Add a new attribute 'enable_if' which can be used to control overload resolution based on the values of the function arguments at the call site.
llvm-svn: 198996
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index bef7768..e836e18 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -474,13 +474,30 @@
/// Evaluate in any way we know how. Don't worry about side-effects that
/// can't be modeled.
- EM_IgnoreSideEffects
+ 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;
+ return EvalMode == EM_PotentialConstantExpression ||
+ EvalMode == EM_PotentialConstantExpressionUnevaluated;
}
/// Are we checking an expression for overflow?
@@ -573,6 +590,8 @@
// some later problem.
case EM_ConstantExpression:
case EM_PotentialConstantExpression:
+ case EM_ConstantExpressionUnevaluated:
+ case EM_PotentialConstantExpressionUnevaluated:
HasActiveDiagnostic = false;
return OptionalDiagnostic();
}
@@ -644,11 +663,13 @@
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;
}
@@ -670,10 +691,12 @@
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;
@@ -696,7 +719,9 @@
Info.EvalStatus.Diag->empty() &&
!Info.EvalStatus.HasSideEffects),
OldMode(Info.EvalMode) {
- if (Enabled && Info.EvalMode == EvalInfo::EM_ConstantExpression)
+ if (Enabled &&
+ (Info.EvalMode == EvalInfo::EM_ConstantExpression ||
+ Info.EvalMode == EvalInfo::EM_ConstantExpressionUnevaluated))
Info.EvalMode = EvalInfo::EM_ConstantFold;
}
void keepDiagnostics() { Enabled = false; }
@@ -5985,7 +6010,17 @@
// Expression had no side effects, but we couldn't statically determine the
// size of the referenced object.
- return Error(E);
+ switch (Info.EvalMode) {
+ case EvalInfo::EM_ConstantExpression:
+ case EvalInfo::EM_PotentialConstantExpression:
+ case EvalInfo::EM_ConstantFold:
+ case EvalInfo::EM_EvaluateForOverflow:
+ case EvalInfo::EM_IgnoreSideEffects:
+ return Error(E);
+ case EvalInfo::EM_ConstantExpressionUnevaluated:
+ case EvalInfo::EM_PotentialConstantExpressionUnevaluated:
+ return Success(-1ULL, E);
+ }
}
case Builtin::BI__builtin_bswap16:
@@ -8656,6 +8691,28 @@
return IsConstExpr;
}
+bool Expr::EvaluateWithSubstitution(APValue &Value, ASTContext &Ctx,
+ const FunctionDecl *Callee,
+ llvm::ArrayRef<const Expr*> Args) const {
+ Expr::EvalStatus Status;
+ EvalInfo Info(Ctx, Status, EvalInfo::EM_ConstantExpressionUnevaluated);
+
+ ArgVector ArgValues(Args.size());
+ for (ArrayRef<const Expr*>::iterator I = Args.begin(), E = Args.end();
+ I != E; ++I) {
+ if (!Evaluate(ArgValues[I - Args.begin()], Info, *I))
+ // If evaluation fails, throw away the argument entirely.
+ ArgValues[I - Args.begin()] = APValue();
+ if (Info.EvalStatus.HasSideEffects)
+ return false;
+ }
+
+ // Build fake call to Callee.
+ CallStackFrame Frame(Info, Callee->getLocation(), Callee, /*This*/0,
+ ArgValues.data());
+ return Evaluate(Value, Info, this) && !Info.EvalStatus.HasSideEffects;
+}
+
bool Expr::isPotentialConstantExpr(const FunctionDecl *FD,
SmallVectorImpl<
PartialDiagnosticAt> &Diags) {
@@ -8696,3 +8753,27 @@
return Diags.empty();
}
+
+bool Expr::isPotentialConstantExprUnevaluated(Expr *E,
+ const FunctionDecl *FD,
+ SmallVectorImpl<
+ PartialDiagnosticAt> &Diags) {
+ Expr::EvalStatus Status;
+ Status.Diag = &Diags;
+
+ EvalInfo Info(FD->getASTContext(), Status,
+ EvalInfo::EM_PotentialConstantExpressionUnevaluated);
+
+ // Fabricate a call stack frame to give the arguments a plausible cover story.
+ ArrayRef<const Expr*> Args;
+ ArgVector ArgValues(0);
+ bool Success = EvaluateArgs(Args, ArgValues, Info);
+ (void)Success;
+ assert(Success &&
+ "Failed to set up arguments for potential constant evaluation");
+ CallStackFrame Frame(Info, SourceLocation(), FD, 0, ArgValues.data());
+
+ APValue ResultScratch;
+ Evaluate(ResultScratch, Info, E);
+ return Diags.empty();
+}