Fix a few issues with comdat handling on COFF.

* Section association cannot use just the section name as many
sections can have the same name. With this patch, the comdat symbol in
an assoc section is interpreted to mean a symbol in the associated
section and the mapping is discovered from it.

* Comdat symbols were not being set correctly. Instead we were getting
whatever was output first for that section.

A consequence is that associative sections now must use .section to
set the association. Using .linkonce would not work since it is not
possible to change a sections comdat symbol (it is used to decide if
we should create a new section or reuse an existing one).

This includes r210298, which was reverted because it was asserting
on an associated section having the same comdat as the associated
section.

llvm-svn: 210367

1 files changed, 7 insertions, 6 deletions

diff --git a/llvm/lib/MC/MCContext.cpp b/llvm/lib/MC/MCContext.cpp
index c16326829d8..130bb99f98b 100644
--- a/llvm/lib/MC/MCContext.cpp
+++ b/llvm/lib/MC/MCContext.cpp
@@ -277,10 +277,11 @@ const MCSectionELF *MCContext::CreateELFGroupSection() {
   return Result;
 }
 
-const MCSectionCOFF *
-MCContext::getCOFFSection(StringRef Section, unsigned Characteristics,
-                          SectionKind Kind, StringRef COMDATSymName,
-                          int Selection, const MCSectionCOFF *Assoc) {
+const MCSectionCOFF *MCContext::getCOFFSection(StringRef Section,
+                                               unsigned Characteristics,
+                                               SectionKind Kind,
+                                               StringRef COMDATSymName,
+                                               int Selection) {
   // Do the lookup, if we have a hit, return it.
 
   SectionGroupPair P(Section, COMDATSymName);
@@ -294,8 +295,8 @@ MCContext::getCOFFSection(StringRef Section, unsigned Characteristics,
     COMDATSymbol = GetOrCreateSymbol(COMDATSymName);
 
   StringRef CachedName = Iter->first.first;
-  MCSectionCOFF *Result = new (*this) MCSectionCOFF(
-      CachedName, Characteristics, COMDATSymbol, Selection, Assoc, Kind);
+  MCSectionCOFF *Result = new (*this)
+      MCSectionCOFF(CachedName, Characteristics, COMDATSymbol, Selection, Kind);
 
   Iter->second = Result;
   return Result;