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C++: Remove an unnecessary column #16299

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May 8, 2024
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C++: Remove an unnecessary column #16299

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92 changes: 37 additions & 55 deletions cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/SsaInternals.qll
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Original file line number Diff line number Diff line change
Expand Up @@ -105,8 +105,8 @@ predicate hasRawIndirectInstruction(Instruction instr, int indirectionIndex) {
cached
private newtype TDefImpl =
TDefAddressImpl(BaseIRVariable v) or
TDirectDefImpl(BaseSourceVariableInstruction base, Operand address, int indirectionIndex) {
isDef(_, _, address, base, _, indirectionIndex)
TDirectDefImpl(Operand address, int indirectionIndex) {
isDef(_, _, address, _, _, indirectionIndex)
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So we never had two TDirectDefImpl with the same address / indirectionIndex but different bases?

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Correct. That would only be possible if an operand somehow had two base instructions. And we don't generate that kind of IR

} or
TGlobalDefImpl(GlobalLikeVariable v, IRFunction f, int indirectionIndex) {
// Represents the initial "definition" of a global variable when entering
Expand All @@ -116,8 +116,8 @@ private newtype TDefImpl =

cached
private newtype TUseImpl =
TDirectUseImpl(BaseSourceVariableInstruction base, Operand operand, int indirectionIndex) {
isUse(_, operand, base, _, indirectionIndex) and
TDirectUseImpl(Operand operand, int indirectionIndex) {
isUse(_, operand, _, _, indirectionIndex) and
not isDef(true, _, operand, _, _, _)
} or
TGlobalUse(GlobalLikeVariable v, IRFunction f, int indirectionIndex) {
Expand Down Expand Up @@ -211,19 +211,11 @@ abstract class DefImpl extends TDefImpl {
*/
abstract int getIndirection();

/**
* Gets the instruction that computes the base of this definition or use.
* This is always a `VariableAddressInstruction` or an `CallInstruction`.
*/
abstract BaseSourceVariableInstruction getBase();

/**
* Gets the base source variable (i.e., the variable without
* any indirection) of this definition or use.
*/
final BaseSourceVariable getBaseSourceVariable() {
this.getBase().getBaseSourceVariable() = result
}
abstract BaseSourceVariable getBaseSourceVariable();

/** Gets the variable that is defined or used. */
SourceVariable getSourceVariable() {
Expand Down Expand Up @@ -283,19 +275,11 @@ abstract class UseImpl extends TUseImpl {
/** Gets the indirection index of this use. */
final int getIndirectionIndex() { result = indirectionIndex }

/**
* Gets the instruction that computes the base of this definition or use.
* This is always a `VariableAddressInstruction` or an `CallInstruction`.
*/
abstract BaseSourceVariableInstruction getBase();

/**
* Gets the base source variable (i.e., the variable without
* any indirection) of this definition or use.
*/
final BaseSourceVariable getBaseSourceVariable() {
this.getBase().getBaseSourceVariable() = result
}
abstract BaseSourceVariable getBaseSourceVariable();

/** Gets the variable that is defined or used. */
SourceVariable getSourceVariable() {
Expand Down Expand Up @@ -377,14 +361,13 @@ private class DefAddressImpl extends DefImpl, TDefAddressImpl {
result.getIndirection() = 0
}

final override BaseSourceVariableInstruction getBase() { none() }
final override BaseSourceVariable getBaseSourceVariable() { result = v }
}

private class DirectDef extends DefImpl, TDirectDefImpl {
Operand address;
BaseSourceVariableInstruction base;

DirectDef() { this = TDirectDefImpl(base, address, indirectionIndex) }
DirectDef() { this = TDirectDefImpl(address, indirectionIndex) }

override Cpp::Location getLocation() { result = this.getAddressOperand().getUse().getLocation() }

Expand All @@ -396,30 +379,36 @@ private class DirectDef extends DefImpl, TDirectDefImpl {

override Operand getAddressOperand() { result = address }

override BaseSourceVariableInstruction getBase() { result = base }
private BaseSourceVariableInstruction getBase() {
isDef(_, _, address, result, _, indirectionIndex)
}

override int getIndirection() { isDef(_, _, address, base, result, indirectionIndex) }
override BaseSourceVariable getBaseSourceVariable() {
result = this.getBase().getBaseSourceVariable()
}

override int getIndirection() { isDef(_, _, address, _, result, indirectionIndex) }

override Node0Impl getValue() { isDef(_, result, address, base, _, _) }
override Node0Impl getValue() { isDef(_, result, address, _, _, _) }

override predicate isCertain() { isDef(true, _, address, base, _, indirectionIndex) }
override predicate isCertain() { isDef(true, _, address, _, _, indirectionIndex) }
}

private class DirectUseImpl extends UseImpl, TDirectUseImpl {
Operand operand;
BaseSourceVariableInstruction base;

