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llvm-project/clang/lib/AST/ExprConstant.cpp

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//===--- ExprConstant.cpp - Expression Constant Evaluator -----------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the Expr constant evaluator.
//
//===----------------------------------------------------------------------===//
#include "clang/AST/APValue.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/StmtVisitor.h"
#include "clang/Basic/Diagnostic.h"
#include "clang/Basic/TargetInfo.h"
#include "llvm/Support/Compiler.h"
using namespace clang;
using llvm::APSInt;
using llvm::APFloat;
/// EvalInfo - This is a private struct used by the evaluator to capture
/// information about a subexpression as it is folded. It retains information
/// about the AST context, but also maintains information about the folded
/// expression.
///
/// If an expression could be evaluated, it is still possible it is not a C
/// "integer constant expression" or constant expression. If not, this struct
/// captures information about how and why not.
///
/// One bit of information passed *into* the request for constant folding
/// indicates whether the subexpression is "evaluated" or not according to C
/// rules. For example, the RHS of (0 && foo()) is not evaluated. We can
/// evaluate the expression regardless of what the RHS is, but C only allows
/// certain things in certain situations.
struct EvalInfo {
ASTContext &Ctx;
/// isEvaluated - True if the subexpression is required to be evaluated, false
/// if it is short-circuited (according to C rules).
bool isEvaluated;
/// ICEDiag - If the expression is unfoldable, then ICEDiag contains the
/// error diagnostic indicating why it is not foldable and DiagLoc indicates a
/// caret position for the error. If it is foldable, but the expression is
/// not an integer constant expression, ICEDiag contains the extension
/// diagnostic to emit which describes why it isn't an integer constant
/// expression. If this expression *is* an integer-constant-expr, then
/// ICEDiag is zero.
///
/// The caller can choose to emit this diagnostic or not, depending on whether
/// they require an i-c-e or a constant or not. DiagLoc indicates the caret
/// position for the report.
///
/// If ICEDiag is zero, then this expression is an i-c-e.
unsigned ICEDiag;
SourceLocation DiagLoc;
EvalInfo(ASTContext &ctx) : Ctx(ctx), isEvaluated(true), ICEDiag(0) {}
};
static bool EvaluatePointer(const Expr *E, APValue &Result, EvalInfo &Info);
static bool EvaluateInteger(const Expr *E, APSInt &Result, EvalInfo &Info);
static bool EvaluateFloat(const Expr *E, APFloat &Result, EvalInfo &Info);
//===----------------------------------------------------------------------===//
// Pointer Evaluation
//===----------------------------------------------------------------------===//
namespace {
class VISIBILITY_HIDDEN PointerExprEvaluator
: public StmtVisitor<PointerExprEvaluator, APValue> {
EvalInfo &Info;
public:
PointerExprEvaluator(EvalInfo &info) : Info(info) {}
APValue VisitStmt(Stmt *S) {
return APValue();
}
APValue VisitParenExpr(ParenExpr *E) { return Visit(E->getSubExpr()); }
APValue VisitBinaryOperator(const BinaryOperator *E);
APValue VisitCastExpr(const CastExpr* E);
};
} // end anonymous namespace
static bool EvaluatePointer(const Expr* E, APValue& Result, EvalInfo &Info) {
if (!E->getType()->isPointerType())
return false;
Result = PointerExprEvaluator(Info).Visit(const_cast<Expr*>(E));
return Result.isLValue();
}
