/**

* Provides classes and predicates for working with an intermediate representation (IR) of Go

* programs that is used as the foundation of the control flow and data flow graphs.

*

* In the IR, the program is represented as a set of instructions, which correspond to expressions

* and statements that compute a value or perform an operation (as opposed to providing syntactic

* structure or type information).

*

* Each instruction is also a control-flow node, but there are control-flow nodes that are not

* instructions (synthetic entry and exit nodes, as well as no-op skip nodes).

*/

overlay[local]

module;

import go

private import semmle.go.controlflow.ControlFlowGraphImpl

/** Provides predicates and classes for working with IR constructs. */

module IR {

/**

* An IR instruction.

*/

class Instruction extends ControlFlow::Node {

Instruction() {

this instanceof MkExprNode or

this instanceof MkLiteralElementInitNode or

this instanceof MkImplicitLiteralElementIndex or

this instanceof MkAssignNode or

this instanceof MkCompoundAssignRhsNode or

this instanceof MkExtractNode or

this instanceof MkZeroInitNode or

this instanceof MkFuncDeclNode or

this instanceof MkDeferNode or

this instanceof MkGoNode or

this instanceof MkConditionGuardNode or

this instanceof MkIncDecNode or

this instanceof MkIncDecRhs or

this instanceof MkImplicitOne or

this instanceof MkReturnNode or

this instanceof MkResultWriteNode or

this instanceof MkResultReadNode or

this instanceof MkSelectNode or

this instanceof MkSendNode or

this instanceof MkParameterInit or

this instanceof MkArgumentNode or

this instanceof MkResultInit or

this instanceof MkNextNode or

this instanceof MkImplicitTrue or

this instanceof MkCaseCheckNode or

this instanceof MkTypeSwitchImplicitVariable or

this instanceof MkImplicitLowerSliceBound or

this instanceof MkImplicitUpperSliceBound or

this instanceof MkImplicitMaxSliceBound or

this instanceof MkImplicitDeref or

this instanceof MkImplicitFieldSelection

}

/** Holds if this instruction reads the value of variable or constant `v`. */

predicate reads(ValueEntity v) { this.readsField(_, v) or this.readsMethod(_, v) }

/** Holds if this instruction updates variable or constant `v` to the value of `rhs`. */

predicate writes(ValueEntity v, Instruction rhs) { this.writesField(_, v, rhs) }

/** Holds if this instruction reads the value of field `f` on the value of `base`. */

predicate readsField(Instruction base, Field f) { none() }

/** Holds if this instruction updates the value of field `f` on the value of `base`. */

predicate writesField(Instruction base, Field f, Instruction rhs) { none() }

/** Holds if this instruction looks up method `m` on the value of `receiver`. */

predicate readsMethod(Instruction receiver, Method m) { none() }

/** Holds if this instruction reads the value of element `index` on the value of `base`. */

predicate readsElement(Instruction base, Instruction index) { none() }

/** Holds if this instruction updates the value of element `index` on the value of `base`. */

predicate writesElement(Instruction base, Instruction index) { none() }

/** Gets the type of the result of this instruction, if any. */

Type getResultType() { none() }

/** Gets the float value of the result of this instruction, if it can be determined. */

float getFloatValue() { none() }

/** Gets the int value of the result of this instruction, if it can be determined. */

int getIntValue() { none() }

/**

* Holds if the complex value of the result of this instruction has real part `real` and

* imaginary part `imag`.

*/

predicate hasComplexValue(float real, float imag) { none() }

/** Gets either `getFloatValue` or `getIntValue` */

float getNumericValue() { result = this.getFloatValue() or result = this.getIntValue() }

/**

* Gets the string representation of the exact value of the result of this instruction,

* if any.

*

* For example, for the constant 3.141592653589793238462, this will

* result in 1570796326794896619231/500000000000000000000

*/

string getExactValue() { none() }

/** Gets the string value of the result of this instruction, if it can be determined. */

string getStringValue() { none() }

/** Gets the Boolean value of the result of this instruction, if it can be determined. */

boolean getBoolValue() { none() }

/** Holds if the result of this instruction is known at compile time. */

predicate isConst() { none() }

/**

* Holds if the result of this instruction is known at compile time, and is guaranteed not to

* depend on the platform where it is evaluated.

