[Lldb-commits] [lldb] [lldb] Implement a formatter bytecode interpreter in C++ (PR #114333)

Adrian Prantl via lldb-commits lldb-commits at lists.llvm.org
Mon Dec 9 16:18:31 PST 2024


https://github.com/adrian-prantl updated https://github.com/llvm/llvm-project/pull/114333

>From 1e51be85ed88857a0ef53cf1a0756b98f7c11a1b Mon Sep 17 00:00:00 2001
From: Dave Lee <davelee.com at gmail.com>
Date: Wed, 24 Jan 2024 12:42:45 -0800
Subject: [PATCH 1/2] [lldb] Load embedded type summary section (#7859) (#8040)

Add support for type summaries embedded into the binary.

These embedded summaries will typically be generated by Swift macros,
but can also be generated by any other means.

rdar://115184658
---
 lldb/include/lldb/lldb-enumerations.h         |  1 +
 lldb/source/Core/Section.cpp                  |  3 +
 .../Plugins/ObjectFile/ELF/ObjectFileELF.cpp  |  1 +
 .../ObjectFile/Mach-O/ObjectFileMachO.cpp     |  4 +
 .../ObjectFile/PECOFF/ObjectFilePECOFF.cpp    |  1 +
 lldb/source/Symbol/ObjectFile.cpp             |  1 +
 lldb/source/Target/Target.cpp                 | 74 +++++++++++++++++++
 .../data-formatter/embedded-summary/Makefile  |  2 +
 .../TestEmbeddedTypeSummary.py                | 12 +++
 .../data-formatter/embedded-summary/main.c    | 22 ++++++
 10 files changed, 121 insertions(+)
 create mode 100644 lldb/test/API/functionalities/data-formatter/embedded-summary/Makefile
 create mode 100644 lldb/test/API/functionalities/data-formatter/embedded-summary/TestEmbeddedTypeSummary.py
 create mode 100644 lldb/test/API/functionalities/data-formatter/embedded-summary/main.c

diff --git a/lldb/include/lldb/lldb-enumerations.h b/lldb/include/lldb/lldb-enumerations.h
index a9a66ea2662f39..e00ec7f17c5cb8 100644
--- a/lldb/include/lldb/lldb-enumerations.h
+++ b/lldb/include/lldb/lldb-enumerations.h
@@ -763,6 +763,7 @@ enum SectionType {
   eSectionTypeDWARFDebugLocListsDwo,
   eSectionTypeDWARFDebugTuIndex,
   eSectionTypeCTF,
+  eSectionTypeLLDBTypeSummaries,
   eSectionTypeSwiftModules,
 };
 
diff --git a/lldb/source/Core/Section.cpp b/lldb/source/Core/Section.cpp
index 0763e88d4608f4..ee01b4ce06ca1e 100644
--- a/lldb/source/Core/Section.cpp
+++ b/lldb/source/Core/Section.cpp
@@ -147,6 +147,8 @@ const char *Section::GetTypeAsCString() const {
     return "dwarf-gnu-debugaltlink";
   case eSectionTypeCTF:
     return "ctf";
+  case eSectionTypeLLDBTypeSummaries:
+    return "lldb-type-summaries";
   case eSectionTypeOther:
     return "regular";
   case eSectionTypeSwiftModules:
@@ -457,6 +459,7 @@ bool Section::ContainsOnlyDebugInfo() const {
   case eSectionTypeDWARFAppleObjC:
   case eSectionTypeDWARFGNUDebugAltLink:
   case eSectionTypeCTF:
+  case eSectionTypeLLDBTypeSummaries:
   case eSectionTypeSwiftModules:
     return true;
   }
diff --git a/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp b/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp
index eac9ab4577d3eb..a8249cf103833e 100644
--- a/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp
+++ b/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp
@@ -1696,6 +1696,7 @@ static SectionType GetSectionTypeFromName(llvm::StringRef Name) {
       .Case(".gnu_debugaltlink", eSectionTypeDWARFGNUDebugAltLink)
       .Case(".gosymtab", eSectionTypeGoSymtab)
       .Case(".text", eSectionTypeCode)
+      .Case(".lldbsummaries", lldb::eSectionTypeLLDBTypeSummaries)
       .Case(".swift_ast", eSectionTypeSwiftModules)
       .Default(eSectionTypeOther);
 }
diff --git a/lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp b/lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp
index daffa1379fe575..7e17fd8c53cd01 100644
--- a/lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp
+++ b/lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp
@@ -1209,6 +1209,7 @@ AddressClass ObjectFileMachO::GetAddressClass(lldb::addr_t file_addr) {
         case eSectionTypeDWARFAppleObjC:
         case eSectionTypeDWARFGNUDebugAltLink:
         case eSectionTypeCTF:
+        case eSectionTypeLLDBTypeSummaries:
         case eSectionTypeSwiftModules:
           return AddressClass::eDebug;
 
@@ -1484,6 +1485,7 @@ static lldb::SectionType GetSectionType(uint32_t flags,
   static ConstString g_sect_name_data("__data");
   static ConstString g_sect_name_go_symtab("__gosymtab");
   static ConstString g_sect_name_ctf("__ctf");
+  static ConstString g_sect_name_lldb_summaries("__lldbsummaries");
   static ConstString g_sect_name_swift_ast("__swift_ast");
 
   if (section_name == g_sect_name_dwarf_debug_abbrev)
@@ -1564,6 +1566,8 @@ static lldb::SectionType GetSectionType(uint32_t flags,
     return eSectionTypeGoSymtab;
   if (section_name == g_sect_name_ctf)
     return eSectionTypeCTF;
+  if (section_name == g_sect_name_lldb_summaries)
+    return lldb::eSectionTypeLLDBTypeSummaries;
   if (section_name == g_sect_name_swift_ast)
     return eSectionTypeSwiftModules;
   if (section_name == g_sect_name_objc_data ||
diff --git a/lldb/source/Plugins/ObjectFile/PECOFF/ObjectFilePECOFF.cpp b/lldb/source/Plugins/ObjectFile/PECOFF/ObjectFilePECOFF.cpp
index 8d9c919bc9b101..bb712da7f6d67d 100644
--- a/lldb/source/Plugins/ObjectFile/PECOFF/ObjectFilePECOFF.cpp
+++ b/lldb/source/Plugins/ObjectFile/PECOFF/ObjectFilePECOFF.cpp
@@ -1010,6 +1010,7 @@ SectionType ObjectFilePECOFF::GetSectionType(llvm::StringRef sect_name,
           // .eh_frame can be truncated to 8 chars.
           .Cases(".eh_frame", ".eh_fram", eSectionTypeEHFrame)
           .Case(".gosymtab", eSectionTypeGoSymtab)
+          .Case(".lldbsummaries", lldb::eSectionTypeLLDBTypeSummaries)
           .Case("swiftast", eSectionTypeSwiftModules)
           .Default(eSectionTypeInvalid);
   if (section_type != eSectionTypeInvalid)
diff --git a/lldb/source/Symbol/ObjectFile.cpp b/lldb/source/Symbol/ObjectFile.cpp
index 35317d209de1f9..3100e6b813b631 100644
--- a/lldb/source/Symbol/ObjectFile.cpp
+++ b/lldb/source/Symbol/ObjectFile.cpp
@@ -366,6 +366,7 @@ AddressClass ObjectFile::GetAddressClass(addr_t file_addr) {
           case eSectionTypeDWARFAppleObjC:
           case eSectionTypeDWARFGNUDebugAltLink:
           case eSectionTypeCTF:
+          case eSectionTypeLLDBTypeSummaries:
           case eSectionTypeSwiftModules:
             return AddressClass::eDebug;
           case eSectionTypeEHFrame:
diff --git a/lldb/source/Target/Target.cpp b/lldb/source/Target/Target.cpp
index 4bac94f35d6cfb..9ac85ad3ed5ee6 100644
--- a/lldb/source/Target/Target.cpp
+++ b/lldb/source/Target/Target.cpp
@@ -24,6 +24,9 @@
 #include "lldb/Core/Section.h"
 #include "lldb/Core/SourceManager.h"
 #include "lldb/Core/StructuredDataImpl.h"
+#include "lldb/Core/ValueObject.h"
+#include "lldb/Core/ValueObjectConstResult.h"
+#include "lldb/DataFormatters/DataVisualization.h"
 #include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/ExpressionVariable.h"
 #include "lldb/Expression/REPL.h"
@@ -1538,6 +1541,76 @@ static void LoadScriptingResourceForModule(const ModuleSP &module_sp,
                                                   feedback_stream.GetData());
 }
 