APValue PointerExprEvaluator::VisitBinaryOperator(const BinaryOperator *E) {
if (E->getOpcode() != BinaryOperator::Add &&
E->getOpcode() != BinaryOperator::Sub)
return APValue();
const Expr *PExp = E->getLHS();
const Expr *IExp = E->getRHS();
if (IExp->getType()->isPointerType())
std::swap(PExp, IExp);
APValue ResultLValue;
if (!EvaluatePointer(PExp, ResultLValue, Info))
return APValue();
llvm::APSInt AdditionalOffset(32);
if (!EvaluateInteger(IExp, AdditionalOffset, Info))
return APValue();
uint64_t Offset = ResultLValue.getLValueOffset();
if (E->getOpcode() == BinaryOperator::Add)
Offset += AdditionalOffset.getZExtValue();
else
Offset -= AdditionalOffset.getZExtValue();
return APValue(ResultLValue.getLValueBase(), Offset);
}
APValue PointerExprEvaluator::VisitCastExpr(const CastExpr* E) {
const Expr* SubExpr = E->getSubExpr();
// Check for pointer->pointer cast
if (SubExpr->getType()->isPointerType()) {
APValue Result;
if (EvaluatePointer(SubExpr, Result, Info))
return Result;
return APValue();
}
if (SubExpr->getType()->isIntegralType()) {
llvm::APSInt Result(32);
if (EvaluateInteger(SubExpr, Result, Info)) {
Result.extOrTrunc((unsigned)Info.Ctx.getTypeSize(E->getType()));
return APValue(0, Result.getZExtValue());
}
}
assert(0 && "Unhandled cast");
return APValue();
}
//===----------------------------------------------------------------------===//
// Integer Evaluation
//===----------------------------------------------------------------------===//
namespace {
class VISIBILITY_HIDDEN IntExprEvaluator
: public StmtVisitor<IntExprEvaluator, bool> {
EvalInfo &Info;
APSInt &Result;
public:
IntExprEvaluator(EvalInfo &info, APSInt &result)
: Info(info), Result(result) {}
unsigned getIntTypeSizeInBits(QualType T) const {
return (unsigned)Info.Ctx.getIntWidth(T);
}
bool Extension(SourceLocation L, diag::kind D) {
Info.DiagLoc = L;
Info.ICEDiag = D;
return true; // still a constant.
}
bool Error(SourceLocation L, diag::kind D, QualType ExprTy) {
// If this is in an unevaluated portion of the subexpression, ignore the
// error.
if (!Info.isEvaluated) {
// If error is ignored because the value isn't evaluated, get the real
// type at least to prevent errors downstream.
Result.zextOrTrunc(getIntTypeSizeInBits(ExprTy));
Result.setIsUnsigned(ExprTy->isUnsignedIntegerType());
return true;
}
// Take the first error.
if (Info.ICEDiag == 0) {
Info.DiagLoc = L;
Info.ICEDiag = D;
}
return false;
}
//===--------------------------------------------------------------------===//
// Visitor Methods
//===--------------------------------------------------------------------===//
bool VisitStmt(Stmt *) {
assert(0 && "This should be called on integers, stmts are not integers");
return false;
}
bool VisitExpr(Expr *E) {
return Error(E->getLocStart(), diag::err_expr_not_constant, E->getType());
}
bool VisitParenExpr(ParenExpr *E) { return Visit(E->getSubExpr()); }
bool VisitIntegerLiteral(const IntegerLiteral *E) {
Result = E->getValue();
Result.setIsUnsigned(E->getType()->isUnsignedIntegerType());
return true;
}
bool VisitCharacterLiteral(const CharacterLiteral *E) {
Result.zextOrTrunc(getIntTypeSizeInBits(E->getType()));
Result = E->getValue();
Result.setIsUnsigned(E->getType()->isUnsignedIntegerType());
return true;
}
bool VisitTypesCompatibleExpr(const TypesCompatibleExpr *E) {
Result.zextOrTrunc(getIntTypeSizeInBits(E->getType()));
// Per gcc docs "this built-in function ignores top level
// qualifiers". We need to use the canonical version to properly
// be able to strip CRV qualifiers from the type.
