Index: clang/lib/Driver/ToolChains/RISCVToolchain.h
===================================================================
--- clang/lib/Driver/ToolChains/RISCVToolchain.h
+++ clang/lib/Driver/ToolChains/RISCVToolchain.h
@@ -25,6 +25,9 @@
   void addClangTargetOptions(const llvm::opt::ArgList &DriverArgs,
                              llvm::opt::ArgStringList &CC1Args,
                              Action::OffloadKind) const override;
+  RuntimeLibType GetDefaultRuntimeLibType() const override;
+  UnwindLibType
+  GetUnwindLibType(const llvm::opt::ArgList &Args) const override;
   void
   AddClangSystemIncludeArgs(const llvm::opt::ArgList &DriverArgs,
                             llvm::opt::ArgStringList &CC1Args) const override;
Index: clang/lib/Driver/ToolChains/RISCVToolchain.cpp
===================================================================
--- clang/lib/Driver/ToolChains/RISCVToolchain.cpp
+++ clang/lib/Driver/ToolChains/RISCVToolchain.cpp
@@ -41,6 +41,16 @@
   return new tools::RISCV::Linker(*this);
 }
 
+ToolChain::RuntimeLibType RISCVToolChain::GetDefaultRuntimeLibType() const {
+  return GCCInstallation.isValid() ?
+    ToolChain::RLT_Libgcc : ToolChain::RLT_CompilerRT;
+}
+
+ToolChain::UnwindLibType
+RISCVToolChain::GetUnwindLibType(const llvm::opt::ArgList &Args) const {
+  return ToolChain::UNW_None;
+}
+
 void RISCVToolChain::addClangTargetOptions(
     const llvm::opt::ArgList &DriverArgs,
     llvm::opt::ArgStringList &CC1Args,
@@ -110,9 +120,22 @@
   bool WantCRTs =
       !Args.hasArg(options::OPT_nostdlib, options::OPT_nostartfiles);
 
+  const char *crtbegin, *crtend;
+  auto RuntimeLib = ToolChain.GetRuntimeLibType(Args);
+  if (RuntimeLib == ToolChain::RLT_Libgcc) {
+    crtbegin = "crtbegin.o";
+    crtend = "crtend.o";
+  } else {
+    assert (RuntimeLib == ToolChain::RLT_CompilerRT);
+    crtbegin = ToolChain.getCompilerRTArgString(Args, "crtbegin",
+                                                ToolChain::FT_Object);
+    crtend = ToolChain.getCompilerRTArgString(Args, "crtend",
+                                              ToolChain::FT_Object);
+  }
+
   if (WantCRTs) {
     CmdArgs.push_back(Args.MakeArgString(ToolChain.GetFilePath("crt0.o")));
-    CmdArgs.push_back(Args.MakeArgString(ToolChain.GetFilePath("crtbegin.o")));
+    CmdArgs.push_back(Args.MakeArgString(ToolChain.GetFilePath(crtbegin)));
   }
 
   Args.AddAllArgs(CmdArgs, options::OPT_L);
@@ -133,11 +156,11 @@
     CmdArgs.push_back("-lc");
     CmdArgs.push_back("-lgloss");
     CmdArgs.push_back("--end-group");
-    CmdArgs.push_back("-lgcc");
+    AddRunTimeLibs(ToolChain, ToolChain.getDriver(), CmdArgs, Args);
   }
 
   if (WantCRTs)
-    CmdArgs.push_back(Args.MakeArgString(ToolChain.GetFilePath("crtend.o")));
+    CmdArgs.push_back(Args.MakeArgString(ToolChain.GetFilePath(crtend)));
 
   CmdArgs.push_back("-o");
   CmdArgs.push_back(Output.getFilename());
Index: clang/test/Driver/riscv32-toolchain-extra.c
===================================================================
--- clang/test/Driver/riscv32-toolchain-extra.c
+++ clang/test/Driver/riscv32-toolchain-extra.c
@@ -19,15 +19,15 @@
 // RUN: ln -s %S/Inputs/basic_riscv32_nogcc_tree/bin/riscv32-unknown-elf-ld %T/testroot-riscv32-baremetal-nogcc/bin/riscv32-unknown-elf-ld
 // RUN: ln -s %S/Inputs/basic_riscv32_nogcc_tree/riscv32-unknown-elf %T/testroot-riscv32-baremetal-nogcc/riscv32-unknown-elf
 // RUN: %T/testroot-riscv32-baremetal-nogcc/bin/clang %s -### -no-canonical-prefixes \
-// RUN:    -target riscv32-unknown-elf 2>&1 \
+// RUN:    -target riscv32-unknown-elf --rtlib=platform 2>&1 \
 // RUN:    | FileCheck -check-prefix=C-RV32-BAREMETAL-ILP32-NOGCC %s
 
