[macho] save the SDK version stored in module metadata into the version min and build version load commands in the object file

[arphaman]

Summary

This patch introduces a new metadata node called "SDK Version". It will be set by the frontend to mark the platform SDK (macOS/iOS/etc) version which was used during that particular compilation.
This node is used when machine code is emitted, by either saving the SDK version into the appropriate macho load command (version min/build version), or by emitting the assembly for these load commands with the SDK version specified as well.
The assembly for both load commands is extended by allowing it to contain the sdk_version X, Y [, Z] trailing directive to represent the SDK version respectively.

[steven_wu]

Don't we need IR support for this as well? sdk version is not in the triple so it is going to get lost when building from IR. Maybe use a metadata node?

[arphaman]

In D55612#1328773, @steven_wu wrote:

Don't we need IR support for this as well? sdk version is not in the triple so it is going to get lost when building from IR. Maybe use a metadata node?

I provide a way to set and retrieve the SDK version from the IR using the "SDK Version" metadata. Do I need something more than that? Clang can set it and we are already getting it in this patch.

[steven_wu]

In D55612#1328937, @arphaman wrote:

In D55612#1328773, @steven_wu wrote:

Don't we need IR support for this as well? sdk version is not in the triple so it is going to get lost when building from IR. Maybe use a metadata node?

I provide a way to set and retrieve the SDK version from the IR using the "SDK Version" metadata. Do I need something more than that? Clang can set it and we are already getting it in this patch.

I am talking about Bitcode format support and Metadata in Bitcode prospective. The reason is that you don't necessary have SDK information when you building from bitcode. I am ok to do that as a followup if you think that is better.

[steven_wu]

I think I missed something before. LGTM now!

include/llvm/IR/Module.h

 class Error;
 class FunctionType;
 class GVMaterializer;
 class LLVMContext;
 class MemoryBuffer;
 class RandomNumberGenerator;
 template <class PtrType> class SmallPtrSetImpl;
 class StructType;
+class VersionTuple;
 
 /// A Module instance is used to store all the information related to an
 /// LLVM module. Modules are the top level container of all other LLVM
 /// Intermediate Representation (IR) objects. Each module directly contains a
 /// list of globals variables, a list of functions, a list of libraries (or
 /// other modules) this module depends on, a symbol table, and various data
 /// about the target's characteristics.
 ///
/// @}
   /// @}
 
   /// Returns true if PLT should be avoided for RTLib calls.
   bool getRtLibUseGOT() const;
 
   /// Set that PLT should be avoid for RTLib calls.
   void setRtLibUseGOT();
 
+  /// @name Utility functions for querying and setting the build SDK version
+  /// @{
+
+  /// Attach a build SDK version metadata to this module.
+  void setSDKVersion(const VersionTuple &V);
+
+  /// Get the build SDK version metadata.
+  ///
+  /// An empty version is returned if no such metadata is attached.
+  VersionTuple getSDKVersion() const;
+  /// @}
 
   /// Take ownership of the given memory buffer.
   void setOwnedMemoryBuffer(std::unique_ptr<MemoryBuffer> MB);
 };
 
 /// Given "llvm.used" or "llvm.compiler.used" as a global name, collect
 /// the initializer elements of that global in Set and return the global itself.
 GlobalVariable *collectUsedGlobalVariables(const Module &M,

include/llvm/MC/MCAssembler.h

 #include "llvm/ADT/iterator_range.h"
 #include "llvm/BinaryFormat/MachO.h"
 #include "llvm/MC/MCDirectives.h"
 #include "llvm/MC/MCDwarf.h"
 #include "llvm/MC/MCFixup.h"
 #include "llvm/MC/MCFragment.h"
 #include "llvm/MC/MCLinkerOptimizationHint.h"
 #include "llvm/MC/MCSymbol.h"
+#include "llvm/Support/VersionTuple.h"
 #include <cassert>
 #include <cstddef>
 #include <cstdint>
 #include <string>
 #include <utility>
 #include <vector>
 
 namespace llvm {
using VersionInfoType = struct {
     bool EmitBuildVersion;
     union {
       MCVersionMinType Type;          ///< Used when EmitBuildVersion==false.
       MachO::PlatformType Platform;   ///< Used when EmitBuildVersion==true.
     } TypeOrPlatform;
     unsigned Major;
     unsigned Minor;
     unsigned Update;
+    /// An optional version of the SDK that was used to build the source.
+    VersionTuple SDKVersion;
   };
 
 private:
   MCContext &Context;
 
   std::unique_ptr<MCAsmBackend> Backend;
 
   std::unique_ptr<MCCodeEmitter> Emitter;
public:
 
   /// ELF e_header flags
   unsigned getELFHeaderEFlags() const { return ELFHeaderEFlags; }
   void setELFHeaderEFlags(unsigned Flags) { ELFHeaderEFlags = Flags; }
 
