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

src/llvm2ice.cpp

Index: src/llvm2ice.cpp
diff --git a/src/llvm2ice.cpp b/src/llvm2ice.cpp
index 774a8e6a88dd8ebfd443c8ebcf75b6cc91ac5cc9..1c524ebc5085e2cd920b4ac0cf82017e6def145d 100644
--- a/src/llvm2ice.cpp
+++ b/src/llvm2ice.cpp
@@ -173,6 +173,11 @@ static cl::opt<bool>
 static cl::alias UseIas("ias", cl::desc("Alias for -integrated-as"),
                         cl::NotHidden, cl::aliasopt(UseIntegratedAssembler));
 
+static cl::opt<bool>
+    UseELFWriter("elf-writer",
+                 cl::desc("Use ELF writer with the integrated assembler"),
+                 cl::init(false));
+
 static cl::opt<bool> AlwaysExitSuccess(
     "exit-success", cl::desc("Exit with success status, even if errors found"),
     cl::init(false));
@@ -242,18 +247,6 @@ int main(int argc, char **argv) {
       VMask |= VerboseList[i];
   }
 
-  std::ofstream Ofs;
-  if (OutputFilename != "-") {
-    Ofs.open(OutputFilename.c_str(), std::ofstream::out);
-  }
-  raw_os_ostream *Os =
-      new raw_os_ostream(OutputFilename == "-" ? std::cout : Ofs);
-  Os->SetUnbuffered();
-
-  ValidateAndGenerateBuildAttributes(GenerateBuildAtts ? Os : nullptr);
-  if (GenerateBuildAtts)
-    return GetReturnValue(0);
-
   std::ofstream Lfs;
   if (LogFilename != "-") {
     Lfs.open(LogFilename.c_str(), std::ofstream::out);
@@ -261,6 +254,10 @@ int main(int argc, char **argv) {
   raw_os_ostream *Ls = new raw_os_ostream(LogFilename == "-" ? std::cout : Lfs);
   Ls->SetUnbuffered();
 
+  ValidateAndGenerateBuildAttributes(GenerateBuildAtts ? Ls : nullptr);
+  if (GenerateBuildAtts)
+    return GetReturnValue(0);
+
   if (!ALLOW_DISABLE_IR_GEN && DisableIRGeneration) {
     *Ls << "Error: Build doesn't allow --no-ir-gen when not "
         << "ALLOW_DISABLE_IR_GEN!\n";
@@ -274,6 +271,7 @@ int main(int argc, char **argv) {
   Flags.FunctionSections = FunctionSections;
   Flags.DataSections = DataSections;
   Flags.UseIntegratedAssembler = UseIntegratedAssembler;
+  Flags.UseELFWriter = UseELFWriter;
   Flags.UseSandboxing = UseSandboxing;
   Flags.PhiEdgeSplit = EnablePhiEdgeSplit;
   Flags.DecorateAsm = DecorateAsm;
@@ -294,11 +292,39 @@ int main(int argc, char **argv) {
                          LLSuffix.length(), LLSuffix) == 0)
     BuildOnRead = false;
 
-  Ice::GlobalContext Ctx(Ls, Os, VMask, TargetArch, OptLevel, TestPrefix,
-                         Flags);
+  // With the ELF writer, use a raw_fd_ostream to allow seeking.
+  // Also don't buffer, otherwise it gets pretty slow.
+  Ice::Ostream *Os;
+  Ice::ELFStreamer *ELFStr = nullptr;
+  std::ofstream Ofs;
+  if (UseELFWriter) {
+    std::string ErrorInfo;
+    raw_fd_ostream *FdOs =
+        new raw_fd_ostream(OutputFilename.c_str(), ErrorInfo);

[Jim Stichnoth, 2014/11/21 21:32:23]

Should we disallow OutputFilename=="-" which is its default value?

The user can specify "./-" if they *really* want that filename. :)

[jvoung (off chromium), 2014/11/24 21:35:47]

Done -- streaming to stdout will have problems because of seeking back, so
disallowing this.

+    if (!ErrorInfo.empty()) {
+      *Ls << "Failed to open output file: " << OutputFilename << ":\n"
+          << ErrorInfo << "\n";
+      return GetReturnValue(1);
+    }
+    ELFStr = new Ice::ELFStreamer(*FdOs);
+    Os = FdOs;
+  } else {
+    if (OutputFilename != "-") {
+      Ofs.open(OutputFilename.c_str(), std::ofstream::out);
+    }
+    Os = new raw_os_ostream(OutputFilename == "-" ? std::cout : Ofs);

[Jim Stichnoth, 2014/11/21 21:32:23]

I know this was just copy/paste, but can we structure this with a single
comparison on OutputFilename=="-" in the !UseElfWriter branch, for clarity?

[jvoung (off chromium), 2014/11/24 21:35:46]

Done. Did something similar for the Ls stream.

+    Os->SetUnbuffered();
+  }
+
+  Ice::GlobalContext Ctx(Ls, Os, ELFStr, VMask, TargetArch, OptLevel,
+                         TestPrefix, Flags);
 
   Ice::TimerMarker T(Ice::TimerStack::TT_szmain, &Ctx);
 
+  if (UseELFWriter) {
+    Ctx.getObjectWriter()->writeInitialELFHeader();
+  }
+
   int ErrorStatus = 0;
   if (BuildOnRead) {
     Ice::PNaClTranslator Translator(&Ctx, Flags);
@@ -324,6 +350,9 @@ int main(int argc, char **argv) {
         << "--build-on-read=0 not allowed\n";
     return GetReturnValue(1);
   }
+  if (UseELFWriter) {
+    Ctx.getObjectWriter()->writeNonUserSections();
+  }
   if (SubzeroTimingEnabled)
     Ctx.dumpTimers();
   if (TimeEachFunction) {
@@ -332,5 +361,6 @@ int main(int argc, char **argv) {
   }
   const bool FinalStats = true;
   Ctx.dumpStats("_FINAL_", FinalStats);
+  Os->flush();

[Jim Stichnoth, 2014/11/21 21:32:23]

Is it enough to just flush Os?  Should it be closed and/or deleted?

[jvoung (off chromium), 2014/11/24 21:35:46]

Switch Os and Ls to a unique_ptr, so it gets deleted and its dtor is run (which
for raw_fd_ostream/raw_os_ostream will flush).

   return GetReturnValue(ErrorStatus);
 }