Debug Info: This patch implements the "emit modules when compiling -g"

proposal.
When compiling with debug info, build a swiftmodule that contains all the
type decls referenced by DWARF and emit it into a special __apple_swiftast
section in the .o file.

Swift SVN r7398

Author: adrian-prantl

include/swift/Subsystems.h

@@ -182,6 +182,11 @@ namespace swift {
   void serialize(const TranslationUnit *TU, const char *outputPath,
                  ArrayRef<unsigned> inputFileBufferIDs = {});
 
+  /// Serializes a translation unit to a stream.
+  void serializeToStream(const TranslationUnit *TU, llvm::raw_ostream &out,
+                         ArrayRef<unsigned> inputFileBufferIDs = {});
+
+
   /// Turn the given translation unit into either LLVM IR or native code.
   ///
   /// \param SILMod  A SIL module to translate to LLVM IR. If null, IRGen works

lib/IRGen/CMakeLists.txt

@@ -23,5 +23,7 @@ add_swift_library(swiftIRGen
   IRGenSIL.cpp
   Linking.cpp
   OptimizeARC.cpp
+  SwiftASTStreamerPass.cpp
+  SwiftTargetMachine.cpp
   StructLayout.cpp
   DEPENDS swiftAST)

lib/IRGen/IRGen.cpp

@@ -14,6 +14,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "SwiftTargetMachine.h"
 #include "swift/Subsystems.h"
 #include "swift/IRGen/Options.h"
 #include "swift/AST/AST.h"
@@ -103,7 +104,7 @@ void swift::performIRGeneration(Options &Opts, llvm::Module *Module,
 //  TargetOpts.NoFramePointerElimNonLeaf = true;
 
   // Create a target machine.
-  TargetMachine *TargetMachine
+  llvm::TargetMachine *TargetMachine
     = Target->createTargetMachine(Opts.Triple, /*cpu*/ "generic",
                                   /*features*/ "",
                                   TargetOpts, Reloc::Default,
@@ -300,13 +301,23 @@ void swift::performIRGeneration(Options &Opts, llvm::Module *Module,
     break;
   case OutputKind::NativeAssembly:
   case OutputKind::ObjectFile: {
-    TargetMachine::CodeGenFileType FileType;
+    llvm::TargetMachine::CodeGenFileType FileType;
     FileType = (Opts.OutputKind == OutputKind::NativeAssembly
-                  ? TargetMachine::CGFT_AssemblyFile
-                  : TargetMachine::CGFT_ObjectFile);
-
-    if (TargetMachine->addPassesToEmitFile(EmitPasses, FormattedOS,
-                                           FileType, !Opts.Verify)) {
+                  ? llvm::TargetMachine::CGFT_AssemblyFile
+                  : llvm::TargetMachine::CGFT_ObjectFile);
+
+    bool fail;
+    if (Opts.DebugInfo) {
+      // Use our own wrapper for TargetMachine which schedules a
+      // SwiftASTStreamerPass to be run after the code generation.
+      swift::irgen::TargetMachine
+        PatchedTargetMachine(TargetMachine, TU, IGM.DebugInfo);
+      fail = PatchedTargetMachine.
+        addPassesToEmitFile(EmitPasses, FormattedOS, FileType, !Opts.Verify);
+    } else
+      fail = TargetMachine->addPassesToEmitFile(EmitPasses, FormattedOS,
+                                                FileType, !Opts.Verify);
+    if (fail) {
       TU->Ctx.Diags.diagnose(SourceLoc(), diag::error_codegen_init_fail);
       return;
     }

lib/IRGen/IRGenDebugInfo.cpp

@@ -100,7 +100,7 @@ IRGenDebugInfo::IRGenDebugInfo(const Options &Opts,
     LastFn(nullptr), LastLoc({}), LastScope(nullptr) {
   assert(Opts.DebugInfo);
   StringRef Dir, Filename;
-  StringRef MainFilename = Opts.MainInputFilename;
+  MainFilename = Opts.MainInputFilename;
   if (MainFilename.empty()) {
     Filename = "<unknown>";
     Dir = getCurrentDirname();

lib/IRGen/IRGenDebugInfo.h

@@ -84,6 +84,7 @@ class IRGenDebugInfo {
   SILBasicBlock::const_bbarg_iterator LastArg, LastEnd;
   unsigned LastArgNo;
 
