Correctly set the comdat symbol on COFF.

We extended the .section syntax to allow multiple sections with the
same name but different comdats, but currently we don't make sure that
the output section has that comdat symbol.

That happens to work with the code llc produces currently because it looks like

.section secName, "dr", one_only, "COMDATSym"
.globl COMDATSym
COMDATSym:
....

but that is not very friendly to anyone coding in assembly or even to
llc once we get comdat support in the IR.

This patch changes the coff object writer to make sure the comdat symbol is
output just after the section symbol, as required by the coff spec.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210298 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 13 insertions, 2 deletions

diff --git a/lib/MC/WinCOFFObjectWriter.cpp b/lib/MC/WinCOFFObjectWriter.cpp
index 961cbc6a8f..c3fc61b290 100644
--- a/lib/MC/WinCOFFObjectWriter.cpp
+++ b/lib/MC/WinCOFFObjectWriter.cpp
@@ -347,6 +347,11 @@ void WinCOFFObjectWriter::DefineSection(MCSectionData const &SectionData) {
 
   COFFSection *coff_section = createSection(Sec.getSectionName());
   COFFSymbol  *coff_symbol = createSymbol(Sec.getSectionName());
+  if (const MCSymbol *S = Sec.getCOMDATSymbol()) {
+    COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(S);
+    assert(!COMDATSymbol->Section);
+    COMDATSymbol->Section = coff_section;
+  }
 
   coff_section->Symbol = coff_symbol;
   coff_symbol->Section = coff_section;
@@ -458,9 +463,15 @@ void WinCOFFObjectWriter::DefineSymbol(MCSymbolData const &SymbolData,
       coff_symbol->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
     } else {
       const MCSymbolData &BaseData = Assembler.getSymbolData(*Base);
-      if (BaseData.Fragment)
-        coff_symbol->Section =
+      if (BaseData.Fragment) {
+        COFFSection *Sec =
             SectionMap[&BaseData.Fragment->getParent()->getSection()];
+
+        if (coff_symbol->Section && coff_symbol->Section != Sec)
+          report_fatal_error("conflicting sections for symbol");
+
+        coff_symbol->Section = Sec;
+      }
     }
 
     coff_symbol->MCData = &ResSymData;