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Constant expression evaluation: support for arrays.

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llvm-svn: 143922
This commit is contained in:
Richard Smith 2011-11-07 09:22:26 +00:00
parent 6e47204b0c
commit f3e9e43da4
5 changed files with 275 additions and 55 deletions
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76
clang/include/clang/AST/APValue.h
View File

@ -25,7 +25,8 @@ namespace clang {
class Decl;
/// APValue - This class implements a discriminated union of [uninitialized]
/// [APSInt] [APFloat], [Complex APSInt] [Complex APFloat], [Expr + Offset].
/// [APSInt] [APFloat], [Complex APSInt] [Complex APFloat], [Expr + Offset],
/// [Vector: N * APValue], [Array: N * APValue]
class APValue {
typedef llvm::APSInt APSInt;
typedef llvm::APFloat APFloat;
@ -37,13 +38,15 @@ public:
ComplexInt,
ComplexFloat,
LValue,
Vector
Vector,
Array
};
union LValuePathEntry {
const Decl *BaseOrMember;
uint64_t ArrayIndex;
};
struct NoLValuePath {};
struct UninitArray {};
private:
ValueKind Kind;
@ -55,15 +58,19 @@ private:
APFloat Real, Imag;
ComplexAPFloat() : Real(0.0), Imag(0.0) {}
};
struct LV;
struct Vec {
APValue *Elts;
unsigned NumElts;
Vec() : Elts(0), NumElts(0) {}
~Vec() { delete[] Elts; }
};
struct LV;
struct Arr {
APValue *Elts;
unsigned NumElts, ArrSize;
Arr(unsigned NumElts, unsigned ArrSize);
~Arr();
};
enum {
MaxSize = (sizeof(ComplexAPSInt) > sizeof(ComplexAPFloat) ?
@ -104,6 +111,9 @@ public:
MakeLValue(); setLValue(B, O, Path);
}
APValue(const Expr *B);
APValue(UninitArray, unsigned InitElts, unsigned Size) : Kind(Uninitialized) {
MakeArray(InitElts, Size);
}
~APValue() {
MakeUninit();
@ -117,6 +127,7 @@ public:
bool isComplexFloat() const { return Kind == ComplexFloat; }
bool isLValue() const { return Kind == LValue; }
bool isVector() const { return Kind == Vector; }
bool isArray() const { return Kind == Array; }
void print(raw_ostream &OS) const;
void dump() const;
@ -137,19 +148,6 @@ public:
return const_cast<APValue*>(this)->getFloat();
}
APValue &getVectorElt(unsigned i) {
assert(isVector() && "Invalid accessor");
return ((Vec*)(char*)Data)->Elts[i];
}
const APValue &getVectorElt(unsigned i) const {
assert(isVector() && "Invalid accessor");
return ((const Vec*)(const char*)Data)->Elts[i];
}
unsigned getVectorLength() const {
assert(isVector() && "Invalid accessor");
return ((const Vec*)(const void *)Data)->NumElts;
}
APSInt &getComplexIntReal() {
assert(isComplexInt() && "Invalid accessor");
return ((ComplexAPSInt*)(char*)Data)->Real;
@ -190,6 +188,47 @@ public:
bool hasLValuePath() const;
ArrayRef<LValuePathEntry> getLValuePath() const;
APValue &getVectorElt(unsigned I) {
assert(isVector() && "Invalid accessor");
assert(I < getVectorLength() && "Index out of range");
return ((Vec*)(char*)Data)->Elts[I];
}
const APValue &getVectorElt(unsigned I) const {
return const_cast<APValue*>(this)->getVectorElt(I);
}
unsigned getVectorLength() const {
assert(isVector() && "Invalid accessor");
return ((const Vec*)(const void *)Data)->NumElts;
}
APValue &getArrayInitializedElt(unsigned I) {
assert(isArray() && "Invalid accessor");
assert(I < getArrayInitializedElts() && "Index out of range");
return ((Arr*)(char*)Data)->Elts[I];
}
const APValue &getArrayInitializedElt(unsigned I) const {
return const_cast<APValue*>(this)->getArrayInitializedElt(I);
}
bool hasArrayFiller() const {
return getArrayInitializedElts() != getArraySize();
}
APValue &getArrayFiller() {
assert(isArray() && "Invalid accessor");
assert(hasArrayFiller() && "No array filler");
return ((Arr*)(char*)Data)->Elts[getArrayInitializedElts()];
}
const APValue &getArrayFiller() const {
return const_cast<APValue*>(this)->getArrayFiller();
}
unsigned getArrayInitializedElts() const {
assert(isArray() && "Invalid accessor");
return ((const Arr*)(const void *)Data)->NumElts;
}
unsigned getArraySize() const {
assert(isArray() && "Invalid accessor");
return ((const Arr*)(const void *)Data)->ArrSize;
}
void setInt(const APSInt &I) {
assert(isInt() && "Invalid accessor");
*(APSInt*)(char*)Data = I;
@ -253,6 +292,7 @@ private:
Kind = ComplexFloat;
}
void MakeLValue();
void MakeArray(unsigned InitElts, unsigned Size);
};
inline raw_ostream &operator<<(raw_ostream &OS, const APValue &V) {

