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Change references to MEthodArgument to FunctionArgument git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@1989 91177308-0d34-0410-b5e6-96231b3b80d8
354 lines
13 KiB
C++
354 lines
13 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/Transforms/Scalar/ConstantHandling.h"
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#include "llvm/Function.h"
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#include "llvm/BasicBlock.h"
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#include <iostream>
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using namespace analysis;
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ExprType::ExprType(Value *Val) {
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if (Val)
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if (ConstantInt *CPI = dyn_cast<ConstantInt>(Val)) {
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Offset = CPI;
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Var = 0;
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ExprTy = Constant;
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Scale = 0;
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return;
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}
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Var = Val; Offset = 0;
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ExprTy = Var ? Linear : Constant;
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Scale = 0;
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}
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ExprType::ExprType(const ConstantInt *scale, Value *var,
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const ConstantInt *offset) {
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Scale = var ? scale : 0; Var = var; Offset = offset;
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ExprTy = Scale ? ScaledLinear : (Var ? Linear : Constant);
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if (Scale && Scale->equalsInt(0)) { // Simplify 0*Var + const
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Scale = 0; Var = 0;
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ExprTy = Constant;
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}
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}
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const Type *ExprType::getExprType(const Type *Default) const {
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if (Offset) return Offset->getType();
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if (Scale) return Scale->getType();
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return Var ? Var->getType() : Default;
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}
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class DefVal {
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const ConstantInt * const Val;
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const Type * const Ty;
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protected:
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inline DefVal(const ConstantInt *val, const Type *ty) : Val(val), Ty(ty) {}
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public:
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inline const Type *getType() const { return Ty; }
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inline const ConstantInt *getVal() const { return Val; }
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inline operator const ConstantInt * () const { return Val; }
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inline const ConstantInt *operator->() const { return Val; }
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};
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struct DefZero : public DefVal {
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inline DefZero(const ConstantInt *val, const Type *ty) : DefVal(val, ty) {}
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inline DefZero(const ConstantInt *val) : DefVal(val, val->getType()) {}
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};
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struct DefOne : public DefVal {
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inline DefOne(const ConstantInt *val, const Type *ty) : DefVal(val, ty) {}
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};
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// getUnsignedConstant - Return a constant value of the specified type. If the
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// constant value is not valid for the specified type, return null. This cannot
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// happen for values in the range of 0 to 127.
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//
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static ConstantInt *getUnsignedConstant(uint64_t V, const Type *Ty) {
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if (Ty->isPointerType()) Ty = Type::ULongTy;
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if (Ty->isSigned()) {
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// If this value is not a valid unsigned value for this type, return null!
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if (V > 127 && ((int64_t)V < 0 ||
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!ConstantSInt::isValueValidForType(Ty, (int64_t)V)))
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return 0;
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return ConstantSInt::get(Ty, V);
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} else {
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// If this value is not a valid unsigned value for this type, return null!
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if (V > 255 && !ConstantUInt::isValueValidForType(Ty, V))
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return 0;
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return ConstantUInt::get(Ty, V);
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}
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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 ConstantInt *Add(const ConstantInt *Arg1,
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const ConstantInt *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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Constant *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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ConstantInt *ResultI = cast<ConstantInt>(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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return 0; // Yes it is, simply return null.
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return ResultI;
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}
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inline const ConstantInt *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, R, false);
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}
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inline const ConstantInt *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 getUnsignedConstant(2, L.getType());
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else
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return Add(getUnsignedConstant(1, L.getType()), R, true);
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} else if (R == 0) {
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return Add(L, getUnsignedConstant(1, L.getType()), true);
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}
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return Add(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 ConstantInt *Mul(const ConstantInt *Arg1,
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const ConstantInt *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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Constant *Result = *Arg1 * *Arg2;
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assert(Result && Result->getType() == Arg1->getType() &&
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"Couldn't perform multiplication!");
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ConstantInt *ResultI = cast<ConstantInt>(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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return 0; // Yes it is, simply return null.
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return ResultI;
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}
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inline const ConstantInt *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, R, false);
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}
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inline const ConstantInt *operator*(const DefOne &L, const DefZero &R) {
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if (R == 0) return getUnsignedConstant(0, L.getType());
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if (L == 0) return R->equalsInt(1) ? 0 : R.getVal();
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return Mul(L, R, true);
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}
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inline const ConstantInt *operator*(const DefZero &L, const DefOne &R) {
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if (L == 0 || R == 0) return L.getVal();
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return Mul(R, L, false);
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}
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// handleAddition - Add two expressions together, creating a new expression that
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// represents the composite of the two...