+// Load type summaries embedded in the binary. These are type summaries provided
+// by the authors of the code.
+static void LoadTypeSummariesForModule(ModuleSP module_sp) {
+  auto *sections = module_sp->GetSectionList();
+  if (!sections)
+    return;
+
+  auto summaries_sp =
+      sections->FindSectionByType(eSectionTypeLLDBTypeSummaries, true);
+  if (!summaries_sp)
+    return;
+
+  Log *log = GetLog(LLDBLog::DataFormatters);
+  const char *module_name = module_sp->GetObjectName().GetCString();
+
+  TypeCategoryImplSP category;
+  DataVisualization::Categories::GetCategory(ConstString("default"), category);
+
+  // The type summary record is serialized as follows.
+  //
+  // Each record contains, in order:
+  //   * Version number of the record format
+  //   * The remaining size of the record
+  //   * The size of the type identifier
+  //   * The type identifier, either a type name, or a regex
+  //   * The size of the summary string
+  //   * The summary string
+  //
+  // Integers are encoded using ULEB.
+  //
+  // Strings are encoded with first a length (ULEB), then the string contents,
+  // and lastly a null terminator. The length includes the null.
+
+  DataExtractor extractor;
+  auto section_size = summaries_sp->GetSectionData(extractor);
+  lldb::offset_t offset = 0;
+  while (offset < section_size) {
+    uint64_t version = extractor.GetULEB128(&offset);
+    uint64_t record_size = extractor.GetULEB128(&offset);
+    if (version == 1) {
+      uint64_t type_size = extractor.GetULEB128(&offset);
+      llvm::StringRef type_name = extractor.GetCStr(&offset, type_size);
+      uint64_t summary_size = extractor.GetULEB128(&offset);
+      llvm::StringRef summary_string = extractor.GetCStr(&offset, summary_size);
+      if (!type_name.empty() && !summary_string.empty()) {
+        TypeSummaryImpl::Flags flags;
+        auto summary_sp =
+            std::make_shared<StringSummaryFormat>(flags, summary_string.data());
+        FormatterMatchType match_type = eFormatterMatchExact;
+        if (summary_string.front() == '^' && summary_string.back() == '$')
+          match_type = eFormatterMatchRegex;
+        category->AddTypeSummary(type_name, match_type, summary_sp);
+        LLDB_LOGF(log, "Loaded embedded type summary for '%s' from %s.",
+                  type_name.data(), module_name);
+      } else {
+        if (type_name.empty())
+          LLDB_LOGF(log, "Missing string(s) in embedded type summary in %s.",
+                    module_name);
+      }
+    } else {
+      // Skip unsupported record.
+      offset += record_size;
+      LLDB_LOGF(
+          log,
+          "Skipping unsupported embedded type summary of version %llu in %s.",
+          version, module_name);
+    }
+  }
+}
+
 void Target::ClearModules(bool delete_locations) {
   ModulesDidUnload(m_images, delete_locations);
   m_section_load_history.Clear();
@@ -1818,6 +1891,7 @@ void Target::ModulesDidLoad(ModuleList &module_list) {
     for (size_t idx = 0; idx < num_images; ++idx) {
       ModuleSP module_sp(module_list.GetModuleAtIndex(idx));
       LoadScriptingResourceForModule(module_sp, this);
+      LoadTypeSummariesForModule(module_sp);
     }
     m_breakpoint_list.UpdateBreakpoints(module_list, true, false);
     m_internal_breakpoint_list.UpdateBreakpoints(module_list, true, false);
diff --git a/lldb/test/API/functionalities/data-formatter/embedded-summary/Makefile b/lldb/test/API/functionalities/data-formatter/embedded-summary/Makefile
new file mode 100644
index 00000000000000..c9319d6e6888a4
--- /dev/null
+++ b/lldb/test/API/functionalities/data-formatter/embedded-summary/Makefile
@@ -0,0 +1,2 @@
+C_SOURCES := main.c
+include Makefile.rules
diff --git a/lldb/test/API/functionalities/data-formatter/embedded-summary/TestEmbeddedTypeSummary.py b/lldb/test/API/functionalities/data-formatter/embedded-summary/TestEmbeddedTypeSummary.py
new file mode 100644
index 00000000000000..b8ce7d9f76eb9e
--- /dev/null
+++ b/lldb/test/API/functionalities/data-formatter/embedded-summary/TestEmbeddedTypeSummary.py
@@ -0,0 +1,12 @@
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+
+class TestCase(TestBase):
+    @skipUnlessDarwin
+    def test(self):
+        self.build()
+        lldbutil.run_to_source_breakpoint(self, "break here", lldb.SBFileSpec("main.c"))
+        self.expect("v player", substrs=['"Dirk" (41)'])
diff --git a/lldb/test/API/functionalities/data-formatter/embedded-summary/main.c b/lldb/test/API/functionalities/data-formatter/embedded-summary/main.c
new file mode 100644
index 00000000000000..9ddd64246f726c
--- /dev/null
+++ b/lldb/test/API/functionalities/data-formatter/embedded-summary/main.c
@@ -0,0 +1,22 @@
+#include <stdio.h>
+
+struct Player {
+  char *name;
+  int number;
+};
+
+__attribute__((used, section("__DATA_CONST,__lldbsummaries"))) unsigned char
+    _Player_type_summary[] = "\x01"     // version
+                             "\x25"     // record size
+                             "\x07"     // type name size
+                             "Player\0" // type name
+                             "\x1c"     // summary string size
+                             "${var.name} (${var.number})"; // summary string
+
+int main() {
+  struct Player player;
+  player.name = "Dirk";
+  player.number = 41;
+  puts("break here");
+  return 0;
+}

>From 4e7eb4780a82e0896e6e8daaff741d3e62051f0a Mon Sep 17 00:00:00 2001
From: Adrian Prantl <aprantl at apple.com>
Date: Mon, 28 Oct 2024 17:18:34 -0700
Subject: [PATCH 2/2] [lldb] Implement a formatter bytecode interpreter in C++

Compared to the python version, this also does type checking and error
handling, so it's slightly longer, however, it's still comfortably
under 500 lines.
---
 .../lldb/DataFormatters/FormatterSection.h    |  26 +
 .../lldb/DataFormatters/FormattersHelpers.h   |   3 +-
 .../include/lldb/DataFormatters/TypeSummary.h |  23 +-
 lldb/include/lldb/lldb-enumerations.h         |   1 +
 lldb/source/API/SBTypeSummary.cpp             |   1 +
 lldb/source/Core/Section.cpp                  |   7 +-
 lldb/source/DataFormatters/CMakeLists.txt     |   2 +
 .../DataFormatters/FormatterBytecode.cpp      | 575 ++++++++++++++++++
 .../DataFormatters/FormatterBytecode.def      | 101 +++
 .../source/DataFormatters/FormatterBytecode.h |  64 ++
 .../DataFormatters/FormatterSection.cpp       | 162 +++++
 lldb/source/DataFormatters/TypeSummary.cpp    |  77 ++-
 .../Plugins/ObjectFile/ELF/ObjectFileELF.cpp  |   1 +
 .../ObjectFile/Mach-O/ObjectFileMachO.cpp     |   4 +
 .../ObjectFile/PECOFF/ObjectFilePECOFF.cpp    |   1 +
 lldb/source/Symbol/ObjectFile.cpp             |   1 +
 lldb/source/Target/Target.cpp                 |  77 +--
 .../data-formatter/bytecode-summary/Makefile  |   2 +
 .../bytecode-summary/TestBytecodeSummary.py   |  15 +
 .../data-formatter/bytecode-summary/main.cpp  |  41 ++
 lldb/unittests/DataFormatter/CMakeLists.txt   |   1 +
 .../DataFormatter/FormatterBytecodeTest.cpp   | 261 ++++++++
 22 files changed, 1363 insertions(+), 83 deletions(-)
 create mode 100644 lldb/include/lldb/DataFormatters/FormatterSection.h
 create mode 100644 lldb/source/DataFormatters/FormatterBytecode.cpp
 create mode 100644 lldb/source/DataFormatters/FormatterBytecode.def
 create mode 100644 lldb/source/DataFormatters/FormatterBytecode.h
 create mode 100644 lldb/source/DataFormatters/FormatterSection.cpp
 create mode 100644 lldb/test/API/functionalities/data-formatter/bytecode-summary/Makefile
 create mode 100644 lldb/test/API/functionalities/data-formatter/bytecode-summary/TestBytecodeSummary.py
 create mode 100644 lldb/test/API/functionalities/data-formatter/bytecode-summary/main.cpp
 create mode 100644 lldb/unittests/DataFormatter/FormatterBytecodeTest.cpp

diff --git a/lldb/include/lldb/DataFormatters/FormatterSection.h b/lldb/include/lldb/DataFormatters/FormatterSection.h
new file mode 100644
index 00000000000000..0613fba6c3a602
--- /dev/null
+++ b/lldb/include/lldb/DataFormatters/FormatterSection.h
@@ -0,0 +1,26 @@
+//===-- FormattersSection.h -------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLDB_DATAFORMATTERS_FORMATTERSECTION_H
+#define LLDB_DATAFORMATTERS_FORMATTERSECTION_H
+
+#include "lldb/lldb-enumerations.h"
+#include "lldb/lldb-forward.h"
+
+namespace lldb_private {
+/// Load type summaries embedded in the binary. These are type summaries
+/// provided by the authors of the code.
+void LoadTypeSummariesForModule(lldb::ModuleSP module_sp);
+
+/// Load data formatters embedded in the binary. These are formatters provided
+/// by the authors of the code using LLDB formatter bytecode.
+void LoadFormattersForModule(lldb::ModuleSP module_sp);
+
+} // namespace lldb_private
+
+#endif // LLDB_DATAFORMATTERS_FORMATTERSECTION_H
diff --git a/lldb/include/lldb/DataFormatters/FormattersHelpers.h b/lldb/include/lldb/DataFormatters/FormattersHelpers.h
index a2e8521d96651b..a98042fd40f93a 100644
--- a/lldb/include/lldb/DataFormatters/FormattersHelpers.h
+++ b/lldb/include/lldb/DataFormatters/FormattersHelpers.h
@@ -1,5 +1,4 @@
-//===-- FormattersHelpers.h --------------------------------------*- C++
-//-*-===//
+//===-- FormattersHelpers.h -------------------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
diff --git a/lldb/include/lldb/DataFormatters/TypeSummary.h b/lldb/include/lldb/DataFormatters/TypeSummary.h
index 382824aa2813da..f4d5563516ecb8 100644
--- a/lldb/include/lldb/DataFormatters/TypeSummary.h
+++ b/lldb/include/lldb/DataFormatters/TypeSummary.h
@@ -22,6 +22,10 @@
 #include "lldb/Utility/Status.h"
 #include "lldb/Utility/StructuredData.h"
 
+namespace llvm {
+class MemoryBuffer;
+}
+
 namespace lldb_private {
 class TypeSummaryOptions {
 public:
@@ -44,7 +48,7 @@ class TypeSummaryOptions {
 
 class TypeSummaryImpl {
 public:
-  enum class Kind { eSummaryString, eScript, eCallback, eInternal };
+  enum class Kind { eSummaryString, eScript, eBytecode, eCallback, eInternal };
 
   virtual ~TypeSummaryImpl() = default;
 
@@ -409,6 +413,23 @@ struct ScriptSummaryFormat : public TypeSummaryImpl {
   ScriptSummaryFormat(const ScriptSummaryFormat &) = delete;
   const ScriptSummaryFormat &operator=(const ScriptSummaryFormat &) = delete;
 };
+
+/// A summary formatter that is defined in LLDB formmater bytecode.
+class BytecodeSummaryFormat : public TypeSummaryImpl {
+  std::unique_ptr<llvm::MemoryBuffer> m_bytecode;
+
+public:
+  BytecodeSummaryFormat(const TypeSummaryImpl::Flags &flags,
+                        std::unique_ptr<llvm::MemoryBuffer> bytecode);
+  bool FormatObject(ValueObject *valobj, std::string &dest,
+                    const TypeSummaryOptions &options) override;
+  std::string GetDescription() override;
+  std::string GetName() override;
+  static bool classof(const TypeSummaryImpl *S) {
+    return S->GetKind() == Kind::eBytecode;
+  }
+};
+
 } // namespace lldb_private
 
