diff --git a/compiler-rt/cmake/Modules/CompilerRTUtils.cmake b/compiler-rt/cmake/Modules/CompilerRTUtils.cmake
index 9f79a9b920db..f567202faa61 100644
--- a/compiler-rt/cmake/Modules/CompilerRTUtils.cmake
+++ b/compiler-rt/cmake/Modules/CompilerRTUtils.cmake
@@ -168,6 +168,7 @@ macro(detect_target_arch)
   check_symbol_exists(__mips64__ "" __MIPS64)
   check_symbol_exists(__powerpc64__ "" __PPC64)
   check_symbol_exists(__powerpc64le__ "" __PPC64LE)
+  check_symbol_exists(__riscv "" __RISCV)
   check_symbol_exists(__s390x__ "" __S390X)
   check_symbol_exists(__wasm32__ "" __WEBASSEMBLY32)
   check_symbol_exists(__wasm64__ "" __WEBASSEMBLY64)
@@ -187,6 +188,14 @@ macro(detect_target_arch)
     add_default_target_arch(powerpc64)
   elseif(__PPC64LE)
     add_default_target_arch(powerpc64le)
+  elseif(__RISCV)
+    if(CMAKE_SIZEOF_VOID_P EQUAL "4")
+      add_default_target_arch(riscv32)
+    elseif(CMAKE_SIZEOF_VOID_P EQUAL "8")
+      add_default_target_arch(riscv64)
+    else()
+      message(FATAL_ERROR "Unsupport XLEN for RISC-V")
+    endif()
   elseif(__S390X)
     add_default_target_arch(s390x)
   elseif(__WEBASSEMBLY32)
diff --git a/compiler-rt/cmake/base-config-ix.cmake b/compiler-rt/cmake/base-config-ix.cmake
index b208f0852408..beb05f6c898d 100644
--- a/compiler-rt/cmake/base-config-ix.cmake
+++ b/compiler-rt/cmake/base-config-ix.cmake
@@ -186,6 +186,10 @@ macro(test_targets)
       test_target_arch(aarch32 "" "-march=armv8-a")
     elseif("${COMPILER_RT_DEFAULT_TARGET_ARCH}" MATCHES "aarch64")
       test_target_arch(aarch64 "" "-march=armv8-a")
+    elseif("${COMPILER_RT_DEFAULT_TARGET_ARCH}" MATCHES "riscv32")
+      test_target_arch(riscv32 "" "")
+    elseif("${COMPILER_RT_DEFAULT_TARGET_ARCH}" MATCHES "riscv64")
+      test_target_arch(riscv64 "" "")
     elseif("${COMPILER_RT_DEFAULT_TARGET_ARCH}" MATCHES "wasm32")
       test_target_arch(wasm32 "" "--target=wasm32-unknown-unknown")
     elseif("${COMPILER_RT_DEFAULT_TARGET_ARCH}" MATCHES "wasm64")
diff --git a/compiler-rt/cmake/builtin-config-ix.cmake b/compiler-rt/cmake/builtin-config-ix.cmake
index bdb2529b5ee2..eda5f46414e3 100644
--- a/compiler-rt/cmake/builtin-config-ix.cmake
+++ b/compiler-rt/cmake/builtin-config-ix.cmake
@@ -30,6 +30,8 @@ set(X86_64 x86_64)
 set(MIPS32 mips mipsel)
 set(MIPS64 mips64 mips64el)
 set(PPC64 powerpc64 powerpc64le)
+set(RISCV32 riscv32)
+set(RISCV64 riscv64)
 set(WASM32 wasm32)
 set(WASM64 wasm64)
 
@@ -40,7 +42,7 @@ if(APPLE)
 endif()
 
 set(ALL_BUILTIN_SUPPORTED_ARCH ${X86} ${X86_64} ${ARM32} ${ARM64}
-    ${MIPS32} ${MIPS64} ${PPC64} ${WASM32} ${WASM64})
+    ${MIPS32} ${MIPS64} ${PPC64} ${RISCV32} ${RISCV64} ${WASM32} ${WASM64})
 
