[RISCV] Teach Barmetal toolchain about GCC installation(1/3)

This patch introduces the baretmetal toolchain object about GCC Installation.
Currently, if `--gcc-installation` ot `--gcc-install-dir` options are passed on
commandline, then sysroot will be formed from there if paths will be valid.
Otherwise, it will be fallback to as it already existed in the Baremetal
toolchaibn object.

Additionally, the restriction to always use integrated assembler is removed
because with valid gcc installation, gnu assembler can be invoked as well.

This patch currently adds and modifies arm related test only. The riscv specific
test will be added in the last PR when driver code related to calling of
RISCVToolchain object will be removed. Currently in this PR, there is no way to
test riscv target.

This is the first PR in the series of 3 PRs for merging and extending Baremetal
toolchain object. The division of the PRs is as follows:
- Teach Baremetal toolchain about GCC installation and make sysroot and assembler
  related changes.
- Changes related to linker job and defaults for CXXStdlib and other runtime libs.
- Finally removing the call to RISCVToolchain object.

The above division will also ensure that riscv and arm specific tests are not
modified in the same PR.

RFC: https://discourse.llvm.org/t/merging-riscvtoolchain-and-baremetal-toolchains/75524

Change-Id: Ibaeb569cf7e2cee03c022aa9ecd1abe29d5c30d4

Author: Garvit Gupta

clang/lib/Driver/ToolChains/BareMetal.cpp

@@ -97,7 +97,8 @@ static bool findRISCVMultilibs(const Driver &D,
   return false;
 }
 
-static std::string computeBaseSysRoot(const Driver &D, bool IncludeTriple) {
+static std::string computeInstalledToolchainSysRoot(const Driver &D,
+                                                    bool IncludeTriple) {
   if (!D.SysRoot.empty())
     return D.SysRoot;
 
@@ -110,20 +111,93 @@ static std::string computeBaseSysRoot(const Driver &D, bool IncludeTriple) {
   return std::string(SysRootDir);
 }
 
