Let Clang invoke CloudABI's linker

[ed]

Summary

Now that CloudABI's target information and header search logic for Clang has been submitted, the only thing that remains to be done is adding support for CloudABI's linker.

CloudABI uses Binutils ld, although there is some work to use lld instead. This means that this code is largely based on what we use on FreeBSD. There are some exceptions, however:

• Only static linking is performed. CloudABI does not support any dynamically linked executables.
• CloudABI uses compiler-rt, libc++ and libc++abi unconditionally. Link in these libraries instead of using libgcc_s, libstdc++, etc.
• We must ensure that the .eh_frame_hdr is present to make C++ exceptions work properly.

[ed]

Hi Chandler,

Would you by any chance have some spare cycles to take a look at this change?

Thanks,
Ed

[echristo]

Why not just pass all of these down via the driver normally instead of hardcoding options via a tool?

-eric

[ed]

Hi Eric,

In D8250#143551, @echristo wrote:

Why not just pass all of these down via the driver normally instead of hardcoding options via a tool?

Could you please clarify this for me? Are you referring to the fact that -Bstatic and --eh-frame-hdr are passed to the linker unconditionally?

The latter already seems to happen for some of the other architectures, for example on NetBSD. Regarding -Bstatic: it turns out it's a no-op. It has no effect, as the linker does not know how to do dynamic linking anyway. Still, it is more consistent to pass it along, as the CRT object files that are passed in are purely intended for static linkage.

If CloudABI would ever gain support for dynamic linkage, we wouldn't want Clang to call the linker in a way where it wants to do dynamic linkage, while still providing CRT object files that can only be used for static linkage.

[echristo]

Sure, ok then.

-eric

cfe/trunk/lib/Driver/Driver.cpp

 const ToolChain &Driver::getToolChain(const ArgList &Args,
                                       StringRef DarwinArchName) const {
   llvm::Triple Target = computeTargetTriple(DefaultTargetTriple, Args,
                                             DarwinArchName);
 
   ToolChain *&TC = ToolChains[Target.str()];
   if (!TC) {
     switch (Target.getOS()) {
+    case llvm::Triple::CloudABI:
+      TC = new toolchains::CloudABI(*this, Target, Args);
+      break;
     case llvm::Triple::Darwin:
     case llvm::Triple::MacOSX:
     case llvm::Triple::IOS:
       TC = new toolchains::DarwinClang(*this, Target, Args);
       break;
     case llvm::Triple::DragonFly:
       TC = new toolchains::DragonFly(*this, Target, Args);
       break;

cfe/trunk/lib/Driver/ToolChains.h

public:
   Generic_ELF(const Driver &D, const llvm::Triple &Triple,
               const llvm::opt::ArgList &Args)
       : Generic_GCC(D, Triple, Args) {}
 
   void addClangTargetOptions(const llvm::opt::ArgList &DriverArgs,
                              llvm::opt::ArgStringList &CC1Args) const override;
 };
 
+class LLVM_LIBRARY_VISIBILITY CloudABI : public Generic_ELF {
+public:
+  CloudABI(const Driver &D, const llvm::Triple &Triple,
+           const llvm::opt::ArgList &Args);
+  bool HasNativeLLVMSupport() const override { return true; }
+
+  bool IsMathErrnoDefault() const override { return false; }
+  bool IsObjCNonFragileABIDefault() const override { return true; }
+
+  CXXStdlibType GetCXXStdlibType(const llvm::opt::ArgList &Args)
+      const override {
+    return ToolChain::CST_Libcxx;
+  }
+  void AddClangCXXStdlibIncludeArgs(
+      const llvm::opt::ArgList &DriverArgs,
+      llvm::opt::ArgStringList &CC1Args) const override;
+  void AddCXXStdlibLibArgs(const llvm::opt::ArgList &Args,
+                           llvm::opt::ArgStringList &CmdArgs) const override;
+
+  bool isPIEDefault() const override { return false; }
+
+protected:
+  Tool *buildLinker() const override;
+};
+
 class LLVM_LIBRARY_VISIBILITY Solaris : public Generic_GCC {
 public:
   Solaris(const Driver &D, const llvm::Triple &Triple,
           const llvm::opt::ArgList &Args);
 
   bool IsIntegratedAssemblerDefault() const override { return true; }
 protected:
   Tool *buildAssembler() const override;

