llvm-mc/Mach-O: Set .subsections_via_symbols flag properly.

llvm-svn: 80144

include/llvm/MC/MCAssembler.h

@@ -496,6 +496,8 @@ private:
 
   std::vector<IndirectSymbolData> IndirectSymbols;
 
+  unsigned SubsectionsViaSymbols : 1;
+
 private:
   /// LayoutSection - Assign offsets and sizes to the fragments in the section
   /// \arg SD, and update the section size. The section file offset should
@@ -521,6 +523,14 @@ public:
   /// Finish - Do final processing and write the object to the output stream.
   void Finish();
 
+  // FIXME: This does not belong here.
+  bool getSubsectionsViaSymbols() const {
+    return SubsectionsViaSymbols;
+  }
+  void setSubsectionsViaSymbols(bool Value) {
+    SubsectionsViaSymbols = Value;
+  }
+
   /// @name Section List Access
   /// @{
 

lib/MC/MCAssembler.cpp

@@ -48,6 +48,10 @@ class MachObjectWriter {
     HFT_Object = 0x1
   };
 
+  enum HeaderFlags {
+    HF_SubsectionsViaSymbols = 0x2000
+  };
+
   enum LoadCommandType {
     LCT_Segment = 0x1,
     LCT_Symtab = 0x2,
@@ -167,7 +171,13 @@ public:
 
   /// @}
   
-  void WriteHeader32(unsigned NumLoadCommands, unsigned LoadCommandsSize) {
+  void WriteHeader32(unsigned NumLoadCommands, unsigned LoadCommandsSize,
+                     bool SubsectionsViaSymbols) {
+    uint32_t Flags = 0;
+
+    if (SubsectionsViaSymbols)
+      Flags |= HF_SubsectionsViaSymbols;
+
     // struct mach_header (28 bytes)
 
     uint64_t Start = OS.tell();
@@ -177,16 +187,13 @@ public:
 
     // FIXME: Support cputype.
     Write32(TargetMachOWriterInfo::HDR_CPU_TYPE_I386);
-
     // FIXME: Support cpusubtype.
     Write32(TargetMachOWriterInfo::HDR_CPU_SUBTYPE_I386_ALL);
-
     Write32(HFT_Object);
-
-    // Object files have a single load command, the segment.
-    Write32(NumLoadCommands);
+    Write32(NumLoadCommands);    // Object files have a single load command, the
+                                 // segment.
     Write32(LoadCommandsSize);
-    Write32(0); // Flags
+    Write32(Flags);
 
     assert(OS.tell() - Start == Header32Size);
   }
@@ -674,7 +681,8 @@ public:
     }
 
     // Write the prolog, starting with the header and load command...
-    WriteHeader32(NumLoadCommands, LoadCommandsSize);
+    WriteHeader32(NumLoadCommands, LoadCommandsSize,
+                  Asm.getSubsectionsViaSymbols());
     WriteSegmentLoadCommand32(NumSections, SectionDataStart, SectionDataSize);
   
     // ... and then the section headers.
@@ -864,7 +872,11 @@ MCSymbolData::MCSymbolData(MCSymbol &_Symbol, MCFragment *_Fragment,
 
 /* *** */
 
-MCAssembler::MCAssembler(raw_ostream &_OS) : OS(_OS) {}
+MCAssembler::MCAssembler(raw_ostream &_OS)
+  : OS(_OS),
+    SubsectionsViaSymbols(false)
+{
+}
 
 MCAssembler::~MCAssembler() {
 }

lib/MC/MCMachOStreamer.cpp

@@ -159,7 +159,14 @@ void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
 }
 
 void MCMachOStreamer::EmitAssemblerFlag(AssemblerFlag Flag) {
-  llvm_unreachable("FIXME: Not yet implemented!");
+  switch (Flag) {
+  default:
+    llvm_unreachable("FIXME: Not yet implemented!");
+
+  case SubsectionsViaSymbols:
+    Assembler.setSubsectionsViaSymbols(true);
+    break;
+  }
 }
 
 void MCMachOStreamer::EmitAssignment(MCSymbol *Symbol,

test/MC/MachO/sections.s

@@ -42,13 +42,14 @@
         
         .objc_selector_strs
 
-
+        .subsections_via_symbols
+        
 // CHECK: ('cputype', 7)
 // CHECK: ('cpusubtype', 3)
 // CHECK: ('filetype', 1)
 // CHECK: ('num_load_commands', 1)
 // CHECK: ('load_commands_size', 2436)
-// CHECK: ('flag', 0)
+// CHECK: ('flag', 8192)
 // CHECK: ('load_commands', [
 // CHECK:   # Load Command 0
 // CHECK:  (('command', 1)