+// GCC sysroot here means form sysroot from either --gcc-install-dir, or from
+// --gcc-toolchain or if the toolchain is installed alongside clang in
+// bin/../<TargetTriple> directory if it is not explicitly specified on the
+// command line through `--sysroot` option. libc here will be newlib.
+std::string BareMetal::computeGCCSysRoot() const {
+  if (!getDriver().SysRoot.empty())
+    return getDriver().SysRoot;
+
+  SmallString<128> SysRootDir;
+  if (GCCInstallation.isValid()) {
+    StringRef LibDir = GCCInstallation.getParentLibPath();
+    StringRef TripleStr = GCCInstallation.getTriple().str();
+    llvm::sys::path::append(SysRootDir, LibDir, "..", TripleStr);
+  } else {
+    // Use the triple as provided to the driver. Unlike the parsed triple
+    // this has not been normalized to always contain every field.
+    llvm::sys::path::append(SysRootDir, getDriver().Dir, "..",
+                            getDriver().getTargetTriple());
+  }
+
+  if (!llvm::sys::fs::exists(SysRootDir))
+    return std::string();
+
+  return std::string(SysRootDir);
+}
+
+std::string BareMetal::computeSysRoot() const {
+  if (!SysRoot.empty())
+    return SysRoot;
+
+  std::string SysRoot = getDriver().SysRoot;
+  if (!SysRoot.empty() && llvm::sys::fs::exists(SysRoot))
+    return SysRoot;
+
+  // Verify the GCC installation from -gcc-install-dir, --gcc-toolchain, or
+  // alongside clang. If valid, form the sysroot. Otherwise, check
+  // lib/clang-runtimes above the driver.
+  SysRoot = computeGCCSysRoot();
+  if (!SysRoot.empty())
+    return SysRoot;
+
+  SysRoot =
+      computeInstalledToolchainSysRoot(getDriver(), /*IncludeTriple*/ true);
+
+  return SysRoot;
+}
+
+static void addMultilibsFilePaths(const Driver &D, const MultilibSet &Multilibs,
+                                  const Multilib &Multilib,
+                                  StringRef InstallPath,
+                                  ToolChain::path_list &Paths) {
+  if (const auto &PathsCallback = Multilibs.filePathsCallback())
+    for (const auto &Path : PathsCallback(Multilib))
+      addPathIfExists(D, InstallPath + Path, Paths);
+}
+
 BareMetal::BareMetal(const Driver &D, const llvm::Triple &Triple,
                      const ArgList &Args)
-    : ToolChain(D, Triple, Args),
-      SysRoot(computeBaseSysRoot(D, /*IncludeTriple=*/true)) {
-  getProgramPaths().push_back(getDriver().Dir);
-
-  findMultilibs(D, Triple, Args);
-  SmallString<128> SysRoot(computeSysRoot());
-  if (!SysRoot.empty()) {
-    for (const Multilib &M : getOrderedMultilibs()) {
-      SmallString<128> Dir(SysRoot);
-      llvm::sys::path::append(Dir, M.osSuffix(), "lib");
-      getFilePaths().push_back(std::string(Dir));
-      getLibraryPaths().push_back(std::string(Dir));
+    : Generic_ELF(D, Triple, Args) {
+  GCCInstallation.init(Triple, Args);
+  SysRoot = computeSysRoot();
+  if (GCCInstallation.isValid()) {
+    Multilibs = GCCInstallation.getMultilibs();
+    SelectedMultilibs.assign({GCCInstallation.getMultilib()});
+    path_list &Paths = getFilePaths();
+    // Add toolchain/multilib specific file paths.
+    addMultilibsFilePaths(D, Multilibs, SelectedMultilibs.back(),
+                          GCCInstallation.getInstallPath(), Paths);
+    getFilePaths().push_back(GCCInstallation.getInstallPath().str());
+    ToolChain::path_list &PPaths = getProgramPaths();
+    // Multilib cross-compiler GCC installations put ld in a triple-prefixed
+    // directory off of the parent of the GCC installation.
+    PPaths.push_back(Twine(GCCInstallation.getParentLibPath() + "/../" +
+                           GCCInstallation.getTriple().str() + "/bin")
+                         .str());
+    PPaths.push_back((GCCInstallation.getParentLibPath() + "/../bin").str());
+    getFilePaths().push_back(computeSysRoot() + "/lib");
+  } else {
+    getProgramPaths().push_back(getDriver().Dir);
+    findMultilibs(D, Triple, Args);
+    if (!SysRoot.empty()) {
+      for (const Multilib &M : getOrderedMultilibs()) {
+        SmallString<128> Dir(SysRoot);
+        llvm::sys::path::append(Dir, M.osSuffix(), "lib");
+        getFilePaths().push_back(std::string(Dir));
+        getLibraryPaths().push_back(std::string(Dir));
+      }
     }
   }
 }
@@ -215,7 +289,7 @@ getMultilibConfigPath(const Driver &D, const llvm::Triple &Triple,
       return {};
     }
   } else {
-    MultilibPath = computeBaseSysRoot(D, /*IncludeTriple=*/false);
+    MultilibPath = computeInstalledToolchainSysRoot(D, /*IncludeTriple=*/false);
     llvm::sys::path::append(MultilibPath, MultilibFilename);
   }
   return MultilibPath;
@@ -233,7 +307,7 @@ void BareMetal::findMultilibs(const Driver &D, const llvm::Triple &Triple,
   if (D.getVFS().exists(*MultilibPath)) {
     // If multilib.yaml is found, update sysroot so it doesn't use a target
     // specific suffix
-    SysRoot = computeBaseSysRoot(D, /*IncludeTriple=*/false);
+    SysRoot = computeInstalledToolchainSysRoot(D, /*IncludeTriple=*/false);
     findMultilibsFromYAML(*this, D, *MultilibPath, Args, Result);
     SelectedMultilibs = Result.SelectedMultilibs;
     Multilibs = Result.Multilibs;
@@ -258,8 +332,6 @@ Tool *BareMetal::buildStaticLibTool() const {
   return new tools::baremetal::StaticLibTool(*this);
 }
 