cfe/trunk/lib/Driver/ToolChains.cpp

 bool TCEToolChain::isPIEDefault() const {
   return false;
 }
 
 bool TCEToolChain::isPICDefaultForced() const {
   return false;
 }
 
+// CloudABI - CloudABI tool chain which can call ld(1) directly.
+
+CloudABI::CloudABI(const Driver &D, const llvm::Triple &Triple,
+                   const ArgList &Args)
+    : Generic_ELF(D, Triple, Args) {
+  SmallString<128> P(getDriver().Dir);
+  llvm::sys::path::append(P, "..", getTriple().str(), "lib");
+  getFilePaths().push_back(P.str());
+}
+
+void CloudABI::AddClangCXXStdlibIncludeArgs(const ArgList &DriverArgs,
+                                            ArgStringList &CC1Args) const {
+  if (DriverArgs.hasArg(options::OPT_nostdlibinc) &&
+      DriverArgs.hasArg(options::OPT_nostdincxx))
+    return;
+
+  SmallString<128> P(getDriver().Dir);
+  llvm::sys::path::append(P, "..", getTriple().str(), "include/c++/v1");
+  addSystemInclude(DriverArgs, CC1Args, P.str());
+}
+
+void CloudABI::AddCXXStdlibLibArgs(const ArgList &Args,
+                                   ArgStringList &CmdArgs) const {
+  CmdArgs.push_back("-lc++");
+  CmdArgs.push_back("-lc++abi");
+  CmdArgs.push_back("-lunwind");
+}
+
+Tool *CloudABI::buildLinker() const { return new tools::cloudabi::Link(*this); }
+
 /// OpenBSD - OpenBSD tool chain which can call as(1) and ld(1) directly.
 
 OpenBSD::OpenBSD(const Driver &D, const llvm::Triple& Triple, const ArgList &Args)
   : Generic_ELF(D, Triple, Args) {
   getFilePaths().push_back(getDriver().Dir + "/../lib");
   getFilePaths().push_back("/usr/lib");
 }
 

cfe/trunk/lib/Driver/Tools.h

namespace mips {
   bool isFPXXDefault(const llvm::Triple &Triple, StringRef CPUName,
                      StringRef ABIName);
 }
 
 namespace ppc {
   bool hasPPCAbiArg(const llvm::opt::ArgList &Args, const char *Value);
 }
 
+  /// cloudabi -- Directly call GNU Binutils linker
+namespace cloudabi {
+class LLVM_LIBRARY_VISIBILITY Link : public GnuTool {
+public:
+  Link(const ToolChain &TC) : GnuTool("cloudabi::Link", "linker", TC) {}
+
+  bool hasIntegratedCPP() const override { return false; }
+  bool isLinkJob() const override { return true; }
+
+  void ConstructJob(Compilation &C, const JobAction &JA,
+                    const InputInfo &Output, const InputInfoList &Inputs,
+                    const llvm::opt::ArgList &TCArgs,
+                    const char *LinkingOutput) const override;
+};
+} // end namespace cloudabi
+
 namespace darwin {
   llvm::Triple::ArchType getArchTypeForMachOArchName(StringRef Str);
   void setTripleTypeForMachOArchName(llvm::Triple &T, StringRef Str);
 
   class LLVM_LIBRARY_VISIBILITY MachOTool : public Tool {
     virtual void anchor();
   protected:
     void AddMachOArch(const llvm::opt::ArgList &Args,

cfe/trunk/lib/Driver/Tools.cpp

if (Arg *OutputOpt = Args.getLastArg(options::OPT_o)) {
     std::string Str(OutputOpt->getValue());
     Res = Str.substr(0, Str.rfind('.'));
   } else {
     Res = getBaseInputStem(Args, Inputs);
   }
   return Args.MakeArgString(Res + ".d");
 }
 
