[clang][Sema] Move computing enum bits into a separate function (llvm#126096)

Move the code that computes `NumNegativeBits` and `NumPositiveBits` for
an enum to a separate function in `ASTContext.h`.
This function needs to be called from LLDB as well (llvm#115005)

Author: kuilpd

clang/include/clang/AST/ASTContext.h

@@ -1733,6 +1733,47 @@ class ASTContext : public RefCountedBase<ASTContext> {
                             unsigned NumPositiveBits, QualType &BestType,
                             QualType &BestPromotionType);
 
+  /// Determine whether the given integral value is representable within
+  /// the given type T.
+  bool isRepresentableIntegerValue(llvm::APSInt &Value, QualType T);
+
+  /// Compute NumNegativeBits and NumPositiveBits for an enum based on
+  /// the constant values of its enumerators.
+  template <typename RangeT>
+  bool computeEnumBits(RangeT EnumConstants, unsigned &NumNegativeBits,
+                       unsigned &NumPositiveBits) {
+    NumNegativeBits = 0;
+    NumPositiveBits = 0;
+    bool MembersRepresentableByInt = true;
+    for (auto *Elem : EnumConstants) {
+      EnumConstantDecl *ECD = cast_or_null<EnumConstantDecl>(Elem);
+      if (!ECD)
+        continue; // Already issued a diagnostic.
+
+      llvm::APSInt InitVal = ECD->getInitVal();
+      if (InitVal.isUnsigned() || InitVal.isNonNegative()) {
+        // If the enumerator is zero that should still be counted as a positive
+        // bit since we need a bit to store the value zero.
+        unsigned ActiveBits = InitVal.getActiveBits();
+        NumPositiveBits = std::max({NumPositiveBits, ActiveBits, 1u});
+      } else {
+        NumNegativeBits =
+            std::max(NumNegativeBits, (unsigned)InitVal.getSignificantBits());
+      }
+
+      MembersRepresentableByInt &= isRepresentableIntegerValue(InitVal, IntTy);
+    }
+
+    // If we have an empty set of enumerators we still need one bit.
+    // From [dcl.enum]p8
+    // If the enumerator-list is empty, the values of the enumeration are as if
+    // the enumeration had a single enumerator with value 0
+    if (!NumPositiveBits && !NumNegativeBits)
+      NumPositiveBits = 1;
+
+    return MembersRepresentableByInt;
+  }
+
   QualType
   getUnresolvedUsingType(const UnresolvedUsingTypenameDecl *Decl) const;
 

clang/lib/AST/ASTContext.cpp

@@ -5320,6 +5320,19 @@ bool ASTContext::computeBestEnumTypes(bool IsPacked, unsigned NumNegativeBits,
   return EnumTooLarge;
 }
 
+bool ASTContext::isRepresentableIntegerValue(llvm::APSInt &Value, QualType T) {
+  assert((T->isIntegralType(*this) || T->isEnumeralType()) &&
+         "Integral type required!");
+  unsigned BitWidth = getIntWidth(T);
+
+  if (Value.isUnsigned() || Value.isNonNegative()) {
+    if (T->isSignedIntegerOrEnumerationType())
+      --BitWidth;
+    return Value.getActiveBits() <= BitWidth;
+  }
+  return Value.getSignificantBits() <= BitWidth;
+}
+
 QualType ASTContext::getUnresolvedUsingType(
     const UnresolvedUsingTypenameDecl *Decl) const {
   if (Decl->TypeForDecl)

clang/lib/Sema/SemaDecl.cpp

@@ -19633,23 +19633,6 @@ void Sema::ActOnFields(Scope *S, SourceLocation RecLoc, Decl *EnclosingDecl,
   ProcessAPINotes(Record);
 }
 
