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);
72 // getStructOffsetType - Return a vector of offsets that are to be used to index
73 // into the specified struct type to get as close as possible to index as we
74 // can. Note that it is possible that we cannot get exactly to Offset, in which
75 // case we update offset to be the offset we actually obtained. The resultant
76 // leaf type is returned.
78 // If StopEarly is set to true (the default), the first object with the
79 // specified type is returned, even if it is a struct type itself. In this
80 // case, this routine will not drill down to the leaf type. Set StopEarly to
81 // false if you want a leaf
83 const Type *getStructOffsetType(const Type *Ty, unsigned &Offset,
84 std::vector<Value*> &Offsets,
85 bool StopEarly = true) {
86 if (Offset == 0 && StopEarly && !Offsets.empty())
87 return Ty; // Return the leaf type
91 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
92 assert(Offset < TD.getTypeSize(STy) && "Offset not in composite!");
93 const StructLayout *SL = TD.getStructLayout(STy);
95 // This loop terminates always on a 0 <= i < MemberOffsets.size()
97 for (i = 0; i < SL->MemberOffsets.size()-1; ++i)
98 if (Offset >= SL->MemberOffsets[i] && Offset < SL->MemberOffsets[i+1])
101 assert(Offset >= SL->MemberOffsets[i] &&
102 (i == SL->MemberOffsets.size()-1 || Offset <SL->MemberOffsets[i+1]));
104 // Make sure to save the current index...
105 Offsets.push_back(ConstantUInt::get(Type::UByteTy, i));
106 ThisOffset = SL->MemberOffsets[i];
107 NextType = STy->getElementTypes()[i];
108 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
109 assert(Offset < TD.getTypeSize(ATy) && "Offset not in composite!");
111 NextType = ATy->getElementType();
112 unsigned ChildSize = TD.getTypeSize(NextType);
113 Offsets.push_back(ConstantUInt::get(Type::UIntTy, Offset/ChildSize));
114 ThisOffset = (Offset/ChildSize)*ChildSize;
116 Offset = 0; // Return the offset that we were able to acheive
117 return Ty; // Return the leaf type
120 unsigned SubOffs = Offset - ThisOffset;
121 const Type *LeafTy = getStructOffsetType(NextType, SubOffs,
123 Offset = ThisOffset + SubOffs;
127 // ConvertableToGEP - This function returns true if the specified value V is
128 // a valid index into a pointer of type Ty. If it is valid, Idx is filled in
129 // with the values that would be appropriate to make this a getelementptr
130 // instruction. The type returned is the root type that the GEP would point to
132 const Type *ConvertableToGEP(const Type *Ty, Value *OffsetVal,
133 std::vector<Value*> &Indices,
134 BasicBlock::iterator *BI = 0) {
135 const CompositeType *CompTy = dyn_cast<CompositeType>(Ty);
136 if (CompTy == 0) return 0;
138 // See if the cast is of an integer expression that is either a constant,
139 // or a value scaled by some amount with a possible offset.
141 analysis::ExprType Expr = analysis::ClassifyExpression(OffsetVal);
143 // Get the offset and scale now...
144 // A scale of zero with Expr.Var != 0 means a scale of 1.
146 // TODO: Handle negative offsets for C code like this:
147 // for (unsigned i = 12; i < 14; ++i) x[j*i-12] = ...
151 // Get the offset value if it exists...
153 int Val = getConstantValue(Expr.Offset);
154 if (Val < 0) return false; // Don't mess with negative offsets
155 Offset = (unsigned)Val;
158 // Get the scale value if it exists...
159 if (Expr.Scale) Scale = getConstantValue(Expr.Scale);
160 if (Expr.Var && Scale == 0) Scale = 1; // Scale != 0 if Expr.Var != 0
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)
175 return 0; // No progress. :(
176 Offset -= ActualOffset;
178 const Type *ElTy = cast<SequentialType>(CompTy)->getElementType();
179 if (!ElTy->isSized())
180 return 0; // Type is unreasonable... escape!
181 unsigned ElSize = TD.getTypeSize(ElTy);
182 int ElSizeS = (int)ElSize;
184 // See if the user is indexing into a different cell of this array...
185 if (Scale && (Scale >= ElSizeS || -Scale >= ElSizeS)) {
186 // A scale n*ElSize might occur if we are not stepping through
187 // array by one. In this case, we will have to insert math to munge
190 int ScaleAmt = Scale/ElSizeS;
191 if (Scale-ScaleAmt*ElSizeS)
192 return 0; // Didn't scale by a multiple of element size, bail out
193 Scale = 0; // Scale is consumed
195 unsigned Index = Offset/ElSize; // is zero unless Offset > ElSize
196 Offset -= Index*ElSize; // Consume part of the offset
198 if (BI) { // Generate code?
199 BasicBlock *BB = (**BI)->getParent();
200 if (Expr.Var->getType() != Type::UIntTy) {
201 CastInst *IdxCast = new CastInst(Expr.Var, Type::UIntTy);
202 if (Expr.Var->hasName())
203 IdxCast->setName(Expr.Var->getName()+"-idxcast");
204 *BI = BB->getInstList().insert(*BI, IdxCast)+1;
208 if (ScaleAmt && ScaleAmt != 1) {
209 // If we have to scale up our index, do so now
210 Value *ScaleAmtVal = ConstantUInt::get(Type::UIntTy,
212 Instruction *Scaler = BinaryOperator::create(Instruction::Mul,
213 Expr.Var, ScaleAmtVal);
214 if (Expr.Var->hasName())
215 Scaler->setName(Expr.Var->getName()+"-scale");
217 *BI = BB->getInstList().insert(*BI, Scaler)+1;
221 if (Index) { // Add an offset to the index
222 Value *IndexAmt = ConstantUInt::get(Type::UIntTy, Index);
223 Instruction *Offseter = BinaryOperator::create(Instruction::Add,
225 if (Expr.Var->hasName())
226 Offseter->setName(Expr.Var->getName()+"-offset");
227 *BI = BB->getInstList().insert(*BI, Offseter)+1;
232 Indices.push_back(Expr.Var);
234 } else if (Offset >= ElSize) {
235 // Calculate the index that we are entering into the array cell with
236 unsigned Index = Offset/ElSize;
237 Indices.push_back(ConstantUInt::get(Type::UIntTy, Index));
238 Offset -= Index*ElSize; // Consume part of the offset
240 } else if (isa<ArrayType>(CompTy) || Indices.empty()) {
241 // Must be indexing a small amount into the first cell of the array
242 // Just index into element zero of the array here.
244 Indices.push_back(ConstantUInt::get(Type::UIntTy, 0));
246 return 0; // Hrm. wierd, can't handle this case. Bail
250 } while (Offset || Scale); // Go until we're done!