*/

predicate isPlatformIndependentConstant() { none() }

/** Gets a textual representation of the kind of this instruction. */

string getInsnKind() {

this instanceof MkExprNode and result = "expression"

or

this instanceof MkLiteralElementInitNode and result = "element init"

or

this instanceof MkImplicitLiteralElementIndex and result = "element index"

or

this instanceof MkAssignNode and result = "assignment"

or

this instanceof MkCompoundAssignRhsNode and result = "right-hand side of compound assignment"

or

this instanceof MkExtractNode and result = "tuple element extraction"

or

this instanceof MkZeroInitNode and result = "zero value"

or

this instanceof MkFuncDeclNode and result = "function declaration"

or

this instanceof MkDeferNode and result = "defer"

or

this instanceof MkGoNode and result = "go"

or

this instanceof MkConditionGuardNode and result = "condition guard"

or

this instanceof MkIncDecNode and result = "increment/decrement"

or

this instanceof MkIncDecRhs and result = "right-hand side of increment/decrement"

or

this instanceof MkImplicitOne and result = "implicit 1"

or

this instanceof MkReturnNode and result = "return"

or

this instanceof MkResultWriteNode and result = "result write"

or

this instanceof MkResultReadNode and result = "result read"

or

this instanceof MkSelectNode and result = "select"

or

this instanceof MkSendNode and result = "send"

or

this instanceof MkParameterInit and result = "parameter initialization"

or

this instanceof MkArgumentNode and result = "argument"

or

this instanceof MkResultInit and result = "result initialization"

or

this instanceof MkNextNode and result = "next key-value pair"

or

this instanceof MkImplicitTrue and result = "implicit true"

or

this instanceof MkCaseCheckNode and result = "case"

or

this instanceof MkTypeSwitchImplicitVariable and

result = "type switch implicit variable declaration"

or

this instanceof MkImplicitLowerSliceBound and result = "implicit lower bound"

or

this instanceof MkImplicitUpperSliceBound and result = "implicit upper bound"

or

this instanceof MkImplicitMaxSliceBound and result = "implicit maximum"

or

this instanceof MkImplicitDeref and result = "implicit dereference"

or

this instanceof MkImplicitFieldSelection and result = "implicit field selection"

}

}

/**

* An IR instruction representing the evaluation of an expression.

*/

class EvalInstruction extends Instruction, MkExprNode {

Expr e;

EvalInstruction() { this = MkExprNode(e) }

/** Gets the expression underlying this instruction. */

Expr getExpr() { result = e }

override predicate reads(ValueEntity v) { e = v.getAReference() }

override Type getResultType() { result = e.getType() }

override ControlFlow::Root getRoot() { result.isRootOf(e) }

override float getFloatValue() { result = e.getFloatValue() }

override int getIntValue() { result = e.getIntValue() }

override predicate hasComplexValue(float real, float imag) { e.hasComplexValue(real, imag) }

override string getExactValue() { result = e.getExactValue() }

override string getStringValue() { result = e.getStringValue() }

override boolean getBoolValue() { result = e.getBoolValue() }

override predicate isConst() { e.isConst() }

override predicate isPlatformIndependentConstant() { e.isPlatformIndependentConstant() }

override string toString() { result = e.toString() }

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

}

/**

* An IR instruction that reads the value of a variable, constant, field or array element,

* or refers to a function.

*/

class ReadInstruction extends Instruction {

ReadInstruction() {

exists(Expr e | e = this.(EvalInstruction).getExpr() |

(e instanceof ValueName or e instanceof IndexExpr) and

e.(ReferenceExpr).isRvalue()

)

or

this instanceof ReadResultInstruction

or

this instanceof MkImplicitFieldSelection

}

}

/**

* Gets the effective base of a selector, index or slice expression, taking implicit dereferences

* and implicit field reads into account.

*

* For a selector expression `b.f`, this could be the implicit dereference `*b`, or the implicit

* field access `b.Embedded` if the field `f` is promoted from an embedded type `Embedded`, or a

* combination of both `*(b.Embedded)`, or simply `b` if neither case applies.

