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"
9 #include "llvm/Method.h"
10 #include "llvm/Type.h"
11 #include "llvm/ConstantVals.h"
12 #include "llvm/Analysis/Expressions.h"
13 #include "llvm/iOther.h"
16 // TargetData Hack: Eventually we will have annotations given to us by the
17 // backend so that we know stuff about type size and alignments. For now
18 // though, just use this, because it happens to match the model that GCC uses.
20 const TargetData TD("LevelRaise: Should be GCC though!");
22 // ReplaceInstWithValue - Replace all uses of an instruction (specified by BI)
23 // with a value, then remove and delete the original instruction.
25 void ReplaceInstWithValue(BasicBlock::InstListType &BIL,
26 BasicBlock::iterator &BI, Value *V) {
28 // Replaces all of the uses of the instruction with uses of the value
29 I->replaceAllUsesWith(V);
31 // Remove the unneccesary instruction now...
34 // Make sure to propogate a name if there is one already...
35 if (I->hasName() && !V->hasName())
36 V->setName(I->getName(), BIL.getParent()->getSymbolTable());
38 // Remove the dead instruction now...
43 // ReplaceInstWithInst - Replace the instruction specified by BI with the
44 // instruction specified by I. The original instruction is deleted and BI is
45 // updated to point to the new instruction.
47 void ReplaceInstWithInst(BasicBlock::InstListType &BIL,
48 BasicBlock::iterator &BI, Instruction *I) {
49 assert(I->getParent() == 0 &&
50 "ReplaceInstWithInst: Instruction already inserted into basic block!");
52 // Insert the new instruction into the basic block...
53 BI = BIL.insert(BI, I)+1; // Increment BI to point to instruction to delete
55 // Replace all uses of the old instruction, and delete it.
56 ReplaceInstWithValue(BIL, BI, I);
58 // Move BI back to point to the newly inserted instruction
62 void ReplaceInstWithInst(Instruction *From, Instruction *To) {
63 BasicBlock *BB = From->getParent();
64 BasicBlock::InstListType &BIL = BB->getInstList();
65 BasicBlock::iterator BI = find(BIL.begin(), BIL.end(), From);
66 assert(BI != BIL.end() && "Inst not in it's parents BB!");
67 ReplaceInstWithInst(BIL, BI, To);
70 // InsertInstBeforeInst - Insert 'NewInst' into the basic block that 'Existing'
71 // is already in, and put it right before 'Existing'. This instruction should
72 // only be used when there is no iterator to Existing already around. The
73 // returned iterator points to the new instruction.
75 BasicBlock::iterator InsertInstBeforeInst(Instruction *NewInst,
76 Instruction *Existing) {
77 BasicBlock *BB = Existing->getParent();
78 BasicBlock::InstListType &BIL = BB->getInstList();
79 BasicBlock::iterator BI = find(BIL.begin(), BIL.end(), Existing);
80 assert(BI != BIL.end() && "Inst not in it's parents BB!");
81 return BIL.insert(BI, NewInst);
86 static const Type *getStructOffsetStep(const StructType *STy, unsigned &Offset,
87 std::vector<Value*> &Indices) {
88 assert(Offset < TD.getTypeSize(STy) && "Offset not in composite!");
89 const StructLayout *SL = TD.getStructLayout(STy);
91 // This loop terminates always on a 0 <= i < MemberOffsets.size()
93 for (i = 0; i < SL->MemberOffsets.size()-1; ++i)
94 if (Offset >= SL->MemberOffsets[i] && Offset < SL->MemberOffsets[i+1])
97 assert(Offset >= SL->MemberOffsets[i] &&
98 (i == SL->MemberOffsets.size()-1 || Offset < SL->MemberOffsets[i+1]));
100 // Make sure to save the current index...
101 Indices.push_back(ConstantUInt::get(Type::UByteTy, i));
102 Offset = SL->MemberOffsets[i];
103 return STy->getContainedType(i);
107 // getStructOffsetType - Return a vector of offsets that are to be used to index
108 // into the specified struct type to get as close as possible to index as we
109 // can. Note that it is possible that we cannot get exactly to Offset, in which
110 // case we update offset to be the offset we actually obtained. The resultant
111 // leaf type is returned.
113 // If StopEarly is set to true (the default), the first object with the
114 // specified type is returned, even if it is a struct type itself. In this
115 // case, this routine will not drill down to the leaf type. Set StopEarly to
116 // false if you want a leaf
118 const Type *getStructOffsetType(const Type *Ty, unsigned &Offset,
119 std::vector<Value*> &Indices,
120 bool StopEarly = true) {
121 if (Offset == 0 && StopEarly && !Indices.empty())
122 return Ty; // Return the leaf type
125 const Type *NextType;
126 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
128 NextType = getStructOffsetStep(STy, ThisOffset, Indices);
129 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
130 assert(Offset < TD.getTypeSize(ATy) && "Offset not in composite!");
132 NextType = ATy->getElementType();
133 unsigned ChildSize = TD.getTypeSize(NextType);
134 Indices.push_back(ConstantUInt::get(Type::UIntTy, Offset/ChildSize));
135 ThisOffset = (Offset/ChildSize)*ChildSize;
137 Offset = 0; // Return the offset that we were able to acheive
138 return Ty; // Return the leaf type
141 unsigned SubOffs = Offset - ThisOffset;
142 const Type *LeafTy = getStructOffsetType(NextType, SubOffs,
144 Offset = ThisOffset + SubOffs;
148 // ConvertableToGEP - This function returns true if the specified value V is
149 // a valid index into a pointer of type Ty. If it is valid, Idx is filled in
150 // with the values that would be appropriate to make this a getelementptr
151 // instruction. The type returned is the root type that the GEP would point to
153 const Type *ConvertableToGEP(const Type *Ty, Value *OffsetVal,
154 std::vector<Value*> &Indices,
155 BasicBlock::iterator *BI = 0) {
156 const CompositeType *CompTy = dyn_cast<CompositeType>(Ty);
157 if (CompTy == 0) return 0;
159 // See if the cast is of an integer expression that is either a constant,
160 // or a value scaled by some amount with a possible offset.