45
clang/lib/AST/APValue.cpp
View File

@ -55,6 +55,13 @@ struct APValue::LV : LVBase {
}
};
// FIXME: Reduce the malloc traffic here.
APValue::Arr::Arr(unsigned NumElts, unsigned Size) :
Elts(new APValue[NumElts + (NumElts != Size ? 1 : 0)]),
NumElts(NumElts), ArrSize(Size) {}
APValue::Arr::~Arr() { delete [] Elts; }
APValue::APValue(const Expr* B) : Kind(Uninitialized) {
MakeLValue();
setLValue(B, CharUnits::Zero(), ArrayRef<LValuePathEntry>());
@ -75,6 +82,8 @@ const APValue &APValue::operator=(const APValue &RHS) {
MakeComplexFloat();
else if (RHS.isLValue())
MakeLValue();
else if (RHS.isArray())
MakeArray(RHS.getArrayInitializedElts(), RHS.getArraySize());
}
if (isInt())
setInt(RHS.getInt());
@ -92,6 +101,11 @@ const APValue &APValue::operator=(const APValue &RHS) {
setLValue(RHS.getLValueBase(), RHS.getLValueOffset(),RHS.getLValuePath());
else
setLValue(RHS.getLValueBase(), RHS.getLValueOffset(), NoLValuePath());
} else if (isArray()) {
for (unsigned I = 0, N = RHS.getArrayInitializedElts(); I != N; ++I)
getArrayInitializedElt(I) = RHS.getArrayInitializedElt(I);
if (RHS.hasArrayFiller())
getArrayFiller() = RHS.getArrayFiller();
}
return *this;
}
@ -107,9 +121,10 @@ void APValue::MakeUninit() {
((ComplexAPSInt*)(char*)Data)->~ComplexAPSInt();
else if (Kind == ComplexFloat)
((ComplexAPFloat*)(char*)Data)->~ComplexAPFloat();
else if (Kind == LValue) {
else if (Kind == LValue)
((LV*)(char*)Data)->~LV();
}
else if (Kind == Array)
((Arr*)(char*)Data)->~Arr();
Kind = Uninitialized;
}
@ -149,9 +164,20 @@ void APValue::print(raw_ostream &OS) const {
case ComplexFloat:
OS << "ComplexFloat: " << GetApproxValue(getComplexFloatReal())
<< ", " << GetApproxValue(getComplexFloatImag());
return;
case LValue:
OS << "LValue: <todo>";
return;
case Array:
OS << "Array: ";
for (unsigned I = 0, N = getArrayInitializedElts(); I != N; ++I) {
OS << getArrayInitializedElt(I);
if (I != getArraySize() - 1) OS << ", ";
}
if (hasArrayFiller())
OS << getArraySize() - getArrayInitializedElts() << " x "
<< getArrayFiller();
return;
}
}
@ -187,6 +213,15 @@ static void WriteShortAPValueToStream(raw_ostream& Out,
case APValue::LValue:
Out << "LValue: <todo>";
break;
case APValue::Array:
Out << '{';
if (unsigned N = V.getArrayInitializedElts()) {
Out << V.getArrayInitializedElt(0);
for (unsigned I = 1; I != N; ++I)
Out << ", " << V.getArrayInitializedElt(I);
}
Out << '}';
break;
}
}
@ -244,3 +279,9 @@ void APValue::MakeLValue() {
new ((void*)(char*)Data) LV();
Kind = LValue;
}
void APValue::MakeArray(unsigned InitElts, unsigned Size) {
assert(isUninit() && "Bad state change");
new ((void*)(char*)Data) Arr(InitElts, Size);
Kind = Array;
}

