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C++: Use the loaded this instead of the this initialization #21105

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Merged
jketema merged 4 commits into from
Jan 7, 2026
+151 −155
Merged

C++: Use the loaded this instead of the this initialization #21105

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740518d
C++: Use the loaded `this` instead of the `this` initialization
jketema Jan 6, 2026
3cd9938
C++: Update expected test results after IR changes
jketema Jan 6, 2026
063e5d3
C++: Remove redundant SSA branch after IR fix
jketema Jan 6, 2026
c567197
C++: Simplify expression
jketema Jan 6, 2026
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12 changes: 3 additions & 9 deletions cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/SsaImplCommon.qll
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Original file line number Diff line number Diff line change
Expand Up @@ -688,15 +688,9 @@ private module Cached {
conversionFlow(mid, instr, false, _)
)
or
exists(int ind0 |
exists(Operand address |
isDereference(operand.getDef(), address, _) and
isUseImpl(address, base, ind0)
)
or
isUseImpl(operand.getDef().(InitializeParameterInstruction).getAnOperand(), base, ind0)
|
ind0 = ind - 1
exists(Operand address |
isDereference(operand.getDef(), address, _) and
isUseImpl(address, base, ind - 1)
)
}

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2 changes: 1 addition & 1 deletion cpp/ql/lib/semmle/code/cpp/ir/implementation/raw/internal/TranslatedExpr.qll
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Expand Up @@ -2679,7 +2679,7 @@ class TranslatedDestructorFieldDestruction extends TranslatedNonConstantExpr, St
final override Instruction getInstructionRegisterOperand(InstructionTag tag, OperandTag operandTag) {
tag = OnlyInstructionTag() and
operandTag instanceof UnaryOperandTag and
result = getTranslatedFunction(getEnclosingFunction(expr)).getInitializeThisInstruction()
result = getTranslatedFunction(getEnclosingFunction(expr)).getLoadThisInstruction()
}

final override Field getInstructionField(InstructionTag tag) {
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10 changes: 5 additions & 5 deletions cpp/ql/lib/semmle/code/cpp/ir/implementation/raw/internal/TranslatedFunction.qll
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Expand Up @@ -306,11 +306,11 @@ class TranslatedFunction extends TranslatedRootElement, TTranslatedFunction {
final predicate hasReturnValue() { hasReturnValue(func) }

/**
* Gets the single `InitializeThis` instruction for this function. Holds only
* if the function is an instance member function, constructor, or destructor.
* Gets the first load of `this` for this function. Holds only if the function
* is an instance member function, constructor, or destructor.
*/
final Instruction getInitializeThisInstruction() {
result = getTranslatedThisParameter(func).getInstruction(InitializerStoreTag())
final Instruction getLoadThisInstruction() {
result = getTranslatedThisParameter(func).getInstruction(InitializerIndirectAddressTag())
}

/**
Expand Down Expand Up @@ -639,7 +639,7 @@ class TranslatedConstructorInitList extends TranslatedElement, InitializationCon
}

override Instruction getTargetAddress() {
result = getTranslatedFunction(func).getInitializeThisInstruction()
result = getTranslatedFunction(func).getLoadThisInstruction()
}

override Type getTargetType() { result = getTranslatedFunction(func).getThisType() }
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4 changes: 2 additions & 2 deletions cpp/ql/lib/semmle/code/cpp/ir/implementation/raw/internal/TranslatedInitialization.qll
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Expand Up @@ -950,7 +950,7 @@ abstract class TranslatedBaseStructorCall extends TranslatedStructorCallFromStru
final override Instruction getInstructionRegisterOperand(InstructionTag tag, OperandTag operandTag) {
tag = OnlyInstructionTag() and
operandTag instanceof UnaryOperandTag and
result = getTranslatedFunction(this.getFunction()).getInitializeThisInstruction()
result = getTranslatedFunction(this.getFunction()).getLoadThisInstruction()
}

final override predicate getInstructionInheritance(
Expand Down Expand Up @@ -1000,7 +1000,7 @@ class TranslatedConstructorDelegationInit extends TranslatedConstructorCallFromC
}

final override Instruction getReceiver() {
result = getTranslatedFunction(this.getFunction()).getInitializeThisInstruction()
result = getTranslatedFunction(this.getFunction()).getLoadThisInstruction()
}
}