QualType T0 = Info.Ctx.getCanonicalType(E->getArgType1());
QualType T1 = Info.Ctx.getCanonicalType(E->getArgType2());
Result = Info.Ctx.typesAreCompatible(T0.getUnqualifiedType(),
T1.getUnqualifiedType());
return true;
}
bool VisitDeclRefExpr(const DeclRefExpr *E);
bool VisitCallExpr(const CallExpr *E);
bool VisitBinaryOperator(const BinaryOperator *E);
bool VisitUnaryOperator(const UnaryOperator *E);
bool VisitCastExpr(CastExpr* E) {
return HandleCast(E->getLocStart(), E->getSubExpr(), E->getType());
}
bool VisitSizeOfAlignOfExpr(const SizeOfAlignOfExpr *E);
private:
bool HandleCast(SourceLocation CastLoc, Expr *SubExpr, QualType DestType);
};
} // end anonymous namespace
static bool EvaluateInteger(const Expr* E, APSInt &Result, EvalInfo &Info) {
return IntExprEvaluator(Info, Result).Visit(const_cast<Expr*>(E));
}
bool IntExprEvaluator::VisitDeclRefExpr(const DeclRefExpr *E) {
// Enums are integer constant exprs.
if (const EnumConstantDecl *D = dyn_cast<EnumConstantDecl>(E->getDecl())) {
Result = D->getInitVal();
return true;
}
// Otherwise, random variable references are not constants.
return Error(E->getLocStart(), diag::err_expr_not_constant, E->getType());
}
/// EvaluateBuiltinClassifyType - Evaluate __builtin_classify_type the same way
/// as GCC.
static int EvaluateBuiltinClassifyType(const CallExpr *E) {
// The following enum mimics the values returned by GCC.
enum gcc_type_class {
no_type_class = -1,
void_type_class, integer_type_class, char_type_class,
enumeral_type_class, boolean_type_class,
pointer_type_class, reference_type_class, offset_type_class,
real_type_class, complex_type_class,
function_type_class, method_type_class,
record_type_class, union_type_class,
array_type_class, string_type_class,
lang_type_class
};
// If no argument was supplied, default to "no_type_class". This isn't
// ideal, however it is what gcc does.
if (E->getNumArgs() == 0)
return no_type_class;
QualType ArgTy = E->getArg(0)->getType();
if (ArgTy->isVoidType())
return void_type_class;
else if (ArgTy->isEnumeralType())
return enumeral_type_class;
else if (ArgTy->isBooleanType())
return boolean_type_class;
else if (ArgTy->isCharType())
return string_type_class; // gcc doesn't appear to use char_type_class
else if (ArgTy->isIntegerType())
return integer_type_class;
else if (ArgTy->isPointerType())
return pointer_type_class;
else if (ArgTy->isReferenceType())
return reference_type_class;
else if (ArgTy->isRealType())
return real_type_class;
else if (ArgTy->isComplexType())
return complex_type_class;
else if (ArgTy->isFunctionType())
return function_type_class;
else if (ArgTy->isStructureType())
return record_type_class;
else if (ArgTy->isUnionType())
return union_type_class;
else if (ArgTy->isArrayType())
return array_type_class;
else if (ArgTy->isUnionType())
return union_type_class;
else // FIXME: offset_type_class, method_type_class, & lang_type_class?
assert(0 && "CallExpr::isBuiltinClassifyType(): unimplemented type");
return -1;
}
bool IntExprEvaluator::VisitCallExpr(const CallExpr *E) {
Result.zextOrTrunc(getIntTypeSizeInBits(E->getType()));
switch (E->isBuiltinCall()) {
default:
return Error(E->getLocStart(), diag::err_expr_not_constant, E->getType());
case Builtin::BI__builtin_classify_type:
Result.setIsSigned(true);
Result = EvaluateBuiltinClassifyType(E);
return true;
case Builtin::BI__builtin_constant_p: {
// __builtin_constant_p always has one operand: it returns true if that
// operand can be folded, false otherwise.