 #endif // LLDB_DATAFORMATTERS_TYPESUMMARY_H
diff --git a/lldb/include/lldb/lldb-enumerations.h b/lldb/include/lldb/lldb-enumerations.h
index e00ec7f17c5cb8..0094fcd596fdf7 100644
--- a/lldb/include/lldb/lldb-enumerations.h
+++ b/lldb/include/lldb/lldb-enumerations.h
@@ -764,6 +764,7 @@ enum SectionType {
   eSectionTypeDWARFDebugTuIndex,
   eSectionTypeCTF,
   eSectionTypeLLDBTypeSummaries,
+  eSectionTypeLLDBFormatters,
   eSectionTypeSwiftModules,
 };
 
diff --git a/lldb/source/API/SBTypeSummary.cpp b/lldb/source/API/SBTypeSummary.cpp
index a5e87188c9f630..856ee0ed3175b3 100644
--- a/lldb/source/API/SBTypeSummary.cpp
+++ b/lldb/source/API/SBTypeSummary.cpp
@@ -343,6 +343,7 @@ bool SBTypeSummary::IsEqualTo(lldb::SBTypeSummary &rhs) {
   case TypeSummaryImpl::Kind::eCallback:
     return llvm::dyn_cast<CXXFunctionSummaryFormat>(m_opaque_sp.get()) ==
            llvm::dyn_cast<CXXFunctionSummaryFormat>(rhs.m_opaque_sp.get());
+  case TypeSummaryImpl::Kind::eBytecode:
   case TypeSummaryImpl::Kind::eScript:
     if (IsFunctionCode() != rhs.IsFunctionCode())
       return false;
diff --git a/lldb/source/Core/Section.cpp b/lldb/source/Core/Section.cpp
index ee01b4ce06ca1e..31273ede618f21 100644
--- a/lldb/source/Core/Section.cpp
+++ b/lldb/source/Core/Section.cpp
@@ -149,10 +149,12 @@ const char *Section::GetTypeAsCString() const {
     return "ctf";
   case eSectionTypeLLDBTypeSummaries:
     return "lldb-type-summaries";
-  case eSectionTypeOther:
-    return "regular";
+  case eSectionTypeLLDBFormatters:
+    return "lldb-formatters";
   case eSectionTypeSwiftModules:
     return "swift-modules";
+  case eSectionTypeOther:
+    return "regular";
   }
   return "unknown";
 }
@@ -460,6 +462,7 @@ bool Section::ContainsOnlyDebugInfo() const {
   case eSectionTypeDWARFGNUDebugAltLink:
   case eSectionTypeCTF:
   case eSectionTypeLLDBTypeSummaries:
+  case eSectionTypeLLDBFormatters:
   case eSectionTypeSwiftModules:
     return true;
   }
diff --git a/lldb/source/DataFormatters/CMakeLists.txt b/lldb/source/DataFormatters/CMakeLists.txt
index 13faf65227d2c9..91b10ba9e0ac8b 100644
--- a/lldb/source/DataFormatters/CMakeLists.txt
+++ b/lldb/source/DataFormatters/CMakeLists.txt
@@ -5,7 +5,9 @@ add_lldb_library(lldbDataFormatters NO_PLUGIN_DEPENDENCIES
   FormatCache.cpp
   FormatClasses.cpp
   FormatManager.cpp
+  FormatterBytecode.cpp
   FormattersHelpers.cpp
+  FormatterSection.cpp
   LanguageCategory.cpp
   StringPrinter.cpp
   TypeCategory.cpp
diff --git a/lldb/source/DataFormatters/FormatterBytecode.cpp b/lldb/source/DataFormatters/FormatterBytecode.cpp
new file mode 100644
index 00000000000000..7cad3474edebd3
--- /dev/null
+++ b/lldb/source/DataFormatters/FormatterBytecode.cpp
@@ -0,0 +1,575 @@
+//===-- FormatterBytecode.cpp ---------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "FormatterBytecode.h"
+#include "lldb/Utility/LLDBLog.h"
+#include "lldb/ValueObject/ValueObject.h"
+#include "llvm/ADT/StringExtras.h"
+#include "llvm/Support/DataExtractor.h"
+#include "llvm/Support/Format.h"
+#include "llvm/Support/FormatProviders.h"
+#include "llvm/Support/FormatVariadicDetails.h"
+
+using namespace lldb;
+namespace lldb_private {
+
+std::string toString(FormatterBytecode::OpCodes op) {
+  switch (op) {
+#define DEFINE_OPCODE(OP, MNEMONIC, NAME)                                      \
+  case OP: {                                                                   \
+    const char *s = MNEMONIC;                                                  \
+    return s ? s : #NAME;                                                      \
+  }
+#include "FormatterBytecode.def"
+#undef DEFINE_SIGNATURE
+  }
+  return llvm::utostr(op);
+}
+
+std::string toString(FormatterBytecode::Selectors sel) {
+  switch (sel) {
+#define DEFINE_SELECTOR(ID, NAME)                                              \
+  case ID:                                                                     \
+    return "@" #NAME;
+#include "FormatterBytecode.def"
+#undef DEFINE_SIGNATURE
+  }
+  return "@" + llvm::utostr(sel);
+}
+
+std::string toString(FormatterBytecode::Signatures sig) {
+  switch (sig) {
+#define DEFINE_SIGNATURE(ID, NAME)                                             \
+  case ID:                                                                     \
+    return "@" #NAME;
+#include "FormatterBytecode.def"
+#undef DEFINE_SIGNATURE
+  }
+  return llvm::utostr(sig);
+}
+
+std::string toString(const FormatterBytecode::DataStack &data) {
+  std::string s;
+  llvm::raw_string_ostream os(s);
+  os << "[ ";
+  for (auto &d : data) {
+    if (auto s = std::get_if<std::string>(&d))
+      os << '"' << *s << '"';
+    else if (auto u = std::get_if<uint64_t>(&d))
+      os << *u << 'u';
+    else if (auto i = std::get_if<int64_t>(&d))
+      os << *i;
+    else if (auto valobj = std::get_if<ValueObjectSP>(&d)) {
+      if (!valobj->get())
+        os << "null";
+      else
+        os << "object(" << valobj->get()->GetValueAsCString() << ')';
+    } else if (auto type = std::get_if<CompilerType>(&d)) {
+      os << '(' << type->GetTypeName(true) << ')';
+    } else if (auto sel = std::get_if<FormatterBytecode::Selectors>(&d)) {
+      os << toString(*sel);
+    }
+    os << ' ';
+  }
+  os << ']';
+  return s;
+}
+
+namespace FormatterBytecode {
+
+/// Implement the @format function.
+static llvm::Error FormatImpl(DataStack &data) {
+  auto fmt = data.Pop<std::string>();
+  auto replacements =
+      llvm::formatv_object_base::parseFormatString(fmt, 0, false);
+  std::string s;
+  llvm::raw_string_ostream os(s);
+  unsigned num_args = 0;
+  for (const auto &r : replacements)
+    if (r.Type == llvm::ReplacementType::Format)
+      num_args = std::max(num_args, r.Index + 1);
+
+  if (data.size() < num_args)
+    return llvm::createStringError("not enough arguments");
+
+  for (const auto &r : replacements) {
+    if (r.Type == llvm::ReplacementType::Literal) {
+      os << r.Spec;
+      continue;
+    }
+    using namespace llvm::support::detail;
+    auto arg = data[data.size() - num_args + r.Index];
+    auto format = [&](format_adapter &&adapter) {
+      llvm::FmtAlign Align(adapter, r.Where, r.Width, r.Pad);
+      Align.format(os, r.Options);
+    };
+
+    if (auto s = std::get_if<std::string>(&arg))
+      format(build_format_adapter(s->c_str()));
+    else if (auto u = std::get_if<uint64_t>(&arg))
+      format(build_format_adapter(u));
+    else if (auto i = std::get_if<int64_t>(&arg))
+      format(build_format_adapter(i));
+    else if (auto valobj = std::get_if<ValueObjectSP>(&arg)) {
+      if (!valobj->get())
+        format(build_format_adapter("null object"));
+      else
+        format(build_format_adapter(valobj->get()->GetValueAsCString()));
+    } else if (auto type = std::get_if<CompilerType>(&arg))
+      format(build_format_adapter(type->GetDisplayTypeName()));
+    else if (auto sel = std::get_if<FormatterBytecode::Selectors>(&arg))
+      format(build_format_adapter(toString(*sel)));
+  }
+  data.Push(s);
+  return llvm::Error::success();
+}
+
+static llvm::Error TypeCheck(llvm::ArrayRef<DataStackElement> data,
+                             DataType type) {
+  if (data.size() < 1)
+    return llvm::createStringError("not enough elements on data stack");
+
+  auto &elem = data.back();
+  switch (type) {
+  case Any:
+    break;
+  case String:
+    if (!std::holds_alternative<std::string>(elem))
+      return llvm::createStringError("expected String");
+    break;
+  case UInt:
+    if (!std::holds_alternative<uint64_t>(elem))
+      return llvm::createStringError("expected UInt");
+    break;
+  case Int:
+    if (!std::holds_alternative<int64_t>(elem))
+      return llvm::createStringError("expected Int");
+    break;
+  case Object:
+    if (!std::holds_alternative<ValueObjectSP>(elem))
+      return llvm::createStringError("expected Object");
+    break;
+  case Type:
+    if (!std::holds_alternative<CompilerType>(elem))
+      return llvm::createStringError("expected Type");
+    break;
+  case Selector:
+    if (!std::holds_alternative<Selectors>(elem))
+      return llvm::createStringError("expected Selector");
+    break;
+  }
+  return llvm::Error::success();
+}
+
+static llvm::Error TypeCheck(llvm::ArrayRef<DataStackElement> data,
+                             DataType type1, DataType type2) {
+  if (auto error = TypeCheck(data, type2))
+    return error;
+  return TypeCheck(data.drop_back(), type1);
+}
+
+static llvm::Error TypeCheck(llvm::ArrayRef<DataStackElement> data,
+                             DataType type1, DataType type2, DataType type3) {
+  if (auto error = TypeCheck(data, type3))
+    return error;
+  return TypeCheck(data.drop_back(1), type2, type1);
+}
+
+llvm::Error Interpret(std::vector<ControlStackElement> &control,
+                      DataStack &data, Selectors sel) {
+  if (control.empty())
+    return llvm::Error::success();
+  // Since the only data types are single endian and ULEBs, the
+  // endianness should not matter.
+  llvm::DataExtractor cur_block(control.back(), true, 64);
+  llvm::DataExtractor::Cursor pc(0);
+
+  while (!control.empty()) {
+    /// Activate the top most block from the control stack.
+    auto activate_block = [&]() {
+      // Save the return address.
+      if (control.size() > 1)
+        control[control.size() - 2] = cur_block.getData().drop_front(pc.tell());
+      cur_block = llvm::DataExtractor(control.back(), true, 64);
+      if (pc)
+        pc = llvm::DataExtractor::Cursor(0);
+    };
+
+    /// Fetch the next byte in the instruction stream.
+    auto next_byte = [&]() -> uint8_t {
+      // At the end of the current block?
+      while (pc.tell() >= cur_block.size() && !control.empty()) {
+        if (control.size() == 1) {
+          control.pop_back();
+          return 0;
+        }
+        control.pop_back();
+        activate_block();
+      }
+
+      // Fetch the next instruction.
+      return cur_block.getU8(pc);
+    };
+
+    // Fetch the next opcode.
+    OpCodes opcode = (OpCodes)next_byte();
+    if (control.empty() || !pc)
+      return pc.takeError();
+
+    LLDB_LOGV(GetLog(LLDBLog::DataFormatters),
+              "[eval {0}] opcode={1}, control={2}, data={3}", toString(sel),
+              toString(opcode), control.size(), toString(data));
+
+    // Various shorthands to improve the readability of error handling.
+#define TYPE_CHECK(...)                                                        \
+  if (auto error = TypeCheck(data, __VA_ARGS__))                               \
+    return error;
+
+    auto error = [&](llvm::Twine msg) {
+      return llvm::createStringError(msg + "(opcode=" + toString(opcode) + ")");
+    };
+
+    switch (opcode) {
+    // Data stack manipulation.
+    case op_dup:
+      TYPE_CHECK(Any);
+      data.Push(data.back());
+      continue;
+    case op_drop:
+      TYPE_CHECK(Any);
+      data.pop_back();
+      continue;
+    case op_pick: {
+      TYPE_CHECK(UInt);
+      uint64_t idx = data.Pop<uint64_t>();
+      if (idx >= data.size())
+        return error("index out of bounds");
+      data.Push(data[idx]);
+      continue;
+    }
+    case op_over:
+      TYPE_CHECK(Any, Any);
+      data.Push(data[data.size() - 2]);
+      continue;
+    case op_swap: {
+      TYPE_CHECK(Any, Any);
