89 lines
2.8 KiB
C
89 lines
2.8 KiB
C
|
//===- ConstraintSystem.h - A system of linear constraints. --------------===//
|
|||
|
|
//
|
|||
|
|
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
|
|||
|
|
// See https://llvm.org/LICENSE.txt for license information.
|
|||
|
|
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
|
|||
|
|
//
|
|||
|
|
//===----------------------------------------------------------------------===//
|
|||
|
|
|
|||
|
|
#ifndef LLVM_ANALYSIS_CONSTRAINTSYSTEM_H
|
|||
|
|
#define LLVM_ANALYSIS_CONSTRAINTSYSTEM_H
|
|||
|
|
|
|||
|
|
#include "llvm/ADT/APInt.h"
|
|||
|
|
#include "llvm/ADT/ArrayRef.h"
|
|||
|
|
#include "llvm/ADT/STLExtras.h"
|
|||
|
|
#include "llvm/ADT/SmallVector.h"
|
|||
|
|
|
|||
|
|
#include <string>
|
|||
|
|
|
|||
|
|
namespace llvm {
|
|||
|
|
|
|||
|
|
class ConstraintSystem {
|
|||
|
|
/// Current linear constraints in the system.
|
|||
|
|
/// An entry of the form c0, c1, ... cn represents the following constraint:
|
|||
|
|
/// c0 >= v0 * c1 + .... + v{n-1} * cn
|
|||
|
|
SmallVector<SmallVector<int64_t, 8>, 4> Constraints;
|
|||
|
|
|
|||
|
|
/// Current greatest common divisor for all coefficients in the system.
|
|||
|
|
uint32_t GCD = 1;
|
|||
|
|
|
|||
|
|
// Eliminate constraints from the system using Fourier–Motzkin elimination.
|
|||
|
|
bool eliminateUsingFM();
|
|||
|
|
|
|||
|
|
/// Print the constraints in the system, using \p Names as variable names.
|
|||
|
|
void dump(ArrayRef<std::string> Names) const;
|
|||
|
|
|
|||
|
|
/// Print the constraints in the system, using x0...xn as variable names.
|
|||
|
|
void dump() const;
|
|||
|
|
|
|||
|
|
/// Returns true if there may be a solution for the constraints in the system.
|
|||
|
|
bool mayHaveSolutionImpl();
|
|||
|
|
|
|||
|
|
public:
|
|||
|
|
bool addVariableRow(const SmallVector<int64_t, 8> &R) {
|
|||
|
|
assert(Constraints.empty() || R.size() == Constraints.back().size());
|
|||
|
|
// If all variable coefficients are 0, the constraint does not provide any
|
|||
|
|
// usable information.
|
|||
|
|
if (all_of(makeArrayRef(R).drop_front(1), [](int64_t C) { return C == 0; }))
|
|||
|
|
return false;
|
|||
|
|
|
|||
|
|
for (const auto &C : R) {
|
|||
|
|
auto A = std::abs(C);
|
|||
|
|
GCD = APIntOps::GreatestCommonDivisor({32, (uint32_t)A}, {32, GCD})
|
|||
|
|
.getZExtValue();
|
|||
|
|
}
|
|||
|
|
Constraints.push_back(R);
|
|||
|
|
return true;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
bool addVariableRowFill(const SmallVector<int64_t, 8> &R) {
|
|||
|
|
for (auto &CR : Constraints) {
|
|||
|
|
while (CR.size() != R.size())
|
|||
|
|
CR.push_back(0);
|
|||
|
|
}
|
|||
|
|
return addVariableRow(R);
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
/// Returns true if there may be a solution for the constraints in the system.
|
|||
|
|
bool mayHaveSolution();
|
|||
|
|
|
|||
|
|
static SmallVector<int64_t, 8> negate(SmallVector<int64_t, 8> R) {
|
|||
|
|
// The negated constraint R is obtained by multiplying by -1 and adding 1 to
|
|||
|
|
// the constant.
|
|||
|
|
R[0] += 1;
|
|||
|
|
for (auto &C : R)
|
|||
|
|
C *= -1;
|
|||
|
|
return R;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
bool isConditionImplied(SmallVector<int64_t, 8> R);
|
|||
|
|
|
|||
|
|
void popLastConstraint() { Constraints.pop_back(); }
|
|||
|
|
|
|||
|
|
/// Returns the number of rows in the constraint system.
|
|||
|
|
unsigned size() const { return Constraints.size(); }
|
|||
|
|
};
|
|||
|
|
} // namespace llvm
|
|||
|
|
|
|||
|
|
#endif // LLVM_ANALYSIS_CONSTRAINTSYSTEM_H
|