-/// Determine whether the given integral value is representable within
-/// the given type T.
-static bool isRepresentableIntegerValue(ASTContext &Context,
-                                        llvm::APSInt &Value,
-                                        QualType T) {
-  assert((T->isIntegralType(Context) || T->isEnumeralType()) &&
-         "Integral type required!");
-  unsigned BitWidth = Context.getIntWidth(T);
-
-  if (Value.isUnsigned() || Value.isNonNegative()) {
-    if (T->isSignedIntegerOrEnumerationType())
-      --BitWidth;
-    return Value.getActiveBits() <= BitWidth;
-  }
-  return Value.getSignificantBits() <= BitWidth;
-}
-
 // Given an integral type, return the next larger integral type
 // (or a NULL type of no such type exists).
 static QualType getNextLargerIntegralType(ASTContext &Context, QualType T) {
@@ -19723,7 +19706,7 @@ EnumConstantDecl *Sema::CheckEnumConstant(EnumDecl *Enum,
           // representable in the underlying type of the enumeration. In C++11,
           // we perform a non-narrowing conversion as part of converted constant
           // expression checking.
-          if (!isRepresentableIntegerValue(Context, EnumVal, EltTy)) {
+          if (!Context.isRepresentableIntegerValue(EnumVal, EltTy)) {
             if (Context.getTargetInfo()
                     .getTriple()
                     .isWindowsMSVCEnvironment()) {
@@ -19752,7 +19735,7 @@ EnumConstantDecl *Sema::CheckEnumConstant(EnumDecl *Enum,
           //   representable as an int.
 
           // Complain if the value is not representable in an int.
-          if (!isRepresentableIntegerValue(Context, EnumVal, Context.IntTy)) {
+          if (!Context.isRepresentableIntegerValue(EnumVal, Context.IntTy)) {
             Diag(IdLoc, getLangOpts().C23
                             ? diag::warn_c17_compat_enum_value_not_int
                             : diag::ext_c23_enum_value_not_int)
@@ -19844,7 +19827,7 @@ EnumConstantDecl *Sema::CheckEnumConstant(EnumDecl *Enum,
                           : diag::ext_c23_enum_value_not_int)
               << 1 << toString(EnumVal, 10) << 1;
       } else if (!getLangOpts().CPlusPlus && !EltTy->isDependentType() &&
-                 !isRepresentableIntegerValue(Context, EnumVal, EltTy)) {
+                 !Context.isRepresentableIntegerValue(EnumVal, EltTy)) {
         // Enforce C99 6.7.2.2p2 even when we compute the next value.
         Diag(IdLoc, getLangOpts().C23 ? diag::warn_c17_compat_enum_value_not_int
                                       : diag::ext_c23_enum_value_not_int)
@@ -20171,35 +20154,8 @@ void Sema::ActOnEnumBody(SourceLocation EnumLoc, SourceRange BraceRange,
   // reverse the list.
   unsigned NumNegativeBits = 0;
   unsigned NumPositiveBits = 0;
-  bool MembersRepresentableByInt = true;
-
-  for (unsigned i = 0, e = Elements.size(); i != e; ++i) {
-    EnumConstantDecl *ECD =
-      cast_or_null<EnumConstantDecl>(Elements[i]);
-    if (!ECD) continue;  // Already issued a diagnostic.
-
-    llvm::APSInt InitVal = ECD->getInitVal();
-
-    // Keep track of the size of positive and negative values.
-    if (InitVal.isUnsigned() || InitVal.isNonNegative()) {
-      // If the enumerator is zero that should still be counted as a positive
-      // bit since we need a bit to store the value zero.
-      unsigned ActiveBits = InitVal.getActiveBits();
-      NumPositiveBits = std::max({NumPositiveBits, ActiveBits, 1u});
-    } else {
-      NumNegativeBits =
-          std::max(NumNegativeBits, (unsigned)InitVal.getSignificantBits());
-    }
-    MembersRepresentableByInt &=
-        isRepresentableIntegerValue(Context, InitVal, Context.IntTy);
-  }
-
-  // If we have an empty set of enumerators we still need one bit.
-  // From [dcl.enum]p8
-  // If the enumerator-list is empty, the values of the enumeration are as if
-  // the enumeration had a single enumerator with value 0
-  if (!NumPositiveBits && !NumNegativeBits)
-    NumPositiveBits = 1;
+  bool MembersRepresentableByInt =
+      Context.computeEnumBits(Elements, NumNegativeBits, NumPositiveBits);
 
   // Figure out the type that should be used for this enum.
   QualType BestType;