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//
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static ExprType handleAddition(ExprType Left, ExprType Right, Value *V) {
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const Type *Ty = V->getType();
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if (Left.ExprTy > Right.ExprTy)
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std::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, Ty) + DefZero(Left.Offset, 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 V; // if not, we don't know anything!
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return ExprType(DefOne(Left.Scale , Ty) + DefOne(Right.Scale , Ty),
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Right.Var,
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DefZero(Left.Offset, Ty) + DefZero(Right.Offset, Ty));
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default:
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assert(0 && "Dont' know how to handle this case!");
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return ExprType();
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}
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}
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// negate - Negate the value of the specified expression...
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//
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static inline ExprType negate(const ExprType &E, Value *V) {
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const Type *Ty = V->getType();
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ConstantInt *Zero = getUnsignedConstant(0, Ty);
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ConstantInt *One = getUnsignedConstant(1, Ty);
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ConstantInt *NegOne = cast<ConstantInt>(*Zero - *One);
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if (NegOne == 0) return V; // Couldn't subtract values...
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return ExprType(DefOne (E.Scale , Ty) * NegOne, E.Var,
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DefZero(E.Offset, Ty) * NegOne);
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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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if (Expr->getType() == Type::FloatTy || Expr->getType() == Type::DoubleTy)
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return Expr; // FIXME: Can't handle FP expressions
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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::FunctionVal: case Value::ModuleVal: default:
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//assert(0 && "Unexpected expression type to classify!");
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std::cerr << "Bizarre thing to expr classify: " << Expr << "\n";
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return Expr;
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case Value::GlobalVariableVal: // Global Variable & Function argument:
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case Value::FunctionArgumentVal: // nothing known, return variable itself
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return Expr;
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case Value::ConstantVal: // Constant value, just return constant
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Constant *CPV = cast<Constant>(Expr);
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if (CPV->getType()->isIntegral()) { // It's an integral constant!
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ConstantInt *CPI = cast<ConstantInt>(Expr);
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return ExprType(CPI->equalsInt(0) ? 0 : CPI);
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}
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return Expr;
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}
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Instruction *I = cast<Instruction>(Expr);
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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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return handleAddition(Left, Right, I);
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} // end case Instruction::Add
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case Instruction::Sub: {
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ExprType Left (ClassifyExpression(I->getOperand(0)));
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ExprType Right(ClassifyExpression(I->getOperand(1)));
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ExprType RightNeg = negate(Right, I);
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if (RightNeg.Var == I && !RightNeg.Offset && !RightNeg.Scale)
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return I; // Could not negate value...
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return handleAddition(Left, RightNeg, I);
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} // end case Instruction::Sub
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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 = ((ConstantUInt*)Right.Offset)->getValue();
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ConstantInt *Multiplier = getUnsignedConstant(1ULL << ShiftAmount, Ty);
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// We don't know how to classify it if they are shifting by more than what
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// is reasonable. In most cases, the result will be zero, but there is one
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// class of cases where it is not, so we cannot optimize without checking
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// for it. The case is when you are shifting a signed value by 1 less than
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// the number of bits in the value. For example:
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// %X = shl sbyte %Y, ubyte 7
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// will try to form an sbyte multiplier of 128, which will give a null
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// multiplier, even though the result is not 0. Until we can check for this
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// case, be conservative. TODO.
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//
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if (Multiplier == 0)
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return Expr;
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return ExprType(DefOne(Left.Scale, Ty) * Multiplier, Left.Var,
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DefZero(Left.Offset, 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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std::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 ConstantInt *Offs = Left.Offset;
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if (Offs == 0) return ExprType();
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return ExprType( DefOne(Right.Scale , Ty) * Offs, Right.Var,
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DefZero(Right.Offset, 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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const Type *DestTy = I->getType();
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if (DestTy->isPointerType())
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DestTy = Type::ULongTy; // Pointer types are represented as ulong
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/*
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if (!Src.getExprType(0)->isLosslesslyConvertableTo(DestTy)) {
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if (Src.ExprTy != ExprType::Constant)
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return I; // Converting cast, and not a constant value...
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}
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*/
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const ConstantInt *Offset = Src.Offset;
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const ConstantInt *Scale = Src.Scale;
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if (Offset) {
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const Constant *CPV = ConstantFoldCastInstruction(Offset, DestTy);
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if (!CPV) return I;
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Offset = cast<ConstantInt>(CPV);
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}
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if (Scale) {
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const Constant *CPV = ConstantFoldCastInstruction(Scale, DestTy);
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if (!CPV) return I;
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Scale = cast<ConstantInt>(CPV);
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}
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return ExprType(Scale, Src.Var, Offset);
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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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