   /// MachO deployment target version information.
   const VersionInfoType &getVersionInfo() const { return VersionInfo; }
   void setVersionMin(MCVersionMinType Type, unsigned Major, unsigned Minor,
-                     unsigned Update) {
+                     unsigned Update,
+                     VersionTuple SDKVersion = VersionTuple()) {
     VersionInfo.EmitBuildVersion = false;
     VersionInfo.TypeOrPlatform.Type = Type;
     VersionInfo.Major = Major;
     VersionInfo.Minor = Minor;
     VersionInfo.Update = Update;
+    VersionInfo.SDKVersion = SDKVersion;
   }
   void setBuildVersion(MachO::PlatformType Platform, unsigned Major,
-                       unsigned Minor, unsigned Update) {
+                       unsigned Minor, unsigned Update,
+                       VersionTuple SDKVersion = VersionTuple()) {
     VersionInfo.EmitBuildVersion = true;
     VersionInfo.TypeOrPlatform.Platform = Platform;
     VersionInfo.Major = Major;
     VersionInfo.Minor = Minor;
     VersionInfo.Update = Update;
+    VersionInfo.SDKVersion = SDKVersion;
   }
 
   /// Reuse an assembler instance
   ///
   void reset();
 
   MCContext &getContext() const { return Context; }
 

include/llvm/MC/MCObjectFileInfo.h

 
 #ifndef LLVM_MC_MCOBJECTFILEINFO_H
 #define LLVM_MC_MCOBJECTFILEINFO_H
 
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/MC/MCSymbol.h"
 #include "llvm/Support/CodeGen.h"
+#include "llvm/Support/VersionTuple.h"
 
 namespace llvm {
 class MCContext;
 class MCSection;
 
 class MCObjectFileInfo {
 protected:
   /// True if .comm supports alignment.  This is a hack for as long as we
public:
 
   bool isPositionIndependent() const { return PositionIndependent; }
 
 private:
   Environment Env;
   bool PositionIndependent;
   MCContext *Ctx;
   Triple TT;
+  VersionTuple SDKVersion;
 
   void initMachOMCObjectFileInfo(const Triple &T);
   void initELFMCObjectFileInfo(const Triple &T, bool Large);
   void initCOFFMCObjectFileInfo(const Triple &T);
   void initWasmMCObjectFileInfo(const Triple &T);
   MCSection *getDwarfComdatSection(const char *Name, uint64_t Hash) const;
 
 public:
   const Triple &getTargetTriple() const { return TT; }
+
+  void setSDKVersion(const VersionTuple &TheSDKVersion) {
+    SDKVersion = TheSDKVersion;
+  }
+
+  const VersionTuple &getSDKVersion() const { return SDKVersion; }
 };
 
 } // end namespace llvm
 
 #endif

include/llvm/MC/MCStreamer.h

 #include "llvm/MC/MCDwarf.h"
 #include "llvm/MC/MCLinkerOptimizationHint.h"
 #include "llvm/MC/MCSymbol.h"
 #include "llvm/MC/MCWinEH.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/MD5.h"
 #include "llvm/Support/SMLoc.h"
 #include "llvm/Support/TargetParser.h"
+#include "llvm/Support/VersionTuple.h"
 #include <cassert>
 #include <cstdint>
 #include <memory>
 #include <string>
 #include <utility>
 #include <vector>
 
 namespace llvm {
public:
   /// options into the output.
   virtual void EmitLinkerOptions(ArrayRef<std::string> Kind) {}
 
   /// Note in the output the specified region \p Kind.
   virtual void EmitDataRegion(MCDataRegionType Kind) {}
 
   /// Specify the Mach-O minimum deployment target version.
   virtual void EmitVersionMin(MCVersionMinType Type, unsigned Major,
-                              unsigned Minor, unsigned Update) {}
+                              unsigned Minor, unsigned Update,
+                              VersionTuple SDKVersion) {}
 
   /// Emit/Specify Mach-O build version command.
   /// \p Platform should be one of MachO::PlatformType.
   virtual void EmitBuildVersion(unsigned Platform, unsigned Major,
-                                unsigned Minor, unsigned Update) {}
+                                unsigned Minor, unsigned Update,
+                                VersionTuple SDKVersion) {}
 
-  void EmitVersionForTarget(const Triple &Target);
+  void EmitVersionForTarget(const Triple &Target,
+                            const VersionTuple &SDKVersion);
 
   /// Note in the output that the specified \p Func is a Thumb mode
   /// function (ARM target only).
   virtual void EmitThumbFunc(MCSymbol *Func);
 
   /// Emit an assignment of \p Value to \p Symbol.
   ///
   /// This corresponds to an assembler statement such as:

lib/CodeGen/AsmPrinter/AsmPrinter.cpp

bool AsmPrinter::doInitialization(Module &M) {
   //
   // FIXME: If we end up with a collection of these sorts of Darwin-specific
   // or ELF-specific things, it may make sense to have a platform helper class
   // that will work with the target helper class. For now keep it here, as the
   // alternative is duplicated code in each of the target asm printers that
   // use the directive, where it would need the same conditionalization
   // anyway.
   const Triple &Target = TM.getTargetTriple();
-  OutStreamer->EmitVersionForTarget(Target);
+  OutStreamer->EmitVersionForTarget(Target, M.getSDKVersion());
 
   // Allow the target to emit any magic that it wants at the start of the file.
   EmitStartOfAsmFile(M);
 
