Merge pull request swiftlang#11747 from swiftlang/bitint-debug-info-to-21.x

🍒 [lldb][TypeSystem] Better support for _BitInt types

This patch ensures we make use of the `DW_AT_bit_size` on
`DW_TAG_base_type`s and adjusts `TypeSystemClang` to recognize `_BitInt`.

For DWARF from older versions of Clang that didn't emit a
`DW_AT_bit_size`, we would create `_BitInt`s using the byte-size. Not
sure we can do much better than that. But the situation beforehand
wasn't much better.

Before:
```
(lldb) v
(char) a = '\x01'
(unsigned char) b = '\x01'
(long) c = 2
(unsigned long) d = 2
```

After:
```
(lldb) v
(_BitInt(2)) a = 1
(unsigned _BitInt(2)) b = 1
(_BitInt(52)) c = 2
(unsigned _BitInt(52)) d = 2
```

(cherry picked from commit swiftlang@deb54ba)

Author: Michael137

clang/lib/CodeGen/CGDebugInfo.cpp

@@ -1146,14 +1146,16 @@ llvm::DIType *CGDebugInfo::CreateType(const BuiltinType *BT) {
 }
 
 llvm::DIType *CGDebugInfo::CreateType(const BitIntType *Ty) {
-
-  StringRef Name = Ty->isUnsigned() ? "unsigned _BitInt" : "_BitInt";
+  SmallString<32> Name;
+  llvm::raw_svector_ostream OS(Name);
+  OS << (Ty->isUnsigned() ? "unsigned _BitInt(" : "_BitInt(")
+     << Ty->getNumBits() << ")";
   llvm::dwarf::TypeKind Encoding = Ty->isUnsigned()
                                        ? llvm::dwarf::DW_ATE_unsigned
                                        : llvm::dwarf::DW_ATE_signed;
-
   return DBuilder.createBasicType(Name, CGM.getContext().getTypeSize(Ty),
-                                  Encoding);
+                                  Encoding, llvm::DINode::FlagZero, 0,
+                                  Ty->getNumBits());
 }
 
 llvm::DIType *CGDebugInfo::CreateType(const ComplexType *Ty) {

clang/test/CodeGen/bit-int.c

@@ -0,0 +1,8 @@
+// RUN: %clang_cc1 -x c++ %s -debug-info-kind=standalone -gno-column-info -emit-llvm -o - | FileCheck %s
+// RUN: %clang_cc1 -x c   %s -debug-info-kind=standalone -gno-column-info -emit-llvm -o - | FileCheck %s
+
+unsigned _BitInt(17) a;
+_BitInt(2) b;
+
+// CHECK: !DIBasicType(name: "_BitInt(2)", size: 8, dataSize: 2, encoding: DW_ATE_signed)
+// CHECK: !DIBasicType(name: "unsigned _BitInt(17)", size: 32,  dataSize: 17, encoding: DW_ATE_unsigned)

lldb/include/lldb/Symbol/CompilerType.h

@@ -433,7 +433,7 @@ class CompilerType {
   std::optional<uint64_t>
   GetByteStride(ExecutionContextScope *exe_scope) const;
 
-  lldb::Encoding GetEncoding(uint64_t &count) const;
+  lldb::Encoding GetEncoding() const;
 
   lldb::Format GetFormat() const;
 

lldb/include/lldb/Symbol/Type.h

@@ -507,7 +507,7 @@ class Type : public std::enable_shared_from_this<Type>, public UserID {
 
   lldb::Format GetFormat();
 
-  lldb::Encoding GetEncoding(uint64_t &count);
+  lldb::Encoding GetEncoding();
 
   SymbolContextScope *GetSymbolContextScope() { return m_context; }
   const SymbolContextScope *GetSymbolContextScope() const { return m_context; }

lldb/include/lldb/Symbol/TypeSystem.h

@@ -349,8 +349,7 @@ class TypeSystem : public PluginInterface,
   GetByteStride(lldb::opaque_compiler_type_t type,
                 ExecutionContextScope *exe_scope) = 0;
 