*/

private Instruction selectorBase(Expr e) {

exists(ImplicitFieldReadInstruction fri | fri.getSelectorExpr() = e and fri.getIndex() = 1 |

result = fri

)

or

not exists(ImplicitFieldReadInstruction fri | fri.getSelectorExpr() = e and fri.getIndex() = 1) and

exists(Expr base |

base = e.(SelectorExpr).getBase()

or

base = e.(IndexExpr).getBase()

or

base = e.(SliceExpr).getBase()

|

result = MkImplicitDeref(base)

or

not exists(MkImplicitDeref(base)) and

result = evalExprInstruction(base)

)

}

/**

* An IR instruction that reads a component from a composite object.

*

* This is either a field of a struct, or an element of an array, map, slice or string.

*/

class ComponentReadInstruction extends ReadInstruction {

ComponentReadInstruction() {

exists(Expr e | e = this.(EvalInstruction).getExpr() |

e instanceof IndexExpr

or

e.(SelectorExpr).getBase() instanceof ValueExpr and

not e.(SelectorExpr).getSelector() = any(Method method).getAReference()

)

or

this instanceof MkImplicitFieldSelection

}

/** Gets the instruction computing the base value on which the field or element is read. */

Instruction getBase() {

result = this.(ImplicitFieldReadInstruction).getBaseInstruction()

or

result = selectorBase(this.(EvalInstruction).getExpr())

}

}

/**

* An IR instruction that reads the value of a field.

*

* On databases with incomplete type information, method expressions may sometimes be

* misclassified as field reads.

*/

class FieldReadInstruction extends ComponentReadInstruction {

SelectorExpr e;

int index;

Field field;

FieldReadInstruction() {

e = this.(EvalInstruction).getExpr() and

index = 0 and

field.getAReference() = e.getSelector()

or

this = MkImplicitFieldSelection(e, index, field)

}

/** Gets the `SelectorExpr` of this field read. */

SelectorExpr getSelectorExpr() { result = e }

/** Gets the index of this field read. */

int getIndex() { result = index }

/** Gets the field being read. */

Field getField() { result = field }

Instruction getBaseInstruction() {

exists(ImplicitFieldReadInstruction fri |

fri.getSelectorExpr() = e and fri.getIndex() = pragma[only_bind_into](index + 1)

|

result = fri

)

or

not exists(ImplicitFieldReadInstruction fri |

fri.getSelectorExpr() = e and fri.getIndex() = pragma[only_bind_into](index + 1)

) and

(

result = MkImplicitDeref(e.getBase())

or

not exists(MkImplicitDeref(e.getBase())) and

result = evalExprInstruction(e.getBase())

)

}

override predicate readsField(Instruction base, Field f) {

base = this.getBaseInstruction() and f = field

}

}

/**

* An IR instruction for an implicit field read as part of reading a

* promoted field.

*

* If the field that is being implicitly read has a pointer type then this

* instruction represents an implicit dereference of it.

*/

class ImplicitFieldReadInstruction extends FieldReadInstruction, MkImplicitFieldSelection {

ImplicitFieldReadInstruction() { this = MkImplicitFieldSelection(e, index, field) }

override predicate reads(ValueEntity v) { v = field }

override Type getResultType() { result = lookThroughPointerType(field.getType()) }

override ControlFlow::Root getRoot() { result.isRootOf(e) }

override string toString() { result = "implicit read of field " + field.toString() }

override Location getLocation() { result = e.getBase().getLocation() }

}

/**

* An IR instruction that looks up a method.

*/

class MethodReadInstruction extends ReadInstruction, EvalInstruction {

Method method;

override SelectorExpr e;

MethodReadInstruction() { e.getSelector() = method.getAReference() }

/** Gets the instruction computing the receiver value on which the method is looked up. */

Instruction getReceiver() { result = selectorBase(e) }

/** Gets the method being looked up. */

Method getMethod() { result = method }

override predicate readsMethod(Instruction receiver, Method m) {

receiver = this.getReceiver() and m = this.getMethod()

}

}

/**

* An IR instruction that reads an element of an array, slice, map or string.

