Write out global initializers and data rel directly to ELF file.

src/IceELFObjectWriter.h

Index: src/IceELFObjectWriter.h
diff --git a/src/IceELFObjectWriter.h b/src/IceELFObjectWriter.h
index 9f468cb05ed5efaec6defbccced13d84cd35e67e..cb49539643f58ea3b19dc5359d38c481f02bab4d 100644
--- a/src/IceELFObjectWriter.h
+++ b/src/IceELFObjectWriter.h
@@ -30,7 +30,7 @@ namespace Ice {
 // sections and write them out.  Expected usage:
 //
 // (1) writeInitialELFHeader
-// (2) writeDataInitializer*
+// (2) writeDataSection
 // (3) writeFunctionCode*
 // (4) writeNonUserSections
 class ELFObjectWriter {
@@ -51,13 +51,11 @@ public:
   void writeFunctionCode(const IceString &FuncName, bool IsInternal,
                          const Assembler *Asm);
 
-  // Copy initializer data for a global to file and note the offset and
-  // size of the global's definition in the symbol table.
-  // TODO(jvoung): This needs to know which section. This also needs the
-  // relocations to hook them up to the symbol table references. Also
-  // TODO is handling BSS (which just needs to note the size).
-  void writeDataInitializer(const IceString &VarName,
-                            const llvm::StringRef Data);
+  // Copy initializer data for globals to file and note the offset and size
+  // of each global's definition in the symbol table.
+  // Use the given target's RelocationKind for relocations.
+  void writeDataSection(const VariableDeclarationList &Vars,
+                        FixupKind RelocationKind);
 
   template <typename ConstType> void writeConstantPool(Type Ty);
 
@@ -65,6 +63,15 @@ public:
   // patch up the initial ELF header with the final info.
   void writeNonUserSections();
 
+  // Which type of ELF section a global variable initializer belongs to.
+  enum SectionType {
+    BaseSectionType = 0,
+    ROData = BaseSectionType,
+    Data,
+    BSS,
+    NumSectionTypes
+  };
+
 private:
   GlobalContext &Ctx;
   ELFStreamer &Str;
@@ -79,8 +86,9 @@ private:
   RelSectionList RelTextSections;
   DataSectionList DataSections;
   RelSectionList RelDataSections;
-  DataSectionList RoDataSections;
-  RelSectionList RelRoDataSections;
+  DataSectionList RODataSections;
+  RelSectionList RelRODataSections;
+  DataSectionList BSSSections;
 
   // Handles to special sections that need incremental bookkeeping.
   ELFSection *NullSection;
@@ -93,6 +101,11 @@ private:
                    Elf64_Xword ShFlags, Elf64_Xword ShAddralign,
                    Elf64_Xword ShEntsize);
 
+  // Create a relocation section, given the related section
+  // (e.g., .text, .data., .rodata).
+  ELFRelocationSection *
+  createRelocationSection(bool IsELF64, const ELFSection *RelatedSection);
+
   // Align the file position before writing out a section's data,
   // and return the position of the file.
   Elf64_Off alignFileOffset(Elf64_Xword Align);
@@ -116,6 +129,12 @@ private:
   // Link the relocation sections to the symbol table.
   void assignRelLinkNum(SizeT SymTabNumber, RelSectionList &RelSections);
 
+  // Helper function for writeDataSection. Writes a data section of type
+  // SectionType, given the global variables Vars belonging to that SectionType.
+  void writeDataOfType(SectionType SectionType,
+                       const VariableDeclarationList &Vars,
+                       FixupKind RelocationKind, bool IsELF64);
+
   // Write the final relocation sections given the final symbol table.
   // May also be able to seek around the file and resolve function calls
   // that are for functions within the same section.