+void cloudabi::Link::ConstructJob(Compilation &C, const JobAction &JA,
+                                  const InputInfo &Output,
+                                  const InputInfoList &Inputs,
+                                  const ArgList &Args,
+                                  const char *LinkingOutput) const {
+  const ToolChain &ToolChain = getToolChain();
+  const Driver &D = ToolChain.getDriver();
+  ArgStringList CmdArgs;
+
+  // Silence warning for "clang -g foo.o -o foo"
+  Args.ClaimAllArgs(options::OPT_g_Group);
+  // and "clang -emit-llvm foo.o -o foo"
+  Args.ClaimAllArgs(options::OPT_emit_llvm);
+  // and for "clang -w foo.o -o foo". Other warning options are already
+  // handled somewhere else.
+  Args.ClaimAllArgs(options::OPT_w);
+
+  if (!D.SysRoot.empty())
+    CmdArgs.push_back(Args.MakeArgString("--sysroot=" + D.SysRoot));
+
+  // CloudABI only supports static linkage.
+  CmdArgs.push_back("-Bstatic");
+  CmdArgs.push_back("--eh-frame-hdr");
+  CmdArgs.push_back("--gc-sections");
+
+  if (Output.isFilename()) {
+    CmdArgs.push_back("-o");
+    CmdArgs.push_back(Output.getFilename());
+  } else {
+    assert(Output.isNothing() && "Invalid output.");
+  }
+
+  if (!Args.hasArg(options::OPT_nostdlib) &&
+      !Args.hasArg(options::OPT_nostartfiles)) {
+    CmdArgs.push_back(Args.MakeArgString(ToolChain.GetFilePath("crt0.o")));
+    CmdArgs.push_back(Args.MakeArgString(ToolChain.GetFilePath("crtbegin.o")));
+  }
+
+  Args.AddAllArgs(CmdArgs, options::OPT_L);
+  const ToolChain::path_list &Paths = ToolChain.getFilePaths();
+  for (const auto &Path : Paths)
+    CmdArgs.push_back(Args.MakeArgString(StringRef("-L") + Path));
+  Args.AddAllArgs(CmdArgs, options::OPT_T_Group);
+  Args.AddAllArgs(CmdArgs, options::OPT_e);
+  Args.AddAllArgs(CmdArgs, options::OPT_s);
+  Args.AddAllArgs(CmdArgs, options::OPT_t);
+  Args.AddAllArgs(CmdArgs, options::OPT_Z_Flag);
+  Args.AddAllArgs(CmdArgs, options::OPT_r);
+
+  if (D.IsUsingLTO(ToolChain, Args))
+    AddGoldPlugin(ToolChain, Args, CmdArgs);
+
+  AddLinkerInputs(ToolChain, Inputs, Args, CmdArgs);
+
+  if (!Args.hasArg(options::OPT_nostdlib) &&
+      !Args.hasArg(options::OPT_nodefaultlibs)) {
+    if (D.CCCIsCXX())
+      ToolChain.AddCXXStdlibLibArgs(Args, CmdArgs);
+    CmdArgs.push_back("-lc");
+    CmdArgs.push_back("-lcompiler_rt");
+  }
+
+  if (!Args.hasArg(options::OPT_nostdlib) &&
+      !Args.hasArg(options::OPT_nostartfiles))
+    CmdArgs.push_back(Args.MakeArgString(ToolChain.GetFilePath("crtend.o")));
+
+  const char *Exec = Args.MakeArgString(ToolChain.GetLinkerPath());
+  C.addCommand(llvm::make_unique<Command>(JA, *this, Exec, CmdArgs));
+}
+
 void darwin::Assemble::ConstructJob(Compilation &C, const JobAction &JA,
                                     const InputInfo &Output,
                                     const InputInfoList &Inputs,
                                     const ArgList &Args,
                                     const char *LinkingOutput) const {
   ArgStringList CmdArgs;
 
   assert(Inputs.size() == 1 && "Unexpected number of inputs.");

cfe/trunk/test/Driver/cloudabi.c

+// RUN: %clang %s -### -target x86_64-unknown-cloudabi 2>&1 | FileCheck %s
+// CHECK: "-cc1" "-triple" "x86_64-unknown-cloudabi"
+// CHECK: "-Bstatic" "--eh-frame-hdr" "--gc-sections" "-o" "a.out" "crt0.o" "crtbegin.o" "{{.*}}" "{{.*}}" "-lc" "-lcompiler_rt" "crtend.o"

cfe/trunk/test/Driver/cloudabi.cpp

+// RUN: %clangxx %s -### -target x86_64-unknown-cloudabi 2>&1 | FileCheck %s
+// CHECK: "-cc1" "-triple" "x86_64-unknown-cloudabi"
+// CHECK: "-Bstatic" "--eh-frame-hdr" "--gc-sections" "-o" "a.out" "crt0.o" "crtbegin.o" "{{.*}}" "{{.*}}" "-lc++" "-lc++abi" "-lunwind" "-lc" "-lcompiler_rt" "crtend.o"