*/

class ElementReadInstruction extends ComponentReadInstruction, EvalInstruction {

override IndexExpr e;

/** Gets the instruction computing the index of the element being looked up. */

Instruction getIndex() { result = evalExprInstruction(e.getIndex()) }

override predicate readsElement(Instruction base, Instruction index) {

base = this.getBase() and index = this.getIndex()

}

}

/**

* An IR instruction that constructs a slice.

*/

class SliceInstruction extends EvalInstruction {

override SliceExpr e;

/** Gets the instruction computing the base value from which the slice is constructed. */

Instruction getBase() { result = selectorBase(e) }

/** Gets the instruction computing the lower bound of the slice. */

Instruction getLow() {

result = evalExprInstruction(e.getLow()) or

result = implicitLowerSliceBoundInstruction(e)

}

/** Gets the instruction computing the upper bound of the slice. */

Instruction getHigh() {

result = evalExprInstruction(e.getHigh()) or

result = implicitUpperSliceBoundInstruction(e)

}

/** Gets the instruction computing the capacity of the slice. */

Instruction getMax() {

result = evalExprInstruction(e.getMax()) or

result = implicitMaxSliceBoundInstruction(e)

}

}

/**

* An IR instruction that writes a memory location.

*/

class WriteInstruction extends Instruction {

WriteTarget lhs;

Boolean initialization;

WriteInstruction() {

(

lhs = MkLhs(this, _)

or

lhs = MkResultWriteTarget(this)

) and

initialization = false

or

lhs = MkLiteralElementTarget(this) and initialization = true

}

/** Gets the target to which this instruction writes. */

WriteTarget getLhs() { result = lhs }

/** Holds if this instruction initializes a literal. */

predicate isInitialization() { initialization = true }

/** Gets the instruction computing the value this instruction writes. */

Instruction getRhs() { none() }

override predicate writes(ValueEntity v, Instruction rhs) {

this.getLhs().refersTo(v) and

rhs = this.getRhs()

}

}

/**

* An IR instruction that initializes a component of a composite literal.

*/

class InitLiteralComponentInstruction extends WriteInstruction, MkLiteralElementInitNode {

CompositeLit lit;

int i;

Expr elt;

InitLiteralComponentInstruction() {

this = MkLiteralElementInitNode(elt) and elt = lit.getElement(i)

}

/** Gets the instruction allocating the composite literal. */

Instruction getBase() { result = evalExprInstruction(lit) }

override Instruction getRhs() {

result = evalExprInstruction(elt) or

result = evalExprInstruction(elt.(KeyValueExpr).getValue())

}

override ControlFlow::Root getRoot() { result.isRootOf(elt) }

override string toString() { result = "init of " + elt }

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

}

/**

* An IR instruction that initializes a field of a struct literal.

*/

class InitLiteralStructFieldInstruction extends InitLiteralComponentInstruction {

override StructLit lit;

/** Gets the name of the initialized field. */

pragma[nomagic]

string getFieldName() {

if elt instanceof KeyValueExpr

then result = elt.(KeyValueExpr).getKey().(Ident).getName()

else pragma[only_bind_out](lit.getStructType()).hasOwnField(i, result, _, _)

}

/** Gets the initialized field. */

Field getField() {

result.getDeclaringType() = lit.getStructType() and

result.getName() = this.getFieldName()

}

}

/**

* An IR instruction that initializes an element of an array, slice or map literal.

*/

class InitLiteralElementInstruction extends InitLiteralComponentInstruction {

Type literalType;

InitLiteralElementInstruction() {

literalType = lit.getType().getUnderlyingType() and

(

literalType instanceof ArrayType or

literalType instanceof SliceType or

literalType instanceof MapType

)

}

/** Gets the instruction computing the index of the initialized element. */

Instruction getIndex() {

result = evalExprInstruction(elt.(KeyValueExpr).getKey())

or

result = MkImplicitLiteralElementIndex(elt)

}

}

/**

* An IR instruction that initializes an element of an array literal.

*/

class InitLiteralArrayElementInstruction extends InitLiteralElementInstruction {

override ArrayType literalType;

}

/**

* An IR instruction that initializes an element of a slice literal.