   // Very minimal debug info. It is ignored if we emit actual debug info. If we
   // don't, this at least helps the user find where a global came from.
   if (MAI->hasSingleParameterDotFile()) {
     // .file "foo.c"

lib/IR/Module.cpp

 #include "llvm/IR/ValueSymbolTable.h"
 #include "llvm/Pass.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/CodeGen.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/RandomNumberGenerator.h"
+#include "llvm/Support/VersionTuple.h"
 #include <algorithm>
 #include <cassert>
 #include <cstdint>
 #include <memory>
 #include <utility>
 #include <vector>
 
 using namespace llvm;
bool Module::getRtLibUseGOT() const {
   auto *Val = cast_or_null<ConstantAsMetadata>(getModuleFlag("RtLibUseGOT"));
   return Val && (cast<ConstantInt>(Val->getValue())->getZExtValue() > 0);
 }
 
 void Module::setRtLibUseGOT() {
   addModuleFlag(ModFlagBehavior::Max, "RtLibUseGOT", 1);
 }
 
+void Module::setSDKVersion(const VersionTuple &V) {
+  SmallVector<unsigned, 3> Entries;
+  Entries.push_back(V.getMajor());
+  if (auto Minor = V.getMinor()) {
+    Entries.push_back(*Minor);
+    if (auto Subminor = V.getSubminor())
+      Entries.push_back(*Subminor);
+    // Ignore the 'build' component as it can't be represented in the object
+    // file.
+  }
+  addModuleFlag(ModFlagBehavior::Warning, "SDK Version",
+                ConstantDataArray::get(Context, Entries));
+}
+
+VersionTuple Module::getSDKVersion() const {
+  auto *CM = dyn_cast_or_null<ConstantAsMetadata>(getModuleFlag("SDK Version"));
+  if (!CM)
+    return {};
+  auto *Arr = dyn_cast_or_null<ConstantDataArray>(CM->getValue());
+  if (!Arr)
+    return {};
+  auto getVersionComponent = [&](unsigned Index) -> Optional<unsigned> {
+    if (Index >= Arr->getNumElements())
+      return None;
+    return (unsigned)Arr->getElementAsInteger(Index);
+  };
+  auto Major = getVersionComponent(0);
+  if (!Major)
+    return {};
+  VersionTuple Result = VersionTuple(*Major);
+  if (auto Minor = getVersionComponent(1)) {
+    Result = VersionTuple(*Major, *Minor);
+    if (auto Subminor = getVersionComponent(2)) {
+      Result = VersionTuple(*Major, *Minor, *Subminor);
+    }
+  }
+  return Result;
+}
+
 GlobalVariable *llvm::collectUsedGlobalVariables(
     const Module &M, SmallPtrSetImpl<GlobalValue *> &Set, bool CompilerUsed) {
   const char *Name = CompilerUsed ? "llvm.compiler.used" : "llvm.used";
   GlobalVariable *GV = M.getGlobalVariable(Name);
   if (!GV || !GV->hasInitializer())
     return GV;
 
   const ConstantArray *Init = cast<ConstantArray>(GV->getInitializer());
   for (Value *Op : Init->operands()) {
     GlobalValue *G = cast<GlobalValue>(Op->stripPointerCastsNoFollowAliases());
     Set.insert(G);
   }
   return GV;
 }

lib/MC/MCAsmStreamer.cpp

public:
 
   void EmitLOHDirective(MCLOHType Kind, const MCLOHArgs &Args) override;
   void EmitLabel(MCSymbol *Symbol, SMLoc Loc = SMLoc()) override;
 
   void EmitAssemblerFlag(MCAssemblerFlag Flag) override;
   void EmitLinkerOptions(ArrayRef<std::string> Options) override;
   void EmitDataRegion(MCDataRegionType Kind) override;
   void EmitVersionMin(MCVersionMinType Kind, unsigned Major, unsigned Minor,
-                      unsigned Update) override;
+                      unsigned Update, VersionTuple SDKVersion) override;
   void EmitBuildVersion(unsigned Platform, unsigned Major, unsigned Minor,
-                        unsigned Update) override;
+                        unsigned Update, VersionTuple SDKVersion) override;
   void EmitThumbFunc(MCSymbol *Func) override;
 
   void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) override;
   void EmitWeakReference(MCSymbol *Alias, const MCSymbol *Symbol) override;
   bool EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute) override;
 
   void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) override;
   void BeginCOFFSymbolDef(const MCSymbol *Symbol) override;
static const char *getVersionMinDirective(MCVersionMinType Type) {
   case MCVM_WatchOSVersionMin: return ".watchos_version_min";
   case MCVM_TvOSVersionMin:    return ".tvos_version_min";
   case MCVM_IOSVersionMin:     return ".ios_version_min";
   case MCVM_OSXVersionMin:     return ".macosx_version_min";
   }
   llvm_unreachable("Invalid MC version min type");
 }
 
