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

2 files changed, 10 insertions, 14 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index cb7cacbb00c..9d822d3cb1a 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -1397,7 +1397,6 @@ void AsmPrinter::EmitXXStructorList(const Constant *List, bool isCtor) {
   for (Structor &S : Structors) {
     const TargetLoweringObjectFile &Obj = getObjFileLowering();
     const MCSymbol *KeySym = nullptr;
-    const MCSection *KeySec = nullptr;
     if (GlobalValue *GV = S.ComdatKey) {
       if (GV->hasAvailableExternallyLinkage())
         // If the associated variable is available_externally, some other TU
@@ -1405,11 +1404,10 @@ void AsmPrinter::EmitXXStructorList(const Constant *List, bool isCtor) {
         continue;
 
       KeySym = getSymbol(GV);
-      KeySec = getObjFileLowering().SectionForGlobal(GV, *Mang, TM);
     }
     const MCSection *OutputSection =
-        (isCtor ? Obj.getStaticCtorSection(S.Priority, KeySym, KeySec)
-                : Obj.getStaticDtorSection(S.Priority, KeySym, KeySec));
+        (isCtor ? Obj.getStaticCtorSection(S.Priority, KeySym)
+                : Obj.getStaticDtorSection(S.Priority, KeySym));
     OutStreamer.SwitchSection(OutputSection);
     if (OutStreamer.getCurrentSection() != OutStreamer.getPreviousSection())
       EmitAlignment(Align);
diff --git a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
index d3494258151..02abc282e6d 100644
--- a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -336,7 +336,7 @@ getSectionForConstant(SectionKind Kind) const {
 }
 
 const MCSection *TargetLoweringObjectFileELF::getStaticCtorSection(
-    unsigned Priority, const MCSymbol *KeySym, const MCSection *KeySec) const {
+    unsigned Priority, const MCSymbol *KeySym) const {
   // The default scheme is .ctor / .dtor, so we have to invert the priority
   // numbering.
   if (Priority == 65535)
@@ -356,7 +356,7 @@ const MCSection *TargetLoweringObjectFileELF::getStaticCtorSection(
 }
 
 const MCSection *TargetLoweringObjectFileELF::getStaticDtorSection(
-    unsigned Priority, const MCSymbol *KeySym, const MCSection *KeySec) const {
+    unsigned Priority, const MCSymbol *KeySym) const {
   // The default scheme is .ctor / .dtor, so we have to invert the priority
   // numbering.
   if (Priority == 65535)
@@ -864,8 +864,7 @@ emitModuleFlags(MCStreamer &Streamer,
 
 static const MCSection *getAssociativeCOFFSection(MCContext &Ctx,
                                                   const MCSection *Sec,
-                                                  const MCSymbol *KeySym,
-                                                  const MCSection *KeySec) {
+                                                  const MCSymbol *KeySym) {
   // Return the normal section if we don't have to be associative.
   if (!KeySym)
     return Sec;
@@ -873,20 +872,19 @@ static const MCSection *getAssociativeCOFFSection(MCContext &Ctx,
   // Make an associative section with the same name and kind as the normal
   // section.
   const MCSectionCOFF *SecCOFF = cast<MCSectionCOFF>(Sec);
-  const MCSectionCOFF *KeySecCOFF = cast<MCSectionCOFF>(KeySec);
   unsigned Characteristics =
       SecCOFF->getCharacteristics() | COFF::IMAGE_SCN_LNK_COMDAT;
   return Ctx.getCOFFSection(SecCOFF->getSectionName(), Characteristics,
                             SecCOFF->getKind(), KeySym->getName(),
-                            COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE, KeySecCOFF);
+                            COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE);
 }
 
 const MCSection *TargetLoweringObjectFileCOFF::getStaticCtorSection(
-    unsigned Priority, const MCSymbol *KeySym, const MCSection *KeySec) const {
-  return getAssociativeCOFFSection(getContext(), StaticCtorSection, KeySym, KeySec);
+    unsigned Priority, const MCSymbol *KeySym) const {
+  return getAssociativeCOFFSection(getContext(), StaticCtorSection, KeySym);
 }
 
 const MCSection *TargetLoweringObjectFileCOFF::getStaticDtorSection(
-    unsigned Priority, const MCSymbol *KeySym, const MCSection *KeySec) const {
-  return getAssociativeCOFFSection(getContext(), StaticDtorSection, KeySym, KeySec);
+    unsigned Priority, const MCSymbol *KeySym) const {
+  return getAssociativeCOFFSection(getContext(), StaticDtorSection, KeySym);
 }