*/

class InitLiteralSliceElementInstruction extends InitLiteralElementInstruction {

override SliceType literalType;

}

/**

* An IR instruction that initializes an element of a map literal.

*/

class InitLiteralMapElementInstruction extends InitLiteralElementInstruction {

override MapType literalType;

}

/**

* An IR instruction that writes to a field.

*/

class FieldWriteInstruction extends WriteInstruction {

override FieldTarget lhs;

/** Gets the instruction computing the base value on which the field is written. */

Instruction getBase() { result = lhs.getBase() }

/** Gets the field being written. */

Field getField() { result = lhs.getField() }

override predicate writesField(Instruction base, Field f, Instruction rhs) {

this.getBase() = base and

this.getField() = f and

this.getRhs() = rhs

}

}

/**

* An IR instruction that writes to an element of an array, slice, or map.

*/

class ElementWriteInstruction extends WriteInstruction {

override ElementTarget lhs;

/** Gets the instruction computing the base value on which the field is written. */

Instruction getBase() { result = lhs.getBase() }

/** Gets the instruction computing the element index being written. */

Instruction getIndex() { result = lhs.getIndex() }

override predicate writesElement(Instruction base, Instruction index) {

this.getBase() = base and

this.getIndex() = index

}

}

/** Holds if `lit` does not specify any explicit keys. */

private predicate noExplicitKeys(CompositeLit lit) {

not lit.getAnElement() instanceof KeyValueExpr

}

/** Gets the index of the `i`th element in (array or slice) literal `lit`. */

private int getElementIndex(CompositeLit lit, int i) {

(

lit.getType().getUnderlyingType() instanceof ArrayType or

lit.getType().getUnderlyingType() instanceof SliceType

) and

exists(Expr elt | elt = lit.getElement(i) |

// short-circuit computation for literals without any explicit keys

noExplicitKeys(lit) and result = i

or

result = elt.(KeyValueExpr).getKey().getIntValue()

or

not elt instanceof KeyValueExpr and

(

i = 0 and result = 0

or

result = getElementIndex(lit, i - 1) + 1

)

)

}

/**

* An IR instruction computing the implicit index of an element in an array or slice literal.

*/

class ImplicitLiteralElementIndexInstruction extends Instruction, MkImplicitLiteralElementIndex {

Expr elt;

ImplicitLiteralElementIndexInstruction() { this = MkImplicitLiteralElementIndex(elt) }

override Type getResultType() { result instanceof IntType }

override ControlFlow::Root getRoot() { result.isRootOf(elt) }

override int getIntValue() {

exists(CompositeLit lit, int i | elt = lit.getElement(i) | result = getElementIndex(lit, i))

}

override string getStringValue() { none() }

override string getExactValue() { result = this.getIntValue().toString() }

override predicate isPlatformIndependentConstant() { any() }

override predicate isConst() { any() }

override string toString() { result = "element index" }

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

}

/**

* An instruction assigning to a variable or field.

*/

class AssignInstruction extends WriteInstruction, MkAssignNode {

AstNode assgn;

int i;

AssignInstruction() { this = MkAssignNode(assgn, i) }

override Instruction getRhs() {

exists(SimpleAssignStmt a | a = assgn |

a.getNumLhs() = a.getNumRhs() and

result = evalExprInstruction(a.getRhs(i))

)

or

exists(ValueSpec spec | spec = assgn |

spec.getNumName() = spec.getNumInit() and

result = evalExprInstruction(spec.getInit(i))

or

result = MkZeroInitNode(any(ValueEntity v | spec.getNameExpr(i) = v.getDeclaration()))

)

or

result = MkCompoundAssignRhsNode(assgn)

or

result = MkExtractNode(assgn, i)

}

override ControlFlow::Root getRoot() { result.isRootOf(assgn) }

override string toString() { result = "assignment to " + this.getLhs() }

override Location getLocation() { result = this.getLhs().getLocation() }

}

/** An instruction computing the value of the right-hand side of a compound assignment. */

class EvalCompoundAssignRhsInstruction extends Instruction, MkCompoundAssignRhsNode {

CompoundAssignStmt assgn;

EvalCompoundAssignRhsInstruction() { this = MkCompoundAssignRhsNode(assgn) }

/** Gets the underlying assignment of this instruction. */

CompoundAssignStmt getAssignment() { result = assgn }

override Type getResultType() { result = assgn.getRhs().getType() }

override ControlFlow::Root getRoot() { result.isRootOf(assgn) }

override string toString() { result = assgn.toString() }

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

}

/**

* An instruction selecting one of multiple values returned by a function, or either the key

* or the value of the iterator in a range loop, or the result or success value from a type

* assertion.