164
clang/lib/AST/ExprConstant.cpp
View File

@ -132,6 +132,7 @@ namespace {
void adjustIndex(uint64_t N) {
if (Invalid) return;
if (ArrayElement) {
// FIXME: Make sure the index stays within bounds, or one past the end.
Entries.back().ArrayIndex += N;
return;
}
@ -475,6 +476,7 @@ static bool HandleConversionToBool(const CCValue &Val, bool &Result) {
return EvalPointerValueAsBool(PointerResult, Result);
}
case APValue::Vector:
case APValue::Array:
return false;
}
@ -569,6 +571,13 @@ static bool EvaluateVarDeclInit(EvalInfo &Info, const VarDecl *VD,
// expression. If not, we should propagate up a diagnostic.
APValue EvalResult;
if (!EvaluateConstantExpression(EvalResult, InitInfo, Init)) {
// FIXME: If the evaluation failure was not permanent (for instance, if we
// hit a variable with no declaration yet, or a constexpr function with no
// definition yet), the standard is unclear as to how we should behave.
//
// Either the initializer should be evaluated when the variable is defined,
// or a failed evaluation of the initializer should be reattempted each time
// it is used.
VD->setEvaluatedValue(APValue());
return false;
}
@ -583,8 +592,48 @@ static bool IsConstNonVolatile(QualType T) {
return Quals.hasConst() && !Quals.hasVolatile();
}
bool HandleLValueToRValueConversion(EvalInfo &Info, QualType Type,
const LValue &LVal, CCValue &RVal) {
/// Extract the designated sub-object of an rvalue.
static bool ExtractSubobject(EvalInfo &Info, CCValue &Obj, QualType ObjType,
const SubobjectDesignator &Sub, QualType SubType) {
if (Sub.Invalid || Sub.OnePastTheEnd)
return false;
if (Sub.Entries.empty()) {
assert(Info.Ctx.hasSameUnqualifiedType(ObjType, SubType) &&
"Unexpected subobject type");
return true;
}
assert(!Obj.isLValue() && "extracting subobject of lvalue");
const APValue *O = &Obj;
for (unsigned I = 0, N = Sub.Entries.size(); I != N; ++I) {
if (O->isUninit())
return false;
if (ObjType->isArrayType()) {
const ConstantArrayType *CAT = Info.Ctx.getAsConstantArrayType(ObjType);
if (!CAT)
return false;
uint64_t Index = Sub.Entries[I].ArrayIndex;
if (CAT->getSize().ule(Index))
return false;
if (O->getArrayInitializedElts() > Index)
O = &O->getArrayInitializedElt(Index);
else
O = &O->getArrayFiller();
ObjType = CAT->getElementType();
} else {
// FIXME: Support handling of subobjects of structs and unions. Also
// for vector elements, if we want to support those?
}
}
assert(Info.Ctx.hasSameUnqualifiedType(ObjType, SubType) &&
"Unexpected subobject type");
Obj = CCValue(*O, CCValue::GlobalValue());
return true;
}
static bool HandleLValueToRValueConversion(EvalInfo &Info, QualType Type,
const LValue &LVal, CCValue &RVal) {
const Expr *Base = LVal.Base;
CallStackFrame *Frame = LVal.Frame;
@ -620,10 +669,7 @@ bool HandleLValueToRValueConversion(EvalInfo &Info, QualType Type,
return false;
if (isa<ParmVarDecl>(VD) || !VD->getAnyInitializer()->isLValue())
// If the lvalue refers to a subobject or has been cast to some other
// type, don't use it.
return LVal.Offset.isZero() &&
Info.Ctx.hasSameUnqualifiedType(Type, VT);
return ExtractSubobject(Info, RVal, VT, LVal.Designator, Type);
// The declaration was initialized by an lvalue, with no lvalue-to-rvalue
// conversion. This happens when the declaration and the lvalue should be
@ -654,31 +700,22 @@ bool HandleLValueToRValueConversion(EvalInfo &Info, QualType Type,
return true;
}
// FIXME: Support accessing subobjects of objects of literal types. A simple
// byte offset is insufficient for C++11 semantics: we need to know how the
// reference was formed (which union member was named, for instance).
// Beyond this point, we don't support accessing subobjects.
if (!LVal.Offset.isZero() ||
!Info.Ctx.hasSameUnqualifiedType(Type, Base->getType()))
if (Frame) {
// If this is a temporary expression with a nontrivial initializer, grab the
// value from the relevant stack frame.
RVal = Frame->Temporaries[Base];
} else if (const CompoundLiteralExpr *CLE
= dyn_cast<CompoundLiteralExpr>(Base)) {
// In C99, a CompoundLiteralExpr is an lvalue, and we defer evaluating the
// initializer until now for such expressions. Such an expression can't be
// an ICE in C, so this only matters for fold.
assert(!Info.getLangOpts().CPlusPlus && "lvalue compound literal in c++?");
if (!Evaluate(RVal, Info, CLE->getInitializer()))
return false;
} else
return false;