+  StringRef MainFilename;
   StringRef CWDName; /// The current working directory.
   llvm::BumpPtrAllocator DebugInfoNames;
   llvm::DICompileUnit TheCU;
@@ -175,6 +176,8 @@ class IRGenDebugInfo {
                                      DebugTypeInfo DebugType,
                                      SILLocation Loc);
 
+  StringRef getMainFilename() const { return MainFilename; }
+
 private:
   llvm::DIType createType(DebugTypeInfo DbgTy, llvm::DIDescriptor Scope,
                           llvm::DIFile File);

lib/IRGen/SwiftASTStreamerPass.cpp

@@ -0,0 +1,58 @@
+//===--- SwiftASTStreamerPass.cpp - DWARF SwiftAST Streamer ---------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2015 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See http://swift.org/LICENSE.txt for license information
+// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the SwiftASTStreamerPass class.
+//
+//===----------------------------------------------------------------------===//
+
+#include "SwiftASTStreamerPass.h"
+#include "IRGenDebugInfo.h"
+#include "swift/Subsystems.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCSectionMachO.h"
+#include "llvm/MC/MCStreamer.h"
+
+namespace swift {
+namespace irgen {
+
+char SwiftASTStreamerPass::ID = 0;
+
+bool SwiftASTStreamerPass::runOnModule(llvm::Module &M) {
+  if (!DebugInfo)
+    return false;
+
+  // FIXME (LLVM-Swift-branch). This shouldn't be hardcoded for Mach-O.
+  auto SwiftASTSection = Context.
+    getMachOSection("__DWARF", "__apple_swiftast",
+                    llvm::MCSectionMachO::S_ATTR_DEBUG,
+                    llvm::SectionKind::getMetadata());
+
+  AsmStreamer.SwitchSection(SwiftASTSection);
+  std::string Buf;
+  llvm::raw_string_ostream out(Buf);
+  serializeToStream(TU, out);
+
+  StringRef ModuleID = DebugInfo->getMainFilename();
+  AsmStreamer.EmitIntValue(ModuleID.size(), 8);
+  AsmStreamer.EmitBytes(ModuleID);
+
+  // FIXME: There is a potential problem with using
+  // MCStreamer::EmitBytes() for this, because (in the assembler
+  // output) it will result in a .asciz directive, but the data
+  // stream _will_ contain NUL characters.
+  AsmStreamer.EmitIntValue(Buf.size(), 8);
+  AsmStreamer.EmitBytes(Buf);
+  return false;
+}
+
+} // namespace irgen
+} // namespace swift

lib/IRGen/SwiftASTStreamerPass.h

@@ -0,0 +1,55 @@
+//===--- SwiftASTStreamerPass.h - DWARF SwiftAST Streamer -------*- C++ -*-===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2015 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See http://swift.org/LICENSE.txt for license information
+// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the SwiftASTStreamerPass class.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SWIFT_IRGEN_SWIFTASTSTREAMERPASS
+#define SWIFT_IRGEN_SWIFTASTSTREAMERPASS
+
+#include "llvm/Pass.h"
+
+namespace llvm {
+  class MCStreamer;
+  class MCContext;
+}
+
+namespace swift {
+
+  class TranslationUnit;
+
+  namespace irgen {
+    class IRGenDebugInfo;
+
+    /// This pass builds a swiftmodule that contains all the decls
+    /// referenced by DWARF and emit it into a special __apple_swiftast
+    /// section in the .o file.
+    class SwiftASTStreamerPass : public llvm::ModulePass {
+      static char ID;
+      llvm::MCStreamer &AsmStreamer;
+      llvm::MCContext &Context;
+      TranslationUnit *TU;
+      IRGenDebugInfo *DebugInfo;
+    public:
+      SwiftASTStreamerPass(llvm::MCStreamer &S, llvm::MCContext &C,
+                           TranslationUnit *TU,
+                           IRGenDebugInfo *DI)
+        : ModulePass(ID), AsmStreamer(S), Context(C), TU(TU), DebugInfo(DI) {}
+      virtual const char *getPassName() const { return "SwiftASTStreamerPass"; }
+      virtual bool runOnModule(llvm::Module &M);
+    };
+
+  } // namespace irgen
+} // namespace swift
+
+#endif