Discard swift.ld and support gold linker

Author: hpux735

CMakeLists.txt

@@ -221,7 +221,7 @@ if("${CMAKE_SOURCE_DIR}" STREQUAL "${CMAKE_CURRENT_SOURCE_DIR}")
 endif()
 
 if(SWIFT_BUILT_STANDALONE)
-  project(Swift)
+  project(Swift C CXX ASM)
 endif()
 
 if("${CMAKE_SYSTEM_NAME}" STREQUAL "")

cmake/modules/AddSwift.cmake

@@ -173,15 +173,9 @@ function(_add_variant_link_flags
       result)
 
   if("${sdk}" STREQUAL "LINUX")
-    if("${arch}" STREQUAL "armv7")
-      list(APPEND result "-lpthread" "-ldl" "-Wl,-Bsymbolic")
-    elseif("${arch}" STREQUAL "armv6")
-      list(APPEND result "-lpthread" "-ldl" "-Wl,-Bsymbolic")
-    else()
-      list(APPEND result "-lpthread" "-ldl")
-    endif()
+    list(APPEND result "-lpthread" "-ldl")
   elseif("${sdk}" STREQUAL "FREEBSD")
-    list(APPEND result "-lpthread" "-Wl,-Bsymbolic")
+    list(APPEND result "-lpthread")
   else()
     list(APPEND result "-lobjc")
   endif()
@@ -856,6 +850,22 @@ function(_add_swift_library_single target name)
     set(SWIFTLIB_SINGLE_API_NOTES "${module_name}")
   endif()
 
+  # On platforms that use ELF binaries (for now that is Linux and FreeBSD)
+  # we add markers for metadata sections in the shared libraries using 
+  # these object files.  This wouldn't be necessary if the link was done by
+  # the swift binary: rdar://problem/19007002
+  if("${CMAKE_SYSTEM_NAME}" STREQUAL "Linux" OR
+     "${CMAKE_SYSTEM_NAME}" STREQUAL "FreeBSD")
+
+    if("${libkind}" STREQUAL "SHARED")
+      set(arch_subdir "${SWIFTLIB_DIR}/${SWIFTLIB_SINGLE_SUBDIR}")
+
+      set(SWIFT_SECTIONS_OBJECT_BEGIN "${arch_subdir}/swift_begin.o")
+      set(SWIFT_SECTIONS_OBJECT_END   "${arch_subdir}/swift_end.o")
+    endif()
+
+  endif()
+
   # FIXME: don't actually depend on the libraries in SWIFTLIB_SINGLE_LINK_LIBRARIES,
   # just any swiftmodule files that are associated with them.
   handle_swift_sources(
@@ -877,8 +887,21 @@ function(_add_swift_library_single target name)
       INSTALL_IN_COMPONENT "${SWIFTLIB_INSTALL_IN_COMPONENT}")
 
   add_library("${target}" ${libkind}
+      ${SWIFT_SECTIONS_OBJECT_BEGIN}
       ${SWIFTLIB_SINGLE_SOURCES}
-      ${SWIFTLIB_SINGLE_EXTERNAL_SOURCES})
+      ${SWIFTLIB_SINGLE_EXTERNAL_SOURCES}
+      ${SWIFT_SECTIONS_OBJECT_END})
+
+  # The section metadata objects are generated sources, and we need to tell CMake
+  # not to expect to find them prior to their generation.
+  if("${CMAKE_SYSTEM_NAME}" STREQUAL "Linux" OR
+     "${CMAKE_SYSTEM_NAME}" STREQUAL "FreeBSD")
+    if("${libkind}" STREQUAL "SHARED")
+      set_source_files_properties(${SWIFT_SECTIONS_OBJECT_BEGIN} PROPERTIES GENERATED 1)
+      set_source_files_properties(${SWIFT_SECTIONS_OBJECT_END} PROPERTIES GENERATED 1)
+      add_dependencies("${target}" section_magic)
+    endif()
+  endif()
 
   if (dtrace_dependency_targets)
     add_dependencies("${target}" ${dtrace_dependency_targets})
@@ -1089,16 +1112,8 @@ function(_add_swift_library_single target name)
       "${analyze_code_coverage}"
       link_flags)
 
-  # Handle gold linker flags for shared libraries.
-  if(SWIFT_ENABLE_GOLD_LINKER AND SWIFTLIB_SINGLE_SHARED)
-    if("${SWIFTLIB_SINGLE_SDK}" STREQUAL "LINUX")
-      # Extend the link_flags for the gold linker so long as this
-      # isn't the standard library.  The standard library uses a
-      # linker script that isn't supported by the gold linker.
-      if(NOT SWIFTLIB_SINGLE_IS_STDLIB)
-        list(APPEND link_flags "-fuse-ld=gold")
-      endif()
-    endif()
+  if(SWIFT_ENABLE_GOLD_LINKER)
+    list(APPEND link_flags "-fuse-ld=gold")
   endif()
 