-// C-RV32-BAREMETAL-ILP32-NOGCC: InstalledDir: [[DRIVERDIR:.*]]
 // C-RV32-BAREMETAL-ILP32-NOGCC: "-fuse-init-array"
-// C-RV32-BAREMETAL-ILP32-NOGCC: "-internal-isystem" "[[DRIVERDIR]]/../riscv32-unknown-elf/include"
-// C-RV32-BAREMETAL-ILP32-NOGCC: "[[DRIVERDIR]]/riscv32-unknown-elf-ld"
-// C-RV32-BAREMETAL-ILP32-NOGCC: "[[DRIVERDIR]]/../riscv32-unknown-elf/lib/crt0.o"
-// C-RV32-BAREMETAL-ILP32-NOGCC: "[[DRIVERDIR]]/../riscv32-unknown-elf/lib/crtbegin.o"
-// C-RV32-BAREMETAL-ILP32-NOGCC: "-L[[DRIVERDIR]]/../riscv32-unknown-elf/lib"
-// C-RV32-BAREMETAL-ILP32-NOGCC: "--start-group" "-lc" "-lgloss" "--end-group" "-lgcc"
-// C-RV32-BAREMETAL-ILP32-NOGCC: "[[DRIVERDIR]]/../riscv32-unknown-elf/lib/crtend.o"
+// C-RV32-BAREMETAL-ILP32-NOGCC: "-internal-isystem" "{{.*}}Output/testroot-riscv32-baremetal-nogcc/bin/../riscv32-unknown-elf/include"
+// C-RV32-BAREMETAL-ILP32-NOGCC: "{{.*}}Output/testroot-riscv32-baremetal-nogcc/bin/riscv32-unknown-elf-ld"
+// C-RV32-BAREMETAL-ILP32-NOGCC: "{{.*}}Output/testroot-riscv32-baremetal-nogcc/bin/../riscv32-unknown-elf/lib/crt0.o"
+// C-RV32-BAREMETAL-ILP32-NOGCC: "{{.*}}Output/testroot-riscv32-baremetal-nogcc/lib/clang/{{[0-9.]*}}/lib/clang_rt.crtbegin-riscv32.o"
+// C-RV32-BAREMETAL-ILP32-NOGCC: "{{.*}}Output/testroot-riscv32-baremetal-nogcc/bin/../riscv32-unknown-elf/lib"
+// C-RV32-BAREMETAL-ILP32-NOGCC: "--start-group" "-lc" "-lgloss" "--end-group"
+// C-RV32-BAREMETAL-ILP32-NOGCC: "{{.*}}Output/testroot-riscv32-baremetal-nogcc/lib/clang/{{[0-9.]*}}/lib/libclang_rt.builtins-riscv32.a"
+// C-RV32-BAREMETAL-ILP32-NOGCC: "{{.*}}Output/testroot-riscv32-baremetal-nogcc/lib/clang/{{[0-9.]*}}/lib/clang_rt.crtend-riscv32.o"
Index: clang/test/Driver/riscv32-toolchain.c
===================================================================
--- clang/test/Driver/riscv32-toolchain.c
+++ clang/test/Driver/riscv32-toolchain.c
@@ -4,7 +4,7 @@
 // CC1: clang{{.*}} "-cc1" "-triple" "riscv32"
 
 // RUN: %clang %s -### -no-canonical-prefixes \
-// RUN:   -target riscv32-unknown-elf \
+// RUN:   -target riscv32-unknown-elf --rtlib=platform \
 // 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
@@ -20,7 +20,7 @@
 // C-RV32-BAREMETAL-ILP32: "{{.*}}/Inputs/basic_riscv32_tree/lib/gcc/riscv32-unknown-elf/8.0.1{{/|\\\\}}crtend.o"
 
 // RUN: %clang %s -### -no-canonical-prefixes \
-// RUN:   -target riscv32-unknown-elf \
+// RUN:   -target riscv32-unknown-elf --rtlib=platform \
 // RUN:   --sysroot= \
 // RUN:   --gcc-toolchain=%S/Inputs/basic_riscv32_tree 2>&1 \
 // RUN:   | FileCheck -check-prefix=C-RV32-BAREMETAL-NOSYSROOT-ILP32 %s
@@ -35,7 +35,7 @@
 // C-RV32-BAREMETAL-NOSYSROOT-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 -stdlib=libstdc++ \
+// RUN:   -target riscv32-unknown-elf -stdlib=libstdc++ --rtlib=platform \
 // 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
@@ -52,7 +52,7 @@
 // CXX-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 -stdlib=libstdc++ \
+// RUN:   -target riscv32-unknown-elf -stdlib=libstdc++ --rtlib=platform \
 // RUN:   --sysroot= \
 // RUN:   --gcc-toolchain=%S/Inputs/basic_riscv32_tree 2>&1 \
 // RUN:   | FileCheck -check-prefix=CXX-RV32-BAREMETAL-NOSYSROOT-ILP32 %s
@@ -68,7 +68,7 @@
 // CXX-RV32-BAREMETAL-NOSYSROOT-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-unknown-linux-gnu -mabi=ilp32 \
+// RUN:   -target riscv32-unknown-linux-gnu --rtlib=platform -mabi=ilp32 \
 // 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
@@ -84,7 +84,7 @@
 // C-RV32-LINUX-MULTI-ILP32: "-L{{.*}}/Inputs/multilib_riscv_linux_sdk/sysroot/usr/lib32/ilp32"
 
