[RISCV] Add driver for riscv32-unknown-elf baremetal target

[asb]

Summary

This patch adds a driver for the baremetal RISC-V target (i.e. riscv32-unknown-elf). For reference, D39963 added basic target info and added support for riscv32-linux-unknown-elf.

Patch by: asb (Alex Bradbury)

[efriedma]

Could you include some documentation for how to construct a baremetal environment like the one this code expects? It's not clear what exactly you expect to be installed where.

[asb]

In D46822#1098764, @efriedma wrote:

Could you include some documentation for how to construct a baremetal environment like the one this code expects? It's not clear what exactly you expect to be installed where.

Thanks for taking a look Eli.

Building gcc+binutils+newlib will spit out a directory tree with the expected setup. e.g. a while ago I wrote a blog post trying to show how to build upstream RISC-V gcc+binutils+newlib in the simplest way possible. You need a multistage build for C++ support and other features, but those instructions are enough to get a baremetal cross compiler. The directory layout is the same as if you use the build script in the riscv-gnu-toolchain repo, doing ./configure --prefix=/my/target/path --with-arch=rv32i --with-abi=ilp32; make -j$(nproc). This is a more advanced multi-stage build.

Would you like to see more information on this added to the commit message, as comments in the code, or elsewhere?

e.g. this is the directory listing of the build output if you follow the linked blog instructions: https://pastebin.com/8HeCMpxF

[efriedma]

Just a brief comment in the code explaining that would be fine.

[mgrang]

LGTM.

lib/Driver/ToolChains/Gnu.cpp

1885

Alphabetically riscv32-unknown-elf should be the first in the list of triples.

[kito-cheng]

ping, Alex, could you commit that?

[efriedma]

Please don't commit patches on behalf of someone else if the author hasn't specifically requested it. There might be some issue which the author forgot to note on the review.

[xbolva00]

In D46822#1183007, @efriedma wrote:

Please don't commit patches on behalf of someone else if the author hasn't specifically requested it. There might be some issue which the author forgot to note on the review.

Oh, ok.

[simoncook]

It seems the ability to link objects has been broken by this change. As an example from our nightly tests:

Executing on host: riscv32-unknown-elf-clang /data/jenkins/workspace/riscv32-llvm-gcc/gcc-tests/gcc/testsuite/gcc.c-torture/execute/20080502-1.c  -march=rv32gc -mabi=ilp32      -O1  -w      -lm  -o ./20080502-1.exe    (timeout = 600)
spawn -ignore SIGHUP riscv32-unknown-elf-clang /data/jenkins/workspace/riscv32-llvm-gcc/gcc-tests/gcc/testsuite/gcc.c-torture/execute/20080502-1.c -march=rv32gc -mabi=ilp32 -O1 -w -lm -o ./20080502-1.exe
/data/jenkins/workspace/riscv32-llvm-gcc/install/bin/riscv32-unknown-elf-ld: cannot find crt0.o: No such file or directory
clang-8: error: ld command failed with exit code 1 (use -v to see invocation)
compiler exited with status 1
FAIL: gcc.c-torture/execute/20080502-1.c   -O1  (test for excess errors)

Running with -v shows the link command as:

"/data/jenkins/workspace/riscv32-llvm-gcc/install/bin/riscv32-unknown-elf-ld" crt0.o /data/jenkins/workspace/riscv32-llvm-gcc/install/bin/../lib/gcc/riscv32-unknown-elf/8.1.0/crtbegin.o -L/lib -L/data/jenkins/workspace/riscv32-llvm-gcc/install/bin/../lib/gcc/riscv32-unknown-elf/8.1.0 /tmp/20080502-1-2b0022.o -lm --start-group -lc -lgloss --end-group -lgcc /data/jenkins/workspace/riscv32-llvm-gcc/install/bin/../lib/gcc/riscv32-unknown-elf/8.1.0/crtend.o -o ./20080502-1.exe

What's noticeable is crt0.o is specified just as a file, and we're trying to link in my host /lib/ (-L/lib)? If I manually specify a sysroot (via --sysroot=$INSTALLDIR/riscv32-unknown-elf), then my link succeeds, adding the path to crt0.o, and the correct /lib:

