r371557 - When evaluating a __builtin_constant_p conditional, always enter
Richard Smith via cfe-commits
cfe-commits at lists.llvm.org
Tue Sep 10 14:24:09 PDT 2019
Author: rsmith
Date: Tue Sep 10 14:24:09 2019
New Revision: 371557
URL: http://llvm.org/viewvc/llvm-project?rev=371557&view=rev
Log:
When evaluating a __builtin_constant_p conditional, always enter
constant-folding mode regardless of the original evaluation mode.
In order for this to be correct, we need to track whether we're checking
for a potential constant expression or checking for undefined behavior
separately from the evaluation mode enum, since we don't want to clobber
those states when entering constant-folding mode.
Modified:
cfe/trunk/lib/AST/ExprConstant.cpp
cfe/trunk/test/Sema/i-c-e.c
Modified: cfe/trunk/lib/AST/ExprConstant.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/ExprConstant.cpp?rev=371557&r1=371556&r2=371557&view=diff
==============================================================================
--- cfe/trunk/lib/AST/ExprConstant.cpp (original)
+++ cfe/trunk/lib/AST/ExprConstant.cpp Tue Sep 10 14:24:09 2019
@@ -794,58 +794,47 @@ namespace {
/// constant value.
bool InConstantContext;
+ /// Whether we're checking that an expression is a potential constant
+ /// expression. If so, do not fail on constructs that could become constant
+ /// later on (such as a use of an undefined global).
+ bool CheckingPotentialConstantExpression = false;
+
+ /// Whether we're checking for an expression that has undefined behavior.
+ /// If so, we will produce warnings if we encounter an operation that is
+ /// always undefined.
+ bool CheckingForUndefinedBehavior = false;
+
enum EvaluationMode {
/// Evaluate as a constant expression. Stop if we find that the expression
/// is not a constant expression.
EM_ConstantExpression,
- /// Evaluate as a potential constant expression. Keep going if we hit a
- /// construct that we can't evaluate yet (because we don't yet know the
- /// value of something) but stop if we hit something that could never be
- /// a constant expression.
- EM_PotentialConstantExpression,
+ /// Evaluate as a constant expression. Stop if we find that the expression
+ /// is not a constant expression. Some expressions can be retried in the
+ /// optimizer if we don't constant fold them here, but in an unevaluated
+ /// context we try to fold them immediately since the optimizer never
+ /// gets a chance to look at it.
+ EM_ConstantExpressionUnevaluated,
/// Fold the expression to a constant. Stop if we hit a side-effect that
/// we can't model.
EM_ConstantFold,
- /// Evaluate the expression looking for integer overflow and similar
- /// issues. Don't worry about side-effects, and try to visit all
- /// subexpressions.
- EM_EvaluateForOverflow,
-
/// Evaluate in any way we know how. Don't worry about side-effects that
/// can't be modeled.
EM_IgnoreSideEffects,
-
- /// Evaluate as a constant expression. Stop if we find that the expression
- /// is not a constant expression. Some expressions can be retried in the
- /// optimizer if we don't constant fold them here, but in an unevaluated
- /// context we try to fold them immediately since the optimizer never
- /// gets a chance to look at it.
- EM_ConstantExpressionUnevaluated,
-
- /// Evaluate as a potential constant expression. Keep going if we hit a
- /// construct that we can't evaluate yet (because we don't yet know the
- /// value of something) but stop if we hit something that could never be
- /// a constant expression. Some expressions can be retried in the
- /// optimizer if we don't constant fold them here, but in an unevaluated
- /// context we try to fold them immediately since the optimizer never
- /// gets a chance to look at it.
- EM_PotentialConstantExpressionUnevaluated,
} EvalMode;
/// Are we checking whether the expression is a potential constant
/// expression?
bool checkingPotentialConstantExpression() const {
- return EvalMode == EM_PotentialConstantExpression ||
- EvalMode == EM_PotentialConstantExpressionUnevaluated;
+ return CheckingPotentialConstantExpression;
}
/// Are we checking an expression for overflow?
// FIXME: We should check for any kind of undefined or suspicious behavior
// in such constructs, not just overflow.
- bool checkingForOverflow() { return EvalMode == EM_EvaluateForOverflow; }
+ bool checkingForUndefinedBehavior() { return CheckingForUndefinedBehavior; }
EvalInfo(const ASTContext &C, Expr::EvalStatus &S, EvaluationMode Mode)
: Ctx(const_cast<ASTContext &>(C)), EvalStatus(S), CurrentCall(nullptr),
@@ -932,15 +921,12 @@ namespace {
switch (EvalMode) {
case EM_ConstantFold:
case EM_IgnoreSideEffects:
- case EM_EvaluateForOverflow:
if (!HasFoldFailureDiagnostic)
break;
// We've already failed to fold something. Keep that diagnostic.