 // RUN: %clang %s -### -no-canonical-prefixes -fuse-ld=ld \
-// RUN:   -target riscv32-unknown-linux-gnu -march=rv32imafd \
+// RUN:   -target riscv32-unknown-linux-gnu --rtlib=platform -march=rv32imafd \
 // 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-ILP32D %s
Index: clang/test/Driver/riscv64-toolchain-extra.c
===================================================================
--- clang/test/Driver/riscv64-toolchain-extra.c
+++ clang/test/Driver/riscv64-toolchain-extra.c
@@ -19,15 +19,15 @@
 // RUN: ln -s %S/Inputs/basic_riscv64_nogcc_tree/bin/riscv64-unknown-elf-ld %T/testroot-riscv64-baremetal-nogcc/bin/riscv64-unknown-elf-ld
 // RUN: ln -s %S/Inputs/basic_riscv64_nogcc_tree/riscv64-unknown-elf %T/testroot-riscv64-baremetal-nogcc/riscv64-unknown-elf
 // RUN: %T/testroot-riscv64-baremetal-nogcc/bin/clang %s -### -no-canonical-prefixes \
-// RUN:    -target riscv64-unknown-elf 2>&1 \
+// RUN:    -target riscv64-unknown-elf --rtlib=platform 2>&1 \
 // RUN:    | FileCheck -check-prefix=C-RV64-BAREMETAL-LP64-NOGCC %s
 
-// C-RV64-BAREMETAL-LP64-NOGCC: InstalledDir: [[DRIVERDIR:.*]]
 // C-RV64-BAREMETAL-LP64-NOGCC: "-fuse-init-array"
-// C-RV64-BAREMETAL-LP64-NOGCC: "-internal-isystem" "[[DRIVERDIR]]/../riscv64-unknown-elf/include"
-// C-RV64-BAREMETAL-LP64-NOGCC: "[[DRIVERDIR]]/riscv64-unknown-elf-ld"
-// C-RV64-BAREMETAL-LP64-NOGCC: "[[DRIVERDIR]]/../riscv64-unknown-elf/lib/crt0.o"
-// C-RV64-BAREMETAL-LP64-NOGCC: "[[DRIVERDIR]]/../riscv64-unknown-elf/lib/crtbegin.o"
-// C-RV64-BAREMETAL-LP64-NOGCC: "-L[[DRIVERDIR]]/../riscv64-unknown-elf/lib"
-// C-RV64-BAREMETAL-LP64-NOGCC: "--start-group" "-lc" "-lgloss" "--end-group" "-lgcc"
-// C-RV64-BAREMETAL-LP64-NOGCC: "[[DRIVERDIR]]/../riscv64-unknown-elf/lib/crtend.o"
+// C-RV64-BAREMETAL-LP64-NOGCC: "-internal-isystem" "{{.*}}Output/testroot-riscv64-baremetal-nogcc/bin/../riscv64-unknown-elf/include"
+// C-RV64-BAREMETAL-LP64-NOGCC: "{{.*}}Output/testroot-riscv64-baremetal-nogcc/bin/riscv64-unknown-elf-ld"
+// C-RV64-BAREMETAL-LP64-NOGCC: "{{.*}}Output/testroot-riscv64-baremetal-nogcc/bin/../riscv64-unknown-elf/lib/crt0.o"
+// C-RV64-BAREMETAL-LP64-NOGCC: "{{.*}}Output/testroot-riscv64-baremetal-nogcc/lib/clang/{{[0-9.]*}}/lib/clang_rt.crtbegin-riscv64.o"
+// C-RV64-BAREMETAL-LP64-NOGCC: "{{.*}}Output/testroot-riscv64-baremetal-nogcc/bin/../riscv64-unknown-elf/lib"
+// C-RV64-BAREMETAL-LP64-NOGCC: "--start-group" "-lc" "-lgloss" "--end-group"
+// C-RV64-BAREMETAL-LP64-NOGCC: "{{.*}}Output/testroot-riscv64-baremetal-nogcc/lib/clang/{{[0-9.]*}}/lib/libclang_rt.builtins-riscv64.a"
+// C-RV64-BAREMETAL-LP64-NOGCC: "{{.*}}Output/testroot-riscv64-baremetal-nogcc/lib/clang/{{[0-9.]*}}/lib/clang_rt.crtend-riscv64.o"
Index: clang/test/Driver/riscv64-toolchain.c
===================================================================
--- clang/test/Driver/riscv64-toolchain.c
+++ clang/test/Driver/riscv64-toolchain.c
@@ -4,7 +4,7 @@
 // CC1: clang{{.*}} "-cc1" "-triple" "riscv64"
 
