1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
|
//== RangedConstraintManager.cpp --------------------------------*- C++ -*--==//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// This file defines RangedConstraintManager, a class that provides a
// range-based constraint manager interface.
//
//===----------------------------------------------------------------------===//
#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/RangedConstraintManager.h"
namespace clang {
namespace ento {
RangedConstraintManager::~RangedConstraintManager() {}
ProgramStateRef RangedConstraintManager::assumeSym(ProgramStateRef State,
SymbolRef Sym,
bool Assumption) {
// Handle SymbolData.
if (isa<SymbolData>(Sym)) {
return assumeSymUnsupported(State, Sym, Assumption);
// Handle symbolic expression.
} else if (const SymIntExpr *SIE = dyn_cast<SymIntExpr>(Sym)) {
// We can only simplify expressions whose RHS is an integer.
BinaryOperator::Opcode op = SIE->getOpcode();
if (BinaryOperator::isComparisonOp(op) && op != BO_Cmp) {
if (!Assumption)
op = BinaryOperator::negateComparisonOp(op);
return assumeSymRel(State, SIE->getLHS(), op, SIE->getRHS());
}
} else if (const SymSymExpr *SSE = dyn_cast<SymSymExpr>(Sym)) {
// Translate "a != b" to "(b - a) != 0".
// We invert the order of the operands as a heuristic for how loop
// conditions are usually written ("begin != end") as compared to length
// calculations ("end - begin"). The more correct thing to do would be to
// canonicalize "a - b" and "b - a", which would allow us to treat
// "a != b" and "b != a" the same.
SymbolManager &SymMgr = getSymbolManager();
BinaryOperator::Opcode Op = SSE->getOpcode();
assert(BinaryOperator::isComparisonOp(Op));
// For now, we only support comparing pointers.
if (Loc::isLocType(SSE->getLHS()->getType()) &&
Loc::isLocType(SSE->getRHS()->getType())) {
QualType DiffTy = SymMgr.getContext().getPointerDiffType();
SymbolRef Subtraction =
SymMgr.getSymSymExpr(SSE->getRHS(), BO_Sub, SSE->getLHS(), DiffTy);
const llvm::APSInt &Zero = getBasicVals().getValue(0, DiffTy);
Op = BinaryOperator::reverseComparisonOp(Op);
if (!Assumption)
Op = BinaryOperator::negateComparisonOp(Op);
return assumeSymRel(State, Subtraction, Op, Zero);
}
}
// If we get here, there's nothing else we can do but treat the symbol as
// opaque.
return assumeSymUnsupported(State, Sym, Assumption);
}
ProgramStateRef RangedConstraintManager::assumeSymInclusiveRange(
ProgramStateRef State, SymbolRef Sym, const llvm::APSInt &From,
const llvm::APSInt &To, bool InRange) {
// Get the type used for calculating wraparound.
BasicValueFactory &BVF = getBasicVals();
APSIntType WraparoundType = BVF.getAPSIntType(Sym->getType());
llvm::APSInt Adjustment = WraparoundType.getZeroValue();
SymbolRef AdjustedSym = Sym;
computeAdjustment(AdjustedSym, Adjustment);
// Convert the right-hand side integer as necessary.
APSIntType ComparisonType = std::max(WraparoundType, APSIntType(From));
llvm::APSInt ConvertedFrom = ComparisonType.convert(From);
llvm::APSInt ConvertedTo = ComparisonType.convert(To);
// Prefer unsigned comparisons.
if (ComparisonType.getBitWidth() == WraparoundType.getBitWidth() &&
ComparisonType.isUnsigned() && !WraparoundType.isUnsigned())
Adjustment.setIsSigned(false);
if (InRange)
return assumeSymWithinInclusiveRange(State, AdjustedSym, ConvertedFrom,
ConvertedTo, Adjustment);
return assumeSymOutsideInclusiveRange(State, AdjustedSym, ConvertedFrom,
ConvertedTo, Adjustment);
}
ProgramStateRef
RangedConstraintManager::assumeSymUnsupported(ProgramStateRef State,
SymbolRef Sym, bool Assumption) {
BasicValueFactory &BVF = getBasicVals();
QualType T = Sym->getType();
// Non-integer types are not supported.
