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;
55 // Replace all uses of the old instruction, and delete it.
56 ReplaceInstWithValue(BIL, BI, I);
58 // Reexamine the instruction just inserted next time around the cleanup pass
63 void ReplaceInstWithInst(Instruction *From, Instruction *To) {
64 BasicBlock *BB = From->getParent();
65 BasicBlock::InstListType &BIL = BB->getInstList();
66 BasicBlock::iterator BI = find(BIL.begin(), BIL.end(), From);
67 assert(BI != BIL.end() && "Inst not in it's parents BB!");
68 ReplaceInstWithInst(BIL, BI, To);
73 // getStructOffsetType - Return a vector of offsets that are to be used to index
74 // into the specified struct type to get as close as possible to index as we
75 // can. Note that it is possible that we cannot get exactly to Offset, in which
76 // case we update offset to be the offset we actually obtained. The resultant
77 // leaf type is returned.
79 // If StopEarly is set to true (the default), the first object with the
80 // specified type is returned, even if it is a struct type itself. In this
81 // case, this routine will not drill down to the leaf type. Set StopEarly to
82 // false if you want a leaf
84 const Type *getStructOffsetType(const Type *Ty, unsigned &Offset,
85 std::vector<Value*> &Offsets,
86 bool StopEarly = true) {
87 if (Offset == 0 && StopEarly && !Offsets.empty())
88 return Ty; // Return the leaf type
92 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
93 assert(Offset < TD.getTypeSize(STy) && "Offset not in composite!");
94 const StructLayout *SL = TD.getStructLayout(STy);
96 // This loop terminates always on a 0 <= i < MemberOffsets.size()
98 for (i = 0; i < SL->MemberOffsets.size()-1; ++i)
99 if (Offset >= SL->MemberOffsets[i] && Offset < SL->MemberOffsets[i+1])
102 assert(Offset >= SL->MemberOffsets[i] &&
103 (i == SL->MemberOffsets.size()-1 || Offset <SL->MemberOffsets[i+1]));
105 // Make sure to save the current index...
106 Offsets.push_back(ConstantUInt::get(Type::UByteTy, i));
107 ThisOffset = SL->MemberOffsets[i];
108 NextType = STy->getElementTypes()[i];
109 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
110 assert(Offset < TD.getTypeSize(ATy) && "Offset not in composite!");
112 NextType = ATy->getElementType();
113 unsigned ChildSize = TD.getTypeSize(NextType);
114 Offsets.push_back(ConstantUInt::get(Type::UIntTy, Offset/ChildSize));
115 ThisOffset = (Offset/ChildSize)*ChildSize;
117 Offset = 0; // Return the offset that we were able to acheive
118 return Ty; // Return the leaf type
121 unsigned SubOffs = Offset - ThisOffset;
122 const Type *LeafTy = getStructOffsetType(NextType, SubOffs,
124 Offset = ThisOffset + SubOffs;
128 // ConvertableToGEP - This function returns true if the specified value V is
129 // a valid index into a pointer of type Ty. If it is valid, Idx is filled in
130 // with the values that would be appropriate to make this a getelementptr
131 // instruction. The type returned is the root type that the GEP would point to
133 const Type *ConvertableToGEP(const Type *Ty, Value *OffsetVal,
134 std::vector<Value*> &Indices,
135 BasicBlock::iterator *BI = 0) {
136 const CompositeType *CompTy = dyn_cast<CompositeType>(Ty);
137 if (CompTy == 0) return 0;
139 // See if the cast is of an integer expression that is either a constant,
140 // or a value scaled by some amount with a possible offset.
142 analysis::ExprType Expr = analysis::ClassifyExpression(OffsetVal);
144 // Get the offset and scale now...
145 unsigned Offset = 0, Scale = Expr.Var != 0;
147 // Get the offset value if it exists...