+      auto x = data.PopAny();
+      auto y = data.PopAny();
+      data.Push(x);
+      data.Push(y);
+      continue;
+    }
+    case op_rot: {
+      TYPE_CHECK(Any, Any, Any);
+      auto z = data.PopAny();
+      auto y = data.PopAny();
+      auto x = data.PopAny();
+      data.Push(z);
+      data.Push(x);
+      data.Push(y);
+      continue;
+    }
+
+    // Control stack manipulation.
+    case op_begin: {
+      uint64_t length = cur_block.getULEB128(pc);
+      if (!pc)
+        return pc.takeError();
+      llvm::StringRef block = cur_block.getBytes(pc, length);
+      if (!pc)
+        return pc.takeError();
+      control.push_back(block);
+      continue;
+    }
+    case op_if:
+      TYPE_CHECK(UInt);
+      if (data.Pop<uint64_t>() != 0) {
+        if (!cur_block.size())
+          return error("empty control stack");
+        activate_block();
+      } else
+        control.pop_back();
+      continue;
+    case op_ifelse:
+      TYPE_CHECK(UInt);
+      if (cur_block.size() < 2)
+        return error("empty control stack");
+      if (data.Pop<uint64_t>() == 0)
+        control[control.size() - 2] = control.back();
+      control.pop_back();
+      activate_block();
+      continue;
+
+    // Literals.
+    case op_lit_uint:
+      data.Push(cur_block.getULEB128(pc));
+      continue;
+    case op_lit_int:
+      data.Push(cur_block.getSLEB128(pc));
+      continue;
+    case op_lit_selector:
+      data.Push(Selectors(cur_block.getU8(pc)));
+      continue;
+    case op_lit_string: {
+      uint64_t length = cur_block.getULEB128(pc);
+      llvm::StringRef bytes = cur_block.getBytes(pc, length);
+      data.Push(bytes.str());
+      continue;
+    }
+    case op_as_uint: {
+      TYPE_CHECK(Int);
+      uint64_t casted;
+      int64_t val = data.Pop<int64_t>();
+      memcpy(&casted, &val, sizeof(val));
+      data.Push(casted);
+      continue;
+    }
+    case op_as_int: {
+      TYPE_CHECK(UInt);
+      int64_t casted;
+      uint64_t val = data.Pop<uint64_t>();
+      memcpy(&casted, &val, sizeof(val));
+      data.Push(casted);
+      continue;
+    }
+    case op_is_null: {
+      TYPE_CHECK(Object);
+      data.Push(data.Pop<ValueObjectSP>() ? 0ULL : 1ULL);
+      continue;
+    }
+
+    // Arithmetic, logic, etc.
+#define BINOP_IMPL(OP, CHECK_ZERO)                                             \
+  {                                                                            \
+    TYPE_CHECK(Any, Any);                                                      \
+    auto y = data.PopAny();                                                    \
+    if (std::holds_alternative<uint64_t>(y)) {                                 \
+      if (CHECK_ZERO && !std::get<uint64_t>(y))                                \
+        return error(#OP " by zero");                                          \
+      TYPE_CHECK(UInt);                                                        \
+      data.Push((uint64_t)(data.Pop<uint64_t>() OP std::get<uint64_t>(y)));    \
+    } else if (std::holds_alternative<int64_t>(y)) {                           \
+      if (CHECK_ZERO && !std::get<int64_t>(y))                                 \
+        return error(#OP " by zero");                                          \
+      TYPE_CHECK(Int);                                                         \
+      data.Push((int64_t)(data.Pop<int64_t>() OP std::get<int64_t>(y)));       \
+    } else                                                                     \
+      return error("unsupported data types");                                  \
+  }
+#define BINOP(OP) BINOP_IMPL(OP, false)
+#define BINOP_CHECKZERO(OP) BINOP_IMPL(OP, true)
+    case op_plus:
+      BINOP(+);
+      continue;
+    case op_minus:
+      BINOP(-);
+      continue;
+    case op_mul:
+      BINOP(*);
+      continue;
+    case op_div:
+      BINOP_CHECKZERO(/);
+      continue;
+    case op_mod:
+      BINOP_CHECKZERO(%);
+      continue;
+    case op_shl:
+#define SHIFTOP(OP)                                                            \
+  {                                                                            \
+    TYPE_CHECK(Any, UInt);                                                     \
+    uint64_t y = data.Pop<uint64_t>();                                         \
+    if (y > 64)                                                                \
+      return error("shift out of bounds");                                     \
+    if (std::holds_alternative<uint64_t>(data.back())) {                       \
+      uint64_t x = data.Pop<uint64_t>();                                       \
+      data.Push(x OP y);                                                       \
+    } else if (std::holds_alternative<int64_t>(data.back())) {                 \
+      int64_t x = data.Pop<int64_t>();                                         \
+      if (y > 64)                                                              \
+        return error("shift out of bounds");                                   \
+      if (y < 0)                                                               \
+        return error("shift out of bounds");                                   \
+      data.Push(x OP y);                                                       \
+    } else                                                                     \
+      return error("unsupported data types");                                  \
+  }
+      SHIFTOP(<<);
+      continue;
+    case op_shr:
+      SHIFTOP(<<);
+      continue;
+    case op_and:
+      BINOP(&);
+      continue;
+    case op_or:
+      BINOP(|);
+      continue;
+    case op_xor:
+      BINOP(^);
+      continue;
+    case op_not:
+      TYPE_CHECK(UInt);
+      data.Push(~data.Pop<uint64_t>());
+      continue;
+    case op_eq:
+      BINOP(==);
+      continue;
+    case op_neq:
+      BINOP(!=);
+      continue;
+    case op_lt:
+      BINOP(<);
+      continue;
+    case op_gt:
+      BINOP(>);
+      continue;
+    case op_le:
+      BINOP(<=);
+      continue;
+    case op_ge:
+      BINOP(>=);
+      continue;
+    case op_call: {
+      TYPE_CHECK(Selector);
+      Selectors sel = data.Pop<Selectors>();
+
+      // Shorthand to improve readability.
+#define POP_VALOBJ(VALOBJ)                                                     \
+  auto VALOBJ = data.Pop<ValueObjectSP>();                                     \
+  if (!VALOBJ)                                                                 \
+    return error("null object");
+
+      auto sel_error = [&](const char *msg) {
+        return llvm::createStringError("{0} (opcode={1}, selector={2})", msg,
+                                       toString(opcode).c_str(),
+                                       toString(sel).c_str());
+      };
+
+      switch (sel) {
+      case sel_summary: {
+        TYPE_CHECK(Object);
+        POP_VALOBJ(valobj);
+        const char *summary = valobj->GetSummaryAsCString();
+        data.Push(summary ? std::string(valobj->GetSummaryAsCString())
+                          : std::string());
+        break;
+      }
+      case sel_get_num_children: {
+        TYPE_CHECK(Object);
+        POP_VALOBJ(valobj);
+        auto result = valobj->GetNumChildren();
+        if (!result)
+          return result.takeError();
+        data.Push((uint64_t)*result);
+        break;
+      }
+      case sel_get_child_at_index: {
+        TYPE_CHECK(Object, UInt);
+        auto index = data.Pop<uint64_t>();
+        POP_VALOBJ(valobj);
+        data.Push(valobj->GetChildAtIndex(index));
+        break;
+      }
+      case sel_get_child_with_name: {
+        TYPE_CHECK(Object, String);
+        auto name = data.Pop<std::string>();
+        POP_VALOBJ(valobj);
+        data.Push(valobj->GetChildMemberWithName(name));
+        break;
+      }
+      case sel_get_child_index: {
+        TYPE_CHECK(Object, String);
+        auto name = data.Pop<std::string>();
+        POP_VALOBJ(valobj);
+        data.Push(valobj->GetIndexOfChildWithName(name));
+        break;
+      }
+      case sel_get_type: {
+        TYPE_CHECK(Object);
+        POP_VALOBJ(valobj);
+        // FIXME: do we need to control dynamic type resolution?
+        data.Push(valobj->GetTypeImpl().GetCompilerType(false));
+        break;
+      }
+      case sel_get_template_argument_type: {
+        TYPE_CHECK(Type, UInt);
+        auto index = data.Pop<uint64_t>();
+        auto type = data.Pop<CompilerType>();
+        // FIXME: There is more code in SBType::GetTemplateArgumentType().
+        data.Push(type.GetTypeTemplateArgument(index, true));
+        break;
+      }
+      case sel_get_value: {
+        TYPE_CHECK(Object);
+        POP_VALOBJ(valobj);
+        data.Push(std::string(valobj->GetValueAsCString()));
+        break;
+      }
+      case sel_get_value_as_unsigned: {
+        TYPE_CHECK(Object);
+        POP_VALOBJ(valobj);
+        bool success;
+        uint64_t val = valobj->GetValueAsUnsigned(0, &success);
+        data.Push(val);
+        if (!success)
+          return sel_error("failed to get value");
+        break;
+      }
+      case sel_get_value_as_signed: {
+        TYPE_CHECK(Object);
+        POP_VALOBJ(valobj);
+        bool success;
+        int64_t val = valobj->GetValueAsSigned(0, &success);
+        data.Push(val);
+        if (!success)
+          return sel_error("failed to get value");
+        break;
+      }
+      case sel_get_value_as_address: {
+        TYPE_CHECK(Object);
+        POP_VALOBJ(valobj);
+        bool success;
+        uint64_t addr = valobj->GetValueAsUnsigned(0, &success);
+        if (!success)
+          return sel_error("failed to get value");
+        if (auto process_sp = valobj->GetProcessSP())
+          addr = process_sp->FixDataAddress(addr);
+        data.Push(addr);
+        break;
+      }
+      case sel_cast: {
+        TYPE_CHECK(Object, Type);
+        auto type = data.Pop<CompilerType>();
+        POP_VALOBJ(valobj);
+        data.Push(valobj->Cast(type));
+        break;
+      }
+      case sel_strlen: {
+        TYPE_CHECK(String);
+        data.Push(data.Pop<std::string>().size());
+        break;
+      }
+      case sel_fmt: {
+        TYPE_CHECK(String);
+        if (auto error = FormatImpl(data))
+          return error;
+        break;
+      }
+      default:
+        return sel_error("selector not implemented");
+      }
+      continue;
+    }
+    }
+    return error("opcode not implemented");
+  }
+  return pc.takeError();
+}
+} // namespace FormatterBytecode
+
+} // namespace lldb_private
diff --git a/lldb/source/DataFormatters/FormatterBytecode.def b/lldb/source/DataFormatters/FormatterBytecode.def
new file mode 100644
index 00000000000000..c6645631fa0065
--- /dev/null
+++ b/lldb/source/DataFormatters/FormatterBytecode.def
@@ -0,0 +1,101 @@
+//===-- FormatterBytecode.def -----------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef DEFINE_OPCODE
+#define DEFINE_OPCODE(OP, MNEMONIC, NAME)
+#endif
+#ifndef DEFINE_SELECTOR
+#define DEFINE_SELECTOR(ID, NAME)
+#endif
+#ifndef DEFINE_SIGNATURE
+#define DEFINE_SIGNATURE(ID, NAME)
+#endif
+
+// Opcodes.
+DEFINE_OPCODE(0x01, "dup",  dup)
+DEFINE_OPCODE(0x02, "drop", drop)
+DEFINE_OPCODE(0x03, "pick", pick)
+DEFINE_OPCODE(0x04, "over", over)