"/data/jenkins/workspace/riscv32-llvm-gcc/install/bin/riscv32-unknown-elf-ld" --sysroot=/data/jenkins/workspace/riscv32-llvm-gcc/install/riscv32-unknown-elf /data/jenkins/workspace/riscv32-llvm-gcc/install/riscv32-unknown-elf/lib/crt0.o /data/jenkins/workspace/riscv32-llvm-gcc/install/bin/../lib/gcc/riscv32-unknown-elf/8.1.0/crtbegin.o -L/data/jenkins/workspace/riscv32-llvm-gcc/install/riscv32-unknown-elf/lib -L/data/jenkins/workspace/riscv32-llvm-gcc/install/bin/../lib/gcc/riscv32-unknown-elf/8.1.0 /tmp/20080502-1-d53be0.o -lm --start-group -lc -lgloss --end-group -lgcc /data/jenkins/workspace/riscv32-llvm-gcc/install/bin/../lib/gcc/riscv32-unknown-elf/8.1.0/crtend.o -o ./20080502-1.exe

I think there's some missing calculate the correct sysroot directory logic missing, unless linking clang to riscv32-unknown-elf-clang is no longer sufficient for everything to work now?

[lewis-revill]

I've submitted a patch to address Simon's issues in D50246

lib/Driver/CMakeLists.txt

add_clang_library(clangDriver
   ToolChains/MinGW.cpp
   ToolChains/Minix.cpp
   ToolChains/MSVC.cpp
   ToolChains/Myriad.cpp
   ToolChains/NaCl.cpp
   ToolChains/NetBSD.cpp
   ToolChains/OpenBSD.cpp
   ToolChains/PS4CPU.cpp
+  ToolChains/RISCV.cpp
   ToolChains/Solaris.cpp
   ToolChains/TCE.cpp
   ToolChains/WebAssembly.cpp
   ToolChains/XCore.cpp
   Types.cpp
   XRayArgs.cpp
 
   DEPENDS
   ClangDriverOptions
 
   LINK_LIBS
   clangBasic
   ${system_libs}
   )

lib/Driver/Driver.cpp

 #include "ToolChains/MinGW.h"
 #include "ToolChains/Minix.h"
 #include "ToolChains/MipsLinux.h"
 #include "ToolChains/Myriad.h"
 #include "ToolChains/NaCl.h"
 #include "ToolChains/NetBSD.h"
 #include "ToolChains/OpenBSD.h"
 #include "ToolChains/PS4CPU.h"
+#include "ToolChains/RISCV.h"
 #include "ToolChains/Solaris.h"
 #include "ToolChains/TCE.h"
 #include "ToolChains/WebAssembly.h"
 #include "ToolChains/XCore.h"
 #include "clang/Basic/Version.h"
 #include "clang/Basic/VirtualFileSystem.h"
 #include "clang/Config/config.h"
 #include "clang/Driver/Action.h"
default:
         break;
       case llvm::Triple::wasm32:
       case llvm::Triple::wasm64:
         TC = llvm::make_unique<toolchains::WebAssembly>(*this, Target, Args);
         break;
       case llvm::Triple::avr:
         TC = llvm::make_unique<toolchains::AVRToolChain>(*this, Target, Args);
         break;
+      case llvm::Triple::riscv32:
+      case llvm::Triple::riscv64:
+        TC = llvm::make_unique<toolchains::RISCVToolChain>(*this, Target, Args);
+        break;
       default:
         if (Target.getVendor() == llvm::Triple::Myriad)
           TC = llvm::make_unique<toolchains::MyriadToolChain>(*this, Target,
                                                               Args);
         else if (toolchains::BareMetal::handlesTarget(Target))
           TC = llvm::make_unique<toolchains::BareMetal>(*this, Target, Args);
         else if (Target.isOSBinFormatELF())
           TC = llvm::make_unique<toolchains::Generic_ELF>(*this, Target, Args);

lib/Driver/ToolChains/Gnu.cpp

static const char *const PPC64Triples[] = {
       "powerpc64-suse-linux", "ppc64-redhat-linux"};
   static const char *const PPC64LELibDirs[] = {"/lib64", "/lib"};
   static const char *const PPC64LETriples[] = {
       "powerpc64le-linux-gnu", "powerpc64le-unknown-linux-gnu",
       "powerpc64le-suse-linux", "ppc64le-redhat-linux"};
 
