diff --git a/clang/lib/Driver/ToolChains/RISCVToolchain.h b/clang/lib/Driver/ToolChains/RISCVToolchain.h
--- a/clang/lib/Driver/ToolChains/RISCVToolchain.h
+++ b/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;
diff --git a/clang/lib/Driver/ToolChains/RISCVToolchain.cpp b/clang/lib/Driver/ToolChains/RISCVToolchain.cpp
--- a/clang/lib/Driver/ToolChains/RISCVToolchain.cpp
+++ b/clang/lib/Driver/ToolChains/RISCVToolchain.cpp
@@ -61,6 +61,16 @@
   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,
@@ -138,9 +148,22 @@
   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);
@@ -161,11 +184,11 @@
     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());
diff --git a/clang/test/Driver/riscv32-toolchain-extra.c b/clang/test/Driver/riscv32-toolchain-extra.c
--- a/clang/test/Driver/riscv32-toolchain-extra.c
+++ b/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"
diff --git a/clang/test/Driver/riscv32-toolchain.c b/clang/test/Driver/riscv32-toolchain.c
--- a/clang/test/Driver/riscv32-toolchain.c
+++ b/clang/test/Driver/riscv32-toolchain.c
@@ -3,8 +3,11 @@
 // RUN: %clang %s -### -no-canonical-prefixes -target riscv32 2>&1 | FileCheck -check-prefix=CC1 %s
 // CC1: clang{{.*}} "-cc1" "-triple" "riscv32"
 
+// In the below tests, --rtlib=platform is used so that the driver ignores
+// the configure-time CLANG_DEFAULT_RTLIB option when choosing the runtime lib
+
 // 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 +23,7 @@
 // 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 +38,7 @@
 // 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 +55,7 @@
 // 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 +71,7 @@
 // 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 +87,7 @@
 // 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
@@ -100,7 +103,7 @@
 // C-RV32-LINUX-MULTI-ILP32D: "-L{{.*}}/Inputs/multilib_riscv_linux_sdk/sysroot/usr/lib32/ilp32d"
 
 // RUN: %clang %s -### -no-canonical-prefixes -fuse-ld=ld \
-// RUN:   -target riscv32-unknown-elf --sysroot= \
+// RUN:   -target riscv32-unknown-elf --rtlib=platform --sysroot= \
 // RUN:   --gcc-toolchain=%S/Inputs/multilib_riscv_elf_sdk 2>&1 \
 // RUN:   | FileCheck -check-prefix=C-RV32I-BAREMETAL-MULTI-ILP32 %s
 
@@ -115,7 +118,8 @@
 // C-RV32I-BAREMETAL-MULTI-ILP32: "{{.*}}/Inputs/multilib_riscv_elf_sdk/lib/gcc/riscv64-unknown-elf/8.2.0/rv32imac/ilp32{{/|\\\\}}crtend.o"
 
 // RUN: %clang %s -### -no-canonical-prefixes -fuse-ld=ld \
-// RUN:   -target riscv32-unknown-elf --sysroot= -march=rv32im -mabi=ilp32\
+// RUN:   -target riscv32-unknown-elf --rtlib=platform --sysroot= \
+// RUN:   -march=rv32im -mabi=ilp32\
 // RUN:   --gcc-toolchain=%S/Inputs/multilib_riscv_elf_sdk 2>&1 \
 // RUN:   | FileCheck -check-prefix=C-RV32IM-BAREMETAL-MULTI-ILP32 %s
 
@@ -130,7 +134,8 @@
 // C-RV32IM-BAREMETAL-MULTI-ILP32: "{{.*}}/Inputs/multilib_riscv_elf_sdk/lib/gcc/riscv64-unknown-elf/8.2.0/rv32im/ilp32{{/|\\\\}}crtend.o"
 
 // RUN: %clang %s -### -no-canonical-prefixes -fuse-ld=ld \
-// RUN:   -target riscv32-unknown-elf --sysroot= -march=rv32iac -mabi=ilp32\
+// RUN:   -target riscv32-unknown-elf --rtlib=platform --sysroot= \
+// RUN:   -march=rv32iac -mabi=ilp32\
 // RUN:   --gcc-toolchain=%S/Inputs/multilib_riscv_elf_sdk 2>&1 \
 // RUN:   | FileCheck -check-prefix=C-RV32IAC-BAREMETAL-MULTI-ILP32 %s
 
@@ -145,7 +150,8 @@
 // C-RV32IAC-BAREMETAL-MULTI-ILP32: "{{.*}}/Inputs/multilib_riscv_elf_sdk/lib/gcc/riscv64-unknown-elf/8.2.0/rv32iac/ilp32{{/|\\\\}}crtend.o"
 