+DEFINE_OPCODE(0x05, "swap", swap)
+DEFINE_OPCODE(0x06, "rot",  rot)
+
+DEFINE_OPCODE(0x10, "{", begin)
+DEFINE_OPCODE(0x11, "if", if)
+DEFINE_OPCODE(0x12, "ifelse", ifelse)
+
+DEFINE_OPCODE(0x20, nullptr, lit_uint)
+DEFINE_OPCODE(0x21, nullptr, lit_int)
+DEFINE_OPCODE(0x22, nullptr, lit_string)
+DEFINE_OPCODE(0x23, nullptr, lit_selector)
+
+DEFINE_OPCODE(0x2a, "as_int", as_int)
+DEFINE_OPCODE(0x2b, "as_uint", as_uint)
+DEFINE_OPCODE(0x2c, "is_null", is_null)
+
+DEFINE_OPCODE(0x30, "+", plus)
+DEFINE_OPCODE(0x31, "-", minus)
+DEFINE_OPCODE(0x32, "*", mul)
+DEFINE_OPCODE(0x33, "/", div)
+DEFINE_OPCODE(0x34, "%", mod)
+DEFINE_OPCODE(0x35, "<<", shl)
+DEFINE_OPCODE(0x36, ">>", shr)
+
+DEFINE_OPCODE(0x40, "&", and)
+DEFINE_OPCODE(0x41, "|", or)
+DEFINE_OPCODE(0x42, "^", xor)
+DEFINE_OPCODE(0x43, "~", not)
+
+DEFINE_OPCODE(0x50, "=", eq)
+DEFINE_OPCODE(0x51, "!=", neq)
+DEFINE_OPCODE(0x52, "<", lt)
+DEFINE_OPCODE(0x53, ">", gt)
+DEFINE_OPCODE(0x54, "=<", le)
+DEFINE_OPCODE(0x55, ">=", ge)
+
+DEFINE_OPCODE(0x60, "call", call)
+
+// Selectors.
+DEFINE_SELECTOR(0x00, summary)
+DEFINE_SELECTOR(0x01, type_summary)
+
+DEFINE_SELECTOR(0x10, get_num_children)
+DEFINE_SELECTOR(0x11, get_child_at_index)
+DEFINE_SELECTOR(0x12, get_child_with_name)
+DEFINE_SELECTOR(0x13, get_child_index)
+DEFINE_SELECTOR(0x15, get_type)
+DEFINE_SELECTOR(0x16, get_template_argument_type)
+DEFINE_SELECTOR(0x17, cast)
+
+DEFINE_SELECTOR(0x20, get_value)
+DEFINE_SELECTOR(0x21, get_value_as_unsigned)
+DEFINE_SELECTOR(0x22, get_value_as_signed)
+DEFINE_SELECTOR(0x23, get_value_as_address)
+
+DEFINE_SELECTOR(0x40, read_memory_byte)
+DEFINE_SELECTOR(0x41, read_memory_uint32)
+DEFINE_SELECTOR(0x42, read_memory_int32)
+DEFINE_SELECTOR(0x43, read_memory_unsigned)
+DEFINE_SELECTOR(0x44, read_memory_signed)
+DEFINE_SELECTOR(0x45, read_memory_address)
+DEFINE_SELECTOR(0x46, read_memory)
+
+DEFINE_SELECTOR(0x50, fmt)
+DEFINE_SELECTOR(0x51, sprintf)
+DEFINE_SELECTOR(0x52, strlen)
+
+// Formatter signatures.
+DEFINE_SIGNATURE(0, summary)
+DEFINE_SIGNATURE(1, init)
+DEFINE_SIGNATURE(2, get_num_children)
+DEFINE_SIGNATURE(3, get_child_index)
+DEFINE_SIGNATURE(4, get_child_at_index)
+DEFINE_SIGNATURE(5, get_value)
+
+#undef DEFINE_OPCODE
+#undef DEFINE_SELECTOR
+#undef DEFINE_SIGNATURE
diff --git a/lldb/source/DataFormatters/FormatterBytecode.h b/lldb/source/DataFormatters/FormatterBytecode.h
new file mode 100644
index 00000000000000..21454d9c7e231f
--- /dev/null
+++ b/lldb/source/DataFormatters/FormatterBytecode.h
@@ -0,0 +1,64 @@
+//===-- FormatterBytecode.h -------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "lldb/DataFormatters/TypeSummary.h"
+#include "lldb/Symbol/CompilerType.h"
+
+namespace lldb_private {
+
+namespace FormatterBytecode {
+
+enum DataType : uint8_t { Any, String, Int, UInt, Object, Type, Selector };
+
+enum OpCodes : uint8_t {
+#define DEFINE_OPCODE(OP, MNEMONIC, NAME) op_##NAME = OP,
+#include "FormatterBytecode.def"
+#undef DEFINE_OPCODE
+};
+
+enum Selectors : uint8_t {
+#define DEFINE_SELECTOR(ID, NAME) sel_##NAME = ID,
+#include "FormatterBytecode.def"
+#undef DEFINE_SELECTOR
+};
+
+enum Signatures : uint8_t {
+#define DEFINE_SIGNATURE(ID, NAME) sig_##NAME = ID,
+#include "FormatterBytecode.def"
+#undef DEFINE_SIGNATURE
+};
+
+using ControlStackElement = llvm::StringRef;
+using DataStackElement =
+    std::variant<std::string, uint64_t, int64_t, lldb::ValueObjectSP,
+                 CompilerType, Selectors>;
+struct DataStack : public std::vector<DataStackElement> {
+  DataStack() = default;
+  DataStack(lldb::ValueObjectSP initial_value)
+      : std::vector<DataStackElement>({initial_value}) {}
+  void Push(DataStackElement el) { push_back(el); }
+  template <typename T> T Pop() {
+    T el = std::get<T>(back());
+    pop_back();
+    return el;
+  }
+  DataStackElement PopAny() {
+    DataStackElement el = back();
+    pop_back();
+    return el;
+  }
+};
+llvm::Error Interpret(std::vector<ControlStackElement> &control,
+                      DataStack &data, Selectors sel);
+} // namespace FormatterBytecode
+
+std::string toString(FormatterBytecode::OpCodes op);
+std::string toString(FormatterBytecode::Selectors sel);
+std::string toString(FormatterBytecode::Signatures sig);
+
+} // namespace lldb_private
diff --git a/lldb/source/DataFormatters/FormatterSection.cpp b/lldb/source/DataFormatters/FormatterSection.cpp
new file mode 100644
index 00000000000000..7316990f66a109
--- /dev/null
+++ b/lldb/source/DataFormatters/FormatterSection.cpp
@@ -0,0 +1,162 @@
+//===-- FormatterBytecode.cpp ---------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "FormatterBytecode.h"
+#include "lldb/Core/Module.h"
+#include "lldb/DataFormatters/DataVisualization.h"
+#include "lldb/Utility/LLDBLog.h"
+
+using namespace lldb;
+
+namespace lldb_private {
+static void ForEachFormatterInModule(
+    Module &module, SectionType section_type,
+    std::function<void(llvm::DataExtractor, llvm::StringRef)> fn) {
+  auto *sections = module.GetSectionList();
+  if (!sections)
+    return;
+
+  auto section_sp = sections->FindSectionByType(section_type, true);
+  if (!section_sp)
+    return;
+
+  TypeCategoryImplSP category;
+  DataVisualization::Categories::GetCategory(ConstString("default"), category);
+
+  // The type summary record is serialized as follows.
+  //
+  // Each record contains, in order:
+  //   * Version number of the record format
+  //   * The remaining size of the record
+  //   * The size of the type identifier
+  //   * The type identifier, either a type name, or a regex
+  //   * The size of the entry
+  //   * The entry
+  //
+  // Integers are encoded using ULEB.
+  //
+  // Strings are encoded with first a length (ULEB), then the string contents,
+  // and lastly a null terminator. The length includes the null.
+
+  DataExtractor lldb_extractor;
+  auto section_size = section_sp->GetSectionData(lldb_extractor);
+  llvm::DataExtractor section = lldb_extractor.GetAsLLVM();
+  bool le = section.isLittleEndian();
+  uint8_t addr_size = section.getAddressSize();
+  llvm::DataExtractor::Cursor cursor(0);
+  while (cursor && cursor.tell() < section_size) {
+    uint64_t version = section.getULEB128(cursor);
+    uint64_t record_size = section.getULEB128(cursor);
+    if (version == 1) {
+      llvm::DataExtractor record(section.getData().drop_front(cursor.tell()),
+                                 le, addr_size);
+      llvm::DataExtractor::Cursor cursor(0);
+      uint64_t type_size = record.getULEB128(cursor);
+      llvm::StringRef type_name = record.getBytes(cursor, type_size);
+      llvm::Error error = cursor.takeError();
+      if (!error)
+        fn(llvm::DataExtractor(record.getData().drop_front(cursor.tell()), le,
+                               addr_size),
+           type_name);
+      else
+        LLDB_LOG_ERROR(GetLog(LLDBLog::DataFormatters), std::move(error),
+                       "{0}");
+    } else {
+      // Skip unsupported record.
+      LLDB_LOG(
+          GetLog(LLDBLog::DataFormatters),
+          "Skipping unsupported embedded type summary of version {0} in {1}.",
+          version, module.GetFileSpec());
+    }
+    section.skip(cursor, record_size);
+  }
+  if (!cursor)
+    LLDB_LOG_ERROR(GetLog(LLDBLog::DataFormatters), cursor.takeError(), "{0}");
+}
+
+void LoadTypeSummariesForModule(ModuleSP module_sp) {
+  ForEachFormatterInModule(
+      *module_sp, eSectionTypeLLDBTypeSummaries,
+      [&](llvm::DataExtractor extractor, llvm::StringRef type_name) {
+        TypeCategoryImplSP category;
+        DataVisualization::Categories::GetCategory(ConstString("default"),
+                                                   category);
+        // The type summary record is serialized as follows.
+        //
+        //   * The size of the summary string
+        //   * The summary string
+        //
+        // Integers are encoded using ULEB.
+        llvm::DataExtractor::Cursor cursor(0);
+        uint64_t summary_size = extractor.getULEB128(cursor);
+        llvm::StringRef summary_string =
+            extractor.getBytes(cursor, summary_size);
+        if (!cursor) {
+          LLDB_LOG_ERROR(GetLog(LLDBLog::DataFormatters), cursor.takeError(),
+                         "{0}");
+          return;
+        }
+        if (type_name.empty() || summary_string.empty()) {
+          LLDB_LOG(GetLog(LLDBLog::DataFormatters),
+                   "Missing string(s) in embedded type summary in {0}.",
+                   module_sp->GetFileSpec());
+          return;
+        }
+        TypeSummaryImpl::Flags flags;
+        auto summary_sp = std::make_shared<StringSummaryFormat>(
+            flags, summary_string.str().c_str());
+        FormatterMatchType match_type = eFormatterMatchExact;
+        if (type_name.front() == '^')
+          match_type = eFormatterMatchRegex;
+        category->AddTypeSummary(type_name, match_type, summary_sp);
+        LLDB_LOG(GetLog(LLDBLog::DataFormatters),
+                 "Loaded embedded type summary for '{0}' from {1}.", type_name,
+                 module_sp->GetFileSpec());
+      });
+}
+
+void LoadFormattersForModule(ModuleSP module_sp) {
+  ForEachFormatterInModule(
+      *module_sp, eSectionTypeLLDBFormatters,
+      [&](llvm::DataExtractor extractor, llvm::StringRef type_name) {
+        // * Function signature (1 byte)
+        // * Length of the program (ULEB128)
+        // * The program bytecode
+        TypeCategoryImplSP category;
+        DataVisualization::Categories::GetCategory(ConstString("default"),
+                                                   category);
+        llvm::DataExtractor::Cursor cursor(0);
+        uint64_t flags = extractor.getULEB128(cursor);
+        while (cursor && cursor.tell() < extractor.size()) {
+          uint8_t signature = extractor.getU8(cursor);
+          uint64_t size = extractor.getULEB128(cursor);
+          llvm::StringRef bytecode = extractor.getBytes(cursor, size);
+          if (!cursor) {
+            LLDB_LOG_ERROR(GetLog(LLDBLog::DataFormatters), cursor.takeError(),
+                           "{0}");
+            return;
+          }
+          if (signature == 0) {
+            auto summary_sp = std::make_shared<BytecodeSummaryFormat>(
+                TypeSummaryImpl::Flags(flags),
+                llvm::MemoryBuffer::getMemBufferCopy(bytecode));
+            FormatterMatchType match_type = eFormatterMatchExact;
+            if (type_name.front() == '^')
+              match_type = eFormatterMatchRegex;
+            category->AddTypeSummary(type_name, match_type, summary_sp);
+            LLDB_LOG(GetLog(LLDBLog::DataFormatters),
+                     "Loaded embedded type summary for '{0}' from {1}.",
+                     type_name, module_sp->GetFileSpec());
+          } else
+            LLDB_LOG(GetLog(LLDBLog::DataFormatters),
+                     "Unsupported formatter signature {0} for '{1}' in {2}",
+                     signature, type_name, module_sp->GetFileSpec());
+        }
+      });
+}
+} // namespace lldb_private
diff --git a/lldb/source/DataFormatters/TypeSummary.cpp b/lldb/source/DataFormatters/TypeSummary.cpp
index 3538c1b60c8e9e..2c863b364538f3 100644
--- a/lldb/source/DataFormatters/TypeSummary.cpp
+++ b/lldb/source/DataFormatters/TypeSummary.cpp
@@ -8,9 +8,7 @@
 