LLVM_FALLTHROUGH;
case EM_ConstantExpression:
- case EM_PotentialConstantExpression:
case EM_ConstantExpressionUnevaluated:
- case EM_PotentialConstantExpressionUnevaluated:
HasActiveDiagnostic = false;
return OptionalDiagnostic();
}
@@ -986,8 +972,8 @@ namespace {
/// Diagnose that the evaluation does not produce a C++11 core constant
/// expression.
///
- /// FIXME: Stop evaluating if we're in EM_ConstantExpression or
- /// EM_PotentialConstantExpression mode and we produce one of these.
+ /// FIXME: Stop evaluating if we're in EM_ConstantExpression mode
+ /// and we produce one of these.
OptionalDiagnostic CCEDiag(SourceLocation Loc, diag::kind DiagId
= diag::note_invalid_subexpr_in_const_expr,
unsigned ExtraNotes = 0) {
@@ -1023,16 +1009,16 @@ namespace {
/// couldn't model?
bool keepEvaluatingAfterSideEffect() {
switch (EvalMode) {
- case EM_PotentialConstantExpression:
- case EM_PotentialConstantExpressionUnevaluated:
- case EM_EvaluateForOverflow:
case EM_IgnoreSideEffects:
return true;
case EM_ConstantExpression:
case EM_ConstantExpressionUnevaluated:
case EM_ConstantFold:
- return false;
+ // By default, assume any side effect might be valid in some other
+ // evaluation of this expression from a different context.
+ return checkingPotentialConstantExpression() ||
+ checkingForUndefinedBehavior();
}
llvm_unreachable("Missed EvalMode case");
}
@@ -1047,16 +1033,13 @@ namespace {
/// Should we continue evaluation after encountering undefined behavior?
bool keepEvaluatingAfterUndefinedBehavior() {
switch (EvalMode) {
- case EM_EvaluateForOverflow:
case EM_IgnoreSideEffects:
case EM_ConstantFold:
return true;
- case EM_PotentialConstantExpression:
- case EM_PotentialConstantExpressionUnevaluated:
case EM_ConstantExpression:
case EM_ConstantExpressionUnevaluated:
- return false;
+ return checkingForUndefinedBehavior();
}
llvm_unreachable("Missed EvalMode case");
}
@@ -1076,16 +1059,12 @@ namespace {
return false;
switch (EvalMode) {
- case EM_PotentialConstantExpression:
- case EM_PotentialConstantExpressionUnevaluated:
- case EM_EvaluateForOverflow:
- return true;
-
case EM_ConstantExpression:
case EM_ConstantExpressionUnevaluated:
case EM_ConstantFold:
case EM_IgnoreSideEffects:
- return false;
+ return checkingPotentialConstantExpression() ||
+ checkingForUndefinedBehavior();
}
llvm_unreachable("Missed EvalMode case");
}
@@ -1142,9 +1121,7 @@ namespace {
Info.EvalStatus.Diag->empty() &&
!Info.EvalStatus.HasSideEffects),
OldMode(Info.EvalMode) {
- if (Enabled &&
- (Info.EvalMode == EvalInfo::EM_ConstantExpression ||
- Info.EvalMode == EvalInfo::EM_ConstantExpressionUnevaluated))
+ if (Enabled)
Info.EvalMode = EvalInfo::EM_ConstantFold;
}
void keepDiagnostics() { Enabled = false; }
@@ -1163,8 +1140,7 @@ namespace {
EvalInfo::EvaluationMode OldMode;
explicit IgnoreSideEffectsRAII(EvalInfo &Info)
: Info(Info), OldMode(Info.EvalMode) {
- if (!Info.checkingPotentialConstantExpression())
- Info.EvalMode = EvalInfo::EM_IgnoreSideEffects;
+ Info.EvalMode = EvalInfo::EM_IgnoreSideEffects;
}
~IgnoreSideEffectsRAII() { Info.EvalMode = OldMode; }
@@ -2323,7 +2299,7 @@ static bool CheckedIntArithmetic(EvalInf
APSInt Value(Op(LHS.extend(BitWidth), RHS.extend(BitWidth)), false);
Result = Value.trunc(LHS.getBitWidth());
if (Result.extend(BitWidth) != Value) {
- if (Info.checkingForOverflow())
+ if (Info.checkingForUndefinedBehavior())
Info.Ctx.getDiagnostics().Report(E->getExprLoc(),
diag::warn_integer_constant_overflow)
<< Result.toString(10) << E->getType();
@@ -6047,6 +6023,8 @@ public:
// Always assume __builtin_constant_p(...) ? ... : ... is a potential
// constant expression; we can't check whether it's potentially foldable.
