MC: Overhaul handling of .lcomm

- Darwin lied about not supporting .lcomm and turned it into zerofill in the
  asm parser. Push the zerofill-conversion down into macho-specific code.
- This makes the tri-state LCOMMType enum superfluous, there are no targets
  without .lcomm.
- Do proper error reporting when trying to use .lcomm with alignment on a target
  that doesn't support it.
- .comm and .lcomm alignment was parsed in bytes on COFF, should be power of 2.
- Fixes PR13755 (.lcomm crashes on ELF).

llvm-svn: 163395

1 files changed, 10 insertions, 3 deletions

diff --git a/llvm/lib/MC/MCMachOStreamer.cpp b/llvm/lib/MC/MCMachOStreamer.cpp
index b75fe2c3a7f..74f6dc62e1c 100644
--- a/llvm/lib/MC/MCMachOStreamer.cpp
+++ b/llvm/lib/MC/MCMachOStreamer.cpp
@@ -70,9 +70,7 @@ public:
     llvm_unreachable("macho doesn't support this directive");
   }
   virtual void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
-                                     unsigned ByteAlignment) {
-    llvm_unreachable("macho doesn't support this directive");
-  }
+                                     unsigned ByteAlignment);
   virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol = 0,
                             uint64_t Size = 0, unsigned ByteAlignment = 0);
   virtual void EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
@@ -325,6 +323,15 @@ void MCMachOStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
   SD.setCommon(Size, ByteAlignment);
 }
 
+void MCMachOStreamer::EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
+                                            unsigned ByteAlignment) {
+  // '.lcomm' is equivalent to '.zerofill'.
+  return EmitZerofill(getContext().getMachOSection("__DATA", "__bss",
+                                                   MCSectionMachO::S_ZEROFILL,
+                                                   0, SectionKind::getBSS()),
+                      Symbol, Size, ByteAlignment);
+}
+
 void MCMachOStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
                                    uint64_t Size, unsigned ByteAlignment) {
   MCSectionData &SectData = getAssembler().getOrCreateSectionData(*Section);