DirectUseImpl() { this = TDirectUseImpl(base, operand, indirectionIndex) }
DirectUseImpl() { this = TDirectUseImpl(operand, indirectionIndex) }

override string toString() { result = "Use of " + this.getSourceVariable() }

final override predicate hasIndexInBlock(IRBlock block, int index) {
// See the comment in `ssa0`'s `OperandBasedUse` for an explanation of this
// predicate's implementation.
if base.getAst() = any(Cpp::PostfixCrementOperation c).getOperand()
if this.getBase().getAst() = any(Cpp::PostfixCrementOperation c).getOperand()
then
exists(Operand op, int indirection |
exists(Operand op, int indirection, Instruction base |
indirection = this.getIndirection() and
base = this.getBase() and
op =
min(Operand cand, int i |
isUse(_, cand, base, indirection, indirectionIndex) and
Expand All @@ -432,15 +421,19 @@ private class DirectUseImpl extends UseImpl, TDirectUseImpl {
else operand.getUse() = block.getInstruction(index)
}

final override BaseSourceVariableInstruction getBase() { result = base }
private BaseSourceVariableInstruction getBase() { isUse(_, operand, result, _, indirectionIndex) }

override BaseSourceVariable getBaseSourceVariable() {
result = this.getBase().getBaseSourceVariable()
}

final Operand getOperand() { result = operand }

final override Cpp::Location getLocation() { result = operand.getLocation() }

override int getIndirection() { isUse(_, operand, base, result, indirectionIndex) }
override int getIndirection() { isUse(_, operand, _, result, indirectionIndex) }

override predicate isCertain() { isUse(true, operand, base, _, indirectionIndex) }
override predicate isCertain() { isUse(true, operand, _, _, indirectionIndex) }

override Node getNode() { nodeHasOperand(result, operand, indirectionIndex) }
}
Expand Down Expand Up @@ -499,13 +492,7 @@ class FinalParameterUse extends UseImpl, TFinalParameterUse {
result instanceof UnknownDefaultLocation
}

override BaseSourceVariableInstruction getBase() {
exists(InitializeParameterInstruction init |
init.getParameter() = p and
// This is always a `VariableAddressInstruction`
result = init.getAnOperand().getDef()
)
}
override BaseIRVariable getBaseSourceVariable() { result.getIRVariable().getAst() = p }
}

/**
Expand Down Expand Up @@ -591,8 +578,8 @@ class GlobalUse extends UseImpl, TGlobalUse {
)
}

override SourceVariable getSourceVariable() {
sourceVariableIsGlobal(result, global, f, this.getIndirection())
override BaseSourceVariable getBaseSourceVariable() {
baseSourceVariableIsGlobal(result, global, f)
}

final override Cpp::Location getLocation() { result = f.getLocation() }
Expand All @@ -609,8 +596,6 @@ class GlobalUse extends UseImpl, TGlobalUse {
Type getUnderlyingType() { result = global.getUnderlyingType() }

override predicate isCertain() { any() }

override BaseSourceVariableInstruction getBase() { none() }
}

/**
Expand Down Expand Up @@ -640,8 +625,8 @@ class GlobalDefImpl extends DefImpl, TGlobalDefImpl {
}

/** Gets the global variable associated with this definition. */
override SourceVariable getSourceVariable() {
sourceVariableIsGlobal(result, global, f, this.getIndirection())
override BaseSourceVariable getBaseSourceVariable() {
baseSourceVariableIsGlobal(result, global, f)
}

override int getIndirection() { result = indirectionIndex }
Expand All @@ -664,8 +649,6 @@ class GlobalDefImpl extends DefImpl, TGlobalDefImpl {
override string toString() { result = "Def of " + this.getSourceVariable() }

override Location getLocation() { result = f.getLocation() }

override BaseSourceVariableInstruction getBase() { none() }
}

/**
Expand Down Expand Up @@ -978,11 +961,10 @@ predicate fromPhiNode(SsaPhiNode nodeFrom, Node nodeTo) {
)
}

private predicate sourceVariableIsGlobal(
SourceVariable sv, GlobalLikeVariable global, IRFunction func, int indirectionIndex
private predicate baseSourceVariableIsGlobal(
BaseIRVariable base, GlobalLikeVariable global, IRFunction func
) {
exists(IRVariable irVar, BaseIRVariable base |
sourceVariableHasBaseAndIndex(sv, base, indirectionIndex) and
exists(IRVariable irVar |
irVar = base.getIRVariable() and
irVar.getEnclosingIRFunction() = func and
global = irVar.getAst() and
Expand Down
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