   static const char *const RISCV32LibDirs[] = {"/lib", "/lib32"};
   static const char *const RISCVTriples[] = {"riscv32-unknown-linux-gnu",
-                                             "riscv64-unknown-linux-gnu"};
+                                             "riscv64-unknown-linux-gnu",
+                                             "riscv32-unknown-elf"};
 
   static const char *const SPARCv8LibDirs[] = {"/lib32", "/lib"};
   static const char *const SPARCv8Triples[] = {"sparc-linux-gnu",
                                                "sparcv8-linux-gnu"};
   static const char *const SPARCv9LibDirs[] = {"/lib64", "/lib"};
   static const char *const SPARCv9Triples[] = {"sparc64-linux-gnu",
                                                "sparcv9-linux-gnu"};
 
   static const char *const SystemZLibDirs[] = {"/lib64", "/lib"};
   static const char *const SystemZTriples[] = {
       "s390x-linux-gnu", "s390x-unknown-linux-gnu", "s390x-ibm-linux-gnu",
       "s390x-suse-linux", "s390x-redhat-linux"};

lib/Driver/ToolChains/RISCV.h

+//===--- RISCV.h - RISCV ToolChain Implementations --------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_LIB_DRIVER_TOOLCHAINS_RISCV_H
+#define LLVM_CLANG_LIB_DRIVER_TOOLCHAINS_RISCV_H
+
+#include "Gnu.h"
+#include "clang/Driver/ToolChain.h"
+
+namespace clang {
+namespace driver {
+namespace toolchains {
+
+class LLVM_LIBRARY_VISIBILITY RISCVToolChain : public Generic_ELF {
+public:
+  RISCVToolChain(const Driver &D, const llvm::Triple &Triple,
+                 const llvm::opt::ArgList &Args);
+
+  bool IsIntegratedAssemblerDefault() const override { return true; }
+  void
+  AddClangSystemIncludeArgs(const llvm::opt::ArgList &DriverArgs,
+                            llvm::opt::ArgStringList &CC1Args) const override;
+  void
+  addLibStdCxxIncludePaths(const llvm::opt::ArgList &DriverArgs,
+                           llvm::opt::ArgStringList &CC1Args) const override;
+
+protected:
+  Tool *buildLinker() const override;
+};
+
+} // end namespace toolchains
+
+namespace tools {
+namespace RISCV {
+class LLVM_LIBRARY_VISIBILITY Linker : public GnuTool {
+public:
+  Linker(const ToolChain &TC) : GnuTool("RISCV::Linker", "ld", 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 RISCV
+} // end namespace tools
+
+} // end namespace driver
+} // end namespace clang
+
+#endif // LLVM_CLANG_LIB_DRIVER_TOOLCHAINS_RISCV_H

