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Commit 726f38c

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author
Robert Marsh
committed
C++: refactor alias analysis for performance
1 parent c70bd28 commit 726f38c

2 files changed

Lines changed: 42 additions & 58 deletions

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‎cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/AliasAnalysis.qll‎

Lines changed: 21 additions & 29 deletions
Original file line numberDiff line numberDiff line change
@@ -155,15 +155,7 @@ predicate operandIsPropagated(Operand operand, IntValue bitOffset) {
155155
// The operand is used in a function call from which the operand does not escape
156156
exists(CallInstruction ci, FunctionIR f, Instruction init |
157157
ci = operand.getUseInstruction() and
158-
f.getFunction() = ci.getStaticCallTarget() and
159-
(
160-
init.(InitializeParameterInstruction).getParameter() = f.getFunction().getParameter(operand.(PositionalArgumentOperand).getIndex())
161-
or
162-
init instanceof InitializeThisInstruction and
163-
init.getEnclosingFunctionIR() = f and
164-
operand instanceof ThisArgumentOperand
165-
) and
166-
not exists(f.getFunction().getAnOverload()) and
158+
isArgumentForParameter(ci, operand, init) and
167159
not resultEscapesNonReturn(init) and
168160
(
169161
not resultReturned(init)
@@ -186,24 +178,16 @@ predicate operandEscapesNonReturn(Operand operand) {
186178
not resultEscapesNonReturn(operand.getUseInstruction())
187179
or
188180
// The operand is used in a function call from which the operand does not escape
189-
exists(CallInstruction ci, FunctionIR f, Instruction init |
190-
ci = operand.getUseInstruction() and
191-
f.getFunction() = ci.getStaticCallTarget() and
192-
(
193-
init.(InitializeParameterInstruction).getParameter() = f.getFunction().getParameter(operand.(PositionalArgumentOperand).getIndex())
194-
or
195-
init instanceof InitializeThisInstruction and
196-
init.getEnclosingFunctionIR() = f and
197-
operand instanceof ThisArgumentOperand
198-
) and
199-
not exists(f.getFunction().getAnOverload()) and
181+
exists(CallInstruction ci, Instruction init |
182+
isArgumentForParameter(ci, operand, init) and
200183
not resultEscapesNonReturn(init) and
201184
not resultEscapesNonReturn(ci)
202185
) or
203186
operand instanceof ReturnValueOperand
204187
)
205188
}
206189

190+
207191
predicate operandReturned(Operand operand) {
208192
// The address is propagated to the result of the instruction, and that result itself is returned
209193
operandIsPropagated(operand, _) and resultReturned(operand.getUseInstruction())
@@ -217,16 +201,9 @@ predicate operandReturned(Operand operand) {
217201
resultReturned(ci)
218202
)
219203
or
220-
exists(CallInstruction ci, FunctionIR f, Instruction init |
204+
exists(CallInstruction ci, Instruction init |
221205
ci = operand.getUseInstruction() and
222-
f.getFunction() = ci.getStaticCallTarget() and
223-
(
224-
init.(InitializeParameterInstruction).getParameter() = f.getFunction().getParameter(operand.(PositionalArgumentOperand).getIndex())
225-
or
226-
init instanceof InitializeThisInstruction and
227-
init.getEnclosingFunctionIR() = f and
228-
operand instanceof ThisArgumentOperand
229-
) and
206+
isArgumentForParameter(ci, operand, init) and
230207
resultReturned(init) and
231208
resultReturned(ci)
232209
)
@@ -235,6 +212,21 @@ predicate operandReturned(Operand operand) {
235212
operand instanceof ReturnValueOperand
236213
}
237214

215+
predicate isArgumentForParameter(CallInstruction ci, Operand operand, Instruction init) {
216+
exists(Function f |
217+
ci = operand.getUseInstruction() and
218+
f = ci.getStaticCallTarget() and
219+
(
220+
init.(InitializeParameterInstruction).getParameter() = f.getParameter(operand.(PositionalArgumentOperand).getIndex())
221+
or
222+
init instanceof InitializeThisInstruction and
223+
init.getEnclosingFunction() = f and
224+
operand instanceof ThisArgumentOperand
225+
) and
226+
not f.isVirtual()
227+
)
228+
}
229+
238230
predicate resultReturned(Instruction instr) {
239231
operandReturned(instr.getAUse())
240232
}