 #include "lldb/DataFormatters/TypeSummary.h"
 
-
-
-
+#include "FormatterBytecode.h"
 #include "lldb/lldb-enumerations.h"
 #include "lldb/lldb-public.h"
 
@@ -58,6 +56,8 @@ std::string TypeSummaryImpl::GetSummaryKindName() {
     return "python";
   case Kind::eInternal:
     return "c++";
+  case Kind::eBytecode:
+    return "bytecode";
   }
 }
 
@@ -230,3 +230,74 @@ std::string ScriptSummaryFormat::GetDescription() {
 }
 
 std::string ScriptSummaryFormat::GetName() { return m_script_formatter_name; }
+
+BytecodeSummaryFormat::BytecodeSummaryFormat(
+    const TypeSummaryImpl::Flags &flags,
+    std::unique_ptr<llvm::MemoryBuffer> bytecode)
+    : TypeSummaryImpl(Kind::eBytecode, flags), m_bytecode(std::move(bytecode)) {
+}
+
+bool BytecodeSummaryFormat::FormatObject(ValueObject *valobj,
+                                         std::string &retval,
+                                         const TypeSummaryOptions &options) {
+  if (!valobj)
+    return false;
+
+  TargetSP target_sp(valobj->GetTargetSP());
+
+  if (!target_sp) {
+    retval.assign("error: no target");
+    return false;
+  }
+
+  std::vector<FormatterBytecode::ControlStackElement> control(
+      {m_bytecode->getBuffer()});
+  FormatterBytecode::DataStack data({valobj->GetSP()});
+  llvm::Error error = FormatterBytecode::Interpret(
+      control, data, FormatterBytecode::sel_summary);
+  if (error) {
+    retval = llvm::toString(std::move(error));
+    return false;
+  }
+  if (!data.size()) {
+    retval = "empty stack";
+    return false;
+  }
+  auto &top = data.back();
+  retval = "";
+  llvm::raw_string_ostream os(retval);
+  if (auto s = std::get_if<std::string>(&top))
+    os << *s;
+  else if (auto u = std::get_if<uint64_t>(&top))
+    os << *u;
+  else if (auto i = std::get_if<int64_t>(&top))
+    os << *i;
+  else if (auto valobj = std::get_if<ValueObjectSP>(&top)) {
+    if (!valobj->get())
+      os << "empty object";
+    else
+      os << valobj->get()->GetValueAsCString();
+  } else if (auto type = std::get_if<CompilerType>(&top)) {
+    os << type->TypeDescription();
+  } else if (auto sel = std::get_if<FormatterBytecode::Selectors>(&top)) {
+    os << toString(*sel);
+  }
+  return true;
+}
+
+std::string BytecodeSummaryFormat::GetDescription() {
+  StreamString sstr;
+  sstr.Printf("%s%s%s%s%s%s%s\n  ", Cascades() ? "" : " (not cascading)",
+              !DoesPrintChildren(nullptr) ? "" : " (show children)",
+              !DoesPrintValue(nullptr) ? " (hide value)" : "",
+              IsOneLiner() ? " (one-line printout)" : "",
+              SkipsPointers() ? " (skip pointers)" : "",
+              SkipsReferences() ? " (skip references)" : "",
+              HideNames(nullptr) ? " (hide member names)" : "");
+  // FIXME: sstr.PutCString(disassembly);
+  return std::string(sstr.GetString());
+}
+
+std::string BytecodeSummaryFormat::GetName() {
+  return "LLDB bytecode formatter";
+}
diff --git a/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp b/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp
index a8249cf103833e..b16cb114bec88e 100644
--- a/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp
+++ b/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp
@@ -1697,6 +1697,7 @@ static SectionType GetSectionTypeFromName(llvm::StringRef Name) {
       .Case(".gosymtab", eSectionTypeGoSymtab)
       .Case(".text", eSectionTypeCode)
       .Case(".lldbsummaries", lldb::eSectionTypeLLDBTypeSummaries)
+      .Case(".lldbformatters", lldb::eSectionTypeLLDBFormatters)
       .Case(".swift_ast", eSectionTypeSwiftModules)
       .Default(eSectionTypeOther);
 }
diff --git a/lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp b/lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp
index 7e17fd8c53cd01..488c9bd1e54af1 100644
--- a/lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp
+++ b/lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp
@@ -1210,6 +1210,7 @@ AddressClass ObjectFileMachO::GetAddressClass(lldb::addr_t file_addr) {
         case eSectionTypeDWARFGNUDebugAltLink:
         case eSectionTypeCTF:
         case eSectionTypeLLDBTypeSummaries:
+        case eSectionTypeLLDBFormatters:
         case eSectionTypeSwiftModules:
           return AddressClass::eDebug;
 