-std::string BareMetal::computeSysRoot() const { return SysRoot; }
-
 BareMetal::OrderedMultilibs BareMetal::getOrderedMultilibs() const {
   // Get multilibs in reverse order because they're ordered most-specific last.
   if (!SelectedMultilibs.empty())
@@ -304,6 +376,19 @@ void BareMetal::addClangTargetOptions(const ArgList &DriverArgs,
   CC1Args.push_back("-nostdsysteminc");
 }
 
+void BareMetal::addLibStdCxxIncludePaths(
+    const llvm::opt::ArgList &DriverArgs,
+    llvm::opt::ArgStringList &CC1Args) const {
+  if (!GCCInstallation.isValid())
+    return;
+  const GCCVersion &Version = GCCInstallation.getVersion();
+  StringRef TripleStr = GCCInstallation.getTriple().str();
+  const Multilib &Multilib = GCCInstallation.getMultilib();
+  addLibStdCXXIncludePaths(computeSysRoot() + "/include/c++/" + Version.Text,
+                           TripleStr, Multilib.includeSuffix(), DriverArgs,
+                           CC1Args);
+}
+
 void BareMetal::AddClangCXXStdlibIncludeArgs(const ArgList &DriverArgs,
                                              ArgStringList &CC1Args) const {
   if (DriverArgs.hasArg(options::OPT_nostdinc, options::OPT_nostdlibinc,
@@ -341,7 +426,7 @@ void BareMetal::AddClangCXXStdlibIncludeArgs(const ArgList &DriverArgs,
       break;
     }
     case ToolChain::CST_Libstdcxx:
-      // We only support libc++ toolchain installation.
+      addLibStdCxxIncludePaths(DriverArgs, CC1Args);
       break;
   }
 

clang/lib/Driver/ToolChains/BareMetal.h

@@ -9,6 +9,7 @@
 #ifndef LLVM_CLANG_LIB_DRIVER_TOOLCHAINS_BAREMETAL_H
 #define LLVM_CLANG_LIB_DRIVER_TOOLCHAINS_BAREMETAL_H
 
+#include "ToolChains/Gnu.h"
 #include "clang/Driver/Tool.h"
 #include "clang/Driver/ToolChain.h"
 
@@ -19,7 +20,7 @@ namespace driver {
 
 namespace toolchains {
 
-class LLVM_LIBRARY_VISIBILITY BareMetal : public ToolChain {
+class LLVM_LIBRARY_VISIBILITY BareMetal : public Generic_ELF {
 public:
   BareMetal(const Driver &D, const llvm::Triple &Triple,
             const llvm::opt::ArgList &Args);
@@ -35,7 +36,6 @@ class LLVM_LIBRARY_VISIBILITY BareMetal : public ToolChain {
   Tool *buildStaticLibTool() const override;
 
 public:
-  bool useIntegratedAs() const override { return true; }
   bool isBareMetal() const override { return true; }
   bool isCrossCompiling() const override { return true; }
   bool HasNativeLLVMSupport() const override { return true; }
@@ -67,6 +67,9 @@ class LLVM_LIBRARY_VISIBILITY BareMetal : public ToolChain {
   void AddClangCXXStdlibIncludeArgs(
       const llvm::opt::ArgList &DriverArgs,
       llvm::opt::ArgStringList &CC1Args) const override;
+  void
+  addLibStdCxxIncludePaths(const llvm::opt::ArgList &DriverArgs,
+                           llvm::opt::ArgStringList &CC1Args) const override;
   std::string computeSysRoot() const override;
   SanitizerMask getSupportedSanitizers() const override;
 
@@ -76,6 +79,7 @@ class LLVM_LIBRARY_VISIBILITY BareMetal : public ToolChain {
   OrderedMultilibs getOrderedMultilibs() const;
 
   std::string SysRoot;
+  std::string computeGCCSysRoot() const;
 };
 
 } // namespace toolchains

clang/test/Driver/Inputs/basic_aarch64_gcc_tree/aarch64-none-elf/bin/ld

@@ -0,0 +1 @@
+#!/bin/true

clang/test/Driver/Inputs/basic_aarch64_gcc_tree/aarch64-none-elf/include/c++/8.2.1/.keep

@@ -0,0 +1 @@
+#!/bin/true