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284 lines
11 KiB
C++
284 lines
11 KiB
C++
//===- Expressions.cpp - Expression Analysis Utilities ----------------------=//
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//
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// This file defines a package of expression analysis utilties:
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//
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// ClassifyExpression: Analyze an expression to determine the complexity of the
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// expression, and which other variables it depends on.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/Expressions.h"
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#include "llvm/Optimizations/ConstantHandling.h"
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#include "llvm/ConstantPool.h"
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#include "llvm/Method.h"
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#include "llvm/BasicBlock.h"
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using namespace opt; // Get all the constant handling stuff
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using namespace analysis;
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class DefVal {
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const ConstPoolInt * const Val;
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ConstantPool &CP;
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const Type * const Ty;
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protected:
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inline DefVal(const ConstPoolInt *val, ConstantPool &cp, const Type *ty)
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: Val(val), CP(cp), Ty(ty) {}
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public:
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inline const Type *getType() const { return Ty; }
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inline ConstantPool &getCP() const { return CP; }
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inline const ConstPoolInt *getVal() const { return Val; }
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inline operator const ConstPoolInt * () const { return Val; }
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inline const ConstPoolInt *operator->() const { return Val; }
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};
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struct DefZero : public DefVal {
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inline DefZero(const ConstPoolInt *val, ConstantPool &cp, const Type *ty)
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: DefVal(val, cp, ty) {}
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inline DefZero(const ConstPoolInt *val)
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: DefVal(val, (ConstantPool&)val->getParent()->getConstantPool(),
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val->getType()) {}
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};
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struct DefOne : public DefVal {
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inline DefOne(const ConstPoolInt *val, ConstantPool &cp, const Type *ty)
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: DefVal(val, cp, ty) {}
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};
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// getIntegralConstant - Wrapper around the ConstPoolInt member of the same
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// name. This method first checks to see if the desired constant is already in
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// the constant pool. If it is, it is quickly recycled, otherwise a new one
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// is allocated and added to the constant pool.
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//
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static ConstPoolInt *getIntegralConstant(ConstantPool &CP, unsigned char V,
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const Type *Ty) {
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// FIXME: Lookup prexisting constant in table!
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ConstPoolInt *CPI = ConstPoolInt::get(Ty, V);
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CP.insert(CPI);
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return CPI;
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}
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static ConstPoolInt *getUnsignedConstant(ConstantPool &CP, uint64_t V,
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const Type *Ty) {
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// FIXME: Lookup prexisting constant in table!
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if (Ty->isPointerType()) Ty = Type::ULongTy;
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ConstPoolInt *CPI;
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CPI = Ty->isSigned() ? new ConstPoolSInt(Ty, V) : new ConstPoolUInt(Ty, V);
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CP.insert(CPI);
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return CPI;
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}
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// Add - Helper function to make later code simpler. Basically it just adds
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// the two constants together, inserts the result into the constant pool, and
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// returns it. Of course life is not simple, and this is no exception. Factors
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// that complicate matters:
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// 1. Either argument may be null. If this is the case, the null argument is
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// treated as either 0 (if DefOne = false) or 1 (if DefOne = true)
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// 2. Types get in the way. We want to do arithmetic operations without
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// regard for the underlying types. It is assumed that the constants are
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// integral constants. The new value takes the type of the left argument.
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// 3. If DefOne is true, a null return value indicates a value of 1, if DefOne
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// is false, a null return value indicates a value of 0.
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//
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static const ConstPoolInt *Add(ConstantPool &CP, const ConstPoolInt *Arg1,
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const ConstPoolInt *Arg2, bool DefOne) {
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assert(Arg1 && Arg2 && "No null arguments should exist now!");
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assert(Arg1->getType() == Arg2->getType() && "Types must be compatible!");
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// Actually perform the computation now!
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ConstPoolVal *Result = *Arg1 + *Arg2;
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assert(Result && Result->getType() == Arg1->getType() &&
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"Couldn't perform addition!");
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ConstPoolInt *ResultI = (ConstPoolInt*)Result;
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// Check to see if the result is one of the special cases that we want to
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// recognize...
