add COFF support for COMDAT sections, patch by Nathan Jeffords!

llvm-svn: 103304

include/llvm/MC/MCContext.h

@@ -98,8 +98,14 @@ namespace llvm {
                                    unsigned Flags, SectionKind Kind,
                                    bool IsExplicit = false);
 
-    const MCSection *getCOFFSection(StringRef Section, unsigned Flags,
-                                    SectionKind Kind);
+    const MCSection *getCOFFSection(StringRef Section, unsigned Characteristics,
+                                    int Selection, SectionKind Kind);
+
+    const MCSection *getCOFFSection(StringRef Section, unsigned Characteristics,
+                                    SectionKind Kind) {
+      return getCOFFSection (Section, Characteristics, 0, Kind);
+    }
+
     
     /// @}
 

include/llvm/MC/MCSectionCOFF.h

@@ -23,14 +23,22 @@ namespace llvm {
     // The memory for this string is stored in the same MCContext as *this.
     StringRef SectionName;
     
-    /// Flags - This is the Characteristics field of a section, drawn
-    /// from the enums below.
-    unsigned Flags;
+    /// Characteristics - This is the Characteristics field of a section,
+    //  drawn from the enums below.
+    unsigned Characteristics;
+
+    /// Selection - This is the Selection field for the section symbol, if
+    /// it is a COMDAT section (Characteristics & IMAGE_SCN_LNK_COMDAT) != 0
+    int Selection;
 
   private:
     friend class MCContext;
-    MCSectionCOFF(StringRef Section, unsigned flags, SectionKind K)
-      : MCSection(K), SectionName(Section), Flags(flags) {
+    MCSectionCOFF(StringRef Section, unsigned Characteristics,
+                  int Selection, SectionKind K)
+      : MCSection(K), SectionName(Section), Characteristics(Characteristics),
+        Selection (Selection) {
+      assert ((Characteristics & 0x00F00000) == 0 &&
+        "alignment must not be set upon section creation");
     }
     ~MCSectionCOFF();
 
@@ -39,6 +47,13 @@ namespace llvm {
     /// should be printed before the section name
     bool ShouldOmitSectionDirective(StringRef Name, const MCAsmInfo &MAI) const;
 
+    //FIXME: all COFF enumerations/flags should be standardized into one place...
+    // Target/X86COFF.h doesn't seem right as COFF can be used for other targets,
+    // MC/WinCOFF.h maybe right as it isn't target or entity specific, and it is
+    //   pretty low on the dependancy graph (is there any need to support non
+    //   windows COFF?)
+    // here is good for section stuff, but others should go elsewhere
+
     /// Valid section flags.
     enum {
       IMAGE_SCN_TYPE_NO_PAD                     = 0x00000008,
@@ -54,6 +69,7 @@ namespace llvm {
       IMAGE_SCN_MEM_16BIT                       = 0x00020000,
       IMAGE_SCN_MEM_LOCKED                      = 0x00040000,
       IMAGE_SCN_MEM_PRELOAD                     = 0x00080000,
+      /* these are handled elsewhere
       IMAGE_SCN_ALIGN_1BYTES                    = 0x00100000,
       IMAGE_SCN_ALIGN_2BYTES                    = 0x00200000,
       IMAGE_SCN_ALIGN_4BYTES                    = 0x00300000,
@@ -61,6 +77,7 @@ namespace llvm {
       IMAGE_SCN_ALIGN_16BYTES                   = 0x00500000,
       IMAGE_SCN_ALIGN_32BYTES                   = 0x00600000,
       IMAGE_SCN_ALIGN_64BYTES                   = 0x00700000,
+      */
       IMAGE_SCN_LNK_NRELOC_OVFL                 = 0x01000000,
       IMAGE_SCN_MEM_DISCARDABLE                 = 0x02000000,
       IMAGE_SCN_MEM_NOT_CACHED                  = 0x04000000,
@@ -71,8 +88,18 @@ namespace llvm {
       IMAGE_SCN_MEM_WRITE                       = 0x80000000
     };
 