*/

class ExtractTupleElementInstruction extends Instruction, MkExtractNode {

AstNode s;

int i;

ExtractTupleElementInstruction() { this = MkExtractNode(s, i) }

/** Gets the instruction computing the tuple value from which one value is extracted. */

Instruction getBase() {

exists(Expr baseExpr |

baseExpr = s.(Assignment).getRhs() or

baseExpr = s.(ValueSpec).getInit()

|

result = evalExprInstruction(baseExpr)

)

or

result = MkNextNode(s)

or

result = evalExprInstruction(s.(ReturnStmt).getExpr())

or

result = evalExprInstruction(s.(CallExpr).getArgument(0).stripParens())

}

/** Holds if this extracts the `idx`th value of the result of `base`. */

predicate extractsElement(Instruction base, int idx) { base = this.getBase() and idx = i }

override Type getResultType() {

exists(Expr e | this.getBase() = evalExprInstruction(e) |

result = e.getType().(TupleType).getComponentType(pragma[only_bind_into](i))

)

or

exists(Type rangeType | rangeType = s.(RangeStmt).getDomain().getType().getUnderlyingType() |

exists(Type baseType |

baseType = rangeType.(ArrayType).getElementType() or

baseType =

rangeType.(PointerType).getBaseType().getUnderlyingType().(ArrayType).getElementType() or

baseType = rangeType.(SliceType).getElementType()

|

i = 0 and

result instanceof IntType

or

i = 1 and

result = baseType

)

or

rangeType instanceof StringType and

(

i = 0 and

result instanceof IntType

or

result = Builtin::rune().getType()

)

or

exists(MapType map | map = rangeType |

i = 0 and

result = map.getKeyType()

or

i = 1 and

result = map.getValueType()

)

or

i = 0 and

result = rangeType.(RecvChanType).getElementType()

or

i = 0 and

result = rangeType.(SendRecvChanType).getElementType()

)

}

override ControlFlow::Root getRoot() { result.isRootOf(s) }

override string toString() { result = s + "[" + i + "]" }

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

}

/**

* An instruction that computes the zero value for a variable or constant.

*/

class EvalImplicitInitInstruction extends Instruction, MkZeroInitNode {

ValueEntity v;

EvalImplicitInitInstruction() { this = MkZeroInitNode(v) }

override Type getResultType() { result = v.getType() }

override ControlFlow::Root getRoot() { result.isRootOf(v.getDeclaration()) }

override int getIntValue() {

v.getType().getUnderlyingType() instanceof IntegerType and result = 0

}

override float getFloatValue() {

v.getType().getUnderlyingType() instanceof FloatType and result = 0.0

}

override string getStringValue() {

v.getType().getUnderlyingType() instanceof StringType and result = ""

}

override boolean getBoolValue() {

v.getType().getUnderlyingType() instanceof BoolType and result = false

}

override string getExactValue() {

result = this.getIntValue().toString() or

result = this.getFloatValue().toString() or

result = this.getStringValue().toString() or

result = this.getBoolValue().toString()

}

override predicate isConst() { any() }

override predicate isPlatformIndependentConstant() { any() }

override string toString() { result = "zero value for " + v }

override Location getLocation() { result = v.getDeclaration().getLocation() }

}

/**

* An instruction that corresponds to the declaration of a function.

*/

class DeclareFunctionInstruction extends Instruction, MkFuncDeclNode {

FuncDecl fd;

DeclareFunctionInstruction() { this = MkFuncDeclNode(fd) }

override Type getResultType() { result = fd.getType() }

override string toString() { result = fd.toString() }

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

}

/**

* An instruction that corresponds to a `defer` statement.

