1 //===- Expressions.cpp - Expression Analysis Utilities ----------------------=//
3 // This file defines a package of expression analysis utilties:
5 // ClassifyExpression: Analyze an expression to determine the complexity of the
6 // expression, and which other variables it depends on.
8 //===----------------------------------------------------------------------===//
10 #include "llvm/Analysis/Expressions.h"
11 #include "llvm/Transforms/Scalar/ConstantHandling.h"
12 #include "llvm/Method.h"
13 #include "llvm/BasicBlock.h"
16 using namespace analysis;
18 ExprType::ExprType(Value *Val) {
20 if (ConstantInt *CPI = dyn_cast<ConstantInt>(Val)) {
28 Var = Val; Offset = 0;
29 ExprTy = Var ? Linear : Constant;
33 ExprType::ExprType(const ConstantInt *scale, Value *var,
34 const ConstantInt *offset) {
35 Scale = var ? scale : 0; Var = var; Offset = offset;
36 ExprTy = Scale ? ScaledLinear : (Var ? Linear : Constant);
37 if (Scale && Scale->equalsInt(0)) { // Simplify 0*Var + const
44 const Type *ExprType::getExprType(const Type *Default) const {
45 if (Offset) return Offset->getType();
46 if (Scale) return Scale->getType();
47 return Var ? Var->getType() : Default;
53 const ConstantInt * const Val;
54 const Type * const Ty;
56 inline DefVal(const ConstantInt *val, const Type *ty) : Val(val), Ty(ty) {}
58 inline const Type *getType() const { return Ty; }
59 inline const ConstantInt *getVal() const { return Val; }
60 inline operator const ConstantInt * () const { return Val; }
61 inline const ConstantInt *operator->() const { return Val; }
64 struct DefZero : public DefVal {
65 inline DefZero(const ConstantInt *val, const Type *ty) : DefVal(val, ty) {}
66 inline DefZero(const ConstantInt *val) : DefVal(val, val->getType()) {}
69 struct DefOne : public DefVal {
70 inline DefOne(const ConstantInt *val, const Type *ty) : DefVal(val, ty) {}
74 static ConstantInt *getUnsignedConstant(uint64_t V, const Type *Ty) {
75 if (Ty->isPointerType()) Ty = Type::ULongTy;
76 return Ty->isSigned() ? (ConstantInt*)ConstantSInt::get(Ty, V)
77 : (ConstantInt*)ConstantUInt::get(Ty, V);
80 // Add - Helper function to make later code simpler. Basically it just adds
81 // the two constants together, inserts the result into the constant pool, and
82 // returns it. Of course life is not simple, and this is no exception. Factors
83 // that complicate matters:
84 // 1. Either argument may be null. If this is the case, the null argument is
85 // treated as either 0 (if DefOne = false) or 1 (if DefOne = true)
86 // 2. Types get in the way. We want to do arithmetic operations without
87 // regard for the underlying types. It is assumed that the constants are
88 // integral constants. The new value takes the type of the left argument.
89 // 3. If DefOne is true, a null return value indicates a value of 1, if DefOne
90 // is false, a null return value indicates a value of 0.
92 static const ConstantInt *Add(const ConstantInt *Arg1,
93 const ConstantInt *Arg2, bool DefOne) {
94 assert(Arg1 && Arg2 && "No null arguments should exist now!");
95 assert(Arg1->getType() == Arg2->getType() && "Types must be compatible!");
97 // Actually perform the computation now!
98 Constant *Result = *Arg1 + *Arg2;
99 assert(Result && Result->getType() == Arg1->getType() &&
100 "Couldn't perform addition!");
101 ConstantInt *ResultI = cast<ConstantInt>(Result);
103 // Check to see if the result is one of the special cases that we want to
105 if (ResultI->equalsInt(DefOne ? 1 : 0))
106 return 0; // Yes it is, simply return null.
