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/Optimizations/ConstantHandling.h"
12 #include "llvm/Method.h"
13 #include "llvm/BasicBlock.h"
15 using namespace opt; // Get all the constant handling stuff
16 using namespace analysis;
18 ExprType::ExprType(Value *Val) {
20 if (ConstPoolInt *CPI = dyn_cast<ConstPoolInt>(Val)) {
28 Var = Val; Offset = 0;
29 ExprTy = Var ? Linear : Constant;
33 ExprType::ExprType(const ConstPoolInt *scale, Value *var,
34 const ConstPoolInt *offset) {
35 Scale = scale; 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 ConstPoolInt * const Val;
54 const Type * const Ty;
56 inline DefVal(const ConstPoolInt *val, const Type *ty) : Val(val), Ty(ty) {}
58 inline const Type *getType() const { return Ty; }
59 inline const ConstPoolInt *getVal() const { return Val; }
60 inline operator const ConstPoolInt * () const { return Val; }
61 inline const ConstPoolInt *operator->() const { return Val; }
64 struct DefZero : public DefVal {
65 inline DefZero(const ConstPoolInt *val, const Type *ty) : DefVal(val, ty) {}
66 inline DefZero(const ConstPoolInt *val) : DefVal(val, val->getType()) {}
69 struct DefOne : public DefVal {
70 inline DefOne(const ConstPoolInt *val, const Type *ty) : DefVal(val, ty) {}
74 static ConstPoolInt *getUnsignedConstant(uint64_t V, const Type *Ty) {
75 if (Ty->isPointerType()) Ty = Type::ULongTy;
76 return Ty->isSigned() ? ConstPoolSInt::get(Ty, V) : ConstPoolUInt::get(Ty, V);
79 // Add - Helper function to make later code simpler. Basically it just adds
80 // the two constants together, inserts the result into the constant pool, and
81 // returns it. Of course life is not simple, and this is no exception. Factors
82 // that complicate matters:
83 // 1. Either argument may be null. If this is the case, the null argument is
84 // treated as either 0 (if DefOne = false) or 1 (if DefOne = true)
85 // 2. Types get in the way. We want to do arithmetic operations without
86 // regard for the underlying types. It is assumed that the constants are
87 // integral constants. The new value takes the type of the left argument.
88 // 3. If DefOne is true, a null return value indicates a value of 1, if DefOne
89 // is false, a null return value indicates a value of 0.
91 static const ConstPoolInt *Add(const ConstPoolInt *Arg1,
92 const ConstPoolInt *Arg2, bool DefOne) {
93 assert(Arg1 && Arg2 && "No null arguments should exist now!");
94 assert(Arg1->getType() == Arg2->getType() && "Types must be compatible!");
96 // Actually perform the computation now!
97 ConstPoolVal *Result = *Arg1 + *Arg2;
98 assert(Result && Result->getType() == Arg1->getType() &&
99 "Couldn't perform addition!");
100 ConstPoolInt *ResultI = cast<ConstPoolInt>(Result);
102 // Check to see if the result is one of the special cases that we want to
104 if (ResultI->equalsInt(DefOne ? 1 : 0))
105 return 0; // Yes it is, simply return null.
110 inline const ConstPoolInt *operator+(const DefZero &L, const DefZero &R) {
111 if (L == 0) return R;
112 if (R == 0) return L;
113 return Add(L, R, false);
116 inline const ConstPoolInt *operator+(const DefOne &L, const DefOne &R) {
119 return getUnsignedConstant(2, L.getType());
121 return Add(getUnsignedConstant(1, L.getType()), R, true);
123 return Add(L, getUnsignedConstant(1, L.getType()), true);
125 return Add(L, R, true);
129 // Mul - Helper function to make later code simpler. Basically it just
130 // multiplies the two constants together, inserts the result into the constant
131 // pool, and returns it. Of course life is not simple, and this is no
132 // exception. Factors that complicate matters:
133 // 1. Either argument may be null. If this is the case, the null argument is
134 // treated as either 0 (if DefOne = false) or 1 (if DefOne = true)
135 // 2. Types get in the way. We want to do arithmetic operations without
136 // regard for the underlying types. It is assumed that the constants are
137 // integral constants.