-  virtual lldb::Encoding GetEncoding(lldb::opaque_compiler_type_t type,
-                                     uint64_t &count) = 0;
+  virtual lldb::Encoding GetEncoding(lldb::opaque_compiler_type_t type) = 0;
 
   virtual lldb::Format GetFormat(lldb::opaque_compiler_type_t type) = 0;
 

lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp

@@ -465,6 +465,10 @@ ParsedDWARFTypeAttributes::ParsedDWARFTypeAttributes(const DWARFDIE &die) {
       byte_size = form_value.Unsigned();
       break;
 
+    case DW_AT_bit_size:
+      data_bit_size = form_value.Unsigned();
+      break;
+
     case DW_AT_alignment:
       alignment = form_value.Unsigned();
       break;
@@ -839,13 +843,18 @@ DWARFASTParserClang::ParseTypeModifier(const SymbolContext &sc,
     // there...
     [[fallthrough]];
 
-  case DW_TAG_base_type:
+  case DW_TAG_base_type: {
     resolve_state = Type::ResolveState::Full;
+    // If a builtin type's size isn't a multiple of a byte, DWARF producers may
+    // add a precise bit-size to the type. Use the most precise bit-size
+    // possible.
+    const uint64_t bit_size = attrs.data_bit_size
+                                  ? *attrs.data_bit_size
+                                  : attrs.byte_size.value_or(0) * 8;
     clang_type = m_ast.GetBuiltinTypeForDWARFEncodingAndBitSize(
-        attrs.name.GetStringRef(), attrs.encoding,
-        attrs.byte_size.value_or(0) * 8);
+        attrs.name.GetStringRef(), attrs.encoding, bit_size);
     break;
-
+  }
   case DW_TAG_pointer_type:
     encoding_data_type = Type::eEncodingIsPointerUID;
     break;

lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.h

@@ -592,6 +592,7 @@ struct ParsedDWARFTypeAttributes {
   lldb_private::plugin::dwarf::DWARFFormValue type;
   lldb::LanguageType class_language = lldb::eLanguageTypeUnknown;
   std::optional<uint64_t> byte_size;
+  std::optional<uint64_t> data_bit_size;
   std::optional<uint64_t> alignment;
   size_t calling_convention = llvm::dwarf::DW_CC_normal;
   uint32_t bit_stride = 0;

lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp

@@ -987,6 +987,8 @@ CompilerType TypeSystemClang::GetBuiltinTypeForDWARFEncodingAndBitSize(
 
   case DW_ATE_signed:
     if (!type_name.empty()) {
+      if (type_name.starts_with("_BitInt"))
+        return GetType(ast.getBitIntType(/*Unsigned=*/false, bit_size));
       if (type_name == "wchar_t" &&
           QualTypeMatchesBitSize(bit_size, ast, ast.WCharTy) &&
           (getTargetInfo() &&
@@ -1043,6 +1045,8 @@ CompilerType TypeSystemClang::GetBuiltinTypeForDWARFEncodingAndBitSize(
 
   case DW_ATE_unsigned:
     if (!type_name.empty()) {
+      if (type_name.starts_with("unsigned _BitInt"))
+        return GetType(ast.getBitIntType(/*Unsigned=*/true, bit_size));
       if (type_name == "wchar_t") {
         if (QualTypeMatchesBitSize(bit_size, ast, ast.WCharTy)) {
           if (!(getTargetInfo() &&
@@ -3925,6 +3929,13 @@ TypeSystemClang::GetTypeInfo(lldb::opaque_compiler_type_t type,
                            ->getModifiedType()
                            .getAsOpaquePtr(),
                        pointee_or_element_clang_type);
+  case clang::Type::BitInt: {
+    uint32_t type_flags = eTypeIsScalar | eTypeIsInteger | eTypeHasValue;
+    if (qual_type->isSignedIntegerType())
+      type_flags |= eTypeIsSigned;
+
+    return type_flags;
+  }
   case clang::Type::Builtin: {
     const clang::BuiltinType *builtin_type =
         llvm::cast<clang::BuiltinType>(qual_type->getCanonicalTypeInternal());
@@ -4955,12 +4966,10 @@ TypeSystemClang::GetTypeBitAlign(lldb::opaque_compiler_type_t type,
   return {};
 }
 