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18 changes: 9 additions & 9 deletions cpp/ql/test/library-tests/dataflow/fields/ir-path-flow.expected
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Expand Up @@ -193,10 +193,10 @@ edges
| C.cpp:18:12:18:18 | call to C [s3] | C.cpp:18:12:18:18 | *new [s3] | provenance | |
| C.cpp:19:5:19:5 | *c [s1] | C.cpp:27:8:27:11 | *this [s1] | provenance | |
| C.cpp:19:5:19:5 | *c [s3] | C.cpp:27:8:27:11 | *this [s3] | provenance | |
| C.cpp:22:3:22:3 | *C [post update] [s1] | C.cpp:22:3:22:3 | *this [Return] [s1] | provenance | |
| C.cpp:22:3:22:3 | *this [Return] [s1] | C.cpp:18:12:18:18 | call to C [s1] | provenance | |
| C.cpp:22:3:22:3 | *this [Return] [s3] | C.cpp:18:12:18:18 | call to C [s3] | provenance | |
| C.cpp:22:3:22:3 | *this [post update] [s1] | C.cpp:22:3:22:3 | *this [Return] [s1] | provenance | |
| C.cpp:22:12:22:21 | new | C.cpp:22:3:22:3 | *this [post update] [s1] | provenance | |
| C.cpp:22:12:22:21 | new | C.cpp:22:3:22:3 | *C [post update] [s1] | provenance | |
| C.cpp:22:12:22:21 | new | C.cpp:22:12:22:21 | new | provenance | |
| C.cpp:24:5:24:8 | *this [post update] [s3] | C.cpp:22:3:22:3 | *this [Return] [s3] | provenance | |
| C.cpp:24:5:24:25 | ... = ... | C.cpp:24:5:24:8 | *this [post update] [s3] | provenance | |
Expand Down Expand Up @@ -736,12 +736,12 @@ edges
| constructors.cpp:19:22:19:23 | *this [b_] | constructors.cpp:19:22:19:23 | b_ | provenance | |
| constructors.cpp:19:22:19:23 | b_ | constructors.cpp:19:9:19:9 | *b | provenance | |
| constructors.cpp:19:22:19:23 | b_ | constructors.cpp:19:22:19:23 | b_ | provenance | |
| constructors.cpp:23:5:23:7 | *this [post update] [a_] | constructors.cpp:23:5:23:7 | *this [Return] [a_] | provenance | |
| constructors.cpp:23:5:23:7 | *this [post update] [b_] | constructors.cpp:23:5:23:7 | *this [Return] [b_] | provenance | |
| constructors.cpp:23:5:23:7 | *Foo [post update] [a_] | constructors.cpp:23:5:23:7 | *this [Return] [a_] | provenance | |
| constructors.cpp:23:5:23:7 | *Foo [post update] [b_] | constructors.cpp:23:5:23:7 | *this [Return] [b_] | provenance | |
| constructors.cpp:23:13:23:13 | a | constructors.cpp:23:28:23:28 | a | provenance | |
| constructors.cpp:23:20:23:20 | b | constructors.cpp:23:35:23:35 | b | provenance | |
| constructors.cpp:23:28:23:28 | a | constructors.cpp:23:5:23:7 | *this [post update] [a_] | provenance | |
| constructors.cpp:23:35:23:35 | b | constructors.cpp:23:5:23:7 | *this [post update] [b_] | provenance | |
| constructors.cpp:23:28:23:28 | a | constructors.cpp:23:5:23:7 | *Foo [post update] [a_] | provenance | |
| constructors.cpp:23:35:23:35 | b | constructors.cpp:23:5:23:7 | *Foo [post update] [b_] | provenance | |
| constructors.cpp:26:15:26:15 | *f [a_] | constructors.cpp:28:10:28:10 | *f [a_] | provenance | |
| constructors.cpp:26:15:26:15 | *f [b_] | constructors.cpp:29:10:29:10 | *f [b_] | provenance | |
| constructors.cpp:28:10:28:10 | *f [a_] | constructors.cpp:18:9:18:9 | *this [a_] | provenance | |
Expand Down Expand Up @@ -1122,9 +1122,9 @@ nodes
| C.cpp:18:12:18:18 | call to C [s3] | semmle.label | call to C [s3] |
| C.cpp:19:5:19:5 | *c [s1] | semmle.label | *c [s1] |
| C.cpp:19:5:19:5 | *c [s3] | semmle.label | *c [s3] |
| C.cpp:22:3:22:3 | *C [post update] [s1] | semmle.label | *C [post update] [s1] |
| C.cpp:22:3:22:3 | *this [Return] [s1] | semmle.label | *this [Return] [s1] |
| C.cpp:22:3:22:3 | *this [Return] [s3] | semmle.label | *this [Return] [s3] |
| C.cpp:22:3:22:3 | *this [post update] [s1] | semmle.label | *this [post update] [s1] |
| C.cpp:22:12:22:21 | new | semmle.label | new |
| C.cpp:22:12:22:21 | new | semmle.label | new |
| C.cpp:24:5:24:8 | *this [post update] [s3] | semmle.label | *this [post update] [s3] |
Expand Down Expand Up @@ -1678,10 +1678,10 @@ nodes
| constructors.cpp:19:22:19:23 | *this [b_] | semmle.label | *this [b_] |
| constructors.cpp:19:22:19:23 | b_ | semmle.label | b_ |
| constructors.cpp:19:22:19:23 | b_ | semmle.label | b_ |
| constructors.cpp:23:5:23:7 | *Foo [post update] [a_] | semmle.label | *Foo [post update] [a_] |
| constructors.cpp:23:5:23:7 | *Foo [post update] [b_] | semmle.label | *Foo [post update] [b_] |
| constructors.cpp:23:5:23:7 | *this [Return] [a_] | semmle.label | *this [Return] [a_] |
| constructors.cpp:23:5:23:7 | *this [Return] [b_] | semmle.label | *this [Return] [b_] |
| constructors.cpp:23:5:23:7 | *this [post update] [a_] | semmle.label | *this [post update] [a_] |
| constructors.cpp:23:5:23:7 | *this [post update] [b_] | semmle.label | *this [post update] [b_] |
| constructors.cpp:23:13:23:13 | a | semmle.label | a |
| constructors.cpp:23:20:23:20 | b | semmle.label | b |
| constructors.cpp:23:28:23:28 | a | semmle.label | a |
Expand Down
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