See http://reviews.llvm.org/D14115

diff -u -r ../pristine/projects/compiler-rt/lib/builtins/clear_cache.c ./projects/compiler-rt/lib/builtins/clear_cache.c
--- ../pristine/projects/compiler-rt/lib/builtins/clear_cache.c	2015-03-11 18:06:53.000000000 -0400
+++ ./projects/compiler-rt/lib/builtins/clear_cache.c	2015-12-27 07:34:11.519445662 -0500
@@ -104,7 +104,7 @@
          const register int flags __asm("r2") = 0;
          const register int syscall_nr __asm("r7") = __ARM_NR_cacheflush;
         __asm __volatile("svc 0x0" : "=r"(start_reg)
-            : "r"(syscall_nr), "r"(start_reg), "r"(end_reg), "r"(flags) : "r0");
+            : "r"(syscall_nr), "r"(start_reg), "r"(end_reg), "r"(flags));
          if (start_reg != 0) {
              compilerrt_abort();
          }