APValue Res;
Result = E->getArg(0)->tryEvaluate(Res, Info.Ctx);
return true;
}
}
}
bool IntExprEvaluator::VisitBinaryOperator(const BinaryOperator *E) {
// The LHS of a constant expr is always evaluated and needed.
llvm::APSInt RHS(32);
if (!Visit(E->getLHS())) {
// If the LHS is unfoldable, we generally can't fold this. However, if this
// is a logical operator like &&/||, and if we know that the RHS determines
// the outcome of the result (e.g. X && 0), return the outcome.
if (!E->isLogicalOp())
return false;
// If this is a logical op, see if the RHS determines the outcome.
EvalInfo Info2(Info.Ctx);
if (!EvaluateInteger(E->getRHS(), RHS, Info2))
return false;
// X && 0 -> 0, X || 1 -> 1.
if (E->getOpcode() == BinaryOperator::LAnd && RHS == 0 ||
E->getOpcode() == BinaryOperator::LOr && RHS != 0) {
Result = RHS != 0;
Result.zextOrTrunc(getIntTypeSizeInBits(E->getType()));
Result.setIsUnsigned(E->getType()->isUnsignedIntegerType());
return true;
}
return false; // error in subexpression.
}
bool OldEval = Info.isEvaluated;
// The short-circuiting &&/|| operators don't necessarily evaluate their
// RHS. Make sure to pass isEvaluated down correctly.
if ((E->getOpcode() == BinaryOperator::LAnd && Result == 0) ||
(E->getOpcode() == BinaryOperator::LOr && Result != 0))
Info.isEvaluated = false;
// FIXME: Handle pointer subtraction
// FIXME Maybe we want to succeed even where we can't evaluate the
// right side of LAnd/LOr?
// For example, see http://llvm.org/bugs/show_bug.cgi?id=2525
if (!EvaluateInteger(E->getRHS(), RHS, Info))
return false;
Info.isEvaluated = OldEval;
switch (E->getOpcode()) {
default:
return Error(E->getOperatorLoc(), diag::err_expr_not_constant,E->getType());
case BinaryOperator::Mul: Result *= RHS; return true;
case BinaryOperator::Add: Result += RHS; return true;
case BinaryOperator::Sub: Result -= RHS; return true;
case BinaryOperator::And: Result &= RHS; return true;
case BinaryOperator::Xor: Result ^= RHS; return true;
case BinaryOperator::Or: Result |= RHS; return true;
case BinaryOperator::Div:
if (RHS == 0)
return Error(E->getOperatorLoc(), diag::err_expr_divide_by_zero,
E->getType());
Result /= RHS;
break;
case BinaryOperator::Rem:
if (RHS == 0)
return Error(E->getOperatorLoc(), diag::err_expr_divide_by_zero,
E->getType());
Result %= RHS;
break;
case BinaryOperator::Shl:
// FIXME: Warn about out of range shift amounts!
Result <<= (unsigned)RHS.getLimitedValue(Result.getBitWidth()-1);
break;
case BinaryOperator::Shr:
Result >>= (unsigned)RHS.getLimitedValue(Result.getBitWidth()-1);
break;
case BinaryOperator::LT:
Result = Result < RHS;
Result.zextOrTrunc(getIntTypeSizeInBits(E->getType()));
break;
case BinaryOperator::GT:
Result = Result > RHS;
Result.zextOrTrunc(getIntTypeSizeInBits(E->getType()));
break;
case BinaryOperator::LE:
Result = Result <= RHS;
Result.zextOrTrunc(getIntTypeSizeInBits(E->getType()));
break;
case BinaryOperator::GE:
Result = Result >= RHS;
Result.zextOrTrunc(getIntTypeSizeInBits(E->getType()));
break;
case BinaryOperator::EQ:
Result = Result == RHS;
Result.zextOrTrunc(getIntTypeSizeInBits(E->getType()));
break;
case BinaryOperator::NE:
Result = Result != RHS;
Result.zextOrTrunc(getIntTypeSizeInBits(E->getType()));
break;
case BinaryOperator::LAnd:
Result = Result != 0 && RHS != 0;
Result.zextOrTrunc(getIntTypeSizeInBits(E->getType()));
break;
case BinaryOperator::LOr:
Result = Result != 0 || RHS != 0;
Result.zextOrTrunc(getIntTypeSizeInBits(E->getType()));
break;
case BinaryOperator::Comma:
// Result of the comma is just the result of the RHS.
