::create(Instruction::Mul, Expr.Var,
150 Expr.Var->getName()+"-scale",*BI);
153 if (Index) { // Add an offset to the index
154 Value *IndexAmt = ConstantSInt::get(Type::LongTy, Index);
155 Expr.Var = BinaryOperator::create(Instruction::Add, Expr.Var,
157 Expr.Var->getName()+"-offset",
162 Indices.push_back(Expr.Var);
164 } else if (Offset >= (int64_t)ElSize || -Offset >= (int64_t)ElSize) {
165 // Calculate the index that we are entering into the array cell with
166 uint64_t Index = Offset/ElSize;
167 Indices.push_back(ConstantSInt::get(Type::LongTy, Index));
168 Offset -= (int64_t)(Index*ElSize); // Consume part of the offset
170 } else if (isa<ArrayType>(CompTy) || Indices.empty()) {
171 // Must be indexing a small amount into the first cell of the array
172 // Just index into element zero of the array here.
174 Indices.push_back(ConstantSInt::get(Type::LongTy, 0));
176 return 0; // Hrm. wierd, can't handle this case. Bail
180 } while (Offset || Scale); // Go until we're done!