111 inline const ConstantInt *operator+(const DefZero &L, const DefZero &R) {
112 if (L == 0) return R;
113 if (R == 0) return L;
114 return Add(L, R, false);
117 inline const ConstantInt *operator+(const DefOne &L, const DefOne &R) {
120 return getUnsignedConstant(2, L.getType());
122 return Add(getUnsignedConstant(1, L.getType()), R, true);
124 return Add(L, getUnsignedConstant(1, L.getType()), true);
126 return Add(L, R, true);
130 // Mul - Helper function to make later code simpler. Basically it just
131 // multiplies the two constants together, inserts the result into the constant
132 // pool, and returns it. Of course life is not simple, and this is no
133 // exception. Factors that complicate matters:
134 // 1. Either argument may be null. If this is the case, the null argument is
135 // treated as either 0 (if DefOne = false) or 1 (if DefOne = true)
136 // 2. Types get in the way. We want to do arithmetic operations without
137 // regard for the underlying types. It is assumed that the constants are
138 // integral constants.
139 // 3. If DefOne is true, a null return value indicates a value of 1, if DefOne
140 // is false, a null return value indicates a value of 0.
142 inline const ConstantInt *Mul(const ConstantInt *Arg1,
143 const ConstantInt *Arg2, bool DefOne) {
144 assert(Arg1 && Arg2 && "No null arguments should exist now!");
145 assert(Arg1->getType() == Arg2->getType() && "Types must be compatible!");
147 // Actually perform the computation now!
148 Constant *Result = *Arg1 * *Arg2;
149 assert(Result && Result->getType() == Arg1->getType() &&
150 "Couldn't perform multiplication!");
151 ConstantInt *ResultI = cast<ConstantInt>(Result);
153 // Check to see if the result is one of the special cases that we want to
155 if (ResultI->equalsInt(DefOne ? 1 : 0))
156 return 0; // Yes it is, simply return null.
161 inline const ConstantInt *operator*(const DefZero &L, const DefZero &R) {
162 if (L == 0 || R == 0) return 0;
163 return Mul(L, R, false);
165 inline const ConstantInt *operator*(const DefOne &L, const DefZero &R) {
166 if (R == 0) return getUnsignedConstant(0, L.getType());
167 if (L == 0) return R->equalsInt(1) ? 0 : R.getVal();
168 return Mul(L, R, true);
170 inline const ConstantInt *operator*(const DefZero &L, const DefOne &R) {
171 if (L == 0 || R == 0) return L.getVal();
172 return Mul(R, L, false);
175 // handleAddition - Add two expressions together, creating a new expression that
176 // represents the composite of the two...
178 static ExprType handleAddition(ExprType Left, ExprType Right, Value *V) {
179 const Type *Ty = V->getType();
180 if (Left.ExprTy > Right.ExprTy)
181 std::swap(Left, Right); // Make left be simpler than right
183 switch (Left.ExprTy) {
184 case ExprType::Constant:
185 return ExprType(Right.Scale, Right.Var,
186 DefZero(Right.Offset, Ty) + DefZero(Left.Offset, Ty));
187 case ExprType::Linear: // RHS side must be linear or scaled
188 case ExprType::ScaledLinear: // RHS must be scaled
189 if (Left.Var != Right.Var) // Are they the same variables?
190 return V; // if not, we don't know anything!
192 return ExprType(DefOne(Left.Scale , Ty) + DefOne(Right.Scale , Ty),
194 DefZero(Left.Offset, Ty) + DefZero(Right.Offset, Ty));
196 assert(0 && "Dont' know how to handle this case!");
201 // negate - Negate the value of the specified expression...
203 static inline ExprType negate(const ExprType &E, Value *V) {
204 const Type *Ty = V->getType();
205 const Type *ETy = E.getExprType(Ty);
206 ConstantInt *Zero = getUnsignedConstant(0, ETy);
207 ConstantInt *One = getUnsignedConstant(1, ETy);
208 ConstantInt *NegOne = cast<ConstantInt>(*Zero - *One);
209 if (NegOne == 0) return V; // Couldn't subtract values...
211 return ExprType(DefOne (E.Scale , Ty) * NegOne, E.Var,
212 DefZero(E.Offset, Ty) * NegOne);
216 // ClassifyExpression: Analyze an expression to determine the complexity of the
217 // expression, and which other values it depends on.
219 // Note that this analysis cannot get into infinite loops because it treats PHI
220 // nodes as being an unknown linear expression.
222 ExprType analysis::ClassifyExpression(Value *Expr) {
223 assert(Expr != 0 && "Can't classify a null expression!");
224 if (Expr->getType() == Type::FloatTy || Expr->getType() == Type::DoubleTy)
225 return Expr; // FIXME: Can't handle FP expressions
227 switch (Expr->getValueType()) {
228 case Value::InstructionVal: break; // Instruction... hmmm... investigate.