+ // FIXME: We should instead treat __builtin_constant_p as non-constant if
+ // it would return 'false' in this mode.
if (Info.checkingPotentialConstantExpression() && IsBcpCall)
return false;
@@ -6329,7 +6307,7 @@ public:
bool VisitStmtExpr(const StmtExpr *E) {
// We will have checked the full-expressions inside the statement expression
// when they were completed, and don't need to check them again now.
- if (Info.checkingForOverflow())
+ if (Info.checkingForUndefinedBehavior())
return Error(E);
BlockScopeRAII Scope(Info);
@@ -9502,14 +9480,11 @@ bool IntExprEvaluator::VisitBuiltinCallE
// size of the referenced object.
switch (Info.EvalMode) {
case EvalInfo::EM_ConstantExpression:
- case EvalInfo::EM_PotentialConstantExpression:
case EvalInfo::EM_ConstantFold:
- case EvalInfo::EM_EvaluateForOverflow:
case EvalInfo::EM_IgnoreSideEffects:
// Leave it to IR generation.
return Error(E);
case EvalInfo::EM_ConstantExpressionUnevaluated:
- case EvalInfo::EM_PotentialConstantExpressionUnevaluated:
// Reduce it to a constant now.
return Success((Type & 2) ? 0 : -1, E);
}
@@ -12549,8 +12524,9 @@ APSInt Expr::EvaluateKnownConstIntCheckO
EvalResult EVResult;
EVResult.Diag = Diag;
- EvalInfo Info(Ctx, EVResult, EvalInfo::EM_EvaluateForOverflow);
+ EvalInfo Info(Ctx, EVResult, EvalInfo::EM_IgnoreSideEffects);
Info.InConstantContext = true;
+ Info.CheckingForUndefinedBehavior = true;
bool Result = ::EvaluateAsRValue(Info, this, EVResult.Val);
(void)Result;
@@ -12567,7 +12543,8 @@ void Expr::EvaluateForOverflow(const AST
bool IsConst;
EvalResult EVResult;
if (!FastEvaluateAsRValue(this, EVResult, Ctx, IsConst)) {
- EvalInfo Info(Ctx, EVResult, EvalInfo::EM_EvaluateForOverflow);
+ EvalInfo Info(Ctx, EVResult, EvalInfo::EM_IgnoreSideEffects);
+ Info.CheckingForUndefinedBehavior = true;
(void)::EvaluateAsRValue(Info, this, EVResult.Val);
}
}
@@ -13181,9 +13158,9 @@ bool Expr::isPotentialConstantExpr(const
Expr::EvalStatus Status;
Status.Diag = &Diags;
- EvalInfo Info(FD->getASTContext(), Status,
- EvalInfo::EM_PotentialConstantExpression);
+ EvalInfo Info(FD->getASTContext(), Status, EvalInfo::EM_ConstantExpression);
Info.InConstantContext = true;
+ Info.CheckingPotentialConstantExpression = true;
const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(FD);
const CXXRecordDecl *RD = MD ? MD->getParent()->getCanonicalDecl() : nullptr;
@@ -13222,8 +13199,9 @@ bool Expr::isPotentialConstantExprUneval
Status.Diag = &Diags;
EvalInfo Info(FD->getASTContext(), Status,
- EvalInfo::EM_PotentialConstantExpressionUnevaluated);
+ EvalInfo::EM_ConstantExpressionUnevaluated);
Info.InConstantContext = true;
+ Info.CheckingPotentialConstantExpression = true;
// Fabricate a call stack frame to give the arguments a plausible cover story.
ArrayRef<const Expr*> Args;
Modified: cfe/trunk/test/Sema/i-c-e.c
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/i-c-e.c?rev=371557&r1=371556&r2=371557&view=diff
==============================================================================
--- cfe/trunk/test/Sema/i-c-e.c (original)
+++ cfe/trunk/test/Sema/i-c-e.c Tue Sep 10 14:24:09 2019
@@ -75,3 +75,6 @@ int realop[(__real__ 4) == 4 ? 1 : -1];
int imagop[(__imag__ 4) == 0 ? 1 : -1];
int *PR14729 = 0 ?: 1/0; // expected-error {{not a compile-time constant}} expected-warning 3{{}}
+
+int bcp_call_v;
+int bcp_call_a[] = {__builtin_constant_p(bcp_call_v && 0) ? bcp_call_v && 0 : -1};
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