MC: correct DWARF header for PE/COFF assembly input

The header contains an offset to the DWARF abbreviations for the CU.  The offset
must be section relative for COFF and absolute for others.  The non-assembly
code path for the DWARF header generation already had the correct emission for
the headers.  This corrects just the assembly path.  Due to the invalid
relocation, processing of the debug information would halt previously on the
first assembly input as the associated abbreviations would be out of range as
they would have the location increased by image base and the section offset.

This address PR20332.

llvm-svn: 213275

1 files changed, 5 insertions, 4 deletions

diff --git a/llvm/lib/MC/MCDwarf.cpp b/llvm/lib/MC/MCDwarf.cpp
index b14a452d85d..ae276868198 100644
--- a/llvm/lib/MC/MCDwarf.cpp
+++ b/llvm/lib/MC/MCDwarf.cpp
@@ -657,11 +657,12 @@ static void EmitGenDwarfInfo(MCStreamer *MCOS,
 
   // The 4 byte offset to the debug abbrevs from the start of the .debug_abbrev,
   // it is at the start of that section so this is zero.
-  if (AbbrevSectionSymbol) {
-    MCOS->EmitSymbolValue(AbbrevSectionSymbol, 4);
-  } else {
+  if (AbbrevSectionSymbol == nullptr)
     MCOS->EmitIntValue(0, 4);
-  }
+  else if (context.getAsmInfo()->needsDwarfSectionOffsetDirective())
+    MCOS->EmitCOFFSecRel32(AbbrevSectionSymbol);
+  else
+    MCOS->EmitSymbolValue(AbbrevSectionSymbol, 4);
 
   const MCAsmInfo *asmInfo = context.getAsmInfo();
   int AddrSize = asmInfo->getPointerSize();