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"
15 // TargetData Hack: Eventually we will have annotations given to us by the
16 // backend so that we know stuff about type size and alignments. For now
17 // though, just use this, because it happens to match the model that GCC uses.
19 const TargetData TD("LevelRaise: Should be GCC though!");
21 // ReplaceInstWithValue - Replace all uses of an instruction (specified by BI)
22 // with a value, then remove and delete the original instruction.
24 void ReplaceInstWithValue(BasicBlock::InstListType &BIL,
25 BasicBlock::iterator &BI, Value *V) {
27 // Replaces all of the uses of the instruction with uses of the value
28 I->replaceAllUsesWith(V);
30 // Remove the unneccesary instruction now...
33 // Make sure to propogate a name if there is one already...
34 if (I->hasName() && !V->hasName())
35 V->setName(I->getName(), BIL.getParent()->getSymbolTable());
37 // Remove the dead instruction now...
42 // ReplaceInstWithInst - Replace the instruction specified by BI with the
43 // instruction specified by I. The original instruction is deleted and BI is
44 // updated to point to the new instruction.
46 void ReplaceInstWithInst(BasicBlock::InstListType &BIL,
47 BasicBlock::iterator &BI, Instruction *I) {
48 assert(I->getParent() == 0 &&
49 "ReplaceInstWithInst: Instruction already inserted into basic block!");
51 // Insert the new instruction into the basic block...
52 BI = BIL.insert(BI, I)+1; // Increment BI to point to instruction to delete
54 // Replace all uses of the old instruction, and delete it.
55 ReplaceInstWithValue(BIL, BI, I);
57 // Move BI back to point to the newly inserted instruction
61 void ReplaceInstWithInst(Instruction *From, Instruction *To) {
62 BasicBlock *BB = From->getParent();
63 BasicBlock::InstListType &BIL = BB->getInstList();
64 BasicBlock::iterator BI = find(BIL.begin(), BIL.end(), From);
65 assert(BI != BIL.end() && "Inst not in it's parents BB!");
66 ReplaceInstWithInst(BIL, BI, To);
69 // InsertInstBeforeInst - Insert 'NewInst' into the basic block that 'Existing'
70 // is already in, and put it right before 'Existing'. This instruction should
71 // only be used when there is no iterator to Existing already around. The
72 // returned iterator points to the new instruction.
74 BasicBlock::iterator InsertInstBeforeInst(Instruction *NewInst,
75 Instruction *Existing) {
76 BasicBlock *BB = Existing->getParent();
77 BasicBlock::InstListType &BIL = BB->getInstList();
78 BasicBlock::iterator BI = find(BIL.begin(), BIL.end(), Existing);
79 assert(BI != BIL.end() && "Inst not in it's parents BB!");
80 return BIL.insert(BI, NewInst);
85 static const Type *getStructOffsetStep(const StructType *STy, unsigned &Offset,
86 std::vector<Value*> &Indices) {
87 assert(Offset < TD.getTypeSize(STy) && "Offset not in composite!");
88 const StructLayout *SL = TD.getStructLayout(STy);
90 // This loop terminates always on a 0 <= i < MemberOffsets.size()
92 for (i = 0; i < SL->MemberOffsets.size()-1; ++i)
93 if (Offset >= SL->MemberOffsets[i] && Offset < SL->MemberOffsets[i+1])
96 assert(Offset >= SL->MemberOffsets[i] &&
97 (i == SL->MemberOffsets.size()-1 || Offset < SL->MemberOffsets[i+1]));
99 // Make sure to save the current index...
100 Indices.push_back(ConstantUInt::get(Type::UByteTy, i));
101 Offset = SL->MemberOffsets[i];
102 return STy->getContainedType(i);
106 // getStructOffsetType - Return a vector of offsets that are to be used to index
107 // into the specified struct type to get as close as possible to index as we
108 // can. Note that it is possible that we cannot get exactly to Offset, in which
109 // case we update offset to be the offset we actually obtained. The resultant
110 // leaf type is returned.
112 // If StopEarly is set to true (the default), the first object with the
113 // specified type is returned, even if it is a struct type itself. In this
114 // case, this routine will not drill down to the leaf type. Set StopEarly to
115 // false if you want a leaf
117 const Type *getStructOffsetType(const Type *Ty, unsigned &Offset,
118 std::vector<Value*> &Indices,
119 bool StopEarly = true) {
120 if (Offset == 0 && StopEarly && !Indices.empty())
121 return Ty; // Return the leaf type
124 const Type *NextType;
125 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
127 NextType = getStructOffsetStep(STy, ThisOffset, Indices);
128 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
129 assert(Offset < TD.getTypeSize(ATy) && "Offset not in composite!");
131 NextType = ATy->getElementType();
132 unsigned ChildSize = TD.getTypeSize(NextType);
133 Indices.push_back(ConstantUInt::get(Type::UIntTy, Offset/ChildSize));
134 ThisOffset = (Offset/ChildSize)*ChildSize;
136 Offset = 0; // Return the offset that we were able to acheive
137 return Ty; // Return the leaf type
140 unsigned SubOffs = Offset - ThisOffset;
141 const Type *LeafTy = getStructOffsetType(NextType, SubOffs,
143 Offset = ThisOffset + SubOffs;
147 // ConvertableToGEP - This function returns true if the specified value V is
148 // a valid index into a pointer of type Ty. If it is valid, Idx is filled in
149 // with the values that would be appropriate to make this a getelementptr
150 // instruction. The type returned is the root type that the GEP would point to
152 const Type *ConvertableToGEP(const Type *Ty, Value *OffsetVal,
153 std::vector<Value*> &Indices,
154 BasicBlock::iterator *BI = 0) {
155 const CompositeType *CompTy = dyn_cast<CompositeType>(Ty);
156 if (CompTy == 0) return 0;
158 // See if the cast is of an integer expression that is either a constant,
159 // or a value scaled by some amount with a possible offset.
