Track the result of evaluating a computed noexcept specification on the

FunctionProtoType.

We previously re-evaluated the expression each time we wanted to know whether
the type is noexcept or not. We now evaluate the expression exactly once.

This is not quite "no functional change": it fixes a crasher bug during AST
deserialization where we would try to evaluate the noexcept specification in a
situation where we have not deserialized sufficient portions of the AST to
permit such evaluation.

1 files changed, 12 insertions, 14 deletions

diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index 95ea8418e1a..1d56fc856e8 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -4381,7 +4381,7 @@ static bool HasNoThrowOperator(const RecordType *RT, OverloadedOperatorKind Op,
         const FunctionProtoType *CPT =
           Operator->getType()->getAs<FunctionProtoType>();
         CPT = Self.ResolveExceptionSpec(KeyLoc, CPT);
-        if (!CPT || !CPT->isNothrow(C))
+        if (!CPT || !CPT->isNothrow())
           return false;
       }
     }
@@ -4629,7 +4629,7 @@ static bool EvaluateUnaryTypeTrait(Sema &Self, TypeTrait UTT,
         const FunctionProtoType *CPT =
             Destructor->getType()->getAs<FunctionProtoType>();
         CPT = Self.ResolveExceptionSpec(KeyLoc, CPT);
-        if (!CPT || !CPT->isNothrow(C))
+        if (!CPT || !CPT->isNothrow())
           return false;
       }
     }
@@ -4722,7 +4722,7 @@ static bool EvaluateUnaryTypeTrait(Sema &Self, TypeTrait UTT,
             return false;
           // TODO: check whether evaluating default arguments can throw.
           // For now, we'll be conservative and assume that they can throw.
-          if (!CPT->isNothrow(C) || CPT->getNumParams() > 1)
+          if (!CPT->isNothrow() || CPT->getNumParams() > 1)
             return false;
         }
       }
@@ -4761,7 +4761,7 @@ static bool EvaluateUnaryTypeTrait(Sema &Self, TypeTrait UTT,
             return false;
           // FIXME: check whether evaluating default arguments can throw.
           // For now, we'll be conservative and assume that they can throw.
-          if (!CPT->isNothrow(C) || CPT->getNumParams() > 0)
+          if (!CPT->isNothrow() || CPT->getNumParams() > 0)
             return false;
         }
       }
@@ -5909,27 +5909,23 @@ mergeExceptionSpecs(Sema &S, FunctionProtoType::ExceptionSpecInfo ESI1,
   if (EST2 == EST_None) return ESI2;
   if (EST1 == EST_MSAny) return ESI1;
   if (EST2 == EST_MSAny) return ESI2;
+  if (EST1 == EST_NoexceptFalse) return ESI1;
+  if (EST2 == EST_NoexceptFalse) return ESI2;
 
   // If either of them is non-throwing, the result is the other.
   if (EST1 == EST_DynamicNone) return ESI2;
   if (EST2 == EST_DynamicNone) return ESI1;
   if (EST1 == EST_BasicNoexcept) return ESI2;
   if (EST2 == EST_BasicNoexcept) return ESI1;
+  if (EST1 == EST_NoexceptTrue) return ESI2;
+  if (EST2 == EST_NoexceptTrue) return ESI1;
 
-  // If either of them is a non-value-dependent computed noexcept, that
-  // determines the result.
-  if (EST2 == EST_ComputedNoexcept && ESI2.NoexceptExpr &&
-      !ESI2.NoexceptExpr->isValueDependent())
-    return !ESI2.NoexceptExpr->EvaluateKnownConstInt(S.Context) ? ESI2 : ESI1;
-  if (EST1 == EST_ComputedNoexcept && ESI1.NoexceptExpr &&
-      !ESI1.NoexceptExpr->isValueDependent())
-    return !ESI1.NoexceptExpr->EvaluateKnownConstInt(S.Context) ? ESI1 : ESI2;
   // If we're left with value-dependent computed noexcept expressions, we're
   // stuck. Before C++17, we can just drop the exception specification entirely,
   // since it's not actually part of the canonical type. And this should never
   // happen in C++17, because it would mean we were computing the composite
   // pointer type of dependent types, which should never happen.
-  if (EST1 == EST_ComputedNoexcept || EST2 == EST_ComputedNoexcept) {
+  if (EST1 == EST_DependentNoexcept || EST2 == EST_DependentNoexcept) {
     assert(!S.getLangOpts().CPlusPlus17 &&
            "computing composite pointer type of dependent types");
     return FunctionProtoType::ExceptionSpecInfo();
@@ -5942,7 +5938,9 @@ mergeExceptionSpecs(Sema &S, FunctionProtoType::ExceptionSpecInfo ESI1,
   case EST_DynamicNone:
   case EST_MSAny:
   case EST_BasicNoexcept:
-  case EST_ComputedNoexcept:
+  case EST_DependentNoexcept:
+  case EST_NoexceptFalse:
+  case EST_NoexceptTrue:
     llvm_unreachable("handled above");
 
   case EST_Dynamic: {