1 files changed, 56 insertions, 0 deletions
diff --git a/clang/lib/Driver/ToolChains/Gnu.cpp b/clang/lib/Driver/ToolChains/Gnu.cpp
index 2dd3450dd1b..eb84a99a16b 100644
--- a/clang/lib/Driver/ToolChains/Gnu.cpp
+++ b/clang/lib/Driver/ToolChains/Gnu.cpp
@@ -1503,9 +1503,65 @@ static bool findMSP430Multilibs(const Driver &D,
   return false;
 }
 
+static void findRISCVBareMetalMultilibs(const Driver &D,
+                                        const llvm::Triple &TargetTriple,
+                                        StringRef Path, const ArgList &Args,
+                                        DetectedMultilibs &Result) {
+  FilterNonExistent NonExistent(Path, "/crtbegin.o", D.getVFS());
+  struct RiscvMultilib {
+    StringRef march;
+    StringRef mabi;
+  };
+  // currently only support the set of multilibs like riscv-gnu-toolchain does.
+  // TODO: support MULTILIB_REUSE
+  SmallVector<RiscvMultilib, 8> RISCVMultilibSet = {
+      {"rv32i", "ilp32"},     {"rv32im", "ilp32"},     {"rv32iac", "ilp32"},
+      {"rv32imac", "ilp32"},  {"rv32imafc", "ilp32f"}, {"rv64imac", "lp64"},
+      {"rv64imafdc", "lp64d"}};
+
+  std::vector<Multilib> Ms;
+  for (auto Element : RISCVMultilibSet) {
+    // multilib path rule is ${march}/${mabi}
+    Ms.emplace_back(
+        makeMultilib((Twine(Element.march) + "/" + Twine(Element.mabi)).str())
+            .flag(Twine("+march=", Element.march).str())
+            .flag(Twine("+mabi=", Element.mabi).str()));
+  }
+  MultilibSet RISCVMultilibs =
+      MultilibSet()
+          .Either(ArrayRef<Multilib>(Ms))
+          .FilterOut(NonExistent)
+          .setFilePathsCallback([](const Multilib &M) {
+            return std::vector<std::string>(
+                {M.gccSuffix(),
+                 "/../../../../riscv64-unknown-elf/lib" + M.gccSuffix(),
+                 "/../../../../riscv32-unknown-elf/lib" + M.gccSuffix()});
+          });
+
+
+  Multilib::flags_list Flags;
+  llvm::StringSet<> Added_ABIs;
+  StringRef ABIName = tools::riscv::getRISCVABI(Args, TargetTriple);
+  StringRef MArch = tools::riscv::getRISCVArch(Args, TargetTriple);
+  for (auto Element : RISCVMultilibSet) {
+    addMultilibFlag(MArch == Element.march,
+                    Twine("march=", Element.march).str().c_str(), Flags);
+    if (!Added_ABIs.count(Element.mabi)) {
+      Added_ABIs.insert(Element.mabi);
+      addMultilibFlag(ABIName == Element.mabi,
+                      Twine("mabi=", Element.mabi).str().c_str(), Flags);
+    }
+  }
+
+  if (RISCVMultilibs.select(Flags, Result.SelectedMultilib))
+    Result.Multilibs = RISCVMultilibs;
+}
+
 static void findRISCVMultilibs(const Driver &D,
                                const llvm::Triple &TargetTriple, StringRef Path,
                                const ArgList &Args, DetectedMultilibs &Result) {
+  if (TargetTriple.getOS() == llvm::Triple::UnknownOS)
+    return findRISCVBareMetalMultilibs(D, TargetTriple, Path, Args, Result);
 
   FilterNonExistent NonExistent(Path, "/crtbegin.o", D.getVFS());
   Multilib Ilp32 = makeMultilib("lib32/ilp32").flag("+m32").flag("+mabi=ilp32");