+    enum {
+      IMAGE_COMDAT_SELECT_NODUPLICATES = 1,
+      IMAGE_COMDAT_SELECT_ANY,
+      IMAGE_COMDAT_SELECT_SAME_SIZE,
+      IMAGE_COMDAT_SELECT_EXACT_MATCH,
+      IMAGE_COMDAT_SELECT_ASSOCIATIVE,
+      IMAGE_COMDAT_SELECT_LARGEST
+    };
+
     StringRef getSectionName() const { return SectionName; }
-    unsigned getFlags() const { return Flags; }
+    unsigned getCharacteristics() const { return Characteristics; }
+    int getSelection () const { return Selection; }
     
     virtual void PrintSwitchToSection(const MCAsmInfo &MAI,
                                       raw_ostream &OS) const;

lib/CodeGen/TargetLoweringObjectFileImpl.cpp

@@ -912,11 +912,17 @@ getCOFFSectionFlags(SectionKind K) {
   unsigned Flags = 0;
 
   if (!K.isMetadata())
-    Flags |= MCSectionCOFF::IMAGE_SCN_MEM_DISCARDABLE;
+    Flags |=
+      MCSectionCOFF::IMAGE_SCN_MEM_DISCARDABLE;
   else if (K.isText())
     Flags |=
       MCSectionCOFF::IMAGE_SCN_MEM_EXECUTE |
       MCSectionCOFF::IMAGE_SCN_CNT_CODE;
+  else if (K.isBSS ())
+    Flags |=
+      MCSectionCOFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA |
+      MCSectionCOFF::IMAGE_SCN_MEM_READ |
+      MCSectionCOFF::IMAGE_SCN_MEM_WRITE;
   else if (K.isReadOnly())
     Flags |=
       MCSectionCOFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
@@ -941,6 +947,8 @@ getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
 static const char *getCOFFSectionPrefixForUniqueGlobal(SectionKind Kind) {
   if (Kind.isText())
     return ".text$linkonce";
+  if (Kind.isBSS ())
+    return ".bss$linkonce";
   if (Kind.isWriteable())
     return ".data$linkonce";
   return ".rdata$linkonce";
@@ -959,9 +967,13 @@ SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
     SmallString<128> Name(Prefix, Prefix+strlen(Prefix));
     MCSymbol *Sym = Mang->getSymbol(GV);
     Name.append(Sym->getName().begin(), Sym->getName().end());
-    return getContext().getCOFFSection(Name.str(),
-                                       getCOFFSectionFlags(Kind),
-                                       Kind);
+
+    unsigned Characteristics = getCOFFSectionFlags(Kind);
+
+    Characteristics |= MCSectionCOFF::IMAGE_SCN_LNK_COMDAT;
+
+    return getContext().getCOFFSection(Name.str(), Characteristics,
+                          MCSectionCOFF::IMAGE_COMDAT_SELECT_EXACT_MATCH, Kind);
   }
 
   if (Kind.isText())

lib/MC/MCContext.cpp

@@ -126,8 +126,10 @@ getELFSection(StringRef Section, unsigned Type, unsigned Flags,
   return Result;
 }
 
-const MCSection *MCContext::
-getCOFFSection(StringRef Section, unsigned Flags, SectionKind Kind) {
+const MCSection *MCContext::getCOFFSection(StringRef Section,
+                                           unsigned Characteristics,
+                                           int Selection,
+                                           SectionKind Kind) {
   if (COFFUniquingMap == 0)
     COFFUniquingMap = new COFFUniqueMapTy();
   COFFUniqueMapTy &Map = *(COFFUniqueMapTy*)COFFUniquingMap;
@@ -136,8 +138,9 @@ getCOFFSection(StringRef Section, unsigned Flags, SectionKind Kind) {
   StringMapEntry<const MCSectionCOFF*> &Entry = Map.GetOrCreateValue(Section);
   if (Entry.getValue()) return Entry.getValue();
   
-  MCSectionCOFF *Result = new (*this) MCSectionCOFF(Entry.getKey(), Flags,
-                                                    Kind);
+  MCSectionCOFF *Result = new (*this) MCSectionCOFF(Entry.getKey(),
+                                                    Characteristics,
+                                                    Selection, Kind);
   
   Entry.setValue(Result);
   return Result;

lib/MC/MCSectionCOFF.cpp

@@ -43,7 +43,7 @@ void MCSectionCOFF::PrintSwitchToSection(const MCAsmInfo &MAI,
     OS << 'w';
   else
     OS << 'r';
-  if (getFlags() & MCSectionCOFF::IMAGE_SCN_MEM_DISCARDABLE)
+  if (getCharacteristics() & MCSectionCOFF::IMAGE_SCN_MEM_DISCARDABLE)
     OS << 'n';
   OS << "\"\n";
 }