Rename embedded bitcode section in MachO

Summary:
Rename the section embeds bitcode from ".llvmbc,.llvmbc" to "__LLVM,__bitcode".
The new name matches MachO section naming convention.

Reviewers: rafael, pcc

Subscribers: davide, llvm-commits, joker.eph

Differential Revision: http://reviews.llvm.org/D17388

llvm-svn: 262245

docs/BitCodeFormat.rst

@@ -467,10 +467,11 @@ Native Object File Wrapper Format
 =================================
 
 Bitcode files for LLVM IR may also be wrapped in a native object file
-(i.e. ELF, COFF, Mach-O).  The bitcode must be stored in a section of the
-object file named ``.llvmbc``.  This wrapper format is useful for accommodating
-LTO in compilation pipelines where intermediate objects must be native object
-files which contain metadata in other sections.
+(i.e. ELF, COFF, Mach-O).  The bitcode must be stored in a section of the object
+file named ``__LLVM,__bitcode`` for MachO and ``.llvmbc`` for the other object
+formats.  This wrapper format is useful for accommodating LTO in compilation
+pipelines where intermediate objects must be native object files which contain
+metadata in other sections.
 
 Not all tools support this format.
 

include/llvm/Object/MachO.h

@@ -226,6 +226,7 @@ public:
   bool isSectionData(DataRefImpl Sec) const override;
   bool isSectionBSS(DataRefImpl Sec) const override;
   bool isSectionVirtual(DataRefImpl Sec) const override;
+  bool isSectionBitcode(DataRefImpl Sec) const override;
   relocation_iterator section_rel_begin(DataRefImpl Sec) const override;
   relocation_iterator section_rel_end(DataRefImpl Sec) const override;
 

include/llvm/Object/ObjectFile.h

@@ -94,6 +94,7 @@ public:
   bool isData() const;
   bool isBSS() const;
   bool isVirtual() const;
+  bool isBitcode() const;
 
   bool containsSymbol(SymbolRef S) const;
 
@@ -219,6 +220,7 @@ protected:
   virtual bool isSectionBSS(DataRefImpl Sec) const = 0;
   // A section is 'virtual' if its contents aren't present in the object image.
   virtual bool isSectionVirtual(DataRefImpl Sec) const = 0;
+  virtual bool isSectionBitcode(DataRefImpl Sec) const;
   virtual relocation_iterator section_rel_begin(DataRefImpl Sec) const = 0;
   virtual relocation_iterator section_rel_end(DataRefImpl Sec) const = 0;
   virtual section_iterator getRelocatedSection(DataRefImpl Sec) const;
@@ -296,6 +298,7 @@ public:
 
   static ErrorOr<std::unique_ptr<MachOObjectFile>>
   createMachOObjectFile(MemoryBufferRef Object);
+
 };
 
 // Inline function definitions.
@@ -394,6 +397,10 @@ inline bool SectionRef::isVirtual() const {
   return OwningObject->isSectionVirtual(SectionPimpl);
 }
 
+inline bool SectionRef::isBitcode() const {
+  return OwningObject->isSectionBitcode(SectionPimpl);
+}
+
 inline relocation_iterator SectionRef::relocation_begin() const {
   return OwningObject->section_rel_begin(SectionPimpl);
 }

lib/Object/FunctionIndexObjectFile.cpp

@@ -35,10 +35,7 @@ std::unique_ptr<FunctionInfoIndex> FunctionIndexObjectFile::takeIndex() {
 ErrorOr<MemoryBufferRef>
 FunctionIndexObjectFile::findBitcodeInObject(const ObjectFile &Obj) {
   for (const SectionRef &Sec : Obj.sections()) {
-    StringRef SecName;
-    if (std::error_code EC = Sec.getName(SecName))
-      return EC;
-    if (SecName == ".llvmbc") {
+    if (Sec.isBitcode()) {
       StringRef SecContents;
       if (std::error_code EC = Sec.getContents(SecContents))
         return EC;

lib/Object/IRObjectFile.cpp

@@ -266,10 +266,7 @@ basic_symbol_iterator IRObjectFile::symbol_end_impl() const {
 
 ErrorOr<MemoryBufferRef> IRObjectFile::findBitcodeInObject(const ObjectFile &Obj) {
   for (const SectionRef &Sec : Obj.sections()) {
-    StringRef SecName;
-    if (std::error_code EC = Sec.getName(SecName))
-      return EC;
-    if (SecName == ".llvmbc") {
+    if (Sec.isBitcode()) {
       StringRef SecContents;
       if (std::error_code EC = Sec.getContents(SecContents))
         return EC;

lib/Object/MachOObjectFile.cpp

@@ -630,6 +630,14 @@ bool MachOObjectFile::isSectionVirtual(DataRefImpl Sec) const {
   return false;
 }
 
+bool MachOObjectFile::isSectionBitcode(DataRefImpl Sec) const {
+  StringRef SegmentName = getSectionFinalSegmentName(Sec);
+  StringRef SectName;
+  if (!getSectionName(Sec, SectName))
+    return (SegmentName == "__LLVM" && SectName == "__bitcode");
+  return false;
+}
+
 relocation_iterator MachOObjectFile::section_rel_begin(DataRefImpl Sec) const {
   DataRefImpl Ret;
   Ret.d.a = Sec.d.a;

lib/Object/ObjectFile.cpp

@@ -55,6 +55,13 @@ std::error_code ObjectFile::printSymbolName(raw_ostream &OS,
 
 uint32_t ObjectFile::getSymbolAlignment(DataRefImpl DRI) const { return 0; }
 
+bool ObjectFile::isSectionBitcode(DataRefImpl Sec) const {
+  StringRef SectName;
+  if (!getSectionName(Sec, SectName))
+    return SectName == ".llvmbc";
+  return false;
+}
+
 section_iterator ObjectFile::getRelocatedSection(DataRefImpl Sec) const {
   return section_iterator(SectionRef(Sec, this));
 }

test/LTO/X86/Inputs/bcsection.macho.s

@@ -1,2 +1,5 @@
-.section .llvmbc,.llvmbc
+.section __FOO,__bitcode
+.asciz "Wrong Section"
+
+.section __LLVM,__bitcode
 .incbin "bcsection.bc"