*/

class DeferInstruction extends Instruction, MkDeferNode {

DeferStmt defer;

DeferInstruction() { this = MkDeferNode(defer) }

override ControlFlow::Root getRoot() { result.isRootOf(defer) }

override string toString() { result = defer.toString() }

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

}

/**

* An instruction that corresponds to a `go` statement.

*/

class GoInstruction extends Instruction, MkGoNode {

GoStmt go;

GoInstruction() { this = MkGoNode(go) }

override ControlFlow::Root getRoot() { result.isRootOf(go) }

override string toString() { result = go.toString() }

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

}

/**

* An instruction that corresponds to an increment or decrement statement.

*/

class IncDecInstruction extends WriteInstruction, MkIncDecNode {

IncDecStmt ids;

IncDecInstruction() { this = MkIncDecNode(ids) }

override Instruction getRhs() { result = MkIncDecRhs(ids) }

override ControlFlow::Root getRoot() { result.isRootOf(ids) }

override string toString() { result = ids.toString() }

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

}

/**

* An instruction that computes the (implicit) right-hand side of an increment or

* decrement statement.

*/

class EvalIncDecRhsInstruction extends Instruction, MkIncDecRhs {

IncDecStmt ids;

EvalIncDecRhsInstruction() { this = MkIncDecRhs(ids) }

/** Gets the corresponding increment or decrement statement. */

IncDecStmt getStmt() { result = ids }

override Type getResultType() { result = ids.getOperand().getType() }

override ControlFlow::Root getRoot() { result.isRootOf(ids) }

override string toString() { result = "rhs of " + ids }

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

}

/**

* An instruction computing the implicit operand `1` in an increment or decrement statement.

*/

class EvalImplicitOneInstruction extends Instruction, MkImplicitOne {

IncDecStmt ids;

EvalImplicitOneInstruction() { this = MkImplicitOne(ids) }

/** Gets the corresponding increment or decrement statement. */

IncDecStmt getStmt() { result = ids }

override Type getResultType() { result = ids.getOperand().getType() }

override ControlFlow::Root getRoot() { result.isRootOf(ids) }

override int getIntValue() { result = 1 }

override string getExactValue() { result = "1" }

override predicate isConst() { any() }

override predicate isPlatformIndependentConstant() { any() }

override string toString() { result = "1" }

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

}

/**

* An instruction corresponding to a return from a function.

*/

class ReturnInstruction extends Instruction, MkReturnNode {

ReturnStmt ret;

ReturnInstruction() { this = MkReturnNode(ret) }

/** Gets the corresponding `ReturnStmt`. */

ReturnStmt getReturnStmt() { result = ret }

/** Holds if this statement returns multiple results. */

predicate returnsMultipleResults() { exists(MkExtractNode(ret, _)) or ret.getNumExpr() > 1 }

/** Gets the instruction whose result is the (unique) result returned by this statement. */

Instruction getResult() {

not this.returnsMultipleResults() and

result = evalExprInstruction(ret.getExpr())

}

/** Gets the instruction whose result is the `i`th result returned by this statement. */

Instruction getResult(int i) {

result = MkExtractNode(ret, i)

or

not exists(MkExtractNode(ret, _)) and

result = evalExprInstruction(ret.getExpr(i))

}

override ControlFlow::Root getRoot() { result.isRootOf(ret) }

override string toString() { result = ret.toString() }

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

}

/**

* An instruction that represents the implicit assignment to a result variable

* performed by a return statement.

*/

class WriteResultInstruction extends WriteInstruction, MkResultWriteNode {

ResultVariable var;

int i;

ReturnInstruction ret;

WriteResultInstruction() {

exists(ReturnStmt retstmt |

this = MkResultWriteNode(var, i, retstmt) and

ret = MkReturnNode(retstmt)

)

}

override Instruction getRhs() { result = ret.getResult(i) }

/** Gets the result variable being assigned. */

ResultVariable getResultVariable() { result = var }

override Type getResultType() { result = var.getType() }

override ControlFlow::Root getRoot() { var = result.(FuncDef).getAResultVar() }

override string toString() { result = "implicit write of " + var }

override Location getLocation() { result = ret.getResult(i).getLocation() }

}

/**

* An instruction that reads the final value of a result variable upon returning