+static void EmitSDKVersionSuffix(raw_ostream &OS,
+                                 const VersionTuple &SDKVersion) {
+  if (SDKVersion.empty())
+    return;
+  OS << '\t' << "sdk_version " << SDKVersion.getMajor();
+  if (auto Minor = SDKVersion.getMinor()) {
+    OS << ", " << *Minor;
+    if (auto Subminor = SDKVersion.getSubminor()) {
+      OS << ", " << *Subminor;
+    }
+  }
+}
+
 void MCAsmStreamer::EmitVersionMin(MCVersionMinType Type, unsigned Major,
-                                   unsigned Minor, unsigned Update) {
+                                   unsigned Minor, unsigned Update,
+                                   VersionTuple SDKVersion) {
   OS << '\t' << getVersionMinDirective(Type) << ' ' << Major << ", " << Minor;
   if (Update)
     OS << ", " << Update;
+  EmitSDKVersionSuffix(OS, SDKVersion);
   EmitEOL();
 }
 
 static const char *getPlatformName(MachO::PlatformType Type) {
   switch (Type) {
   case MachO::PLATFORM_MACOS:    return "macos";
   case MachO::PLATFORM_IOS:      return "ios";
   case MachO::PLATFORM_TVOS:     return "tvos";
   case MachO::PLATFORM_WATCHOS:  return "watchos";
   case MachO::PLATFORM_BRIDGEOS: return "bridgeos";
   }
   llvm_unreachable("Invalid Mach-O platform type");
 }
 
 void MCAsmStreamer::EmitBuildVersion(unsigned Platform, unsigned Major,
-                                     unsigned Minor, unsigned Update) {
+                                     unsigned Minor, unsigned Update,
+                                     VersionTuple SDKVersion) {
   const char *PlatformName = getPlatformName((MachO::PlatformType)Platform);
   OS << "\t.build_version " << PlatformName << ", " << Major << ", " << Minor;
   if (Update)
     OS << ", " << Update;
+  EmitSDKVersionSuffix(OS, SDKVersion);
   EmitEOL();
 }
 
 void MCAsmStreamer::EmitThumbFunc(MCSymbol *Func) {
   // This needs to emit to a temporary string to get properly quoted
   // MCSymbols when they have spaces in them.
   OS << "\t.thumb_func";
   // Only Mach-O hasSubsectionsViaSymbols()

lib/MC/MCAssembler.cpp

void MCAssembler::reset() {
   ThumbFuncs.clear();
   BundleAlignSize = 0;
   RelaxAll = false;
   SubsectionsViaSymbols = false;
   IncrementalLinkerCompatible = false;
   ELFHeaderEFlags = 0;
   LOHContainer.reset();
   VersionInfo.Major = 0;
+  VersionInfo.SDKVersion = VersionTuple();
 
   // reset objects owned by us
   if (getBackendPtr())
     getBackendPtr()->reset();
   if (getEmitterPtr())
     getEmitterPtr()->reset();
   if (getWriterPtr())
     getWriterPtr()->reset();

lib/MC/MCMachOStreamer.cpp

public:
 
   void ChangeSection(MCSection *Sect, const MCExpr *Subsect) override;
   void EmitLabel(MCSymbol *Symbol, SMLoc Loc = SMLoc()) override;
   void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) override;
   void EmitEHSymAttributes(const MCSymbol *Symbol, MCSymbol *EHSymbol) override;
   void EmitAssemblerFlag(MCAssemblerFlag Flag) override;
   void EmitLinkerOptions(ArrayRef<std::string> Options) override;
   void EmitDataRegion(MCDataRegionType Kind) override;
-  void EmitVersionMin(MCVersionMinType Kind, unsigned Major,
-                      unsigned Minor, unsigned Update) override;
-  void EmitBuildVersion(unsigned Platform, unsigned Major,
-                        unsigned Minor, unsigned Update) override;
+  void EmitVersionMin(MCVersionMinType Kind, unsigned Major, unsigned Minor,
+                      unsigned Update, VersionTuple SDKVersion) override;
+  void EmitBuildVersion(unsigned Platform, unsigned Major, unsigned Minor,
+                        unsigned Update, VersionTuple SDKVersion) override;
   void EmitThumbFunc(MCSymbol *Func) override;
   bool EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute) override;
   void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) override;
   void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
                         unsigned ByteAlignment) override;
 
   void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
                              unsigned ByteAlignment) override;
case MCDR_DataRegionJT32:
     return;
   case MCDR_DataRegionEnd:
     EmitDataRegionEnd();
     return;
   }
 }
 
 void MCMachOStreamer::EmitVersionMin(MCVersionMinType Kind, unsigned Major,
-                                     unsigned Minor, unsigned Update) {
-  getAssembler().setVersionMin(Kind, Major, Minor, Update);
+                                     unsigned Minor, unsigned Update,
+                                     VersionTuple SDKVersion) {
+  getAssembler().setVersionMin(Kind, Major, Minor, Update, SDKVersion);
 }
 
 void MCMachOStreamer::EmitBuildVersion(unsigned Platform, unsigned Major,
-                                       unsigned Minor, unsigned Update) {
+                                       unsigned Minor, unsigned Update,
+                                       VersionTuple SDKVersion) {
   getAssembler().setBuildVersion((MachO::PlatformType)Platform, Major, Minor,
-                                 Update);
+                                 Update, SDKVersion);
 }
 