   # Configure plist creation for OS X.
@@ -1133,16 +1148,6 @@ function(_add_swift_library_single target name)
     set(PLIST_INFO_BUILD_VERSION)
   endif()
 
-  # On Linux and FreeBSD add the linker script that coalesces protocol
-  # conformance sections. This wouldn't be necessary if the link was done by
-  # the swift binary: rdar://problem/19007002
-  if("${CMAKE_SYSTEM_NAME}" STREQUAL "Linux" OR
-     "${CMAKE_SYSTEM_NAME}" STREQUAL "FreeBSD")
-    list(APPEND link_flags
-        "-Xlinker" "-T"
-        "-Xlinker" "${SWIFTLIB_DIR}/${SWIFTLIB_SINGLE_SUBDIR}/swift.ld")
-  endif()
-
   # Convert variables to space-separated strings.
   _list_escape_for_shell("${c_compile_flags}" c_compile_flags)
   _list_escape_for_shell("${link_flags}" link_flags)

lib/Driver/Driver.cpp

@@ -2009,24 +2009,7 @@ void Driver::printHelp(bool ShowHidden) const {
 }
 
 static llvm::Triple computeTargetTriple(StringRef DefaultTargetTriple) {
-  llvm::Triple triple = llvm::Triple(DefaultTargetTriple);
-
-  // armv6l and armv7l (which come from linux) are mapped to armv6 and 
-  // armv7 (respectively) within llvm.  When a Triple is created by llvm,
-  // the string is preserved, which keeps the 'l'.  This extra character
-  // causes problems later down the line.
-  // By explicitly setting the architecture to the subtype that it aliases to,
-  // we remove that extra character while not introducing other side effects.
-  if (triple.getOS() == llvm::Triple::Linux) {
-    if (triple.getSubArch() == llvm::Triple::SubArchType::ARMSubArch_v7) {
-      triple.setArchName("armv7");
-    }
-    if (triple.getSubArch() == llvm::Triple::SubArchType::ARMSubArch_v6) {
-      triple.setArchName("armv6");
-    }
-  }
-
-  return triple;
+  return llvm::Triple(DefaultTargetTriple); 
 }
 
 const ToolChain *Driver::getToolChain(const ArgList &Args) const {

lib/Driver/ToolChains.cpp

@@ -1091,6 +1091,28 @@ toolchains::GenericUnix::constructInvocation(const AutolinkExtractJobAction &job
   return {"swift-autolink-extract", Arguments};
 }
 
+// This function maps triples to the architecture component of the path
+// where the swift_begin.o and swift_end.o objects can be found.  This
+// is a stop-gap until full Triple support (ala Clang) exists within swiftc.
+StringRef
+getSectionMagicArch(const llvm::Triple &Triple) {
+  if (Triple.isOSLinux()) {
+    switch(Triple.getSubArch()) {
+    default:
+      return Triple.getArchName();
+      break;
+    case llvm::Triple::SubArchType::ARMSubArch_v7:
+      return "armv7";
+      break;
+    case llvm::Triple::SubArchType::ARMSubArch_v6:
+      return "armv6";
+      break;
+    }
+  } else {
+    return Triple.getArchName();
+  }
+}
+
 ToolChain::InvocationInfo
 toolchains::GenericUnix::constructInvocation(const LinkJobAction &job,
                                              const JobContext &context) const {
@@ -1109,32 +1131,28 @@ toolchains::GenericUnix::constructInvocation(const LinkJobAction &job,
     break;
   case LinkKind::DynamicLibrary:
     Arguments.push_back("-shared");
-    if (getTriple().getOS() == llvm::Triple::Linux) {
-      if (getTriple().getSubArch() == llvm::Triple::SubArchType::ARMSubArch_v7 ||
-          getTriple().getSubArch() == llvm::Triple::SubArchType::ARMSubArch_v6) {
-        Arguments.push_back("-Wl,-Bsymbolic");
-      }
-    }
     break;
   }
 
