diff --git a/compiler-rt/cmake/Modules/CompilerRTDarwinUtils.cmake b/compiler-rt/cmake/Modules/CompilerRTDarwinUtils.cmake
--- a/compiler-rt/cmake/Modules/CompilerRTDarwinUtils.cmake
+++ b/compiler-rt/cmake/Modules/CompilerRTDarwinUtils.cmake
@@ -406,6 +406,8 @@
 
   append_list_if(COMPILER_RT_HAS_ASM_LSE -DHAS_ASM_LSE CFLAGS)
 
+  append_list_if(COMPILER_RT_HAS_BFLOAT16 -DCOMPILER_RT_HAS_BFLOAT16 CFLAGS)
+
   set(PROFILE_SOURCES ../profile/InstrProfiling.c
                       ../profile/InstrProfilingBuffer.c
                       ../profile/InstrProfilingPlatformDarwin.c
diff --git a/compiler-rt/cmake/builtin-config-ix.cmake b/compiler-rt/cmake/builtin-config-ix.cmake
--- a/compiler-rt/cmake/builtin-config-ix.cmake
+++ b/compiler-rt/cmake/builtin-config-ix.cmake
@@ -30,6 +30,14 @@
 "
 )
 
+builtin_check_c_compiler_source(COMPILER_RT_HAS_BFLOAT16
+"
+__bf16 foo(__bf16 x) {
+ return x;
+}
+"
+)
+
 builtin_check_c_compiler_source(COMPILER_RT_HAS_ASM_LSE
 "
 asm(\".arch armv8-a+lse\");
diff --git a/compiler-rt/lib/builtins/CMakeLists.txt b/compiler-rt/lib/builtins/CMakeLists.txt
--- a/compiler-rt/lib/builtins/CMakeLists.txt
+++ b/compiler-rt/lib/builtins/CMakeLists.txt
@@ -697,6 +697,8 @@
 
   append_list_if(COMPILER_RT_HAS_FLOAT16 -DCOMPILER_RT_HAS_FLOAT16 BUILTIN_CFLAGS)
 
+  append_list_if(COMPILER_RT_HAS_BFLOAT16 -DCOMPILER_RT_HAS_BFLOAT16 BUILTIN_CFLAGS)
+
   append_list_if(COMPILER_RT_HAS_STD_C11_FLAG -std=c11 BUILTIN_CFLAGS)
 
   # These flags would normally be added to CMAKE_C_FLAGS by the llvm
diff --git a/compiler-rt/lib/builtins/fp_trunc.h b/compiler-rt/lib/builtins/fp_trunc.h
--- a/compiler-rt/lib/builtins/fp_trunc.h
+++ b/compiler-rt/lib/builtins/fp_trunc.h
@@ -60,7 +60,7 @@
 static const int dstSigBits = 10;
 
 #elif defined DST_BFLOAT
-typedef uint16_t dst_t;
+typedef __bf16 dst_t;
 typedef uint16_t dst_rep_t;
 #define DST_REP_C UINT16_C
 static const int dstSigBits = 7;
diff --git a/compiler-rt/lib/builtins/truncsfbf2.c b/compiler-rt/lib/builtins/truncsfbf2.c
--- a/compiler-rt/lib/builtins/truncsfbf2.c
+++ b/compiler-rt/lib/builtins/truncsfbf2.c
@@ -6,8 +6,11 @@
 //
 //===----------------------------------------------------------------------===//
 
+#if defined(COMPILER_RT_HAS_BFLOAT16)
 #define SRC_SINGLE
 #define DST_BFLOAT
 #include "fp_trunc_impl.inc"
 
 COMPILER_RT_ABI dst_t __truncsfbf2(float a) { return __truncXfYf2__(a); }
+
+#endif