 void MCMachOStreamer::EmitThumbFunc(MCSymbol *Symbol) {
   // Remember that the function is a thumb function. Fixup and relocation
   // values will need adjusted.
   getAssembler().setIsThumbFunc(Symbol);
   cast<MCSymbolMachO>(Symbol)->setThumbFunc();
 }
MCStreamer *llvm::createMachOStreamer(MCContext &Context,
                                       std::unique_ptr<MCObjectWriter> &&OW,
                                       std::unique_ptr<MCCodeEmitter> &&CE,
                                       bool RelaxAll, bool DWARFMustBeAtTheEnd,
                                       bool LabelSections) {
   MCMachOStreamer *S =
       new MCMachOStreamer(Context, std::move(MAB), std::move(OW), std::move(CE),
                           DWARFMustBeAtTheEnd, LabelSections);
   const Triple &Target = Context.getObjectFileInfo()->getTargetTriple();
-  S->EmitVersionForTarget(Target);
+  S->EmitVersionForTarget(Target, Context.getObjectFileInfo()->getSDKVersion());
   if (RelaxAll)
     S->getAssembler().setRelaxAll(true);
   return S;
 }

lib/MC/MCParser/DarwinAsmParser.cpp

bool parseIOSVersionMin(StringRef Directive, SMLoc Loc) {
     return parseVersionMin(Directive, Loc, MCVM_IOSVersionMin);
   }
   bool parseMacOSXVersionMin(StringRef Directive, SMLoc Loc) {
     return parseVersionMin(Directive, Loc, MCVM_OSXVersionMin);
   }
 
   bool parseBuildVersion(StringRef Directive, SMLoc Loc);
   bool parseVersionMin(StringRef Directive, SMLoc Loc, MCVersionMinType Type);
+  bool parseMajorMinorVersionComponent(unsigned *Major, unsigned *Minor,
+                                       const char *VersionName);
+  bool parseOptionalTrailingVersionComponent(unsigned *Component,
+                                             const char *ComponentName);
   bool parseVersion(unsigned *Major, unsigned *Minor, unsigned *Update);
+  bool parseSDKVersion(VersionTuple &SDKVersion);
   void checkVersion(StringRef Directive, StringRef Arg, SMLoc Loc,
                     Triple::OSType ExpectedOS);
 };
 
 } // end anonymous namespace
 
 bool DarwinAsmParser::parseSectionSwitch(StringRef Segment, StringRef Section,
                                          unsigned TAA, unsigned Align,
bool DarwinAsmParser::parseDirectiveDataRegionEnd(StringRef, SMLoc) {
   if (getLexer().isNot(AsmToken::EndOfStatement))
     return TokError("unexpected token in '.end_data_region' directive");
 
   Lex();
   getStreamer().EmitDataRegion(MCDR_DataRegionEnd);
   return false;
 }
 
-/// parseVersion ::= major, minor [, update]
-bool DarwinAsmParser::parseVersion(unsigned *Major, unsigned *Minor,
-                                   unsigned *Update) {
+static bool isSDKVersionToken(const AsmToken &Tok) {
+  return Tok.is(AsmToken::Identifier) && Tok.getIdentifier() == "sdk_version";
+}
+
+/// parseMajorMinorVersionComponent ::= major, minor
+bool DarwinAsmParser::parseMajorMinorVersionComponent(unsigned *Major,
+                                                      unsigned *Minor,
+                                                      const char *VersionName) {
   // Get the major version number.
   if (getLexer().isNot(AsmToken::Integer))
-    return TokError("invalid OS major version number, integer expected");
+    return TokError(Twine("invalid ") + VersionName +
+                    " major version number, integer expected");
   int64_t MajorVal = getLexer().getTok().getIntVal();
   if (MajorVal > 65535 || MajorVal <= 0)
-    return TokError("invalid OS major version number");
+    return TokError(Twine("invalid ") + VersionName + " major version number");
   *Major = (unsigned)MajorVal;
   Lex();
   if (getLexer().isNot(AsmToken::Comma))
-    return TokError("OS minor version number required, comma expected");
+    return TokError(Twine(VersionName) +
+                    " minor version number required, comma expected");
   Lex();
   // Get the minor version number.
   if (getLexer().isNot(AsmToken::Integer))
-    return TokError("invalid OS minor version number, integer expected");
+    return TokError(Twine("invalid ") + VersionName +
+                    " minor version number, integer expected");
   int64_t MinorVal = getLexer().getTok().getIntVal();
   if (MinorVal > 255 || MinorVal < 0)
-    return TokError("invalid OS minor version number");
+    return TokError(Twine("invalid ") + VersionName + " minor version number");
   *Minor = MinorVal;
   Lex();
+  return false;
+}
+
+/// parseOptionalTrailingVersionComponent ::= , version_number
+bool DarwinAsmParser::parseOptionalTrailingVersionComponent(
+    unsigned *Component, const char *ComponentName) {
+  assert(getLexer().is(AsmToken::Comma) && "comma expected");
+  Lex();
+  if (getLexer().isNot(AsmToken::Integer))
+    return TokError(Twine("invalid ") + ComponentName +
+                    " version number, integer expected");
+  int64_t Val = getLexer().getTok().getIntVal();
+  if (Val > 255 || Val < 0)
+    return TokError(Twine("invalid ") + ComponentName + " version number");
+  *Component = Val;
+  Lex();
+  return false;
+}
+
+/// parseVersion ::= parseMajorMinorVersionComponent
+///                      parseOptionalTrailingVersionComponent
+bool DarwinAsmParser::parseVersion(unsigned *Major, unsigned *Minor,
+                                   unsigned *Update) {
+  if (parseMajorMinorVersionComponent(Major, Minor, "OS"))
+    return true;
 
