Index: head/contrib/compiler-rt/lib/builtins/int_lib.h
===================================================================
--- head/contrib/compiler-rt/lib/builtins/int_lib.h
+++ head/contrib/compiler-rt/lib/builtins/int_lib.h
@@ -74,11 +74,13 @@
  * global header to prevent other C files from making the detour
  * through __c?zdi2() as well.
  *
- * This problem has only been observed on FreeBSD for sparc64 and
- * mips64 with GCC 4.2.1.
+ * This problem has been observed on FreeBSD for sparc64 and
+ * mips64 with GCC 4.2.1, and for riscv with GCC 5.2.0.
+ * Presumably it's any version of GCC, and targeting an arch that
+ * does not have dedicated bit counting instructions.
  */
 #if defined(__FreeBSD__) && (defined(__sparc64__) || \
-    defined(__mips_n64) || defined(__mips_o64))
+    defined(__mips_n64) || defined(__mips_o64) || defined(__riscv__))
 si_int __clzsi2(si_int);
 si_int __ctzsi2(si_int);
 #define	__builtin_clz __clzsi2
Index: head/contrib/compiler-rt/lib/sanitizer_common/sanitizer_platform_limits_posix.h
===================================================================
--- head/contrib/compiler-rt/lib/sanitizer_common/sanitizer_platform_limits_posix.h
+++ head/contrib/compiler-rt/lib/sanitizer_common/sanitizer_platform_limits_posix.h
@@ -76,6 +76,10 @@
 #elif defined(__powerpc64__)
   const unsigned struct_kernel_stat_sz = 144;
   const unsigned struct_kernel_stat64_sz = 104;
+#elif defined(__riscv__)
+  /* RISCVTODO: check that these values are correct */
+  const unsigned struct_kernel_stat_sz = 128;
+  const unsigned struct_kernel_stat64_sz = 128;
 #elif defined(__mips__)
   #if SANITIZER_WORDSIZE == 64
   const unsigned struct_kernel_stat_sz = 216;
@@ -103,7 +107,7 @@
 
 #if SANITIZER_LINUX || SANITIZER_FREEBSD
 
-#if defined(__powerpc64__)
+#if defined(__powerpc64__) || defined(__riscv__)
   const unsigned struct___old_kernel_stat_sz = 0;
 #else
   const unsigned struct___old_kernel_stat_sz = 32;
@@ -481,7 +485,7 @@
   typedef long __sanitizer___kernel_off_t;
 #endif
 
-#if defined(__powerpc__) || defined(__mips__)
+#if defined(__powerpc__) || defined(__mips__) || defined(__riscv__)
   typedef unsigned int __sanitizer___kernel_old_uid_t;
   typedef unsigned int __sanitizer___kernel_old_gid_t;
 #else