 // RUN: %clang %s -### -no-canonical-prefixes -fuse-ld=ld \
-// RUN:   -target riscv32-unknown-elf --sysroot= -march=rv32imac -mabi=ilp32\
+// RUN:   -target riscv32-unknown-elf --rtlib=platform --sysroot= \
+// RUN:   -march=rv32imac -mabi=ilp32\
 // RUN:   --gcc-toolchain=%S/Inputs/multilib_riscv_elf_sdk 2>&1 \
 // RUN:   | FileCheck -check-prefix=C-RV32IMAC-BAREMETAL-MULTI-ILP32 %s
 
@@ -160,7 +166,8 @@
 // C-RV32IMAC-BAREMETAL-MULTI-ILP32: "{{.*}}/Inputs/multilib_riscv_elf_sdk/lib/gcc/riscv64-unknown-elf/8.2.0/rv32imac/ilp32{{/|\\\\}}crtend.o"
 
 // RUN: %clang %s -### -no-canonical-prefixes -fuse-ld=ld \
-// RUN:   -target riscv32-unknown-elf --sysroot= -march=rv32imafc -mabi=ilp32f \
+// RUN:   -target riscv32-unknown-elf --rtlib=platform --sysroot= \
+// RUN:   -march=rv32imafc -mabi=ilp32f \
 // RUN:   --gcc-toolchain=%S/Inputs/multilib_riscv_elf_sdk 2>&1 \
 // RUN:   | FileCheck -check-prefix=C-RV32IMAFC-BAREMETAL-MULTI-ILP32F %s
 
@@ -174,6 +181,23 @@
 // C-RV32IMAFC-BAREMETAL-MULTI-ILP32F: "--start-group" "-lc" "-lgloss" "--end-group" "-lgcc"
 // C-RV32IMAFC-BAREMETAL-MULTI-ILP32F: "{{.*}}/Inputs/multilib_riscv_elf_sdk/lib/gcc/riscv64-unknown-elf/8.2.0/rv32imafc/ilp32f{{/|\\\\}}crtend.o"
 
+// Check that --rtlib can be used to override the used runtime library
+// RUN: %clang %s -### -no-canonical-prefixes \
+// RUN:   -target riscv32-unknown-elf --rtlib=libgcc 2>&1 \
+// RUN:   | FileCheck -check-prefix=C-RV32-RTLIB-LIBGCC-ILP32 %s
+// C-RV32-RTLIB-LIBGCC-ILP32: "{{.*}}crt0.o"
+// C-RV32-RTLIB-LIBGCC-ILP32: "{{.*}}crtbegin.o"
+// C-RV32-RTLIB-LIBGCC-ILP32: "--start-group" "-lc" "-lgloss" "--end-group" "-lgcc"
+// C-RV32-RTLIB-LIBGCC-ILP32: "{{.*}}crtend.o"
+
+// RUN: %clang %s -### -no-canonical-prefixes \
+// RUN:   -target riscv32-unknown-elf --rtlib=compiler-rt 2>&1 \
+// RUN:   | FileCheck -check-prefix=C-RV32-RTLIB-COMPILERRT-ILP32 %s
+// C-RV32-RTLIB-COMPILERRT-ILP32: "{{.*}}crt0.o"
+// C-RV32-RTLIB-COMPILERRT-ILP32: "{{.*}}clang_rt.crtbegin-riscv32.o"
+// C-RV32-RTLIB-COMPILERRT-ILP32: "--start-group" "-lc" "-lgloss" "--end-group" "{{.*}}libclang_rt.builtins-riscv32.a"
+// C-RV32-RTLIB-COMPILERRT-ILP32: "{{.*}}clang_rt.crtend-riscv32.o"
+
 // RUN: %clang -target riscv32 %s -emit-llvm -S -o - | FileCheck %s
 
 typedef __builtin_va_list va_list;
diff --git a/clang/test/Driver/riscv64-toolchain-extra.c b/clang/test/Driver/riscv64-toolchain-extra.c
--- a/clang/test/Driver/riscv64-toolchain-extra.c
+++ b/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"
diff --git a/clang/test/Driver/riscv64-toolchain.c b/clang/test/Driver/riscv64-toolchain.c
--- a/clang/test/Driver/riscv64-toolchain.c
+++ b/clang/test/Driver/riscv64-toolchain.c
@@ -3,8 +3,11 @@
 // RUN: %clang %s -### -no-canonical-prefixes -target riscv64 2>&1 | FileCheck -check-prefix=CC1 %s
 // CC1: clang{{.*}} "-cc1" "-triple" "riscv64"
 