   // Get the update level, if specified
   *Update = 0;
-  if (getLexer().is(AsmToken::EndOfStatement))
+  if (getLexer().is(AsmToken::EndOfStatement) ||
+      isSDKVersionToken(getLexer().getTok()))
     return false;
   if (getLexer().isNot(AsmToken::Comma))
     return TokError("invalid OS update specifier, comma expected");
+  if (parseOptionalTrailingVersionComponent(Update, "OS update"))
+    return true;
+  return false;
+}
+
+bool DarwinAsmParser::parseSDKVersion(VersionTuple &SDKVersion) {
+  assert(isSDKVersionToken(getLexer().getTok()) && "expected sdk_version");
   Lex();
-  if (getLexer().isNot(AsmToken::Integer))
-    return TokError("invalid OS update version number, integer expected");
-  int64_t UpdateVal = getLexer().getTok().getIntVal();
-  if (UpdateVal > 255 || UpdateVal < 0)
-    return TokError("invalid OS update version number");
-  *Update = UpdateVal;
-  Lex();
+  unsigned Major, Minor;
+  if (parseMajorMinorVersionComponent(&Major, &Minor, "SDK"))
+    return true;
+  SDKVersion = VersionTuple(Major, Minor);
+
+  // Get the subminor version, if specified.
+  if (getLexer().is(AsmToken::Comma)) {
+    unsigned Subminor;
+    if (parseOptionalTrailingVersionComponent(&Subminor, "SDK subminor"))
+      return true;
+    SDKVersion = VersionTuple(Major, Minor, Subminor);
+  }
   return false;
 }
 
 void DarwinAsmParser::checkVersion(StringRef Directive, StringRef Arg,
                                    SMLoc Loc, Triple::OSType ExpectedOS) {
   const Triple &Target = getContext().getObjectFileInfo()->getTargetTriple();
   if (Target.getOS() != ExpectedOS)
     Warning(Loc, Twine(Directive) +
static Triple::OSType getOSTypeFromMCVM(MCVersionMinType Type) {
   case MCVM_TvOSVersionMin:    return Triple::TvOS;
   case MCVM_IOSVersionMin:     return Triple::IOS;
   case MCVM_OSXVersionMin:     return Triple::MacOSX;
   }
   llvm_unreachable("Invalid mc version min type");
 }
 
 /// parseVersionMin
-///   ::= .ios_version_min parseVersion
-///   |   .macosx_version_min parseVersion
-///   |   .tvos_version_min parseVersion
-///   |   .watchos_version_min parseVersion
+///   ::= .ios_version_min parseVersion parseSDKVersion
+///   |   .macosx_version_min parseVersion parseSDKVersion
+///   |   .tvos_version_min parseVersion parseSDKVersion
+///   |   .watchos_version_min parseVersion parseSDKVersion
 bool DarwinAsmParser::parseVersionMin(StringRef Directive, SMLoc Loc,
                                       MCVersionMinType Type) {
   unsigned Major;
   unsigned Minor;
   unsigned Update;
   if (parseVersion(&Major, &Minor, &Update))
     return true;
 
+  VersionTuple SDKVersion;
+  if (isSDKVersionToken(getLexer().getTok()) && parseSDKVersion(SDKVersion))
+    return true;
+
   if (parseToken(AsmToken::EndOfStatement))
     return addErrorSuffix(Twine(" in '") + Directive + "' directive");
 
   Triple::OSType ExpectedOS = getOSTypeFromMCVM(Type);
   checkVersion(Directive, StringRef(), Loc, ExpectedOS);
-
-  getStreamer().EmitVersionMin(Type, Major, Minor, Update);
+  getStreamer().EmitVersionMin(Type, Major, Minor, Update, SDKVersion);
   return false;
 }
 
 static Triple::OSType getOSTypeFromPlatform(MachO::PlatformType Type) {
   switch (Type) {
   case MachO::PLATFORM_MACOS:   return Triple::MacOSX;
   case MachO::PLATFORM_IOS:     return Triple::IOS;
   case MachO::PLATFORM_TVOS:    return Triple::TvOS;
   case MachO::PLATFORM_WATCHOS: return Triple::WatchOS;
   case MachO::PLATFORM_BRIDGEOS: /* silence warning */break;
   }
   llvm_unreachable("Invalid mach-o platform type");
 }
 
 /// parseBuildVersion
-///   ::= .build_version (macos|ios|tvos|watchos), parseVersion
+///   ::= .build_version (macos|ios|tvos|watchos), parseVersion parseSDKVersion
 bool DarwinAsmParser::parseBuildVersion(StringRef Directive, SMLoc Loc) {
   StringRef PlatformName;
   SMLoc PlatformLoc = getTok().getLoc();
   if (getParser().parseIdentifier(PlatformName))
     return TokError("platform name expected");
 
   unsigned Platform = StringSwitch<unsigned>(PlatformName)
     .Case("macos", MachO::PLATFORM_MACOS)
bool DarwinAsmParser::parseBuildVersion(StringRef Directive, SMLoc Loc) {
   Lex();
 
   unsigned Major;
   unsigned Minor;
   unsigned Update;
   if (parseVersion(&Major, &Minor, &Update))
     return true;
 