// If this is a temporary expression with a nontrivial initializer, grab the
// value from the relevant stack frame.
if (Frame) {
RVal = Frame->Temporaries[Base];
return true;
}
// In C99, a CompoundLiteralExpr is an lvalue, and we defer evaluating the
// initializer until now for such expressions. Such an expression can't be
// an ICE in C, so this only matters for fold.
if (const CompoundLiteralExpr *CLE = dyn_cast<CompoundLiteralExpr>(Base)) {
assert(!Info.getLangOpts().CPlusPlus && "lvalue compound literal in c++?");
return Evaluate(RVal, Info, CLE->getInitializer());
}
return false;
return ExtractSubobject(Info, RVal, Base->getType(), LVal.Designator, Type);
}
namespace {
@ -1599,6 +1636,55 @@ bool VectorExprEvaluator::VisitUnaryImag(const UnaryOperator *E) {
return ValueInitialization(E);
}
//===----------------------------------------------------------------------===//
// Array Evaluation
//===----------------------------------------------------------------------===//
namespace {
class ArrayExprEvaluator
: public ExprEvaluatorBase<ArrayExprEvaluator, bool> {
APValue &Result;
public:
ArrayExprEvaluator(EvalInfo &Info, APValue &Result)
: ExprEvaluatorBaseTy(Info), Result(Result) {}
bool Success(const APValue &V, const Expr *E) {
assert(V.isArray() && "Expected array type");
Result = V;
return true;
}
bool Error(const Expr *E) { return false; }
bool VisitInitListExpr(const InitListExpr *E);
};
} // end anonymous namespace
static bool EvaluateArray(const Expr* E, APValue& Result, EvalInfo &Info) {
assert(E->isRValue() && E->getType()->isArrayType() &&
E->getType()->isLiteralType() && "not a literal array rvalue");
return ArrayExprEvaluator(Info, Result).Visit(E);
}
bool ArrayExprEvaluator::VisitInitListExpr(const InitListExpr *E) {
const ConstantArrayType *CAT = Info.Ctx.getAsConstantArrayType(E->getType());
if (!CAT)
return false;
Result = APValue(APValue::UninitArray(), E->getNumInits(),
CAT->getSize().getZExtValue());
for (InitListExpr::const_iterator I = E->begin(), End = E->end();
I != End; ++I)
if (!EvaluateConstantExpression(Result.getArrayInitializedElt(I-E->begin()),
Info, cast<Expr>(*I)))
return false;
if (!Result.hasArrayFiller()) return true;
assert(E->hasArrayFiller() && "no array filler for incomplete init list");
return EvaluateConstantExpression(Result.getArrayFiller(), Info,
E->getArrayFiller());
}
//===----------------------------------------------------------------------===//
// Integer Evaluation
//
@ -2173,6 +2259,10 @@ bool IntExprEvaluator::VisitBinaryOperator(const BinaryOperator *E) {
return Success(E->getOpcode() == BO_NE, E);
}
// FIXME: Implement the C++11 restrictions:
// - Pointer subtractions must be on elements of the same array.
// - Pointer comparisons must be between members with the same access.
if (E->getOpcode() == BO_Sub) {
QualType Type = E->getLHS()->getType();
QualType ElementType = Type->getAs<PointerType>()->getPointeeType();
@ -3258,8 +3348,8 @@ static bool Evaluate(CCValue &Result, EvalInfo &Info, const Expr *E) {
// FIXME: Implement evaluation of pointer-to-member types.
return false;
} else if (E->getType()->isArrayType() && E->getType()->isLiteralType()) {
// FIXME: Implement evaluation of array rvalues.
return false;
if (!EvaluateArray(E, Result, Info))
return false;
} else if (E->getType()->isRecordType() && E->getType()->isLiteralType()) {
// FIXME: Implement evaluation of record rvalues.
return false;
@ -3278,10 +3368,10 @@ static bool EvaluateConstantExpression(APValue &Result, EvalInfo &Info,
if (E->isRValue() && E->getType()->isLiteralType()) {
// Evaluate arrays and record types in-place, so that later initializers can
// refer to earlier-initialized members of the object.
if (E->getType()->isArrayType())
// FIXME: Implement evaluation of array rvalues.
return false;
else if (E->getType()->isRecordType())
if (E->getType()->isArrayType()) {
if (!EvaluateArray(E, Result, Info))
return false;
} else if (E->getType()->isRecordType())
// FIXME: Implement evaluation of record rvalues.
return false;
}
@ -3312,6 +3402,10 @@ bool Expr::EvaluateAsRValue(EvalResult &Result, const ASTContext &Ctx) const {
return false;
}
// Don't produce array constants until CodeGen is taught to handle them.
if (Value.isArray())
return false;
// Check this core constant expression is a constant expression, and if so,
// convert it to one.
return CheckConstantExpression(Value, Result.Val);

