Subzero: Add basic ELFObjectWriter (text section, symtab, strtab, headers)

src/IceCfg.cpp

Index: src/IceCfg.cpp
diff --git a/src/IceCfg.cpp b/src/IceCfg.cpp
index 950a3f8ee6e9572abf6fbe4f64399264ff9d4be2..e40bd1609c0088d28d2ae4be7034c3da3b579218 100644
--- a/src/IceCfg.cpp
+++ b/src/IceCfg.cpp
@@ -405,8 +405,9 @@ void Cfg::emitTextHeader(const IceString &MangledName) {
     Str << "\t.globl\t" << MangledName << "\n";
     Str << "\t.type\t" << MangledName << ",@function\n";
   }
-  Str << "\t.p2align " << getTarget()->getBundleAlignLog2Bytes() << ",0x";
-  for (AsmCodeByte I : getTarget()->getNonExecBundlePadding())
+  Assembler *Asm = getAssembler<Assembler>();
+  Str << "\t.p2align " << Asm->getBundleAlignLog2Bytes() << ",0x";
+  for (uint8_t I : Asm->getNonExecBundlePadding())
     Str.write_hex(I);
   Str << "\n";
   Str << MangledName << ":\n";
@@ -444,10 +445,20 @@ void Cfg::emitIAS() {
   TimerMarker T(TimerStack::TT_emit, this);
   assert(!Ctx->getFlags().DecorateAsm);
   IceString MangledName = getContext()->mangleName(getFunctionName());
-  emitTextHeader(MangledName);
+  if (!Ctx->getFlags().UseELFWriter)
+    emitTextHeader(MangledName);
   for (CfgNode *Node : Nodes)
     Node->emitIAS(this);
-  getAssembler<Assembler>()->emitIASBytes(Ctx);
+  // Now write the function to the file and track.
+  if (Ctx->getFlags().UseELFWriter) {
+    getAssembler<Assembler>()->alignFunction();
+    // TODO(jvoung): Transfer remaining fixups too. They may need their
+    // offsets adjusted.
+    Ctx->getObjectWriter()->writeFunctionCode(
+        MangledName, getInternal(), getAssembler<Assembler>()->getBufferView());
+  } else {
+    getAssembler<Assembler>()->emitIASBytes(Ctx);
+  }
 }
 
 // Dumps the IR with an optional introductory message.