Result = RHS;
// C99 6.6p3: "shall not contain assignment, ..., or comma operators,
// *except* when they are contained within a subexpression that is not
// evaluated". Note that Assignment can never happen due to constraints
// on the LHS subexpr, so we don't need to check it here.
if (!Info.isEvaluated)
return true;
// If the value is evaluated, we can accept it as an extension.
return Extension(E->getOperatorLoc(), diag::ext_comma_in_constant_expr);
}
Result.setIsUnsigned(E->getType()->isUnsignedIntegerType());
return true;
}
/// VisitSizeAlignOfExpr - Evaluate a sizeof or alignof with a result as the
/// expression's type.
bool IntExprEvaluator::VisitSizeOfAlignOfExpr(const SizeOfAlignOfExpr *E) {
QualType DstTy = E->getType();
// Return the result in the right width.
Result.zextOrTrunc(getIntTypeSizeInBits(DstTy));
Result.setIsUnsigned(DstTy->isUnsignedIntegerType());
QualType SrcTy = E->getTypeOfArgument();
// sizeof(void) and __alignof__(void) = 1 as a gcc extension.
if (SrcTy->isVoidType())
Result = 1;
// sizeof(vla) is not a constantexpr: C99 6.5.3.4p2.
if (!SrcTy->isConstantSizeType()) {
// FIXME: Should we attempt to evaluate this?
return false;
}
bool isSizeOf = E->isSizeOf();
// GCC extension: sizeof(function) = 1.
if (SrcTy->isFunctionType()) {
// FIXME: AlignOf shouldn't be unconditionally 4!
Result = isSizeOf ? 1 : 4;
return true;
}
// Get information about the size or align.
unsigned CharSize = Info.Ctx.Target.getCharWidth();
if (isSizeOf)
Result = getIntTypeSizeInBits(SrcTy) / CharSize;
else
Result = Info.Ctx.getTypeAlign(SrcTy) / CharSize;
return true;
}
bool IntExprEvaluator::VisitUnaryOperator(const UnaryOperator *E) {
// Special case unary operators that do not need their subexpression
// evaluated. offsetof/sizeof/alignof are all special.
if (E->isOffsetOfOp()) {
Result.zextOrTrunc(getIntTypeSizeInBits(E->getType()));
Result = E->evaluateOffsetOf(Info.Ctx);
Result.setIsUnsigned(E->getType()->isUnsignedIntegerType());
return true;
}
// Get the operand value into 'Result'.
if (!Visit(E->getSubExpr()))
return false;
switch (E->getOpcode()) {
default:
// Address, indirect, pre/post inc/dec, etc are not valid constant exprs.
// See C99 6.6p3.
return Error(E->getOperatorLoc(), diag::err_expr_not_constant,
E->getType());
case UnaryOperator::LNot: {
bool Val = Result == 0;
Result.zextOrTrunc(getIntTypeSizeInBits(E->getType()));
Result = Val;
break;
}
case UnaryOperator::Extension:
// FIXME: Should extension allow i-c-e extension expressions in its scope?
