[Lldb-commits] [clang] [lldb] [lldb] Analyze enum promotion type during parsing (PR #115005)

[Ilia Kuklin via lldb-commits]

================
@@ -2299,11 +2301,103 @@ size_t DWARFASTParserClang::ParseChildEnumerators(
     }
 
     if (name && name[0] && got_value) {
-      m_ast.AddEnumerationValueToEnumerationType(
+      auto ECD = m_ast.AddEnumerationValueToEnumerationType(
           clang_type, decl, name, enum_value, enumerator_byte_size * 8);
       ++enumerators_added;
+
+      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());
+      }
     }
   }
+
+  /// The following code follows the same logic as in Sema::ActOnEnumBody
+  /// clang/lib/Sema/SemaDecl.cpp
+  // 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;
+
+  clang::EnumDecl *enum_decl =
+      ClangUtil::GetQualType(clang_type)->getAs<clang::EnumType>()->getDecl();
+  enum_decl->setNumPositiveBits(NumPositiveBits);
+  enum_decl->setNumNegativeBits(NumNegativeBits);
+
+  // C++0x N3000 [conv.prom]p3:
+  //   An rvalue of an unscoped enumeration type whose underlying
+  //   type is not fixed can be converted to an rvalue of the first
+  //   of the following types that can represent all the values of
+  //   the enumeration: int, unsigned int, long int, unsigned long
+  //   int, long long int, or unsigned long long int.
+  // C99 6.4.4.3p2:
+  //   An identifier declared as an enumeration constant has type int.
+  // The C99 rule is modified by C23.
+  clang::QualType BestPromotionType;
+  unsigned BestWidth;
+
+  auto &Context = m_ast.getASTContext();
+  unsigned LongWidth = Context.getTargetInfo().getLongWidth();
+  unsigned IntWidth = Context.getTargetInfo().getIntWidth();
+  unsigned CharWidth = Context.getTargetInfo().getCharWidth();
+  unsigned ShortWidth = Context.getTargetInfo().getShortWidth();
+
+  bool is_cpp = Language::LanguageIsCPlusPlus(
+      SymbolFileDWARF::GetLanguage(*parent_die.GetCU()));
+
+  if (NumNegativeBits) {
----------------
kuilpd wrote:

If I understood you correctly, I created this separate function in clang's SemaDecl.cpp, and then called it from both LLDB and Sema itself. Seems to be working, but it needed a lot of arguments, since when called from LLDB Sema doesn't have any information stored at all, so ASTContext, EnumDecl and other arguments have to come from LLDB, and it also returns 3 values.
This looks clunky because of it, any suggestions how to make it better?

https://github.com/llvm/llvm-project/pull/115005