 include(CompilerRTUtils)
 include(CompilerRTDarwinUtils)
diff --git a/compiler-rt/cmake/config-ix.cmake b/compiler-rt/cmake/config-ix.cmake
index 9f24b9d50b37..1e04da7bb74d 100644
--- a/compiler-rt/cmake/config-ix.cmake
+++ b/compiler-rt/cmake/config-ix.cmake
@@ -179,6 +179,8 @@ set(X86_64 x86_64)
 set(MIPS32 mips mipsel)
 set(MIPS64 mips64 mips64el)
 set(PPC64 powerpc64 powerpc64le)
+set(RISCV32 riscv32)
+set(RISCV64 riscv64)
 set(S390X s390x)
 set(WASM32 wasm32)
 set(WASM64 wasm64)
diff --git a/compiler-rt/lib/builtins/CMakeLists.txt b/compiler-rt/lib/builtins/CMakeLists.txt
index 13158b903789..6c48a404a181 100644
--- a/compiler-rt/lib/builtins/CMakeLists.txt
+++ b/compiler-rt/lib/builtins/CMakeLists.txt
@@ -480,6 +480,12 @@ set(powerpc64_SOURCES
   ${GENERIC_SOURCES})
 set(powerpc64le_SOURCES ${powerpc64_SOURCES})
 
+set(riscv_SOURCES ${GENERIC_SOURCES} ${GENERIC_TF_SOURCES})
+set(riscv32_SOURCES
+  riscv/mulsi3.S
+  ${riscv_SOURCES})
+set(riscv64_SOURCES ${riscv_SOURCES})
+
 set(wasm32_SOURCES
   ${GENERIC_TF_SOURCES}
   ${GENERIC_SOURCES})
diff --git a/compiler-rt/lib/builtins/int_types.h b/compiler-rt/lib/builtins/int_types.h
index a92238c5b730..f53f343d35d5 100644
--- a/compiler-rt/lib/builtins/int_types.h
+++ b/compiler-rt/lib/builtins/int_types.h
@@ -60,7 +60,7 @@ typedef union
     }s;
 } udwords;
 
-#if (defined(__LP64__) || defined(__wasm__) || defined(__mips64))
+#if (defined(__LP64__) || defined(__wasm__) || defined(__mips64)) || defined(__riscv)
 #define CRT_HAS_128BIT
 #endif
 
diff --git a/compiler-rt/lib/builtins/riscv/mulsi3.S b/compiler-rt/lib/builtins/riscv/mulsi3.S
new file mode 100644
index 000000000000..a58d237040b6
--- /dev/null
+++ b/compiler-rt/lib/builtins/riscv/mulsi3.S
@@ -0,0 +1,28 @@
+//===--- mulsi3.S - Integer multiplication routines routines ---===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#if !defined(__riscv_mul) && __riscv_xlen == 32
+	.text
+	.align 2
+
+	.globl __mulsi3
+	.type  __mulsi3, @function
+__mulsi3:
+	mv     a2, a0
+	mv     a0, zero
+.L1:
+	andi   a3, a1, 1
+	beqz   a3, .L2
+	add    a0, a0, a2
+.L2:
+	srli   a1, a1, 1
+	slli   a2, a2, 1
+	bnez   a1, .L1
+	ret
+#endif
diff --git a/compiler-rt/test/builtins/CMakeLists.txt b/compiler-rt/test/builtins/CMakeLists.txt
index cabf767223cc..a9199ebf10df 100644
--- a/compiler-rt/test/builtins/CMakeLists.txt
+++ b/compiler-rt/test/builtins/CMakeLists.txt
@@ -26,6 +26,11 @@ foreach(arch ${BUILTIN_SUPPORTED_ARCH})
     string(REPLACE ";" " " BUILTINS_TEST_TARGET_CFLAGS "${BUILTINS_TEST_TARGET_CFLAGS}")
   endif()
 