lib/Driver/ToolChains/RISCV.cpp

+//===--- RISCV.cpp - RISCV ToolChain Implementations ------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "RISCV.h"
+#include "CommonArgs.h"
+#include "InputInfo.h"
+#include "clang/Driver/Compilation.h"
+#include "clang/Driver/Options.h"
+#include "llvm/Option/ArgList.h"
+#include "llvm/Support/Path.h"
+#include "llvm/Support/raw_ostream.h"
+
+using namespace clang::driver;
+using namespace clang::driver::toolchains;
+using namespace clang::driver::tools;
+using namespace clang;
+using namespace llvm::opt;
+
+/// RISCV Toolchain
+RISCVToolChain::RISCVToolChain(const Driver &D, const llvm::Triple &Triple,
+                               const ArgList &Args)
+    : Generic_ELF(D, Triple, Args) {
+  GCCInstallation.init(Triple, Args);
+  getFilePaths().push_back(D.SysRoot + "/lib");
+  if (GCCInstallation.isValid()) {
+    getFilePaths().push_back(GCCInstallation.getInstallPath().str());
+    getProgramPaths().push_back(
+        (GCCInstallation.getParentLibPath() + "/../bin").str());
+  }
+}
+
+Tool *RISCVToolChain::buildLinker() const {
+  return new tools::RISCV::Linker(*this);
+}
+
+void RISCVToolChain::AddClangSystemIncludeArgs(const ArgList &DriverArgs,
+                                               ArgStringList &CC1Args) const {
+  if (DriverArgs.hasArg(options::OPT_nostdinc))
+    return;
+
+  if (!DriverArgs.hasArg(options::OPT_nostdlibinc)) {
+    SmallString<128> Dir(getDriver().SysRoot);
+    llvm::sys::path::append(Dir, "include");
+    addSystemInclude(DriverArgs, CC1Args, Dir.str());
+  }
+}
+
+void RISCVToolChain::addLibStdCxxIncludePaths(
+    const llvm::opt::ArgList &DriverArgs,
+    llvm::opt::ArgStringList &CC1Args) const {
+  StringRef LibDir = GCCInstallation.getParentLibPath();
+  const GCCVersion &Version = GCCInstallation.getVersion();
+  StringRef TripleStr = GCCInstallation.getTriple().str();
+  const Multilib &Multilib = GCCInstallation.getMultilib();
+  addLibStdCXXIncludePaths(
+      LibDir.str() + "/../" + TripleStr.str() + "/include/c++/" + Version.Text,
+      "", TripleStr, "", "", Multilib.includeSuffix(), DriverArgs, CC1Args);
+}
+
+void RISCV::Linker::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;
+
+  if (!D.SysRoot.empty())
+    CmdArgs.push_back(Args.MakeArgString("--sysroot=" + D.SysRoot));
+
+  std::string Linker = getToolChain().GetProgramPath(getShortName());
+
+  bool WantCRTs =
+      !Args.hasArg(options::OPT_nostdlib, options::OPT_nostartfiles);
+
+  if (WantCRTs) {
+    CmdArgs.push_back(Args.MakeArgString(ToolChain.GetFilePath("crt0.o")));
+    CmdArgs.push_back(Args.MakeArgString(ToolChain.GetFilePath("crtbegin.o")));
+  }
+
+  Args.AddAllArgs(CmdArgs, options::OPT_L);
+  ToolChain.AddFilePathLibArgs(Args, CmdArgs);
+  Args.AddAllArgs(CmdArgs,
+                  {options::OPT_T_Group, options::OPT_e, options::OPT_s,
+                   options::OPT_t, options::OPT_Z_Flag, options::OPT_r});
+
+  AddLinkerInputs(ToolChain, Inputs, Args, CmdArgs, JA);
+
+  // TODO: add C++ includes and libs if compiling C++.
+
+  if (!Args.hasArg(options::OPT_nostdlib) &&
+      !Args.hasArg(options::OPT_nodefaultlibs)) {
+    if (ToolChain.ShouldLinkCXXStdlib(Args))
+      ToolChain.AddCXXStdlibLibArgs(Args, CmdArgs);
+    CmdArgs.push_back("--start-group");
+    CmdArgs.push_back("-lc");
+    CmdArgs.push_back("-lgloss");
+    CmdArgs.push_back("--end-group");
+    CmdArgs.push_back("-lgcc");
+  }
+
+  if (WantCRTs)
+    CmdArgs.push_back(Args.MakeArgString(ToolChain.GetFilePath("crtend.o")));
+
+  CmdArgs.push_back("-o");
+  CmdArgs.push_back(Output.getFilename());
+  C.addCommand(llvm::make_unique<Command>(JA, *this, Args.MakeArgString(Linker),
+                                          CmdArgs, Inputs));
+}
+// RISCV tools end.

test/Driver/Inputs/basic_riscv32_tree/bin/riscv32-unknown-elf-ld

+#!/bin/true

test/Driver/riscv32-toolchain.c

 // A basic clang -cc1 command-line, and simple environment check.
 
 // RUN: %clang %s -### -no-canonical-prefixes -target riscv32 2>&1 | FileCheck -check-prefix=CC1 %s
 // CC1: clang{{.*}} "-cc1" "-triple" "riscv32"
 
