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

src/IceELFSection.cpp

 //===- subzero/src/IceELFSection.cpp - Representation of ELF sections -----===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file defines how ELF sections are represented.
 //
 //===----------------------------------------------------------------------===//
 
+#include "llvm/Support/MathExtras.h"
+
 #include "IceDefs.h"
 #include "IceELFSection.h"
 #include "IceELFStreamer.h"
 
 using namespace llvm::ELF;
 
 namespace Ice {
 
 // Text sections.
 
 void ELFTextSection::appendData(ELFStreamer &Str,
                                 const llvm::StringRef MoreData) {
   Str.writeBytes(MoreData);
   Header.sh_size += MoreData.size();
 }
 
 // Data sections.
 
 void ELFDataSection::appendData(ELFStreamer &Str,
                                 const llvm::StringRef MoreData) {
   Str.writeBytes(MoreData);
   Header.sh_size += MoreData.size();
 }
 
+void ELFDataSection::appendZeros(ELFStreamer &Str, SizeT NumBytes) {
+  Str.writeZeroPadding(NumBytes);
+  Header.sh_size += NumBytes;
+}
+
+void ELFDataSection::appendRelocationOffset(ELFStreamer &Str, bool IsRela,
+                                            RelocOffsetT RelocOffset) {
+  if (IsRela) {
+    appendZeros(Str, RelocAddrSize);
+    return;
+  }
+  static_assert(RelocAddrSize == 4, " writeLE32 assumes RelocAddrSize is 4");
+  Str.writeLE32(RelocOffset);
+  Header.sh_size += RelocAddrSize;
+}
+
+void ELFDataSection::padToAlignment(ELFStreamer &Str, Elf64_Xword Align) {
+  assert(llvm::isPowerOf2_32(Align));
+  Elf64_Xword Mod = Header.sh_size & (Align - 1);
+  if (Mod == 0)
+    return;
+  Elf64_Xword AlignDiff = Align - Mod;

[Jim Stichnoth, 2015/01/27 16:44:55]

I've seen this pattern (which I think takes a bit of head-scratching to convince
oneself of its correctness) in a few other places, e.g.
ELFObjectWriter::alignFileOffset() and AssemblerX86::alignFunction(), maybe
more.  Would it be practical to refactor it?

[jvoung (off chromium), 2015/01/28 17:46:22]

How about having something like OffsetToAlignment() (or whatever name) for
calculating the diff, and then the padding adjustment just uses that diff (but
is different for each function)? That'll hide the math at least.

+  if (Header.sh_type != llvm::ELF::SHT_NOBITS)
+    Str.writeZeroPadding(AlignDiff);
+  Header.sh_size += AlignDiff;
+  assert((Header.sh_size & (Align - 1)) == 0);
+}
+
 // Relocation sections.
 
 void ELFRelocationSection::addRelocations(RelocOffsetT BaseOff,
                                           const FixupRefList &FixupRefs) {
   for (const AssemblerFixup *FR : FixupRefs) {
     Fixups.push_back(*FR);
     AssemblerFixup &F = Fixups.back();
     F.set_position(BaseOff + F.position());
   }
 }
@@ skipping 18 matching lines @@
                                              uint8_t Type, uint8_t Binding,
                                              ELFSection *Section,
                                              RelocOffsetT Offset, SizeT Size) {
   ELFSym NewSymbol = ELFSym();
   NewSymbol.Sym.setBindingAndType(Binding, Type);
   NewSymbol.Sym.st_value = Offset;
   NewSymbol.Sym.st_size = Size;
   NewSymbol.Section = Section;
   NewSymbol.Number = ELFSym::UnknownNumber;
   bool Unique;
-  if (Type == STB_LOCAL)
+  if (Binding == STB_LOCAL)
     Unique = LocalSymbols.insert(std::make_pair(Name, NewSymbol)).second;
   else
     Unique = GlobalSymbols.insert(std::make_pair(Name, NewSymbol)).second;
   assert(Unique);
   (void)Unique;
 }
 
 void ELFSymbolTableSection::noteUndefinedSym(const IceString &Name,
                                              ELFSection *NullSection) {
   ELFSym NewSymbol = ELFSym();
@@ skipping 97 matching lines @@
       continue;
     }
     StringIndex.second = StringData.size();
     std::copy(Cur.begin(), Cur.end(), back_inserter(StringData));
     StringData.push_back(0);
     Prev = Cur;
   }
 }
 
 } // end of namespace Ice