 // RUN: %clang %s -### -no-canonical-prefixes \
-// RUN:   -target riscv64-unknown-elf \
+// RUN:   -target riscv64-unknown-elf --rtlib=platform \
 // RUN:   --gcc-toolchain=%S/Inputs/basic_riscv64_tree \
 // RUN:   --sysroot=%S/Inputs/basic_riscv64_tree/riscv64-unknown-elf 2>&1 \
 // RUN:   | FileCheck -check-prefix=C-RV64-BAREMETAL-LP64 %s
@@ -20,7 +20,7 @@
 // C-RV64-BAREMETAL-LP64: "{{.*}}/Inputs/basic_riscv64_tree/lib/gcc/riscv64-unknown-elf/8.0.1{{/|\\\\}}crtend.o"
 
 // RUN: %clang %s -### -no-canonical-prefixes \
-// RUN:   -target riscv64-unknown-elf \
+// RUN:   -target riscv64-unknown-elf --rtlib=platform \
 // RUN:   --sysroot= \
 // RUN:   --gcc-toolchain=%S/Inputs/basic_riscv64_tree 2>&1 \
 // RUN:   | FileCheck -check-prefix=C-RV64-BAREMETAL-NOSYSROOT-LP64 %s
@@ -35,7 +35,7 @@
 // C-RV64-BAREMETAL-NOSYSROOT-LP64: "{{.*}}/Inputs/basic_riscv64_tree/lib/gcc/riscv64-unknown-elf/8.0.1{{/|\\\\}}crtend.o"
 
 // RUN: %clangxx %s -### -no-canonical-prefixes \
-// RUN:   -target riscv64-unknown-elf -stdlib=libstdc++ \
+// RUN:   -target riscv64-unknown-elf -stdlib=libstdc++ --rtlib=platform \
 // RUN:   --gcc-toolchain=%S/Inputs/basic_riscv64_tree \
 // RUN:   --sysroot=%S/Inputs/basic_riscv64_tree/riscv64-unknown-elf 2>&1 \
 // RUN:   | FileCheck -check-prefix=CXX-RV64-BAREMETAL-LP64 %s
@@ -52,7 +52,7 @@
 // CXX-RV64-BAREMETAL-LP64: "{{.*}}/Inputs/basic_riscv64_tree/lib/gcc/riscv64-unknown-elf/8.0.1{{/|\\\\}}crtend.o"
 
 // RUN: %clangxx %s -### -no-canonical-prefixes \
-// RUN:   -target riscv64-unknown-elf -stdlib=libstdc++ \
+// RUN:   -target riscv64-unknown-elf -stdlib=libstdc++ --rtlib=platform \
 // RUN:   --sysroot= \
 // RUN:   --gcc-toolchain=%S/Inputs/basic_riscv64_tree 2>&1 \
 // RUN:   | FileCheck -check-prefix=CXX-RV64-BAREMETAL-NOSYSROOT-LP64 %s
@@ -68,7 +68,7 @@
 // CXX-RV64-BAREMETAL-NOSYSROOT-LP64: "{{.*}}/Inputs/basic_riscv64_tree/lib/gcc/riscv64-unknown-elf/8.0.1{{/|\\\\}}crtend.o"
 
 // RUN: %clang %s -### -no-canonical-prefixes -fuse-ld=ld \
-// RUN:   -target riscv64-unknown-linux-gnu -mabi=lp64 \
+// RUN:   -target riscv64-unknown-linux-gnu --rtlib=platform -mabi=lp64 \
 // 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-RV64-LINUX-MULTI-LP64 %s
@@ -84,7 +84,7 @@
 // C-RV64-LINUX-MULTI-LP64: "-L{{.*}}/Inputs/multilib_riscv_linux_sdk/sysroot/usr/lib64/lp64"
 
 // RUN: %clang %s -### -no-canonical-prefixes -fuse-ld=ld \
-// RUN:   -target riscv64-unknown-linux-gnu -march=rv64imafd \
+// RUN:   -target riscv64-unknown-linux-gnu --rtlib=platform -march=rv64imafd \
 // 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-RV64-LINUX-MULTI-LP64D %s