+// RUN: %clang %s -### -no-canonical-prefixes \
+// RUN:   -target riscv32-unknown-elf \
+// RUN:   --gcc-toolchain=%S/Inputs/basic_riscv32_tree \
+// RUN:   --sysroot=%S/Inputs/basic_riscv32_tree/riscv32-unknown-elf 2>&1 \
+// RUN:   | FileCheck -check-prefix=C-RV32-BAREMETAL-ILP32 %s
+
+// C-RV32-BAREMETAL-ILP32: "{{.*}}Inputs/basic_riscv32_tree/lib/gcc/riscv32-unknown-elf/8.0.1/../../../../bin{{/|\\\\}}riscv32-unknown-elf-ld"
+// C-RV32-BAREMETAL-ILP32: "--sysroot={{.*}}/Inputs/basic_riscv32_tree/riscv32-unknown-elf"
+// C-RV32-BAREMETAL-ILP32: "{{.*}}/Inputs/basic_riscv32_tree/riscv32-unknown-elf/lib{{/|\\\\}}crt0.o"
+// C-RV32-BAREMETAL-ILP32: "{{.*}}/Inputs/basic_riscv32_tree/lib/gcc/riscv32-unknown-elf/8.0.1{{/|\\\\}}crtbegin.o"
+// C-RV32-BAREMETAL-ILP32: "-L{{.*}}/Inputs/basic_riscv32_tree/riscv32-unknown-elf/lib"
+// C-RV32-BAREMETAL-ILP32: "-L{{.*}}/Inputs/basic_riscv32_tree/lib/gcc/riscv32-unknown-elf/8.0.1"
+// C-RV32-BAREMETAL-ILP32: "--start-group" "-lc" "-lgloss" "--end-group" "-lgcc"
+// C-RV32-BAREMETAL-ILP32: "{{.*}}/Inputs/basic_riscv32_tree/lib/gcc/riscv32-unknown-elf/8.0.1{{/|\\\\}}crtend.o"
+
+// RUN: %clangxx %s -### -no-canonical-prefixes \
+// RUN:   -target riscv32-unknown-elf \
+// RUN:   --gcc-toolchain=%S/Inputs/basic_riscv32_tree \
+// RUN:   --sysroot=%S/Inputs/basic_riscv32_tree/riscv32-unknown-elf 2>&1 \
+// RUN:   | FileCheck -check-prefix=CXX-RV32-BAREMETAL-ILP32 %s
+
+// CXX-RV32-BAREMETAL-ILP32: "-internal-isystem" "{{.*}}Inputs/basic_riscv32_tree/lib/gcc/riscv32-unknown-elf/8.0.1/../../../../riscv32-unknown-elf/include/c++{{/|\\\\}}8.0.1"
+// CXX-RV32-BAREMETAL-ILP32: "{{.*}}Inputs/basic_riscv32_tree/lib/gcc/riscv32-unknown-elf/8.0.1/../../../../bin{{/|\\\\}}riscv32-unknown-elf-ld"
+// CXX-RV32-BAREMETAL-ILP32: "--sysroot={{.*}}/Inputs/basic_riscv32_tree/riscv32-unknown-elf"
+// CXX-RV32-BAREMETAL-ILP32: "{{.*}}/Inputs/basic_riscv32_tree/riscv32-unknown-elf/lib{{/|\\\\}}crt0.o"
+// CXX-RV32-BAREMETAL-ILP32: "{{.*}}/Inputs/basic_riscv32_tree/lib/gcc/riscv32-unknown-elf/8.0.1{{/|\\\\}}crtbegin.o"
+// CXX-RV32-BAREMETAL-ILP32: "-L{{.*}}/Inputs/basic_riscv32_tree/riscv32-unknown-elf/lib"
+// CXX-RV32-BAREMETAL-ILP32: "-L{{.*}}/Inputs/basic_riscv32_tree/lib/gcc/riscv32-unknown-elf/8.0.1"
+// CXX-RV32-BAREMETAL-ILP32: "-lstdc++" "--start-group" "-lc" "-lgloss" "--end-group" "-lgcc"
+// CXX-RV32-BAREMETAL-ILP32: "{{.*}}/Inputs/basic_riscv32_tree/lib/gcc/riscv32-unknown-elf/8.0.1{{/|\\\\}}crtend.o"
 
 // RUN: %clang %s -### -no-canonical-prefixes -fuse-ld=ld \
 // RUN:   -target riscv32-linux-unknown-elf \
 // RUN:   --gcc-toolchain=%S/Inputs/multilib_riscv_linux_sdk \
 // RUN:   --sysroot=%S/Inputs/multilib_riscv_linux_sdk/sysroot 2>&1 \
 // RUN:   | FileCheck -check-prefix=C-RV32-LINUX-MULTI-ILP32 %s
 
 // C-RV32-LINUX-MULTI-ILP32: "{{.*}}/Inputs/multilib_riscv_linux_sdk/lib/gcc/riscv64-unknown-linux-gnu/7.2.0/../../../../riscv64-unknown-linux-gnu/bin{{/|\\\\}}ld"