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if (ResultI->equalsInt(DefOne ? 1 : 0)) {
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// Yes it is, simply delete the constant and return null.
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delete ResultI;
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return 0;
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}
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CP.insert(ResultI);
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return ResultI;
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}
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inline const ConstPoolInt *operator+(const DefZero &L, const DefZero &R) {
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if (L == 0) return R;
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if (R == 0) return L;
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return Add(L.getCP(), L, R, false);
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}
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inline const ConstPoolInt *operator+(const DefOne &L, const DefOne &R) {
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if (L == 0) {
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if (R == 0)
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return getIntegralConstant(L.getCP(), 2, L.getType());
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else
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return Add(L.getCP(), getIntegralConstant(L.getCP(), 1, L.getType()),
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R, true);
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} else if (R == 0) {
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return Add(L.getCP(), L,
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getIntegralConstant(L.getCP(), 1, L.getType()), true);
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}
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return Add(L.getCP(), L, R, true);
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}
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// Mul - Helper function to make later code simpler. Basically it just
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// multiplies the two constants together, inserts the result into the constant
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// pool, and returns it. Of course life is not simple, and this is no
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// exception. Factors that complicate matters:
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// 1. Either argument may be null. If this is the case, the null argument is
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// treated as either 0 (if DefOne = false) or 1 (if DefOne = true)
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// 2. Types get in the way. We want to do arithmetic operations without
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// regard for the underlying types. It is assumed that the constants are
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// integral constants.
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// 3. If DefOne is true, a null return value indicates a value of 1, if DefOne
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// is false, a null return value indicates a value of 0.
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//
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inline const ConstPoolInt *Mul(ConstantPool &CP, const ConstPoolInt *Arg1,
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const ConstPoolInt *Arg2, bool DefOne = false) {
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assert(Arg1 && Arg2 && "No null arguments should exist now!");
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assert(Arg1->getType() == Arg2->getType() && "Types must be compatible!");
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// Actually perform the computation now!
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ConstPoolVal *Result = *Arg1 * *Arg2;
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assert(Result && Result->getType() == Arg1->getType() &&
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"Couldn't perform mult!");
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ConstPoolInt *ResultI = (ConstPoolInt*)Result;
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// Check to see if the result is one of the special cases that we want to
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// recognize...
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if (ResultI->equalsInt(DefOne ? 1 : 0)) {
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// Yes it is, simply delete the constant and return null.
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delete ResultI;
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return 0;
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}
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CP.insert(ResultI);
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return ResultI;
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}
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inline const ConstPoolInt *operator*(const DefZero &L, const DefZero &R) {
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if (L == 0 || R == 0) return 0;
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return Mul(L.getCP(), L, R, false);
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}
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inline const ConstPoolInt *operator*(const DefOne &L, const DefZero &R) {
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if (R == 0) return getIntegralConstant(L.getCP(), 0, L.getType());
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if (L == 0) return R->equalsInt(1) ? 0 : R.getVal();
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return Mul(L.getCP(), L, R, false);
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}
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inline const ConstPoolInt *operator*(const DefZero &L, const DefOne &R) {
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return R*L;
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}
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// ClassifyExpression: Analyze an expression to determine the complexity of the
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// expression, and which other values it depends on.
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//
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// Note that this analysis cannot get into infinite loops because it treats PHI
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// nodes as being an unknown linear expression.
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//
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ExprType analysis::ClassifyExpression(Value *Expr) {
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assert(Expr != 0 && "Can't classify a null expression!");
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switch (Expr->getValueType()) {
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case Value::InstructionVal: break; // Instruction... hmmm... investigate.
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case Value::TypeVal: case Value::BasicBlockVal:
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case Value::MethodVal: case Value::ModuleVal:
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assert(0 && "Unexpected expression type to classify!");
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case Value::MethodArgumentVal: // Method arg: nothing known, return var
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return Expr;
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case Value::ConstantVal: // Constant value, just return constant
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ConstPoolVal *CPV = Expr->castConstantAsserting();
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if (CPV->getType()->isIntegral()) { // It's an integral constant!
