Generate version min load commands when the platform is unknown.

In the case where we are emitting to an object file, the platform is
possibly unknown, and the source object files contained load commands
for version min, we can take the maximum of those min versions and
emit in in the output object file.

This test also tests r259739.

llvm-svn: 259742

1 files changed, 52 insertions, 6 deletions

diff --git a/lld/lib/ReaderWriter/MachO/MachONormalizedFileFromAtoms.cpp b/lld/lib/ReaderWriter/MachO/MachONormalizedFileFromAtoms.cpp
index a2b33796b8f..087b557bf8d 100644
--- a/lld/lib/ReaderWriter/MachO/MachONormalizedFileFromAtoms.cpp
+++ b/lld/lib/ReaderWriter/MachO/MachONormalizedFileFromAtoms.cpp
@@ -128,6 +128,18 @@ public:
   void      copyEntryPointAddress(NormalizedFile &file);
   void      copySectionContent(NormalizedFile &file);
 
+  bool allSourceFilesHaveMinVersions() const {
+    return _allSourceFilesHaveMinVersions;
+  }
+
+  uint32_t minVersion() const {
+    return _minVersion;
+  }
+
+  LoadCommandType minVersionCommandType() const {
+    return _minVersionCommandType;
+  }
+
 private:
   typedef std::map<DefinedAtom::ContentType, SectionInfo*> TypeToSection;
   typedef llvm::DenseMap<const Atom*, uint64_t> AtomToAddress;
@@ -183,6 +195,9 @@ private:
   std::vector<const Atom *>     _machHeaderAliasAtoms;
   bool                          _hasTLVDescriptors;
   bool                          _subsectionsViaSymbols;
+  bool                          _allSourceFilesHaveMinVersions = true;
+  LoadCommandType               _minVersionCommandType = (LoadCommandType)0;
+  uint32_t                      _minVersion = 0;
 };
 
 Util::~Util() {
@@ -378,11 +393,25 @@ void Util::processDefinedAtoms(const lld::File &atomFile) {
 }
 
 void Util::processAtomAttributes(const DefinedAtom *atom) {
-  // If the file doesn't use subsections via symbols, then make sure we don't
-  // add that flag to the final output file if we have a relocatable file.
-  if (auto *machoFile = dyn_cast<mach_o::MachOFile>(&atom->file()))
+  if (auto *machoFile = dyn_cast<mach_o::MachOFile>(&atom->file())) {
+    // If the file doesn't use subsections via symbols, then make sure we don't
+    // add that flag to the final output file if we have a relocatable file.
     if (!machoFile->subsectionsViaSymbols())
       _subsectionsViaSymbols = false;
+
+    // All the source files must have min versions for us to output an object
+    // file with a min version.
+    if (auto v = machoFile->minVersion())
+      _minVersion = std::max(_minVersion, v);
+    else
+      _allSourceFilesHaveMinVersions = false;
+
+    // If we don't have a platform load command, but one of the source files
+    // does, then take the one from the file.
+    if (!_minVersionCommandType)
+      if (auto v = machoFile->minVersionLoadCommandKind())
+        _minVersionCommandType = v;
+  }
 }
 
 void Util::assignAtomToSection(const DefinedAtom *atom) {
@@ -1245,14 +1274,31 @@ normalizedFromAtoms(const lld::File &atomFile,
   normFile.currentVersion = context.currentVersion();
   normFile.compatVersion = context.compatibilityVersion();
   normFile.os = context.os();
-  normFile.minOSverson = context.osMinVersion();
-  // FIXME: We need to get the SDK version from the system.  For now the min
-  // OS version is better than nothing.
+
+  // If we are emitting an object file, then the min version is the maximum
+  // of the min's of all the source files and the cmdline.
+  if (normFile.fileType == llvm::MachO::MH_OBJECT)
+    normFile.minOSverson = std::max(context.osMinVersion(), util.minVersion());
+  else
+    normFile.minOSverson = context.osMinVersion();
+
+  normFile.minOSVersionKind = util.minVersionCommandType();
+
   normFile.sdkVersion = context.sdkVersion();
 
   if (context.generateVersionLoadCommand() &&
       context.os() != MachOLinkingContext::OS::unknown)
     normFile.hasMinVersionLoadCommand = true;
+  else if (normFile.fileType == llvm::MachO::MH_OBJECT &&
+           util.allSourceFilesHaveMinVersions() &&
+           ((normFile.os != MachOLinkingContext::OS::unknown) ||
+            util.minVersionCommandType())) {
+    // If we emit an object file, then it should contain a min version load
+    // command if all of the source files also contained min version commands.
+    // Also, we either need to have a platform, or found a platform from the
+    // source object files.
+    normFile.hasMinVersionLoadCommand = true;
+  }
   normFile.pageSize = context.pageSize();
   normFile.rpaths = context.rpaths();
   util.addDependentDylibs(atomFile, normFile);