@@ -1486,6 +1487,7 @@ static lldb::SectionType GetSectionType(uint32_t flags,
   static ConstString g_sect_name_go_symtab("__gosymtab");
   static ConstString g_sect_name_ctf("__ctf");
   static ConstString g_sect_name_lldb_summaries("__lldbsummaries");
+  static ConstString g_sect_name_lldb_formatters("__lldbformatters");
   static ConstString g_sect_name_swift_ast("__swift_ast");
 
   if (section_name == g_sect_name_dwarf_debug_abbrev)
@@ -1568,6 +1570,8 @@ static lldb::SectionType GetSectionType(uint32_t flags,
     return eSectionTypeCTF;
   if (section_name == g_sect_name_lldb_summaries)
     return lldb::eSectionTypeLLDBTypeSummaries;
+  if (section_name == g_sect_name_lldb_formatters)
+    return lldb::eSectionTypeLLDBFormatters;
   if (section_name == g_sect_name_swift_ast)
     return eSectionTypeSwiftModules;
   if (section_name == g_sect_name_objc_data ||
diff --git a/lldb/source/Plugins/ObjectFile/PECOFF/ObjectFilePECOFF.cpp b/lldb/source/Plugins/ObjectFile/PECOFF/ObjectFilePECOFF.cpp
index bb712da7f6d67d..bfdb8140e40aff 100644
--- a/lldb/source/Plugins/ObjectFile/PECOFF/ObjectFilePECOFF.cpp
+++ b/lldb/source/Plugins/ObjectFile/PECOFF/ObjectFilePECOFF.cpp
@@ -1011,6 +1011,7 @@ SectionType ObjectFilePECOFF::GetSectionType(llvm::StringRef sect_name,
           .Cases(".eh_frame", ".eh_fram", eSectionTypeEHFrame)
           .Case(".gosymtab", eSectionTypeGoSymtab)
           .Case(".lldbsummaries", lldb::eSectionTypeLLDBTypeSummaries)
+          .Case(".lldbformatters", lldb::eSectionTypeLLDBFormatters)
           .Case("swiftast", eSectionTypeSwiftModules)
           .Default(eSectionTypeInvalid);
   if (section_type != eSectionTypeInvalid)
diff --git a/lldb/source/Symbol/ObjectFile.cpp b/lldb/source/Symbol/ObjectFile.cpp
index 3100e6b813b631..d3881f8ccf7fe8 100644
--- a/lldb/source/Symbol/ObjectFile.cpp
+++ b/lldb/source/Symbol/ObjectFile.cpp
@@ -366,6 +366,7 @@ AddressClass ObjectFile::GetAddressClass(addr_t file_addr) {
           case eSectionTypeDWARFAppleObjC:
           case eSectionTypeDWARFGNUDebugAltLink:
           case eSectionTypeCTF:
+          case eSectionTypeLLDBFormatters:
           case eSectionTypeLLDBTypeSummaries:
           case eSectionTypeSwiftModules:
             return AddressClass::eDebug;
diff --git a/lldb/source/Target/Target.cpp b/lldb/source/Target/Target.cpp
index 9ac85ad3ed5ee6..46216ba2d566d7 100644
--- a/lldb/source/Target/Target.cpp
+++ b/lldb/source/Target/Target.cpp
@@ -24,9 +24,7 @@
 #include "lldb/Core/Section.h"
 #include "lldb/Core/SourceManager.h"
 #include "lldb/Core/StructuredDataImpl.h"
-#include "lldb/Core/ValueObject.h"
-#include "lldb/Core/ValueObjectConstResult.h"
-#include "lldb/DataFormatters/DataVisualization.h"
+#include "lldb/DataFormatters/FormatterSection.h"
 #include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/ExpressionVariable.h"
 #include "lldb/Expression/REPL.h"
@@ -66,8 +64,6 @@
 #include "lldb/Utility/State.h"
 #include "lldb/Utility/StreamString.h"
 #include "lldb/Utility/Timer.h"
-#include "lldb/ValueObject/ValueObject.h"
-#include "lldb/ValueObject/ValueObjectConstResult.h"
 
 #include "llvm/ADT/ScopeExit.h"
 #include "llvm/ADT/SetVector.h"
@@ -1541,76 +1537,6 @@ static void LoadScriptingResourceForModule(const ModuleSP &module_sp,
                                                   feedback_stream.GetData());
 }
 
-// Load type summaries embedded in the binary. These are type summaries provided
-// by the authors of the code.
-static void LoadTypeSummariesForModule(ModuleSP module_sp) {
-  auto *sections = module_sp->GetSectionList();
-  if (!sections)
-    return;
-
-  auto summaries_sp =
-      sections->FindSectionByType(eSectionTypeLLDBTypeSummaries, true);
-  if (!summaries_sp)
-    return;
-
-  Log *log = GetLog(LLDBLog::DataFormatters);
-  const char *module_name = module_sp->GetObjectName().GetCString();
-
-  TypeCategoryImplSP category;
-  DataVisualization::Categories::GetCategory(ConstString("default"), category);
-
-  // The type summary record is serialized as follows.
-  //
-  // Each record contains, in order:
-  //   * Version number of the record format
-  //   * The remaining size of the record
-  //   * The size of the type identifier
-  //   * The type identifier, either a type name, or a regex
-  //   * The size of the summary string
-  //   * The summary string
-  //
-  // Integers are encoded using ULEB.
-  //
-  // Strings are encoded with first a length (ULEB), then the string contents,
-  // and lastly a null terminator. The length includes the null.
-
-  DataExtractor extractor;
-  auto section_size = summaries_sp->GetSectionData(extractor);
-  lldb::offset_t offset = 0;
-  while (offset < section_size) {
-    uint64_t version = extractor.GetULEB128(&offset);
-    uint64_t record_size = extractor.GetULEB128(&offset);
-    if (version == 1) {
-      uint64_t type_size = extractor.GetULEB128(&offset);
-      llvm::StringRef type_name = extractor.GetCStr(&offset, type_size);
-      uint64_t summary_size = extractor.GetULEB128(&offset);
-      llvm::StringRef summary_string = extractor.GetCStr(&offset, summary_size);
-      if (!type_name.empty() && !summary_string.empty()) {
-        TypeSummaryImpl::Flags flags;
-        auto summary_sp =
-            std::make_shared<StringSummaryFormat>(flags, summary_string.data());
-        FormatterMatchType match_type = eFormatterMatchExact;
-        if (summary_string.front() == '^' && summary_string.back() == '$')
-          match_type = eFormatterMatchRegex;
-        category->AddTypeSummary(type_name, match_type, summary_sp);
-        LLDB_LOGF(log, "Loaded embedded type summary for '%s' from %s.",
-                  type_name.data(), module_name);
-      } else {
-        if (type_name.empty())
-          LLDB_LOGF(log, "Missing string(s) in embedded type summary in %s.",
-                    module_name);
-      }
-    } else {
-      // Skip unsupported record.
-      offset += record_size;
-      LLDB_LOGF(
-          log,
-          "Skipping unsupported embedded type summary of version %llu in %s.",
-          version, module_name);
-    }
-  }
-}
-
 void Target::ClearModules(bool delete_locations) {
   ModulesDidUnload(m_images, delete_locations);
   m_section_load_history.Clear();
@@ -1892,6 +1818,7 @@ void Target::ModulesDidLoad(ModuleList &module_list) {
       ModuleSP module_sp(module_list.GetModuleAtIndex(idx));
       LoadScriptingResourceForModule(module_sp, this);
       LoadTypeSummariesForModule(module_sp);
+      LoadFormattersForModule(module_sp);
     }
     m_breakpoint_list.UpdateBreakpoints(module_list, true, false);
     m_internal_breakpoint_list.UpdateBreakpoints(module_list, true, false);
diff --git a/lldb/test/API/functionalities/data-formatter/bytecode-summary/Makefile b/lldb/test/API/functionalities/data-formatter/bytecode-summary/Makefile
new file mode 100644
index 00000000000000..c9319d6e6888a4
--- /dev/null
+++ b/lldb/test/API/functionalities/data-formatter/bytecode-summary/Makefile
@@ -0,0 +1,2 @@
+C_SOURCES := main.c
+include Makefile.rules
diff --git a/lldb/test/API/functionalities/data-formatter/bytecode-summary/TestBytecodeSummary.py b/lldb/test/API/functionalities/data-formatter/bytecode-summary/TestBytecodeSummary.py
new file mode 100644
index 00000000000000..7c39f5ef740140
--- /dev/null
+++ b/lldb/test/API/functionalities/data-formatter/bytecode-summary/TestBytecodeSummary.py
@@ -0,0 +1,15 @@
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+
+class TestCase(TestBase):
+    @skipUnlessDarwin
+    def test(self):
+        self.build()
+        if self.TraceOn():
+            self.expect('log enable -v lldb formatters')
+        lldbutil.run_to_source_breakpoint(self, "break here", lldb.SBFileSpec("main.cpp"))
+        self.expect("v x", substrs=['(MyOptional<int>) x = None'])
+        self.expect("v y", substrs=['(MyOptional<int>) y = 42'])
diff --git a/lldb/test/API/functionalities/data-formatter/bytecode-summary/main.cpp b/lldb/test/API/functionalities/data-formatter/bytecode-summary/main.cpp
new file mode 100644
index 00000000000000..36cbd988029fdb
--- /dev/null
+++ b/lldb/test/API/functionalities/data-formatter/bytecode-summary/main.cpp
@@ -0,0 +1,41 @@
+// A bare-bones llvm::Optional reimplementation.
+
+template <typename T> struct MyOptionalStorage {
+  MyOptionalStorage(T val) : value(val), hasVal(true) {}
+  MyOptionalStorage() {}
+  T value;
+  bool hasVal = false;
+};
+
+template <typename T> struct MyOptional {
+  MyOptionalStorage<T> Storage;
+  MyOptional(T val) : Storage(val) {}
+  MyOptional() {}
+  T &operator*() { return Storage.value; }
+};
+
+void stop() {}
+
+int main(int argc, char **argv) {
+  MyOptional<int> x, y = 42;
+  stop(); // break here
+  return *y;
+}
+
+__attribute__((used, section("__DATA_CONST,__lldbformatters"))) unsigned char
+    _MyOptional_type_summary[] =
+        "\x01"             // version
+        "\xa4"             // record size
+        "\x01"             // record size
+        "\x10"             // type name size
+        "^MyOptional<.+>$" // type name
+        "\x00"             // flags
+        "\x00"             // sig_summary
+        "\x8d"             // program size
+        "\x01"             // program size
+        "\x1\x22\x7Storage#\x12\x60\x1,C\x10\x1\x5\x11\x2\x1\x22\x6hasVal#"
+        "\x12\x60\x1,\x10\x1e\x2\x22\x1b<could not read MyOptional>\x10G#!\x60 "
+        "\x0P\x10\x6\x22\x4None\x10\x36\x1#\x15\x60 "
+        "\x0#\x16\x60\x5\x22\x5value#\x12\x60\x5#\x17\x60\x1,"
+        "\x10\x6\x22\x4None\x10\x11\x1#\x0\x60\x1#R\x60\x10\x3# "
+        "\x60\x10\x1\x2\x12\x12\x12\x12"; // summary function
diff --git a/lldb/unittests/DataFormatter/CMakeLists.txt b/lldb/unittests/DataFormatter/CMakeLists.txt
index 9d967a72bfd1fa..b858db1c716347 100644
--- a/lldb/unittests/DataFormatter/CMakeLists.txt
+++ b/lldb/unittests/DataFormatter/CMakeLists.txt
@@ -1,6 +1,7 @@
 add_lldb_unittest(LLDBFormatterTests
   FormatManagerTests.cpp
   FormattersContainerTest.cpp
+  FormatterBytecodeTest.cpp
   StringPrinterTests.cpp
 