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ConstPoolInt *CPI = (ConstPoolInt*)Expr;
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return ExprType(CPI->equalsInt(0) ? 0 : (ConstPoolInt*)Expr);
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}
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return Expr;
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}
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Instruction *I = Expr->castInstructionAsserting();
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ConstantPool &CP = I->getParent()->getParent()->getConstantPool();
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const Type *Ty = I->getType();
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switch (I->getOpcode()) { // Handle each instruction type seperately
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case Instruction::Add: {
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ExprType Left (ClassifyExpression(I->getOperand(0)));
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ExprType Right(ClassifyExpression(I->getOperand(1)));
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if (Left.ExprTy > Right.ExprTy)
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swap(Left, Right); // Make left be simpler than right
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switch (Left.ExprTy) {
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case ExprType::Constant:
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return ExprType(Right.Scale, Right.Var,
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DefZero(Right.Offset,CP,Ty) + DefZero(Left.Offset, CP,Ty));
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case ExprType::Linear: // RHS side must be linear or scaled
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case ExprType::ScaledLinear: // RHS must be scaled
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if (Left.Var != Right.Var) // Are they the same variables?
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return ExprType(I); // if not, we don't know anything!
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return ExprType(DefOne(Left.Scale ,CP,Ty) + DefOne(Right.Scale , CP,Ty),
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Left.Var,
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DefZero(Left.Offset,CP,Ty) + DefZero(Right.Offset, CP,Ty));
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}
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} // end case Instruction::Add
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case Instruction::Shl: {
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ExprType Right(ClassifyExpression(I->getOperand(1)));
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if (Right.ExprTy != ExprType::Constant) break;
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ExprType Left(ClassifyExpression(I->getOperand(0)));
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if (Right.Offset == 0) return Left; // shl x, 0 = x
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assert(Right.Offset->getType() == Type::UByteTy &&
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"Shift amount must always be a unsigned byte!");
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uint64_t ShiftAmount = ((ConstPoolUInt*)Right.Offset)->getValue();
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ConstPoolInt *Multiplier = getUnsignedConstant(CP, 1ULL << ShiftAmount, Ty);
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return ExprType(DefOne(Left.Scale, CP, Ty) * Multiplier,
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Left.Var,
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DefZero(Left.Offset, CP, Ty) * Multiplier);
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} // end case Instruction::Shl
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case Instruction::Mul: {
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ExprType Left (ClassifyExpression(I->getOperand(0)));
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ExprType Right(ClassifyExpression(I->getOperand(1)));
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if (Left.ExprTy > Right.ExprTy)
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swap(Left, Right); // Make left be simpler than right
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if (Left.ExprTy != ExprType::Constant) // RHS must be > constant
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return I; // Quadratic eqn! :(
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const ConstPoolInt *Offs = Left.Offset;
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if (Offs == 0) return ExprType();
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return ExprType(DefOne(Right.Scale, CP, Ty) * Offs,
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Right.Var,
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DefZero(Right.Offset, CP, Ty) * Offs);
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} // end case Instruction::Mul
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case Instruction::Cast: {
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ExprType Src(ClassifyExpression(I->getOperand(0)));
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if (Src.ExprTy != ExprType::Constant)
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return I;
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const ConstPoolInt *Offs = Src.Offset;
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if (Offs == 0) return ExprType();
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if (I->getType()->isPointerType())
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return Offs; // Pointer types do not lose precision
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assert(I->getType()->isIntegral() && "Can only handle integral types!");
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const ConstPoolVal *CPV = ConstRules::get(*Offs)->castTo(Offs, I->getType());
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if (!CPV) return I;
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assert(CPV->getType()->isIntegral() && "Must have an integral type!");
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return (ConstPoolInt*)CPV;
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} // end case Instruction::Cast
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// TODO: Handle SUB, SHR?
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} // end switch
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// Otherwise, I don't know anything about this value!
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return I;
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}
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