161 analysis::ExprType Expr = analysis::ClassifyExpression(OffsetVal);
163 // Get the offset and scale values if they exists...
164 // A scale of zero with Expr.Var != 0 means a scale of 1.
166 int Offset = Expr.Offset ? getConstantValue(Expr.Offset) : 0;
167 int Scale = Expr.Scale ? getConstantValue(Expr.Scale) : 0;
169 if (Expr.Var && Scale == 0) Scale = 1; // Scale != 0 if Expr.Var != 0
171 // Loop over the Scale and Offset values, filling in the Indices vector for
172 // our final getelementptr instruction.
174 const Type *NextTy = CompTy;
176 if (!isa<CompositeType>(NextTy))
177 return 0; // Type must not be ready for processing...
178 CompTy = cast<CompositeType>(NextTy);
180 if (const StructType *StructTy = dyn_cast<StructType>(CompTy)) {
181 // Step into the appropriate element of the structure...
182 unsigned ActualOffset = (Offset < 0) ? 0 : (unsigned)Offset;
183 NextTy = getStructOffsetStep(StructTy, ActualOffset, Indices);
184 Offset -= ActualOffset;
186 const Type *ElTy = cast<SequentialType>(CompTy)->getElementType();
187 if (!ElTy->isSized())
188 return 0; // Type is unreasonable... escape!
189 unsigned ElSize = TD.getTypeSize(ElTy);
190 int ElSizeS = (int)ElSize;
192 // See if the user is indexing into a different cell of this array...
193 if (Scale && (Scale >= ElSizeS || -Scale >= ElSizeS)) {
194 // A scale n*ElSize might occur if we are not stepping through
195 // array by one. In this case, we will have to insert math to munge
198 int ScaleAmt = Scale/ElSizeS;
199 if (Scale-ScaleAmt*ElSizeS)
200 return 0; // Didn't scale by a multiple of element size, bail out
201 Scale = 0; // Scale is consumed
203 int Index = Offset/ElSize; // is zero unless Offset > ElSize
204 Offset -= Index*ElSize; // Consume part of the offset
206 if (BI) { // Generate code?
207 BasicBlock *BB = (**BI)->getParent();
208 if (Expr.Var->getType() != Type::UIntTy) {
209 CastInst *IdxCast = new CastInst(Expr.Var, Type::UIntTy);
210 if (Expr.Var->hasName())
211 IdxCast->setName(Expr.Var->getName()+"-idxcast");
212 *BI = BB->getInstList().insert(*BI, IdxCast)+1;
216 if (ScaleAmt && ScaleAmt != 1) {
217 // If we have to scale up our index, do so now
218 Value *ScaleAmtVal = ConstantUInt::get(Type::UIntTy,
220 Instruction *Scaler = BinaryOperator::create(Instruction::Mul,
221 Expr.Var, ScaleAmtVal);
222 if (Expr.Var->hasName())
223 Scaler->setName(Expr.Var->getName()+"-scale");
225 *BI = BB->getInstList().insert(*BI, Scaler)+1;
229 if (Index) { // Add an offset to the index
230 Value *IndexAmt = ConstantUInt::get(Type::UIntTy, (unsigned)Index);
231 Instruction *Offseter = BinaryOperator::create(Instruction::Add,
233 if (Expr.Var->hasName())
234 Offseter->setName(Expr.Var->getName()+"-offset");
235 *BI = BB->getInstList().insert(*BI, Offseter)+1;
240 Indices.push_back(Expr.Var);
242 } else if (Offset >= (int)ElSize || -Offset >= (int)ElSize) {
243 // Calculate the index that we are entering into the array cell with
244 unsigned Index = Offset/ElSize;
245 Indices.push_back(ConstantUInt::get(Type::UIntTy, Index));
246 Offset -= (int)(Index*ElSize); // Consume part of the offset
248 } else if (isa<ArrayType>(CompTy) || Indices.empty()) {
249 // Must be indexing a small amount into the first cell of the array
250 // Just index into element zero of the array here.
252 Indices.push_back(ConstantUInt::get(Type::UIntTy, 0));
254 return 0; // Hrm. wierd, can't handle this case. Bail
258 } while (Offset || Scale); // Go until we're done!