149 int Val = getConstantValue(Expr.Offset);
150 if (Val < 0) return false; // Don't mess with negative offsets
151 Offset = (unsigned)Val;
154 // Get the scale value if it exists...
156 int Val = getConstantValue(Expr.Scale);
157 if (Val < 0) return false; // Don't mess with negative scales
158 Scale = (unsigned)Val;
159 if (Scale == 1) Scale = 0; // No interesting scale if *1
162 // Loop over the Scale and Offset values, filling in the Indices vector for
163 // our final getelementptr instruction.
165 const Type *NextTy = CompTy;
167 if (!isa<CompositeType>(NextTy))
168 return 0; // Type must not be ready for processing...
169 CompTy = cast<CompositeType>(NextTy);
171 if (const StructType *StructTy = dyn_cast<StructType>(CompTy)) {
172 unsigned ActualOffset = Offset;
173 NextTy = getStructOffsetType(StructTy, ActualOffset, Indices);
174 if (StructTy == NextTy && ActualOffset == 0) return 0; // No progress. :(
175 Offset -= ActualOffset;
177 const Type *ElTy = cast<SequentialType>(CompTy)->getElementType();
178 if (!ElTy->isSized()) return 0; // Type is unreasonable... escape!
179 unsigned ElSize = TD.getTypeSize(ElTy);
181 // See if the user is indexing into a different cell of this array...
182 if (Scale && Scale >= ElSize) {
183 // A scale n*ElSize might occur if we are not stepping through
184 // array by one. In this case, we will have to insert math to munge
187 unsigned ScaleAmt = Scale/ElSize;
188 if (Scale-ScaleAmt*ElSize)
189 return 0; // Didn't scale by a multiple of element size, bail out
190 Scale = 0; // Scale is consumed
192 unsigned Index = Offset/ElSize; // is zero unless Offset > ElSize
193 Offset -= Index*ElSize; // Consume part of the offset
195 if (BI) { // Generate code?
196 BasicBlock *BB = (**BI)->getParent();
197 if (Expr.Var->getType() != Type::UIntTy) {
198 CastInst *IdxCast = new CastInst(Expr.Var, Type::UIntTy);
199 if (Expr.Var->hasName())
200 IdxCast->setName(Expr.Var->getName()+"-idxcast");
201 *BI = BB->getInstList().insert(*BI, IdxCast)+1;
205 if (ScaleAmt && ScaleAmt != 1) {
206 // If we have to scale up our index, do so now
207 Value *ScaleAmtVal = ConstantUInt::get(Type::UIntTy, ScaleAmt);
208 Instruction *Scaler = BinaryOperator::create(Instruction::Mul,
209 Expr.Var,ScaleAmtVal);
210 if (Expr.Var->hasName())
211 Scaler->setName(Expr.Var->getName()+"-scale");
213 *BI = BB->getInstList().insert(*BI, Scaler)+1;
217 if (Index) { // Add an offset to the index
218 Value *IndexAmt = ConstantUInt::get(Type::UIntTy, Index);
219 Instruction *Offseter = BinaryOperator::create(Instruction::Add,
221 if (Expr.Var->hasName())
222 Offseter->setName(Expr.Var->getName()+"-offset");
223 *BI = BB->getInstList().insert(*BI, Offseter)+1;
228 Indices.push_back(Expr.Var);
229 } else if (Offset >= ElSize) {
230 // Calculate the index that we are entering into the array cell with
231 unsigned Index = Offset/ElSize;
232 Indices.push_back(ConstantUInt::get(Type::UIntTy, Index));
233 Offset -= Index*ElSize; // Consume part of the offset
235 } else if (!isa<PointerType>(CompTy) || CompTy == Ty) {
236 // Must be indexing a small amount into the first cell of the array
237 // Just index into element zero of the array here.
239 Indices.push_back(ConstantUInt::get(Type::UIntTy, 0));
241 return 0; // Hrm. wierd, can't handle this case. Bail
245 } while (Offset || Scale); // Go until we're done!