+  VersionTuple SDKVersion;
+  if (isSDKVersionToken(getLexer().getTok()) && parseSDKVersion(SDKVersion))
+    return true;
+
   if (parseToken(AsmToken::EndOfStatement))
     return addErrorSuffix(" in '.build_version' directive");
 
   Triple::OSType ExpectedOS
     = getOSTypeFromPlatform((MachO::PlatformType)Platform);
   checkVersion(Directive, PlatformName, Loc, ExpectedOS);
-
-  getStreamer().EmitBuildVersion(Platform, Major, Minor, Update);
+  getStreamer().EmitBuildVersion(Platform, Major, Minor, Update, SDKVersion);
   return false;
 }
 
 
 namespace llvm {
 
 MCAsmParserExtension *createDarwinAsmParser() {
   return new DarwinAsmParser;
 }
 
 } // end llvm namespace

lib/MC/MCStreamer.cpp

MCSymbol *MCStreamer::endSection(MCSection *Section) {
   if (Sym->isInSection())
     return Sym;
 
   SwitchSection(Section);
   EmitLabel(Sym);
   return Sym;
 }
 
-void MCStreamer::EmitVersionForTarget(const Triple &Target) {
+void MCStreamer::EmitVersionForTarget(const Triple &Target,
+                                      const VersionTuple &SDKVersion) {
   if (!Target.isOSBinFormatMachO() || !Target.isOSDarwin())
     return;
   // Do we even know the version?
   if (Target.getOSMajorVersion() == 0)
     return;
 
   unsigned Major;
   unsigned Minor;
if (Target.isWatchOS()) {
     VersionType = MCVM_OSXVersionMin;
     if (!Target.getMacOSXVersion(Major, Minor, Update))
       Major = 0;
   } else {
     VersionType = MCVM_IOSVersionMin;
     Target.getiOSVersion(Major, Minor, Update);
   }
   if (Major != 0)
-    EmitVersionMin(VersionType, Major, Minor, Update);
+    EmitVersionMin(VersionType, Major, Minor, Update, SDKVersion);
 }

lib/MC/MachObjectWriter.cpp

if (Sec.hasInstructions())
       Flags |= MachO::S_ATTR_SOME_INSTRUCTIONS;
     writeSection(Layout, Sec, getSectionAddress(&Sec), SectionStart, Flags,
                  RelocTableEnd, NumRelocs);
     RelocTableEnd += NumRelocs * sizeof(MachO::any_relocation_info);
   }
 
   // Write out the deployment target information, if it's available.
   if (VersionInfo.Major != 0) {
-    assert(VersionInfo.Update < 256 && "unencodable update target version");
-    assert(VersionInfo.Minor < 256 && "unencodable minor target version");
-    assert(VersionInfo.Major < 65536 && "unencodable major target version");
-    uint32_t EncodedVersion = VersionInfo.Update | (VersionInfo.Minor << 8) |
-      (VersionInfo.Major << 16);
+    auto EncodeVersion = [](VersionTuple V) -> uint32_t {
+      assert(!V.empty() && "empty version");
+      unsigned Update = V.getSubminor() ? *V.getSubminor() : 0;
+      unsigned Minor = V.getMinor() ? *V.getMinor() : 0;
+      assert(Update < 256 && "unencodable update target version");
+      assert(Minor < 256 && "unencodable minor target version");
+      assert(V.getMajor() < 65536 && "unencodable major target version");
+      return Update | (Minor << 8) | (V.getMajor() << 16);
+    };
+    uint32_t EncodedVersion = EncodeVersion(
+        VersionTuple(VersionInfo.Major, VersionInfo.Minor, VersionInfo.Update));
+    uint32_t SDKVersion = !VersionInfo.SDKVersion.empty()
+                              ? EncodeVersion(VersionInfo.SDKVersion)
+                              : 0;
     if (VersionInfo.EmitBuildVersion) {
       // FIXME: Currently empty tools. Add clang version in the future.
       W.write<uint32_t>(MachO::LC_BUILD_VERSION);
       W.write<uint32_t>(sizeof(MachO::build_version_command));
       W.write<uint32_t>(VersionInfo.TypeOrPlatform.Platform);
       W.write<uint32_t>(EncodedVersion);
-      W.write<uint32_t>(0);         // SDK version.
+      W.write<uint32_t>(SDKVersion);
       W.write<uint32_t>(0);         // Empty tools list.
     } else {
       MachO::LoadCommandType LCType
         = getLCFromMCVM(VersionInfo.TypeOrPlatform.Type);
       W.write<uint32_t>(LCType);
       W.write<uint32_t>(sizeof(MachO::version_min_command));
       W.write<uint32_t>(EncodedVersion);
-      W.write<uint32_t>(0);         // reserved.
+      W.write<uint32_t>(SDKVersion);
     }
   }
 
   // Write the data-in-code load command, if used.
   uint64_t DataInCodeTableEnd = RelocTableEnd + NumDataRegions * 8;
   if (NumDataRegions) {
     uint64_t DataRegionsOffset = RelocTableEnd;
     uint64_t DataRegionsSize = NumDataRegions * 8;

lib/Object/ModuleSymbolTable.cpp

initializeRecordStreamer(const Module &M,
 
   std::unique_ptr<MCInstrInfo> MCII(T->createMCInstrInfo());
   if (!MCII)
     return;
 
