[lldb][SymbolFileDWARF][NFC] Add FindFunctionDefinition helper (#152733)

Factors out code to locate a definition DIE from a `FunctionCallLabel`
into a helper. This will be useful for an upcoming refactor that extends
`FindFunctionDefinition`.

Drive-by:
* adjusts some error messages in the `FunctionCallLabel` support code.

Author: Michael137

lldb/source/Expression/IRExecutionUnit.cpp

@@ -799,7 +799,7 @@ ResolveFunctionCallLabel(const FunctionCallLabel &label,
   auto sc_or_err = symbol_file->ResolveFunctionCallLabel(label);
   if (!sc_or_err)
     return llvm::joinErrors(
-        llvm::createStringError("failed to resolve function by UID"),
+        llvm::createStringError("failed to resolve function by UID:"),
         sc_or_err.takeError());
 
   SymbolContextList sc_list;

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

@@ -2483,6 +2483,30 @@ bool SymbolFileDWARF::ResolveFunction(const DWARFDIE &orig_die,
   return false;
 }
 
+DWARFDIE
+SymbolFileDWARF::FindFunctionDefinition(const FunctionCallLabel &label) {
+  DWARFDIE definition;
+  Module::LookupInfo info(ConstString(label.lookup_name),
+                          lldb::eFunctionNameTypeFull,
+                          lldb::eLanguageTypeUnknown);
+
+  m_index->GetFunctions(info, *this, {}, [&](DWARFDIE entry) {
+    if (entry.GetAttributeValueAsUnsigned(llvm::dwarf::DW_AT_declaration, 0))
+      return IterationAction::Continue;
+
+    // We don't check whether the specification DIE for this function
+    // corresponds to the declaration DIE because the declaration might be in
+    // a type-unit but the definition in the compile-unit (and it's
+    // specifcation would point to the declaration in the compile-unit). We
+    // rely on the mangled name within the module to be enough to find us the
+    // unique definition.
+    definition = entry;
+    return IterationAction::Stop;
+  });
+
+  return definition;
+}
+
 llvm::Expected<SymbolContext>
 SymbolFileDWARF::ResolveFunctionCallLabel(const FunctionCallLabel &label) {
   std::lock_guard<std::recursive_mutex> guard(GetModuleMutex());
@@ -2495,37 +2519,19 @@ SymbolFileDWARF::ResolveFunctionCallLabel(const FunctionCallLabel &label) {
   // Label was created using a declaration DIE. Need to fetch the definition
   // to resolve the function call.
   if (die.GetAttributeValueAsUnsigned(llvm::dwarf::DW_AT_declaration, 0)) {
-    Module::LookupInfo info(ConstString(label.lookup_name),
-                            lldb::eFunctionNameTypeFull,
-                            lldb::eLanguageTypeUnknown);
-
-    m_index->GetFunctions(info, *this, {}, [&](DWARFDIE entry) {
-      if (entry.GetAttributeValueAsUnsigned(llvm::dwarf::DW_AT_declaration, 0))
-        return IterationAction::Continue;
-
-      // We don't check whether the specification DIE for this function
-      // corresponds to the declaration DIE because the declaration might be in
-      // a type-unit but the definition in the compile-unit (and it's
-      // specifcation would point to the declaration in the compile-unit). We
-      // rely on the mangled name within the module to be enough to find us the
-      // unique definition.
-      die = entry;
-      return IterationAction::Stop;
-    });
+    auto definition = FindFunctionDefinition(label);
+    if (!definition)
+      return llvm::createStringError("failed to find definition DIE");
 
-    if (die.GetAttributeValueAsUnsigned(llvm::dwarf::DW_AT_declaration, 0))
-      return llvm::createStringError(
-          llvm::formatv("failed to find definition DIE for {0}", label));
+    die = std::move(definition);
   }
 
   SymbolContextList sc_list;
   if (!ResolveFunction(die, /*include_inlines=*/false, sc_list))
-    return llvm::createStringError(
-        llvm::formatv("failed to resolve function for {0}", label));
+    return llvm::createStringError("failed to resolve function");
 
   if (sc_list.IsEmpty())
-    return llvm::createStringError(
-        llvm::formatv("failed to find function for {0}", label));
+    return llvm::createStringError("failed to find function");
 
   assert(sc_list.GetSize() == 1);
 

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

@@ -373,6 +373,13 @@ class SymbolFileDWARF : public SymbolFileCommon {
   /// Returns the DWARFIndex for this symbol, if it exists.
   DWARFIndex *getIndex() { return m_index.get(); }
 
+private:
+  /// Find the definition DIE for the specified \c label in this
+  /// SymbolFile.
+  ///
+  /// \returns A valid definition DIE on success.
+  DWARFDIE FindFunctionDefinition(const FunctionCallLabel &label);
+
 protected:
   SymbolFileDWARF(const SymbolFileDWARF &) = delete;
   const SymbolFileDWARF &operator=(const SymbolFileDWARF &) = delete;