// If so, we could clear the diagnostic ID.
case UnaryOperator::Plus:
// The result is always just the subexpr.
break;
case UnaryOperator::Minus:
Result = -Result;
break;
case UnaryOperator::Not:
Result = ~Result;
break;
}
Result.setIsUnsigned(E->getType()->isUnsignedIntegerType());
return true;
}
/// HandleCast - This is used to evaluate implicit or explicit casts where the
/// result type is integer.
bool IntExprEvaluator::HandleCast(SourceLocation CastLoc,
Expr *SubExpr, QualType DestType) {
unsigned DestWidth = getIntTypeSizeInBits(DestType);
// Handle simple integer->integer casts.
if (SubExpr->getType()->isIntegerType()) {
if (!Visit(SubExpr))
return false;
// Figure out if this is a truncate, extend or noop cast.
// If the input is signed, do a sign extend, noop, or truncate.
if (DestType->isBooleanType()) {
// Conversion to bool compares against zero.
Result = Result != 0;
Result.zextOrTrunc(DestWidth);
} else
Result.extOrTrunc(DestWidth);
Result.setIsUnsigned(DestType->isUnsignedIntegerType());
return true;
}
// FIXME: Clean this up!
if (SubExpr->getType()->isPointerType()) {
APValue LV;
if (!EvaluatePointer(SubExpr, LV, Info))
return false;
if (LV.getLValueBase())
return false;
Result.extOrTrunc(DestWidth);
Result = LV.getLValueOffset();
Result.setIsUnsigned(DestType->isUnsignedIntegerType());
return true;
}
if (!SubExpr->getType()->isRealFloatingType())
return Error(CastLoc, diag::err_expr_not_constant, DestType);
APFloat F(0.0);
if (!EvaluateFloat(SubExpr, F, Info))
return Error(CastLoc, diag::err_expr_not_constant, DestType);
// If the destination is boolean, compare against zero.
if (DestType->isBooleanType()) {
Result = !F.isZero();
Result.zextOrTrunc(DestWidth);
Result.setIsUnsigned(DestType->isUnsignedIntegerType());
return true;
}
// Determine whether we are converting to unsigned or signed.
bool DestSigned = DestType->isSignedIntegerType();
// FIXME: Warning for overflow.
uint64_t Space[4];
bool ignored;
(void)F.convertToInteger(Space, DestWidth, DestSigned,
llvm::APFloat::rmTowardZero, &ignored);
Result = llvm::APInt(DestWidth, 4, Space);
Result.setIsUnsigned(!DestSigned);
return true;
}
//===----------------------------------------------------------------------===//
// Float Evaluation
//===----------------------------------------------------------------------===//
namespace {
class VISIBILITY_HIDDEN FloatExprEvaluator
: public StmtVisitor<FloatExprEvaluator, bool> {
EvalInfo &Info;
APFloat &Result;
public:
FloatExprEvaluator(EvalInfo &info, APFloat &result)
: Info(info), Result(result) {}
bool VisitStmt(Stmt *S) {
return false;
}
bool VisitParenExpr(ParenExpr *E) { return Visit(E->getSubExpr()); }
bool VisitCallExpr(const CallExpr *E);
bool VisitUnaryOperator(const UnaryOperator *E);
bool VisitBinaryOperator(const BinaryOperator *E);
bool VisitFloatingLiteral(const FloatingLiteral *E);
};
} // end anonymous namespace
static bool EvaluateFloat(const Expr* E, APFloat& Result, EvalInfo &Info) {
return FloatExprEvaluator(Info, Result).Visit(const_cast<Expr*>(E));
}
bool FloatExprEvaluator::VisitCallExpr(const CallExpr *E) {
switch (E->isBuiltinCall()) {
default: return false;
case Builtin::BI__builtin_huge_val:
case Builtin::BI__builtin_huge_valf:
case Builtin::BI__builtin_huge_vall:
case Builtin::BI__builtin_inf:
case Builtin::BI__builtin_inff:
case Builtin::BI__builtin_infl: {
const llvm::fltSemantics &Sem =
Info.Ctx.getFloatTypeSemantics(E->getType());
Result = llvm::APFloat::getInf(Sem);
return true;
}
case Builtin::BI__builtin_nan:
case Builtin::BI__builtin_nanf:
case Builtin::BI__builtin_nanl:
// If this is __builtin_nan("") turn this into a simple nan, otherwise we
// can't constant fold it.
