[lldb][TypeSystemClang] Added unique builtins types for __bf16 and _Float16 (#157674)

During debugging applization with __bf16 and _Float16 float types it was
discovered that lldb creates the same CompilerType for them. This can
cause an infinite recursion error, if one tries to create two struct
specializations with these types and then inherit one specialization
from another.

Author: tgs-sc

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

@@ -960,6 +960,12 @@ CompilerType TypeSystemClang::GetBuiltinTypeForDWARFEncodingAndBitSize(
     if (type_name == "long double" &&
         QualTypeMatchesBitSize(bit_size, ast, ast.LongDoubleTy))
       return GetType(ast.LongDoubleTy);
+    if (type_name == "__bf16" &&
+        QualTypeMatchesBitSize(bit_size, ast, ast.BFloat16Ty))
+      return GetType(ast.BFloat16Ty);
+    if (type_name == "_Float16" &&
+        QualTypeMatchesBitSize(bit_size, ast, ast.Float16Ty))
+      return GetType(ast.Float16Ty);
     // As Rust currently uses `TypeSystemClang`, match `f128` here as well so it
     // doesn't get misinterpreted as `long double` on targets where they are
     // the same size but different formats.
@@ -1792,6 +1798,8 @@ bool TypeSystemClang::RecordHasFields(const RecordDecl *record_decl) {
     for (base_class = cxx_record_decl->bases_begin(),
         base_class_end = cxx_record_decl->bases_end();
          base_class != base_class_end; ++base_class) {
+      assert(record_decl != base_class->getType()->getAsCXXRecordDecl() &&
+             "Base can't inherit from itself.");
       if (RecordHasFields(base_class->getType()->getAsCXXRecordDecl()))
         return true;
     }

lldb/test/API/lang/cpp/floating-types-specialization/Makefile

@@ -0,0 +1,3 @@
+CXX_SOURCES := main.cpp
+
+include Makefile.rules

lldb/test/API/lang/cpp/floating-types-specialization/TestCppFloatingTypesSpecialization.py

@@ -0,0 +1,22 @@
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+
+class TestCase(TestBase):
+    def test(self):
+        self.build()
+        lldbutil.run_to_source_breakpoint(
+            self, "// break here", lldb.SBFileSpec("main.cpp", False)
+        )
+
+        self.expect_expr("f0", result_type="Foo<__bf16>")
+        self.expect_expr("f1", result_type="Foo<__fp16>")
+
+        # Test sizeof to ensure while computing layout we don't do
+        # infinite recursion.
+        v = self.frame().EvaluateExpression("sizeof(f0)")
+        self.assertEqual(v.GetValueAsUnsigned() > 0, True)
+        v = self.frame().EvaluateExpression("sizeof(f1)")
+        self.assertEqual(v.GetValueAsUnsigned() > 0, True)

lldb/test/API/lang/cpp/floating-types-specialization/main.cpp

@@ -0,0 +1,11 @@
+template <typename T> struct Foo;
+
+template <> struct Foo<__bf16> {};
+
+template <> struct Foo<_Float16> : Foo<__bf16> {};
+
+int main() {
+  Foo<__bf16> f0;
+  Foo<_Float16> f1;
+  return 0; // break here
+}

lldb/test/API/lang/cpp/template-arguments/TestCppTemplateArguments.py

@@ -82,7 +82,7 @@ def test(self):
         value = self.expect_expr("temp7", result_type="Foo<__fp16, __fp16>")
         self.assertFalse(value.GetType().GetTemplateArgumentValue(target, 1))
 
-        value = self.expect_expr("temp8", result_type="Foo<__fp16, __fp16>")
+        value = self.expect_expr("temp8", result_type="Foo<__bf16, __bf16>")
         self.assertFalse(value.GetType().GetTemplateArgumentValue(target, 1))
 
         value = self.expect_expr("temp9", result_type="Bar<double, 1.200000e+00>")