[lldb][TypeSystem] Remove count parameter from TypeSystem::GetEncoding (llvm#165702)

There were a couple of quirks with this parameter:
1. It wasn't being set consistently. E.g., vector types would be of
count `1` but complex types would be `2`. Hence, it wasn't clear what
count was referring to.
2. `count` was not being set if the input type was invalid, possibly
leaving the input reference uninitialized.
3. Only one callsite actually made use of `count`, and that in itself
seems like it could be improved (added a FIXME).

If we ever need a "how many elements does this type represent", we can
implement one with a new `TypeSystem` API that does exactly that.

Author: Michael137

lldb/include/lldb/Symbol/CompilerType.h

@@ -400,7 +400,7 @@ class CompilerType {
   /// Return the size of the type in bits.
   llvm::Expected<uint64_t> GetBitSize(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

@@ -317,8 +317,7 @@ class TypeSystem : public PluginInterface,
   GetBitSize(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/TypeSystem/Clang/TypeSystemClang.cpp

@@ -4864,12 +4864,10 @@ 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()) {
@@ -4903,7 +4901,6 @@ 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:
@@ -5104,11 +5101,10 @@ 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;
   }
 
@@ -5165,7 +5161,7 @@ lldb::Encoding TypeSystemClang::GetEncoding(lldb::opaque_compiler_type_t type,
   case clang::Type::SubstBuiltinTemplatePack:
     break;
   }
-  count = 0;
+
   return lldb::eEncodingInvalid;
 }
 

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

@@ -837,8 +837,7 @@ class TypeSystemClang : public TypeSystem {
   GetBitSize(lldb::opaque_compiler_type_t type,
              ExecutionContextScope *exe_scope) override;
 
-  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/Symbol/CompilerType.cpp

@@ -793,10 +793,10 @@ CompilerType::GetTypeBitAlign(ExecutionContextScope *exe_scope) const {
   return {};
 }
 
-lldb::Encoding CompilerType::GetEncoding(uint64_t &count) const {
+lldb::Encoding CompilerType::GetEncoding() const {
   if (IsValid())
     if (auto type_system_sp = GetTypeSystem())
-      return type_system_sp->GetEncoding(m_type, count);
+      return type_system_sp->GetEncoding(m_type);
   return lldb::eEncodingInvalid;
 }
 
@@ -1093,10 +1093,10 @@ bool CompilerType::GetValueAsScalar(const lldb_private::DataExtractor &data,
   if (IsAggregateType()) {
     return false; // Aggregate types don't have scalar values
   } else {
-    uint64_t count = 0;
-    lldb::Encoding encoding = GetEncoding(count);
+    // FIXME: check that type is scalar instead of checking encoding?
+    lldb::Encoding encoding = GetEncoding();
 
-    if (encoding == lldb::eEncodingInvalid || count != 1)
+    if (encoding == lldb::eEncodingInvalid || (GetTypeInfo() & eTypeIsComplex))
       return false;
 
     auto byte_size_or_err = GetByteSize(exe_scope);

lldb/source/Symbol/Type.cpp

@@ -531,9 +531,9 @@ lldb::TypeSP Type::GetTypedefType() {
 
 lldb::Format Type::GetFormat() { return GetForwardCompilerType().GetFormat(); }
 
-lldb::Encoding Type::GetEncoding(uint64_t &count) {
+lldb::Encoding Type::GetEncoding() {
   // Make sure we resolve our type if it already hasn't been.
-  return GetForwardCompilerType().GetEncoding(count);
+  return GetForwardCompilerType().GetEncoding();
 }
 
 bool Type::ReadFromMemory(ExecutionContext *exe_ctx, lldb::addr_t addr,

lldb/source/ValueObject/ValueObject.cpp

@@ -790,8 +790,7 @@ bool ValueObject::SetData(DataExtractor &data, Status &error) {
     return false;
   }
 
-  uint64_t count = 0;
-  const Encoding encoding = GetCompilerType().GetEncoding(count);
+  const Encoding encoding = GetCompilerType().GetEncoding();
 
   const size_t byte_size = llvm::expectedToOptional(GetByteSize()).value_or(0);
 
@@ -1669,8 +1668,7 @@ bool ValueObject::SetValueFromCString(const char *value_str, Status &error) {
     return false;
   }
 
-  uint64_t count = 0;
-  const Encoding encoding = GetCompilerType().GetEncoding(count);
+  const Encoding encoding = GetCompilerType().GetEncoding();
 
   const size_t byte_size = llvm::expectedToOptional(GetByteSize()).value_or(0);