Constant expression evaluation: support for arrays.
llvm-svn: 143922
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index a9408f6..746b094 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -132,6 +132,7 @@
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 @@
return EvalPointerValueAsBool(PointerResult, Result);
}
case APValue::Vector:
+ case APValue::Array:
return false;
}
@@ -569,6 +571,13 @@
// 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 @@
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 @@
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 @@
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 {
@@ -1600,6 +1637,55 @@
}
//===----------------------------------------------------------------------===//
+// 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
//
// As a GNU extension, we support casting pointers to sufficiently-wide integer
@@ -2173,6 +2259,10 @@
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 @@
// 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 @@
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 @@
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);