162 analysis::ExprType Expr = analysis::ClassifyExpression(OffsetVal);
164 // Get the offset and scale now...
165 // A scale of zero with Expr.Var != 0 means a scale of 1.
167 // TODO: Handle negative offsets for C code like this:
168 // for (unsigned i = 12; i < 14; ++i) x[j*i-12] = ...
172 // Get the offset value if it exists...
174 int Val = getConstantValue(Expr.Offset);
175 if (Val < 0) return false; // Don't mess with negative offsets
176 Offset = (unsigned)Val;
179 // Get the scale value if it exists...
180 if (Expr.Scale) Scale = getConstantValue(Expr.Scale);
181 if (Expr.Var && Scale == 0) Scale = 1; // Scale != 0 if Expr.Var != 0
183 // Loop over the Scale and Offset values, filling in the Indices vector for
184 // our final getelementptr instruction.
186 const Type *NextTy = CompTy;
188 if (!isa<CompositeType>(NextTy))
189 return 0; // Type must not be ready for processing...
190 CompTy = cast<CompositeType>(NextTy);
192 if (const StructType *StructTy = dyn_cast<StructType>(CompTy)) {
193 // Step into the appropriate element of the structure...
194 unsigned ActualOffset = Offset;
195 NextTy = getStructOffsetStep(StructTy, ActualOffset, Indices);
196 Offset -= ActualOffset;
198 const Type *ElTy = cast<SequentialType>(CompTy)->getElementType();
199 if (!ElTy->isSized())
200 return 0; // Type is unreasonable... escape!
201 unsigned ElSize = TD.getTypeSize(ElTy);
202 int ElSizeS = (int)ElSize;
204 // See if the user is indexing into a different cell of this array...
205 if (Scale && (Scale >= ElSizeS || -Scale >= ElSizeS)) {
206 // A scale n*ElSize might occur if we are not stepping through
207 // array by one. In this case, we will have to insert math to munge
210 int ScaleAmt = Scale/ElSizeS;
211 if (Scale-ScaleAmt*ElSizeS)
212 return 0; // Didn't scale by a multiple of element size, bail out
213 Scale = 0; // Scale is consumed
215 unsigned Index = Offset/ElSize; // is zero unless Offset > ElSize
216 Offset -= Index*ElSize; // Consume part of the offset
218 if (BI) { // Generate code?
219 BasicBlock *BB = (**BI)->getParent();
220 if (Expr.Var->getType() != Type::UIntTy) {
221 CastInst *IdxCast = new CastInst(Expr.Var, Type::UIntTy);
222 if (Expr.Var->hasName())
223 IdxCast->setName(Expr.Var->getName()+"-idxcast");
224 *BI = BB->getInstList().insert(*BI, IdxCast)+1;
228 if (ScaleAmt && ScaleAmt != 1) {
229 // If we have to scale up our index, do so now
230 Value *ScaleAmtVal = ConstantUInt::get(Type::UIntTy,
232 Instruction *Scaler = BinaryOperator::create(Instruction::Mul,
233 Expr.Var, ScaleAmtVal);
234 if (Expr.Var->hasName())
235 Scaler->setName(Expr.Var->getName()+"-scale");
237 *BI = BB->getInstList().insert(*BI, Scaler)+1;
241 if (Index) { // Add an offset to the index
242 Value *IndexAmt = ConstantUInt::get(Type::UIntTy, Index);
243 Instruction *Offseter = BinaryOperator::create(Instruction::Add,
245 if (Expr.Var->hasName())
246 Offseter->setName(Expr.Var->getName()+"-offset");
247 *BI = BB->getInstList().insert(*BI, Offseter)+1;
252 Indices.push_back(Expr.Var);
254 } else if (Offset >= ElSize) {
255 // Calculate the index that we are entering into the array cell with
256 unsigned Index = Offset/ElSize;
257 Indices.push_back(ConstantUInt::get(Type::UIntTy, Index));
258 Offset -= Index*ElSize; // Consume part of the offset
260 } else if (isa<ArrayType>(CompTy) || Indices.empty()) {
261 // Must be indexing a small amount into the first cell of the array
262 // Just index into element zero of the array here.
264 Indices.push_back(ConstantUInt::get(Type::UIntTy, 0));
266 return 0; // Hrm. wierd, can't handle this case. Bail
270 } while (Offset || Scale); // Go until we're done!