Handle local commons for XCOFF object file writing

Summary:
Adds support for emitting common local global symbols to an XCOFF object file.
Local commons are emitted into the .bss section with a storage class of
C_HIDEXT.

Patch by: daltenty

Reviewers: sfertile, hubert.reinterpretcast

Differential Revision: https://reviews.llvm.org/D66097

llvm-svn: 370070

2 files changed, 13 insertions, 4 deletions

diff --git a/llvm/lib/MC/MCXCOFFStreamer.cpp b/llvm/lib/MC/MCXCOFFStreamer.cpp
index 5880c3d814a..760bdefd424 100644
--- a/llvm/lib/MC/MCXCOFFStreamer.cpp
+++ b/llvm/lib/MC/MCXCOFFStreamer.cpp
@@ -10,11 +10,12 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/MC/MCXCOFFStreamer.h"
+#include "llvm/BinaryFormat/XCOFF.h"
 #include "llvm/MC/MCAsmBackend.h"
 #include "llvm/MC/MCCodeEmitter.h"
 #include "llvm/MC/MCObjectWriter.h"
 #include "llvm/MC/MCSymbolXCOFF.h"
+#include "llvm/MC/MCXCOFFStreamer.h"
 #include "llvm/Support/TargetRegistry.h"
 
 using namespace llvm;
@@ -72,7 +73,8 @@ MCStreamer *llvm::createXCOFFStreamer(MCContext &Context,
   return S;
 }
 
-void MCXCOFFStreamer::EmitXCOFFLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
-                                            unsigned ByteAlign) {
-  report_fatal_error("Emission of local commons not implemented yet.");
+void MCXCOFFStreamer::EmitXCOFFLocalCommonSymbol(MCSymbol *Symbol,
+                                                 uint64_t Size,
+                                                 unsigned ByteAlignment) {
+  EmitCommonSymbol(Symbol, Size, ByteAlignment);
 }
diff --git a/llvm/lib/MC/XCOFFObjectWriter.cpp b/llvm/lib/MC/XCOFFObjectWriter.cpp
index d4dfd467976..e831d3e763f 100644
--- a/llvm/lib/MC/XCOFFObjectWriter.cpp
+++ b/llvm/lib/MC/XCOFFObjectWriter.cpp
@@ -235,6 +235,13 @@ void XCOFFObjectWriter::executePostLayoutBinding(
         break;
       }
       report_fatal_error("Unhandled mapping of read-write csect to section.");
+    case XCOFF::XMC_BS:
+      assert(XCOFF::XTY_CM == MCSec->getCSectType() &&
+             "Mapping invalid csect. CSECT with bss storage class must be "
+             "common type.");
+      BSSCsects.emplace_back(MCSec);
+      WrapperMap[MCSec] = &BSSCsects.back();
+      break;
     default:
       report_fatal_error("Unhandled mapping of csect to section.");
     }