3
clang/lib/CodeGen/CGExprConstant.cpp
View File

@ -1070,6 +1070,9 @@ llvm::Constant *CodeGenModule::EmitConstantExpr(const Expr *E,
}
return llvm::ConstantVector::get(Inits);
}
case APValue::Array:
assert(0 && "shouldn't see array constants here yet");
break;
}
}

42
clang/test/SemaCXX/constant-expression-cxx11.cpp
View File

@ -280,3 +280,45 @@ static_assert_fold(*max == 'z', "");
static_assert_fold(max == str + 38, "");
}
namespace Array {
// FIXME: Use templates for these once we support constexpr templates.
constexpr int Sum(const int *begin, const int *end) {
return begin == end ? 0 : *begin + Sum(begin+1, end);
}
constexpr const int *begin(const int (&xs)[5]) { return xs; }
constexpr const int *end(const int (&xs)[5]) { return xs + 5; }
constexpr int xs[] = { 1, 2, 3, 4, 5 };
constexpr int ys[] = { 5, 4, 3, 2, 1 };
constexpr int sum_xs = Sum(begin(xs), end(xs));
static_assert_fold(sum_xs == 15, "");
constexpr int ZipFoldR(int (*F)(int x, int y, int c), int n,
const int *xs, const int *ys, int c) {
return n ? F(*xs, *ys, ZipFoldR(F, n-1, xs+1, ys+1, c)) : c;
}
constexpr int MulAdd(int x, int y, int c) { return x * y + c; }
constexpr int InnerProduct = ZipFoldR(MulAdd, 5, xs, ys, 0);
static_assert_fold(InnerProduct == 35, "");
constexpr int SubMul(int x, int y, int c) { return (x - y) * c; }
constexpr int DiffProd = ZipFoldR(SubMul, 2, xs+3, ys+3, 1);
static_assert_fold(DiffProd == 8, "");
static_assert_fold(ZipFoldR(SubMul, 3, xs+3, ys+3, 1), ""); // expected-error {{constant expression}}
constexpr const int *p = xs + 3;
constexpr int xs4 = p[1]; // ok
constexpr int xs5 = p[2]; // expected-error {{constant expression}}
constexpr int xs0 = p[-3]; // ok
constexpr int xs_1 = p[-4]; // expected-error {{constant expression}}
constexpr int zs[2][2][2][2] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 };
static_assert_fold(zs[0][0][0][0] == 1, "");
static_assert_fold(zs[1][1][1][1] == 16, "");
static_assert_fold(zs[0][0][0][2] == 3, ""); // expected-error {{constant expression}}
static_assert_fold((&zs[0][0][0][2])[-1] == 2, "");
static_assert_fold(**(**(zs + 1) + 1) == 11, "");
}