+  if (${arch} STREQUAL "riscv32")
+    list(APPEND BUILTINS_TEST_TARGET_CFLAGS -fforce-enable-int128)
+    string(REPLACE ";" " " BUILTINS_TEST_TARGET_CFLAGS "${BUILTINS_TEST_TARGET_CFLAGS}")
+  endif()
+
   string(TOUPPER ${arch} ARCH_UPPER_CASE)
   set(CONFIG_NAME ${ARCH_UPPER_CASE}${OS_NAME}Config)
   configure_lit_site_cfg(
diff --git a/compiler-rt/test/builtins/Unit/riscv/mulsi3_test.c b/compiler-rt/test/builtins/Unit/riscv/mulsi3_test.c
new file mode 100644
index 000000000000..9033004f11dd
--- /dev/null
+++ b/compiler-rt/test/builtins/Unit/riscv/mulsi3_test.c
@@ -0,0 +1,119 @@
+// REQUIRES-ANY: riscv32-target-arch
+// RUN: %clang_builtins %s %librt -o %t && %run %t
+//===-- mulsi3_test.c - Test __mulsi3 -------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file tests __mulsi3 for the compiler_rt library.
+//
+//===----------------------------------------------------------------------===//
+
+#include "int_lib.h"
+#include <stdio.h>
+#include <limits.h>
+
+#if !defined(__riscv_mul) && __riscv_xlen == 32
+// Based on mulsi3_test.c
+
+COMPILER_RT_ABI si_int __mulsi3(si_int a, si_int b);
+
+int test__mulsi3(si_int a, si_int b, si_int expected)
+{
+    si_int x = __mulsi3(a, b);
+    if (x != expected)
+        printf("error in __mulsi3: %d * %d = %d, expected %d\n",
+               a, b, __mulsi3(a, b), expected);
+    return x != expected;
+}
+#endif
+
+int main()
+{
+#if !defined(__riscv_mul) && __riscv_xlen == 32
+    if (test__mulsi3(0, 0, 0))
+        return 1;
+    if (test__mulsi3(0, 1, 0))
+        return 1;
+    if (test__mulsi3(1, 0, 0))
+        return 1;
+    if (test__mulsi3(0, 10, 0))
+        return 1;
+    if (test__mulsi3(10, 0, 0))
+        return 1;
+    if (test__mulsi3(0, INT_MAX, 0))
+        return 1;
+    if (test__mulsi3(INT_MAX, 0, 0))
+        return 1;
+
+    if (test__mulsi3(0, -1, 0))
+        return 1;
+    if (test__mulsi3(-1, 0, 0))
+        return 1;
+    if (test__mulsi3(0, -10, 0))
+        return 1;
+    if (test__mulsi3(-10, 0, 0))
+        return 1;
+    if (test__mulsi3(0, INT_MIN, 0))
+        return 1;
+    if (test__mulsi3(INT_MIN, 0, 0))
+        return 1;
+
+    if (test__mulsi3(1, 1, 1))
+        return 1;
+    if (test__mulsi3(1, 10, 10))
+        return 1;
+    if (test__mulsi3(10, 1, 10))
+        return 1;
+    if (test__mulsi3(1, INT_MAX, INT_MAX))
+        return 1;
+    if (test__mulsi3(INT_MAX, 1, INT_MAX))
+        return 1;
+
+    if (test__mulsi3(1, -1, -1))
+        return 1;
+    if (test__mulsi3(1, -10, -10))
+        return 1;
+    if (test__mulsi3(-10, 1, -10))
+        return 1;
+    if (test__mulsi3(1, INT_MIN, INT_MIN))
+        return 1;
+    if (test__mulsi3(INT_MIN, 1, INT_MIN))
+        return 1;
+
+    if (test__mulsi3(46340, 46340, 2147395600))
+        return 1;
+    if (test__mulsi3(-46340, 46340, -2147395600))
+        return 1;
+    if (test__mulsi3(46340, -46340, -2147395600))
+        return 1;
+    if (test__mulsi3(-46340, -46340, 2147395600))
+        return 1;
+
+    if (test__mulsi3(4194303, 8192, 34359730176))
+        return 1;
+    if (test__mulsi3(-4194303, 8192, -34359730176))
+        return 1;
+    if (test__mulsi3(4194303, -8192, -34359730176))
+        return 1;
+    if (test__mulsi3(-4194303, -8192, 34359730176))
+        return 1;
+
+    if (test__mulsi3(8192, 4194303, 34359730176))
+        return 1;
+    if (test__mulsi3(-8192, 4194303, -34359730176))
+        return 1;
+    if (test__mulsi3(8192, -4194303, -34359730176))
+        return 1;
+    if (test__mulsi3(-8192, -4194303, 34359730176))
+        return 1;
+#else
+    printf("skipped\n");
+#endif
+
+    return 0;
+}