138 // 3. If DefOne is true, a null return value indicates a value of 1, if DefOne
139 // is false, a null return value indicates a value of 0.
141 inline const ConstPoolInt *Mul(const ConstPoolInt *Arg1,
142 const ConstPoolInt *Arg2, bool DefOne = false) {
143 assert(Arg1 && Arg2 && "No null arguments should exist now!");
144 assert(Arg1->getType() == Arg2->getType() && "Types must be compatible!");
146 // Actually perform the computation now!
147 ConstPoolVal *Result = *Arg1 * *Arg2;
148 assert(Result && Result->getType() == Arg1->getType() &&
149 "Couldn't perform mult!");
150 ConstPoolInt *ResultI = cast<ConstPoolInt>(Result);
152 // Check to see if the result is one of the special cases that we want to
154 if (ResultI->equalsInt(DefOne ? 1 : 0))
155 return 0; // Yes it is, simply return null.
160 inline const ConstPoolInt *operator*(const DefZero &L, const DefZero &R) {
161 if (L == 0 || R == 0) return 0;
162 return Mul(L, R, false);
164 inline const ConstPoolInt *operator*(const DefOne &L, const DefZero &R) {
165 if (R == 0) return getUnsignedConstant(0, L.getType());
166 if (L == 0) return R->equalsInt(1) ? 0 : R.getVal();
167 return Mul(L, R, false);
169 inline const ConstPoolInt *operator*(const DefZero &L, const DefOne &R) {
173 // handleAddition - Add two expressions together, creating a new expression that
174 // represents the composite of the two...
176 static ExprType handleAddition(ExprType Left, ExprType Right, Value *V) {
177 const Type *Ty = V->getType();
178 if (Left.ExprTy > Right.ExprTy)
179 swap(Left, Right); // Make left be simpler than right
181 switch (Left.ExprTy) {
182 case ExprType::Constant:
183 return ExprType(Right.Scale, Right.Var,
184 DefZero(Right.Offset, Ty) + DefZero(Left.Offset, Ty));
185 case ExprType::Linear: // RHS side must be linear or scaled
186 case ExprType::ScaledLinear: // RHS must be scaled
187 if (Left.Var != Right.Var) // Are they the same variables?
188 return ExprType(V); // if not, we don't know anything!
190 return ExprType(DefOne(Left.Scale , Ty) + DefOne(Right.Scale , Ty),
192 DefZero(Left.Offset, Ty) + DefZero(Right.Offset, Ty));
194 assert(0 && "Dont' know how to handle this case!");
199 // negate - Negate the value of the specified expression...
201 static inline ExprType negate(const ExprType &E, Value *V) {
202 const Type *Ty = V->getType();
203 const Type *ETy = E.getExprType(Ty);
204 ConstPoolInt *Zero = getUnsignedConstant(0, ETy);
205 ConstPoolInt *One = getUnsignedConstant(1, ETy);
206 ConstPoolInt *NegOne = cast<ConstPoolInt>(*Zero - *One);
207 if (NegOne == 0) return V; // Couldn't subtract values...
209 return ExprType(DefOne (E.Scale , Ty) * NegOne, E.Var,
210 DefZero(E.Offset, Ty) * NegOne);
214 // ClassifyExpression: Analyze an expression to determine the complexity of the
215 // expression, and which other values it depends on.
217 // Note that this analysis cannot get into infinite loops because it treats PHI
218 // nodes as being an unknown linear expression.
220 ExprType analysis::ClassifyExpression(Value *Expr) {
221 assert(Expr != 0 && "Can't classify a null expression!");
222 switch (Expr->getValueType()) {
223 case Value::InstructionVal: break; // Instruction... hmmm... investigate.
