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)) {
56 if (STy->getElementTypes().empty()) {
62 NextType = getStructOffsetStep(STy, ThisOffset, Indices, TD);
63 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
64 assert(Offset == 0 || Offset < TD.getTypeSize(ATy) &&
65 "Offset not in composite!");
67 NextType = ATy->getElementType();
68 unsigned ChildSize = TD.getTypeSize(NextType);
69 Indices.push_back(ConstantSInt::get(Type::LongTy, Offset/ChildSize));
70 ThisOffset = (Offset/ChildSize)*ChildSize;
72 Offset = 0; // Return the offset that we were able to achieve
73 return Ty; // Return the leaf type
76 unsigned SubOffs = Offset - ThisOffset;
77 const Type *LeafTy = getStructOffsetType(NextType, SubOffs,
78 Indices, TD, StopEarly);
79 Offset = ThisOffset + SubOffs;
83 // ConvertibleToGEP - This function returns true if the specified value V is
84 // a valid index into a pointer of type Ty. If it is valid, Idx is filled in
85 // with the values that would be appropriate to make this a getelementptr
86 // instruction. The type returned is the root type that the GEP would point to
88 const Type *ConvertibleToGEP(const Type *Ty, Value *OffsetVal,
89 std::vector<Value*> &Indices,
91 BasicBlock::iterator *BI) {
92 const CompositeType *CompTy = dyn_cast<CompositeType>(Ty);
93 if (CompTy == 0) return 0;
95 // See if the cast is of an integer expression that is either a constant,
96 // or a value scaled by some amount with a possible offset.
98 ExprType Expr = ClassifyExpression(OffsetVal);
100 // Get the offset and scale values if they exists...
101 // A scale of zero with Expr.Var != 0 means a scale of 1.
103 int64_t Offset = Expr.Offset ? getConstantValue(Expr.Offset) : 0;
104 int64_t Scale = Expr.Scale ? getConstantValue(Expr.Scale) : 0;
106 if (Expr.Var && Scale == 0) Scale = 1; // Scale != 0 if Expr.Var != 0
108 // Loop over the Scale and Offset values, filling in the Indices vector for
109 // our final getelementptr instruction.
111 const Type *NextTy = CompTy;
113 if (!isa<CompositeType>(NextTy))
114 return 0; // Type must not be ready for processing...
115 CompTy = cast<CompositeType>(NextTy);
117 if (const StructType *StructTy = dyn_cast<StructType>(CompTy)) {
118 // Step into the appropriate element of the structure...
119 uint64_t ActualOffset = (Offset < 0) ? 0 : (uint64_t)Offset;
120 NextTy = getStructOffsetStep(StructTy, ActualOffset, Indices, TD);
121 Offset -= ActualOffset;
123 const Type *ElTy = cast<SequentialType>(CompTy)->getElementType();
124 if (!ElTy->isSized() || (isa<PointerType>(CompTy) && !Indices.empty()))
125 return 0; // Type is unreasonable... escape!
126 unsigned ElSize = TD.getTypeSize(ElTy);
127 if (ElSize == 0) return 0; // Avoid division by zero...
128 int64_t ElSizeS = ElSize;
130 // See if the user is indexing into a different cell of this array...
131 if (Scale && (Scale >= ElSizeS || -Scale >= ElSizeS)) {
132 // A scale n*ElSize might occur if we are not stepping through
133 // array by one. In this case, we will have to insert math to munge
136 int64_t ScaleAmt = Scale/ElSizeS;
137 if (Scale-ScaleAmt*ElSizeS)
138 return 0; // Didn't scale by a multiple of element size, bail out
139 Scale = 0; // Scale is consumed
141 int64_t Index = Offset/ElSize; // is zero unless Offset > ElSize
142 Offset -= Index*ElSize; // Consume part of the offset
144 if (BI) { // Generate code?
145 BasicBlock *BB = (*BI)->getParent();
146 if (Expr.Var->getType() != Type::LongTy)
147 Expr.Var = new CastInst(Expr.Var, Type::LongTy,
148 Expr.Var->getName()+"-idxcast", *BI);
150 if (ScaleAmt && ScaleAmt != 1) {
151 // If we have to scale up our index, do so now
152 Value *ScaleAmtVal = ConstantSInt::get(Type::LongTy, ScaleAmt);
153 Expr.Var = BinaryOperator::create(Instruction::Mul, Expr.Var,
155 Expr.Var->getName()+"-scale",*BI);
158 if (Index) { // Add an offset to the index
159 Value *IndexAmt = ConstantSInt::get(Type::LongTy, Index);
160 Expr.Var = BinaryOperator::create(Instruction::Add, Expr.Var,
162 Expr.Var->getName()+"-offset",
167 Indices.push_back(Expr.Var);
169 } else if (Offset >= (int64_t)ElSize || -Offset >= (int64_t)ElSize) {
170 // Calculate the index that we are entering into the array cell with
171 uint64_t Index = Offset/ElSize;
172 Indices.push_back(ConstantSInt::get(Type::LongTy, Index));
173 Offset -= (int64_t)(Index*ElSize); // Consume part of the offset
175 } else if (isa<ArrayType>(CompTy) || Indices.empty()) {
176 // Must be indexing a small amount into the first cell of the array
177 // Just index into element zero of the array here.
179 Indices.push_back(ConstantSInt::get(Type::LongTy, 0));
181 return 0; // Hrm. wierd, can't handle this case. Bail
185 } while (Offset || Scale); // Go until we're done!