-  addPrimaryInputsOfType(Arguments, context.Inputs, types::TY_Object);
-  addInputsOfType(Arguments, context.InputActions, types::TY_Object);
-
-  context.Args.AddAllArgs(Arguments, options::OPT_Xlinker);
-  context.Args.AddAllArgs(Arguments, options::OPT_linker_option_Group);
-  context.Args.AddAllArgs(Arguments, options::OPT_F);
-
-  if (!context.OI.SDKPath.empty()) {
-    Arguments.push_back("--sysroot");
-    Arguments.push_back(context.Args.MakeArgString(context.OI.SDKPath));
-  }
-
   // Select the linker to use
-  llvm::SmallString<128> Linker;
+  StringRef Linker;
 
   if (const Arg *A = context.Args.getLastArg(options::OPT_use_ld)) {
     Linker = A->getValue();
+  } else {
+    switch(getTriple().getArch()) {
+    default:
+      break;
+    case llvm::Triple::arm:
+    case llvm::Triple::armeb:
+    case llvm::Triple::thumb:
+    case llvm::Triple::thumbeb:
+    // BFD linker has issues wrt relocation of the protocol conformance
+    // section on these targets, it also generates COPY relocations for
+    // final executables, as such, unless specified, we default to gold
+    // linker.
+      Linker = "gold";
+    }
   }
 
   if (!Linker.empty()) {
@@ -1158,9 +1176,27 @@ toolchains::GenericUnix::constructInvocation(const LinkJobAction &job,
   }
   llvm::sys::path::append(RuntimeLibPath,
                           getPlatformNameForTriple(getTriple()));
+
+ // On Linux and FreeBSD (really, ELF binaries) we need to add objects
+ // to provide markers and size for the metadata sections.
+  Arguments.push_back(context.Args.MakeArgString(
+    Twine(RuntimeLibPath) + "/" + getSectionMagicArch(getTriple()) + "/swift_begin.o"));
+  addPrimaryInputsOfType(Arguments, context.Inputs, types::TY_Object);
+  addInputsOfType(Arguments, context.InputActions, types::TY_Object);
+
+  context.Args.AddAllArgs(Arguments, options::OPT_Xlinker);
+  context.Args.AddAllArgs(Arguments, options::OPT_linker_option_Group);
+  context.Args.AddAllArgs(Arguments, options::OPT_F);
+
+  if (!context.OI.SDKPath.empty()) {
+    Arguments.push_back("--sysroot");
+    Arguments.push_back(context.Args.MakeArgString(context.OI.SDKPath));
+  }
+
   Arguments.push_back("-L");
   Arguments.push_back(context.Args.MakeArgString(RuntimeLibPath));
 
+  // Explicitly pass the target to the linker
   Arguments.push_back(context.Args.MakeArgString("--target=" + getTriple().str()));
 
   if (context.Args.hasArg(options::OPT_profile_generate)) {
@@ -1193,13 +1229,10 @@ toolchains::GenericUnix::constructInvocation(const LinkJobAction &job,
         Twine("@") + OutputInfo.getPrimaryOutputFilename()));
   }
 
-  // Add the linker script that coalesces protocol conformance sections.
-  Arguments.push_back("-Xlinker");
-  Arguments.push_back("-T");
-    
-  // FIXME: This should also query the abi type (i.e. gnueabihf)
+  // It is important that swift_end.o be the last object on the link line
+  // therefore, it is included just before the output filename.
   Arguments.push_back(context.Args.MakeArgString(
-    Twine(RuntimeLibPath) + "/" + getTriple().getArchName() + "/swift.ld"));
+    Twine(RuntimeLibPath) + "/" + getSectionMagicArch(getTriple()) + "/swift_end.o"));
 
   // This should be the last option, for convenience in checking output.
   Arguments.push_back("-o");

lib/Frontend/CompilerInvocation.cpp

@@ -47,7 +47,27 @@ static void updateRuntimeLibraryPath(SearchPathOptions &SearchPathOpts,
   llvm::sys::path::append(LibPath, getPlatformNameForTriple(Triple));
   SearchPathOpts.RuntimeLibraryPath = LibPath.str();
 
-  llvm::sys::path::append(LibPath, Triple.getArchName());
+  // The linux provided triple for ARM contains a trailing 'l'
+  // denoting little-endian.  This is not used in the path for
+  // libraries.  LLVM matches these SubArchTypes to the generic
+  // ARMSubArch_v7 (for example) type.  If that is the case,
+  // use the base of the architecture type in the library path.
+  if (Triple.isOSLinux()) {
+    switch(Triple.getSubArch()) {
+    default:
+      llvm::sys::path::append(LibPath, Triple.getArchName());
+      break;
+    case llvm::Triple::SubArchType::ARMSubArch_v7:
+      llvm::sys::path::append(LibPath, "armv7");
+      break;
+    case llvm::Triple::SubArchType::ARMSubArch_v6:
+      llvm::sys::path::append(LibPath, "armv6");
+      break;
+    }
+  } else {
+    llvm::sys::path::append(LibPath, Triple.getArchName());
+  }
+
   SearchPathOpts.RuntimeLibraryImportPath = LibPath.str();
 }
 