224 case Value::TypeVal: case Value::BasicBlockVal:
225 case Value::MethodVal: case Value::ModuleVal: default:
226 assert(0 && "Unexpected expression type to classify!");
227 case Value::GlobalVariableVal: // Global Variable & Method argument:
228 case Value::MethodArgumentVal: // nothing known, return variable itself
230 case Value::ConstantVal: // Constant value, just return constant
231 ConstPoolVal *CPV = cast<ConstPoolVal>(Expr);
232 if (CPV->getType()->isIntegral()) { // It's an integral constant!
233 ConstPoolInt *CPI = cast<ConstPoolInt>(Expr);
234 return ExprType(CPI->equalsInt(0) ? 0 : CPI);
239 Instruction *I = cast<Instruction>(Expr);
240 const Type *Ty = I->getType();
242 switch (I->getOpcode()) { // Handle each instruction type seperately
243 case Instruction::Add: {
244 ExprType Left (ClassifyExpression(I->getOperand(0)));
245 ExprType Right(ClassifyExpression(I->getOperand(1)));
246 return handleAddition(Left, Right, I);
247 } // end case Instruction::Add
249 case Instruction::Sub: {
250 ExprType Left (ClassifyExpression(I->getOperand(0)));
251 ExprType Right(ClassifyExpression(I->getOperand(1)));
252 return handleAddition(Left, negate(Right, I), I);
253 } // end case Instruction::Sub
255 case Instruction::Shl: {
256 ExprType Right(ClassifyExpression(I->getOperand(1)));
257 if (Right.ExprTy != ExprType::Constant) break;
258 ExprType Left(ClassifyExpression(I->getOperand(0)));
259 if (Right.Offset == 0) return Left; // shl x, 0 = x
260 assert(Right.Offset->getType() == Type::UByteTy &&
261 "Shift amount must always be a unsigned byte!");
262 uint64_t ShiftAmount = ((ConstPoolUInt*)Right.Offset)->getValue();
263 ConstPoolInt *Multiplier = getUnsignedConstant(1ULL << ShiftAmount, Ty);
265 return ExprType(DefOne(Left.Scale, Ty) * Multiplier, Left.Var,
266 DefZero(Left.Offset, Ty) * Multiplier);
267 } // end case Instruction::Shl
269 case Instruction::Mul: {
270 ExprType Left (ClassifyExpression(I->getOperand(0)));
271 ExprType Right(ClassifyExpression(I->getOperand(1)));
272 if (Left.ExprTy > Right.ExprTy)
273 swap(Left, Right); // Make left be simpler than right
275 if (Left.ExprTy != ExprType::Constant) // RHS must be > constant
276 return I; // Quadratic eqn! :(
278 const ConstPoolInt *Offs = Left.Offset;
279 if (Offs == 0) return ExprType();
280 return ExprType( DefOne(Right.Scale , Ty) * Offs, Right.Var,
281 DefZero(Right.Offset, Ty) * Offs);
282 } // end case Instruction::Mul
284 case Instruction::Cast: {
285 ExprType Src(ClassifyExpression(I->getOperand(0)));
286 if (Src.ExprTy != ExprType::Constant)
288 const ConstPoolInt *Offs = Src.Offset;
289 if (Offs == 0) return ExprType();
291 const Type *DestTy = I->getType();
292 if (DestTy->isPointerType())
293 DestTy = Type::ULongTy; // Pointer types are represented as ulong
295 assert(DestTy->isIntegral() && "Can only handle integral types!");
297 const ConstPoolVal *CPV =ConstRules::get(*Offs)->castTo(Offs, DestTy);
299 assert(CPV->getType()->isIntegral() && "Must have an integral type!");
300 return cast<ConstPoolInt>(CPV);
301 } // end case Instruction::Cast
302 // TODO: Handle SUB, SHR?
306 // Otherwise, I don't know anything about this value!