if (!T->isIntegralOrEnumerationType())
return State;
// Reverse the operation and add directly to state.
const llvm::APSInt &Zero = BVF.getValue(0, T);
if (Assumption)
return assumeSymNE(State, Sym, Zero, Zero);
else
return assumeSymEQ(State, Sym, Zero, Zero);
}
ProgramStateRef RangedConstraintManager::assumeSymRel(ProgramStateRef State,
SymbolRef Sym,
BinaryOperator::Opcode Op,
const llvm::APSInt &Int) {
assert(BinaryOperator::isComparisonOp(Op) &&
"Non-comparison ops should be rewritten as comparisons to zero.");
// Simplification: translate an assume of a constraint of the form
// "(exp comparison_op expr) != 0" to true into an assume of
// "exp comparison_op expr" to true. (And similarly, an assume of the form
// "(exp comparison_op expr) == 0" to true into an assume of
// "exp comparison_op expr" to false.)
if (Int == 0 && (Op == BO_EQ || Op == BO_NE)) {
if (const BinarySymExpr *SE = dyn_cast<BinarySymExpr>(Sym))
if (BinaryOperator::isComparisonOp(SE->getOpcode()))
return assumeSym(State, Sym, (Op == BO_NE ? true : false));
}
// Get the type used for calculating wraparound.
BasicValueFactory &BVF = getBasicVals();
APSIntType WraparoundType = BVF.getAPSIntType(Sym->getType());
// We only handle simple comparisons of the form "$sym == constant"
// or "($sym+constant1) == constant2".
// The adjustment is "constant1" in the above expression. It's used to
// "slide" the solution range around for modular arithmetic. For example,
// x < 4 has the solution [0, 3]. x+2 < 4 has the solution [0-2, 3-2], which
// in modular arithmetic is [0, 1] U [UINT_MAX-1, UINT_MAX]. It's up to
// the subclasses of SimpleConstraintManager to handle the adjustment.
llvm::APSInt Adjustment = WraparoundType.getZeroValue();
computeAdjustment(Sym, Adjustment);
// Convert the right-hand side integer as necessary.
APSIntType ComparisonType = std::max(WraparoundType, APSIntType(Int));
llvm::APSInt ConvertedInt = ComparisonType.convert(Int);
// Prefer unsigned comparisons.
if (ComparisonType.getBitWidth() == WraparoundType.getBitWidth() &&
ComparisonType.isUnsigned() && !WraparoundType.isUnsigned())
Adjustment.setIsSigned(false);
switch (Op) {
default:
llvm_unreachable("invalid operation not caught by assertion above");
case BO_EQ:
return assumeSymEQ(State, Sym, ConvertedInt, Adjustment);
case BO_NE:
return assumeSymNE(State, Sym, ConvertedInt, Adjustment);
case BO_GT:
return assumeSymGT(State, Sym, ConvertedInt, Adjustment);
case BO_GE:
return assumeSymGE(State, Sym, ConvertedInt, Adjustment);
case BO_LT:
return assumeSymLT(State, Sym, ConvertedInt, Adjustment);
case BO_LE:
return assumeSymLE(State, Sym, ConvertedInt, Adjustment);
} // end switch
}
void RangedConstraintManager::computeAdjustment(SymbolRef &Sym,
llvm::APSInt &Adjustment) {
// Is it a "($sym+constant1)" expression?
if (const SymIntExpr *SE = dyn_cast<SymIntExpr>(Sym)) {
BinaryOperator::Opcode Op = SE->getOpcode();
if (Op == BO_Add || Op == BO_Sub) {
Sym = SE->getLHS();
Adjustment = APSIntType(Adjustment).convert(SE->getRHS());
// Don't forget to negate the adjustment if it's being subtracted.
// This should happen /after/ promotion, in case the value being
// subtracted is, say, CHAR_MIN, and the promoted type is 'int'.
if (Op == BO_Sub)
Adjustment = -Adjustment;
}
}
}
void *ProgramStateTrait<ConstraintRange>::GDMIndex() {
static int Index;
return &Index;
}
} // end of namespace ento
} // end of namespace clang
|