stdlib/public/core/CMakeLists.txt

@@ -180,6 +180,7 @@ add_swift_library(swiftCore SHARED IS_STDLIB IS_STDLIB_CORE
   # and the generated directory as dependencies.
   FILE_DEPENDS
     copy_shim_headers "${SWIFTLIB_DIR}/shims"
+    section_magic
   LINK_FLAGS ${swift_core_link_flags}
   PRIVATE_LINK_LIBRARIES ${swift_core_private_link_libraries}
   FRAMEWORK_DEPENDS ${swift_core_framework_depends}

stdlib/public/runtime/CMakeLists.txt

@@ -19,7 +19,8 @@ endif()
 
 # Acknowledge that the following sources are known.
 set(LLVM_OPTIONAL_SOURCES
-    Remangle.cpp)
+    Remangle.cpp
+    swift_sections.S)
 
 set(swift_runtime_objc_sources)
 set(swift_runtime_unicode_normalization_sources)
@@ -52,20 +53,40 @@ add_swift_library(swiftRuntime IS_STDLIB IS_STDLIB_CORE
   C_COMPILE_FLAGS ${swift_runtime_compile_flags}
   INSTALL_IN_COMPONENT stdlib)
 
+set(object_target_list)
 foreach(sdk ${SWIFT_CONFIGURED_SDKS})
   if("${sdk}" STREQUAL "LINUX" OR "${sdk}" STREQUAL "FREEBSD")
     foreach(arch ${SWIFT_SDK_${sdk}_ARCHITECTURES})
       set(arch_subdir "${SWIFT_SDK_${sdk}_LIB_SUBDIR}/${arch}")
 
-      # FIXME: We will need a different linker script for 32-bit builds.
-      configure_file(
-          "swift.ld" "${SWIFTLIB_DIR}/${arch_subdir}/swift.ld" COPYONLY)
+      set(section_magic_begin_name "section_magic_begin_${SWIFT_SDK_${sdk}_ARCH_${arch}_TRIPLE}")
+      set(section_magic_end_name "section_magic_end_${SWIFT_SDK_${sdk}_ARCH_${arch}_TRIPLE}")
+
+      add_library(${section_magic_begin_name} STATIC swift_sections.S)
+      set_target_properties(${section_magic_begin_name} PROPERTIES COMPILE_FLAGS "-DSWIFT_BEGIN")
+
+      add_library(${section_magic_end_name} STATIC swift_sections.S)
+      set_target_properties(${section_magic_end_name} PROPERTIES COMPILE_FLAGS "-DSWIFT_END")
+
+      add_custom_command_target(${section_magic_begin_name}_begin
+        OUTPUT  "${SWIFTLIB_DIR}/${arch_subdir}/swift_begin.o"
+        COMMAND "${CMAKE_COMMAND}" -E copy "${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles/${section_magic_begin_name}.dir/swift_sections.S${CMAKE_C_OUTPUT_EXTENSION}" "${SWIFTLIB_DIR}/${arch_subdir}/swift_begin.o"
+        DEPENDS ${section_magic_begin_name})
+
+      add_custom_command_target(${section_magic_begin_name}_end
+        OUTPUT  "${SWIFTLIB_DIR}/${arch_subdir}/swift_end.o"
+        COMMAND "${CMAKE_COMMAND}" -E copy "${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles/${section_magic_end_name}.dir/swift_sections.S${CMAKE_C_OUTPUT_EXTENSION}" "${SWIFTLIB_DIR}/${arch_subdir}/swift_end.o"
+        DEPENDS ${section_magic_end_name})
+
+      list(APPEND object_target_list "${SWIFTLIB_DIR}/${arch_subdir}/swift_begin.o" "${SWIFTLIB_DIR}/${arch_subdir}/swift_end.o")
 
       swift_install_in_component(compiler
-          FILES "swift.ld"
+          FILES "${SWIFTLIB_DIR}/${arch_subdir}/swift_begin.o" "${SWIFTLIB_DIR}/${arch_subdir}/swift_end.o"
           DESTINATION "lib/swift/${arch_subdir}")
 
     endforeach()
   endif()
 endforeach()
 
+add_custom_target(section_magic ALL DEPENDS ${object_target_list})
+