‎cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/internal/AliasAnalysis.qll‎

Lines changed: 21 additions & 29 deletions
Original file line numberDiff line numberDiff line change
@@ -155,15 +155,7 @@ predicate operandIsPropagated(Operand operand, IntValue bitOffset) {
155155
// The operand is used in a function call from which the operand does not escape
156156
exists(CallInstruction ci, FunctionIR f, Instruction init |
157157
ci = operand.getUseInstruction() and
158-
f.getFunction() = ci.getStaticCallTarget() and
159-
(
160-
init.(InitializeParameterInstruction).getParameter() = f.getFunction().getParameter(operand.(PositionalArgumentOperand).getIndex())
161-
or
162-
init instanceof InitializeThisInstruction and
163-
init.getEnclosingFunctionIR() = f and
164-
operand instanceof ThisArgumentOperand
165-
) and
166-
not exists(f.getFunction().getAnOverload()) and
158+
isArgumentForParameter(ci, operand, init) and
167159
not resultEscapesNonReturn(init) and
168160
(
169161
not resultReturned(init)
@@ -186,24 +178,16 @@ predicate operandEscapesNonReturn(Operand operand) {
186178
not resultEscapesNonReturn(operand.getUseInstruction())
187179
or
188180
// The operand is used in a function call from which the operand does not escape
189-
exists(CallInstruction ci, FunctionIR f, Instruction init |
190-
ci = operand.getUseInstruction() and
191-
f.getFunction() = ci.getStaticCallTarget() and
192-
(
193-
init.(InitializeParameterInstruction).getParameter() = f.getFunction().getParameter(operand.(PositionalArgumentOperand).getIndex())
194-
or
195-
init instanceof InitializeThisInstruction and
196-
init.getEnclosingFunctionIR() = f and
197-
operand instanceof ThisArgumentOperand
198-
) and
199-
not exists(f.getFunction().getAnOverload()) and
181+
exists(CallInstruction ci, Instruction init |
182+
isArgumentForParameter(ci, operand, init) and
200183
not resultEscapesNonReturn(init) and
201184
not resultEscapesNonReturn(ci)
202185
) or
203186
operand instanceof ReturnValueOperand
204187
)
205188
}
206189

190+
207191
predicate operandReturned(Operand operand) {
208192
// The address is propagated to the result of the instruction, and that result itself is returned
209193
operandIsPropagated(operand, _) and resultReturned(operand.getUseInstruction())
@@ -217,16 +201,9 @@ predicate operandReturned(Operand operand) {
217201
resultReturned(ci)
218202
)
219203
or
220-
exists(CallInstruction ci, FunctionIR f, Instruction init |
204+
exists(CallInstruction ci, Instruction init |
221205
ci = operand.getUseInstruction() and
222-
f.getFunction() = ci.getStaticCallTarget() and
223-
(
224-
init.(InitializeParameterInstruction).getParameter() = f.getFunction().getParameter(operand.(PositionalArgumentOperand).getIndex())
225-
or
226-
init instanceof InitializeThisInstruction and
227-
init.getEnclosingFunctionIR() = f and
228-
operand instanceof ThisArgumentOperand
229-
) and
206+
isArgumentForParameter(ci, operand, init) and
230207
resultReturned(init) and
231208
resultReturned(ci)
232209
)
@@ -235,6 +212,21 @@ predicate operandReturned(Operand operand) {
235212
operand instanceof ReturnValueOperand
236213
}
237214

215+
predicate isArgumentForParameter(CallInstruction ci, Operand operand, Instruction init) {
216+
exists(Function f |
217+
ci = operand.getUseInstruction() and
218+
f = ci.getStaticCallTarget() and
219+
(
220+
init.(InitializeParameterInstruction).getParameter() = f.getParameter(operand.(PositionalArgumentOperand).getIndex())
221+
or
222+
init instanceof InitializeThisInstruction and
223+
init.getEnclosingFunction() = f and
224+
operand instanceof ThisArgumentOperand
225+
) and
226+
not f.isVirtual()
227+
)
228+
}
229+
238230
predicate resultReturned(Instruction instr) {
239231
operandReturned(instr.getAUse())
240232
}

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