229 case Value::TypeVal: case Value::BasicBlockVal:
230 case Value::MethodVal: case Value::ModuleVal: default:
231 //assert(0 && "Unexpected expression type to classify!");
232 std::cerr << "Bizarre thing to expr classify: " << Expr << "\n";
234 case Value::GlobalVariableVal: // Global Variable & Method argument:
235 case Value::MethodArgumentVal: // nothing known, return variable itself
237 case Value::ConstantVal: // Constant value, just return constant
238 Constant *CPV = cast<Constant>(Expr);
239 if (CPV->getType()->isIntegral()) { // It's an integral constant!
240 ConstantInt *CPI = cast<ConstantInt>(Expr);
241 return ExprType(CPI->equalsInt(0) ? 0 : CPI);
246 Instruction *I = cast<Instruction>(Expr);
247 const Type *Ty = I->getType();
249 switch (I->getOpcode()) { // Handle each instruction type seperately
250 case Instruction::Add: {
251 ExprType Left (ClassifyExpression(I->getOperand(0)));
252 ExprType Right(ClassifyExpression(I->getOperand(1)));
253 return handleAddition(Left, Right, I);
254 } // end case Instruction::Add
256 case Instruction::Sub: {
257 ExprType Left (ClassifyExpression(I->getOperand(0)));
258 ExprType Right(ClassifyExpression(I->getOperand(1)));
259 ExprType RightNeg = negate(Right, I);
260 if (RightNeg.Var == I && !RightNeg.Offset && !RightNeg.Scale)
261 return I; // Could not negate value...
262 return handleAddition(Left, RightNeg, I);
263 } // end case Instruction::Sub
265 case Instruction::Shl: {
266 ExprType Right(ClassifyExpression(I->getOperand(1)));
267 if (Right.ExprTy != ExprType::Constant) break;
268 ExprType Left(ClassifyExpression(I->getOperand(0)));
269 if (Right.Offset == 0) return Left; // shl x, 0 = x
270 assert(Right.Offset->getType() == Type::UByteTy &&
271 "Shift amount must always be a unsigned byte!");
272 uint64_t ShiftAmount = ((ConstantUInt*)Right.Offset)->getValue();
273 ConstantInt *Multiplier = getUnsignedConstant(1ULL << ShiftAmount, Ty);
275 return ExprType(DefOne(Left.Scale, Ty) * Multiplier, Left.Var,
276 DefZero(Left.Offset, Ty) * Multiplier);
277 } // end case Instruction::Shl
279 case Instruction::Mul: {
280 ExprType Left (ClassifyExpression(I->getOperand(0)));
281 ExprType Right(ClassifyExpression(I->getOperand(1)));
282 if (Left.ExprTy > Right.ExprTy)
283 std::swap(Left, Right); // Make left be simpler than right
285 if (Left.ExprTy != ExprType::Constant) // RHS must be > constant
286 return I; // Quadratic eqn! :(
288 const ConstantInt *Offs = Left.Offset;
289 if (Offs == 0) return ExprType();
290 return ExprType( DefOne(Right.Scale , Ty) * Offs, Right.Var,
291 DefZero(Right.Offset, Ty) * Offs);
292 } // end case Instruction::Mul
294 case Instruction::Cast: {
295 ExprType Src(ClassifyExpression(I->getOperand(0)));
296 const Type *DestTy = I->getType();
297 if (DestTy->isPointerType())
298 DestTy = Type::ULongTy; // Pointer types are represented as ulong
301 if (!Src.getExprType(0)->isLosslesslyConvertableTo(DestTy)) {
302 if (Src.ExprTy != ExprType::Constant)
303 return I; // Converting cast, and not a constant value...
307 const ConstantInt *Offset = Src.Offset;
308 const ConstantInt *Scale = Src.Scale;
310 const Constant *CPV = ConstantFoldCastInstruction(Offset, DestTy);
312 Offset = cast<ConstantInt>(CPV);
315 const Constant *CPV = ConstantFoldCastInstruction(Scale, DestTy);
317 Scale = cast<ConstantInt>(CPV);
319 return ExprType(Scale, Src.Var, Offset);
320 } // end case Instruction::Cast
321 // TODO: Handle SUB, SHR?
325 // Otherwise, I don't know anything about this value!