+// In the below tests, --rtlib=platform is used so that the driver ignores
+// the configure-time CLANG_DEFAULT_RTLIB option when choosing the runtime lib
+
 // 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 +23,7 @@
 // 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 +38,7 @@
 // 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 +55,7 @@
 // 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 +71,7 @@
 // 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 +87,7 @@
 // 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
@@ -100,7 +103,8 @@
 // C-RV64-LINUX-MULTI-LP64D: "-L{{.*}}/Inputs/multilib_riscv_linux_sdk/sysroot/usr/lib64/lp64d"
 
 // RUN: %clang %s -### -no-canonical-prefixes -fuse-ld=ld \
-// RUN:   -target riscv64-unknown-elf --sysroot= -march=rv64imac -mabi=lp64\
+// RUN:   -target riscv64-unknown-elf --rtlib=platform --sysroot= \
+// RUN:   -march=rv64imac -mabi=lp64\
 // RUN:   --gcc-toolchain=%S/Inputs/multilib_riscv_elf_sdk 2>&1 \
 // RUN:   | FileCheck -check-prefix=C-RV64IMAC-BAREMETAL-MULTI-LP64 %s
 
@@ -115,7 +119,8 @@
 // C-RV64IMAC-BAREMETAL-MULTI-LP64: "{{.*}}/Inputs/multilib_riscv_elf_sdk/lib/gcc/riscv64-unknown-elf/8.2.0/rv64imac/lp64{{/|\\\\}}crtend.o"
 
 // RUN: %clang %s -### -no-canonical-prefixes -fuse-ld=ld \
-// RUN:   -target riscv64-unknown-elf --sysroot= -march=rv64imafdc -mabi=lp64d \
+// RUN:   -target riscv64-unknown-elf --rtlib=platform --sysroot= \
+// RUN:   -march=rv64imafdc -mabi=lp64d \
 // RUN:   --gcc-toolchain=%S/Inputs/multilib_riscv_elf_sdk 2>&1 \
 // RUN:   | FileCheck -check-prefix=C-RV64IMAFDC-BAREMETAL-MULTI-ILP64D %s
 
@@ -129,6 +134,23 @@
 // C-RV64IMAFDC-BAREMETAL-MULTI-ILP64D: "--start-group" "-lc" "-lgloss" "--end-group" "-lgcc"
 // C-RV64IMAFDC-BAREMETAL-MULTI-ILP64D: "{{.*}}/Inputs/multilib_riscv_elf_sdk/lib/gcc/riscv64-unknown-elf/8.2.0/rv64imafdc/lp64d{{/|\\\\}}crtend.o"
 
+// Check that --rtlib can be used to override the used runtime library
+// RUN: %clang %s -### -no-canonical-prefixes \
+// RUN:   -target riscv64-unknown-elf --rtlib=libgcc 2>&1 \
+// RUN:   | FileCheck -check-prefix=C-RV64-RTLIB-LIBGCC-LP64 %s
+// C-RV64-RTLIB-LIBGCC-LP64: "{{.*}}crt0.o"
+// C-RV64-RTLIB-LIBGCC-LP64: "{{.*}}crtbegin.o"
+// C-RV64-RTLIB-LIBGCC-LP64: "--start-group" "-lc" "-lgloss" "--end-group" "-lgcc"
+// C-RV64-RTLIB-LIBGCC-LP64: "{{.*}}crtend.o"
+
+// RUN: %clang %s -### -no-canonical-prefixes \
+// RUN:   -target riscv64-unknown-elf --rtlib=compiler-rt 2>&1 \
+// RUN:   | FileCheck -check-prefix=C-RV64-RTLIB-COMPILERRT-LP64 %s
+// C-RV64-RTLIB-COMPILERRT-LP64: "{{.*}}crt0.o"
+// C-RV64-RTLIB-COMPILERRT-LP64: "{{.*}}clang_rt.crtbegin-riscv64.o"
+// C-RV64-RTLIB-COMPILERRT-LP64: "--start-group" "-lc" "-lgloss" "--end-group" "{{.*}}libclang_rt.builtins-riscv64.a"
+// C-RV64-RTLIB-COMPILERRT-LP64: "{{.*}}clang_rt.crtend-riscv64.o"
+
 // RUN: %clang -target riscv64 %s -emit-llvm -S -o - | FileCheck %s
 
 typedef __builtin_va_list va_list;