if (const StringLiteral *S =
dyn_cast<StringLiteral>(E->getArg(0)->IgnoreParenCasts())) {
if (!S->isWide() && S->getByteLength() == 0) { // empty string.
const llvm::fltSemantics &Sem =
Info.Ctx.getFloatTypeSemantics(E->getType());
Result = llvm::APFloat::getNaN(Sem);
return true;
}
}
return false;
case Builtin::BI__builtin_fabs:
case Builtin::BI__builtin_fabsf:
case Builtin::BI__builtin_fabsl:
if (!EvaluateFloat(E->getArg(0), Result, Info))
return false;
if (Result.isNegative())
Result.changeSign();
return true;
case Builtin::BI__builtin_copysign:
case Builtin::BI__builtin_copysignf:
case Builtin::BI__builtin_copysignl: {
APFloat RHS(0.);
if (!EvaluateFloat(E->getArg(0), Result, Info) ||
!EvaluateFloat(E->getArg(1), RHS, Info))
return false;
Result.copySign(RHS);
return true;
}
}
}
bool FloatExprEvaluator::VisitUnaryOperator(const UnaryOperator *E) {
if (!EvaluateFloat(E->getSubExpr(), Result, Info))
return false;
switch (E->getOpcode()) {
default: return false;
case UnaryOperator::Plus:
return true;
case UnaryOperator::Minus:
Result.changeSign();
return true;
}
}
bool FloatExprEvaluator::VisitBinaryOperator(const BinaryOperator *E) {
// FIXME: Diagnostics? I really don't understand how the warnings
// and errors are supposed to work.
APFloat RHS(0.0);
if (!EvaluateFloat(E->getLHS(), Result, Info))
return false;
if (!EvaluateFloat(E->getRHS(), RHS, Info))
return false;
switch (E->getOpcode()) {
default: return false;
case BinaryOperator::Mul:
Result.multiply(RHS, APFloat::rmNearestTiesToEven);
return true;
case BinaryOperator::Add:
Result.add(RHS, APFloat::rmNearestTiesToEven);
return true;
case BinaryOperator::Sub:
Result.subtract(RHS, APFloat::rmNearestTiesToEven);
return true;
case BinaryOperator::Div:
Result.divide(RHS, APFloat::rmNearestTiesToEven);
return true;
case BinaryOperator::Rem:
Result.mod(RHS, APFloat::rmNearestTiesToEven);
return true;
}
}
bool FloatExprEvaluator::VisitFloatingLiteral(const FloatingLiteral *E) {
Result = E->getValue();
return true;
}
//===----------------------------------------------------------------------===//
// Top level TryEvaluate.
//===----------------------------------------------------------------------===//
/// tryEvaluate - Return true if this is a constant which we can fold using
/// any crazy technique (that has nothing to do with language standards) that
/// we want to. If this function returns true, it returns the folded constant
/// in Result.
bool Expr::tryEvaluate(APValue &Result, ASTContext &Ctx) const {
EvalInfo Info(Ctx);
if (getType()->isIntegerType()) {
llvm::APSInt sInt(32);
if (EvaluateInteger(this, sInt, Info)) {
Result = APValue(sInt);
return true;
}
} else if (getType()->isPointerType()) {
if (EvaluatePointer(this, Result, Info)) {
return true;
}
} else if (getType()->isRealFloatingType()) {
llvm::APFloat f(0.0);
if (EvaluateFloat(this, f, Info)) {
Result = APValue(f);
return true;
}
}
return false;
}
/// isEvaluatable - Call tryEvaluate to see if this expression can be constant
/// folded, but discard the result.
bool Expr::isEvaluatable(ASTContext &Ctx) const {
APValue V;
return tryEvaluate(V, Ctx);
}
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