   MCObjectFileInfo MOFI;
   MCContext MCCtx(MAI.get(), MRI.get(), &MOFI);
   MOFI.InitMCObjectFileInfo(TT, /*PIC*/ false, MCCtx);
+  MOFI.setSDKVersion(M.getSDKVersion());
   RecordStreamer Streamer(MCCtx, M);
   T->createNullTargetStreamer(Streamer);
 
   std::unique_ptr<MemoryBuffer> Buffer(MemoryBuffer::getMemBuffer(InlineAsm));
   SourceMgr SrcMgr;
   SrcMgr.AddNewSourceBuffer(std::move(Buffer), SMLoc());
   std::unique_ptr<MCAsmParser> Parser(
       createMCAsmParser(SrcMgr, MCCtx, Streamer, *MAI));

test/MC/MachO/ARM/build-version-sdk-version-errors.c

+// RUN: not llvm-mc -triple x86_64-apple-macos %s 2>&1 | FileCheck %s
+
+.build_version macos,3,4,5 sdk_version
+// CHECK: invalid SDK major version number, integer expected
+
+.build_version macos,3,4,5 sdk_version 10
+// CHECK: SDK minor version number required, comma expected
+
+.build_version macos,3,4,5 sdk_version 10,
+// CHECK: invalid SDK minor version number, integer expected
+
+.build_version macos,3,4,5 sdk_version 10,1,
+// CHECK: invalid SDK subminor version number, integer expected
+
+.build_version macos,3,4,5 sdk_version 10,10000
+// CHECK: invalid SDK minor version number
+
+.build_version macos,3,4,5 sdk_version 10,255,10000
+// CHECK: invalid SDK subminor version number

test/MC/MachO/ARM/build-version-sdk-version.s

+// RUN: llvm-mc -triple x86_64-apple-macos %s | FileCheck %s
+
+.build_version macos,3,4,5 sdk_version 10,14
+// CHECK: .build_version macos, 3, 4, 5 sdk_version 10, 14
+
+.build_version ios,6,7 sdk_version 6,1,0
+// CHECK: .build_version ios, 6, 7 sdk_version 6, 1, 0
+
+.build_version tvos,8,9 sdk_version 9,0,10
+// CHECK: .build_version tvos, 8, 9 sdk_version 9, 0, 10
+
+.build_version watchos,10,11 sdk_version 10,11
+// CHECK: .build_version watchos, 10, 11 sdk_version 10, 11

test/MC/MachO/build-version-with-sdk-version.s

+// RUN: llvm-mc -triple x86_64-apple-macos %s -filetype=obj -o - | llvm-readobj --macho-version-min | FileCheck %s
+
+// Test the formation of the sdk_version component of the version load
+// command in the MachO.
+.build_version macos, 10,13,2 sdk_version 10,14,1
+
+// CHECK: MinVersion {
+// CHECK:   Cmd: LC_BUILD_VERSION
+// CHECK:   Size: 24
+// CHECK:   Platform: macos
+// CHECK:   Version: 10.13.2
+// CHECK:   SDK: 10.14.1
+// CHECK: }

test/MC/MachO/darwin-sdk-version.ll

+; RUN: llc %s -filetype=obj -o - | llvm-objdump -macho -private-headers - | FileCheck %s
+; RUN: llc %s -filetype=asm -o - | FileCheck --check-prefix=ASM %s
+
+target triple = "x86_64-apple-macos10.14";
+!llvm.module.flags = !{!0};
+!0 = !{i32 2, !"SDK Version", [3 x i32] [ i32 10, i32 14, i32 2 ] };
+
+define void @foo() {
+entry:
+  ret void
+}
+
+; CHECK:           cmd LC_VERSION_MIN_MACOSX
+; CHECK-NEXT:  cmdsize 16
+; CHECK-NEXT:  version 10.14
+; CHECK-NEXT:      sdk 10.14.2
+
+; ASM: .macosx_version_min 10, 14 sdk_version 10, 14, 2

test/MC/MachO/osx-version-min-load-command-with-sdk-errors.s

+// RUN: not llvm-mc -triple x86_64-apple-macos %s -o - 2>&1 | FileCheck %s
+
+.macosx_version_min 10,13,2 sdk_version 10
+// CHECK: SDK minor version number required, comma expected
+
+.macosx_version_min 10,13,2 sdk_version 10,
+// CHECK: invalid SDK minor version number, integer expected
+
+.macosx_version_min 10,13,2 sdk_version 10
+// CHECK: SDK minor version number required, comma expected

test/MC/MachO/osx-version-min-load-command-with-sdk.s

+// RUN: llvm-mc -triple x86_64-apple-macos %s -filetype=obj -o - | llvm-readobj --macho-version-min | FileCheck %s
+
+// Test the formation of the sdk_version component of the version load
+// command in the MachO.
+.macosx_version_min 10,13,2 sdk_version 10,14
+
+// CHECK: MinVersion {
+// CHECK:   Cmd: LC_VERSION_MIN_MACOSX
+// CHECK:   Size: 16
+// CHECK:   Version: 10.13.2
+// CHECK:   SDK: 10.14
+// CHECK: }