   LINK_LIBS
diff --git a/lldb/unittests/DataFormatter/FormatterBytecodeTest.cpp b/lldb/unittests/DataFormatter/FormatterBytecodeTest.cpp
new file mode 100644
index 00000000000000..15d9229de00332
--- /dev/null
+++ b/lldb/unittests/DataFormatter/FormatterBytecodeTest.cpp
@@ -0,0 +1,261 @@
+#include "DataFormatters/FormatterBytecode.h"
+#include "lldb/Utility/StreamString.h"
+
+#include "gtest/gtest.h"
+
+using namespace lldb_private;
+using namespace lldb;
+using namespace FormatterBytecode;
+using llvm::StringRef;
+
+namespace {
+class FormatterBytecodeTest : public ::testing::Test {};
+
+bool Interpret(std::vector<uint8_t> code, DataStack &data) {
+  auto buf =
+      StringRef(reinterpret_cast<const char *>(code.data()), code.size());
+  std::vector<ControlStackElement> control({buf});
+  if (auto error = Interpret(control, data, sel_summary)) {
+#ifndef NDEBUG
+    llvm::errs() << llvm::toString(std::move(error)) << '\n';
+#else
+    llvm::consumeError(std::move(error));
+#endif
+    return false;
+  }
+  return true;
+}
+
+} // namespace
+
+TEST_F(FormatterBytecodeTest, StackOps) {
+  {
+    DataStack data;
+    ASSERT_TRUE(Interpret({op_lit_uint, 23, op_dup, op_plus}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 46u);
+  }
+  {
+    DataStack data;
+    ASSERT_TRUE(Interpret({op_lit_uint, 0, op_drop}, data));
+    ASSERT_EQ(data.size(), 0u);
+  }
+  {
+    for (unsigned char i = 0; i < 3; ++i) {
+      DataStack data;
+
+      ASSERT_TRUE(Interpret({op_lit_uint, 0, op_lit_uint, 1, op_lit_uint, 2,
+                             op_lit_uint, i, op_pick},
+                            data));
+      ASSERT_EQ(data.Pop<uint64_t>(), i);
+    }
+  }
+  {
+    DataStack data;
+    ASSERT_TRUE(Interpret({op_lit_uint, 0, op_lit_uint, 1, op_over}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 0u);
+  }
+  {
+    DataStack data;
+    ASSERT_TRUE(Interpret({op_lit_uint, 0, op_lit_uint, 1, op_swap}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 0u);
+    ASSERT_EQ(data.Pop<uint64_t>(), 1u);
+  }
+  {
+    DataStack data;
+    ASSERT_TRUE(Interpret(
+        {op_lit_uint, 0, op_lit_uint, 1, op_lit_uint, 2, op_rot}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 1u);
+    ASSERT_EQ(data.Pop<uint64_t>(), 0u);
+    ASSERT_EQ(data.Pop<uint64_t>(), 2u);
+  }
+}
+
+TEST_F(FormatterBytecodeTest, ControlOps) {
+  {
+    DataStack data;
+    ASSERT_TRUE(
+        Interpret({op_lit_uint, 0, op_begin, 2, op_lit_uint, 42, op_if}, data));
+    ASSERT_EQ(data.size(), 0u);
+  }
+  {
+    DataStack data;
+    ASSERT_TRUE(
+        Interpret({op_lit_uint, 1, op_begin, 2, op_lit_uint, 42, op_if}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 42u);
+  }
+  {
+    DataStack data;
+    ASSERT_TRUE(Interpret({op_lit_uint, 0, op_begin, 2, op_lit_uint, 42,
+                           op_begin, 2, op_lit_uint, 23, op_ifelse},
+                          data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 23u);
+  }
+  {
+    DataStack data;
+    ASSERT_TRUE(Interpret({op_lit_uint, 1, op_begin, 2, op_lit_uint, 42,
+                           op_begin, 2, op_lit_uint, 23, op_ifelse},
+                          data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 42u);
+  }
+  {
+    DataStack data(lldb::ValueObjectSP{});
+    ASSERT_TRUE(Interpret({op_is_null}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 1u);
+  }
+  {
+    DataStack data;
+    ASSERT_TRUE(Interpret({op_lit_uint, 1u, op_as_int}, data));
+    ASSERT_EQ(data.Pop<int64_t>(), 1);
+  }
+  {
+    DataStack data;
+    ASSERT_TRUE(Interpret({op_lit_int, 126, op_as_uint}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), ~1ULL);
+  }
+}
+
+TEST_F(FormatterBytecodeTest, ArithOps) {
+  {
+    DataStack data;
+    ASSERT_TRUE(Interpret({op_lit_uint, 2, op_lit_uint, 3, op_plus}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 5u);
+  }
+  {
+    DataStack data;
+    ASSERT_TRUE(Interpret({op_lit_uint, 3, op_lit_uint, 2, op_minus}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 1u);
+  }
+  {
+    DataStack data;
+    ASSERT_TRUE(Interpret({op_lit_uint, 3, op_lit_uint, 2, op_mul}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 6u);
+  }
+  {
+    DataStack data;
+    ASSERT_TRUE(Interpret({op_lit_uint, 6, op_lit_uint, 2, op_div}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 3u);
+  }
+  {
+    DataStack data;
+    ASSERT_FALSE(Interpret({op_lit_uint, 23, op_lit_uint, 0, op_div}, data));
+  }
+  {
+    DataStack data;
+    ASSERT_TRUE(Interpret({op_lit_uint, 1, op_lit_uint, 2, op_shl}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 4u);
+  }
+  {
+    DataStack data;
+    unsigned char minus_one = 127;
+    ASSERT_TRUE(
+        Interpret({op_lit_int, minus_one, op_lit_uint, 2, op_shl}, data));
+    ASSERT_EQ(data.Pop<int64_t>(), -4);
+  }
+  {
+    DataStack data;
+    ASSERT_FALSE(Interpret({op_lit_uint, 1, op_lit_uint, 65, op_shl}, data));
+    ASSERT_FALSE(Interpret({op_lit_uint, 1, op_lit_uint, 65, op_shr}, data));
+  }
+  {
+    DataStack data;
+    ASSERT_TRUE(Interpret({op_lit_uint, 1, op_lit_uint, 1, op_and}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 1u);
+    ASSERT_TRUE(Interpret({op_lit_uint, 0, op_lit_uint, 1, op_and}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 0u);
+  }
+  {
+    DataStack data;
+    ASSERT_TRUE(Interpret({op_lit_uint, 1, op_lit_uint, 1, op_or}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 1u);
+    ASSERT_TRUE(Interpret({op_lit_uint, 0, op_lit_uint, 1, op_or}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 1u);
+    ASSERT_TRUE(Interpret({op_lit_uint, 0, op_lit_uint, 0, op_or}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 0u);
+  }
+  {
+    DataStack data;
+    ASSERT_TRUE(Interpret({op_lit_uint, 1, op_lit_uint, 1, op_xor}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 0u);
+    ASSERT_TRUE(Interpret({op_lit_uint, 0, op_lit_uint, 1, op_xor}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 1u);
+    ASSERT_TRUE(Interpret({op_lit_uint, 0, op_lit_uint, 0, op_xor}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 0u);
+  }
+  {
+    DataStack data;
+    ASSERT_TRUE(Interpret({op_lit_uint, 0, op_not}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 0xffffffffffffffff);
+  }
+  {
+    DataStack data;
+    ASSERT_TRUE(Interpret({op_lit_uint, 0, op_lit_uint, 1, op_eq}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 0u);
+    ASSERT_TRUE(Interpret({op_lit_uint, 0, op_lit_uint, 0, op_eq}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 1u);
+  }
+  {
+    DataStack data;
+    ASSERT_TRUE(Interpret({op_lit_uint, 0, op_lit_uint, 1, op_neq}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 1u);
+    ASSERT_TRUE(Interpret({op_lit_uint, 0, op_lit_uint, 0, op_neq}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 0u);
+  }
+  {
+    DataStack data;
+    ASSERT_TRUE(Interpret({op_lit_uint, 0, op_lit_uint, 1, op_lt}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 1u);
+    ASSERT_TRUE(Interpret({op_lit_uint, 1, op_lit_uint, 0, op_lt}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 0u);
+    ASSERT_TRUE(Interpret({op_lit_uint, 1, op_lit_uint, 1, op_lt}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 0u);
+  }
+  {
+    DataStack data;
+    ASSERT_TRUE(Interpret({op_lit_uint, 0, op_lit_uint, 1, op_gt}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 0u);
+    ASSERT_TRUE(Interpret({op_lit_uint, 1, op_lit_uint, 0, op_gt}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 1u);
+    ASSERT_TRUE(Interpret({op_lit_uint, 1, op_lit_uint, 1, op_gt}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 0u);
+  }
+  {
+    DataStack data;
+    ASSERT_TRUE(Interpret({op_lit_uint, 0, op_lit_uint, 1, op_le}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 1u);
+    ASSERT_TRUE(Interpret({op_lit_uint, 1, op_lit_uint, 0, op_le}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 0u);
+    ASSERT_TRUE(Interpret({op_lit_uint, 1, op_lit_uint, 1, op_le}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 1u);
+  }
+  {
+    DataStack data;
+    ASSERT_TRUE(Interpret({op_lit_uint, 0, op_lit_uint, 1, op_ge}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 0u);
+    ASSERT_TRUE(Interpret({op_lit_uint, 1, op_lit_uint, 0, op_ge}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 1u);
+    ASSERT_TRUE(Interpret({op_lit_uint, 1, op_lit_uint, 1, op_ge}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 1u);
+  }
+}
+
+TEST_F(FormatterBytecodeTest, CallOps) {
+  {
+    DataStack data;
+    data.Push(std::string{"hello"});
+    ASSERT_TRUE(Interpret({op_lit_selector, sel_strlen, op_call}, data));
+    ASSERT_EQ(data.Pop<uint64_t>(), 5u);
+  }
+  {
+    DataStack data;
+    data.Push(std::string{"A"});
+    data.Push(std::string{"B"});
+    data.Push(std::string{"{1}{0}"});
+    ASSERT_TRUE(Interpret({op_lit_selector, sel_fmt, op_call}, data));
+    ASSERT_EQ(data.Pop<std::string>(), "BA");
+  }
+  {
+    DataStack data;
+    data.Push(std::string{"{0}"});
+    ASSERT_FALSE(Interpret({op_lit_selector, sel_fmt, op_call}, data));
+  }
+}



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