-lldb::Encoding TypeSystemClang::GetEncoding(lldb::opaque_compiler_type_t type,
-                                            uint64_t &count) {
+lldb::Encoding TypeSystemClang::GetEncoding(lldb::opaque_compiler_type_t type) {
   if (!type)
     return lldb::eEncodingInvalid;
 
-  count = 1;
   clang::QualType qual_type = RemoveWrappingTypes(GetCanonicalQualType(type));
 
   switch (qual_type->getTypeClass()) {
@@ -4996,7 +5005,6 @@ lldb::Encoding TypeSystemClang::GetEncoding(lldb::opaque_compiler_type_t type,
   case clang::Type::DependentVector:
   case clang::Type::ExtVector:
   case clang::Type::Vector:
-    // TODO: Set this to more than one???
     break;
 
   case clang::Type::BitInt:
@@ -5196,11 +5204,10 @@ lldb::Encoding TypeSystemClang::GetEncoding(lldb::opaque_compiler_type_t type,
       const clang::ComplexType *complex_type =
           qual_type->getAsComplexIntegerType();
       if (complex_type)
-        encoding = GetType(complex_type->getElementType()).GetEncoding(count);
+        encoding = GetType(complex_type->getElementType()).GetEncoding();
       else
         encoding = lldb::eEncodingSint;
     }
-    count = 2;
     return encoding;
   }
 
@@ -5256,7 +5263,7 @@ lldb::Encoding TypeSystemClang::GetEncoding(lldb::opaque_compiler_type_t type,
   case clang::Type::HLSLInlineSpirv:
     break;
   }
-  count = 0;
+
   return lldb::eEncodingInvalid;
 }
 

lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.h

@@ -907,8 +907,7 @@ class TypeSystemClang : public TypeSystem {
     return {};
   }
 
-  lldb::Encoding GetEncoding(lldb::opaque_compiler_type_t type,
-                             uint64_t &count) override;
+  lldb::Encoding GetEncoding(lldb::opaque_compiler_type_t type) override;
 
   lldb::Format GetFormat(lldb::opaque_compiler_type_t type) override;
 

lldb/source/Plugins/TypeSystem/Swift/SwiftASTContext.cpp

@@ -6775,11 +6775,9 @@ SwiftASTContext::GetTypeBitAlign(opaque_compiler_type_t type,
   return {};
 }
 
-lldb::Encoding SwiftASTContext::GetEncoding(opaque_compiler_type_t type,
-                                            uint64_t &count) {
+lldb::Encoding SwiftASTContext::GetEncoding(opaque_compiler_type_t type) {
   VALID_OR_RETURN_CHECK_TYPE(type, lldb::eEncodingInvalid);
 
-  count = 1;
   swift::CanType swift_can_type(GetCanonicalSwiftType(type));
 
   const swift::TypeKind type_kind = swift_can_type->getKind();
@@ -6842,7 +6840,7 @@ lldb::Encoding SwiftASTContext::GetEncoding(opaque_compiler_type_t type,
   case swift::TypeKind::UnownedStorage:
   case swift::TypeKind::WeakStorage:
     return ToCompilerType(swift_can_type->getReferenceStorageReferent())
-        .GetEncoding(count);
+        .GetEncoding();
     break;
 
   case swift::TypeKind::ExistentialMetatype:
@@ -6877,7 +6875,6 @@ lldb::Encoding SwiftASTContext::GetEncoding(opaque_compiler_type_t type,
     assert(false && "Not a canonical type");
     break;
   }
-  count = 0;
   return lldb::eEncodingInvalid;
 }