diff --git a/compiler-rt/lib/builtins/CMakeLists.txt b/compiler-rt/lib/builtins/CMakeLists.txt
index 9a0a50ee7003f1..97a9e508d37a32 100644
--- a/compiler-rt/lib/builtins/CMakeLists.txt
+++ b/compiler-rt/lib/builtins/CMakeLists.txt
@@ -104,6 +104,7 @@ set(GENERIC_SOURCES
   divti3.c
   extendsfdf2.c
   extendhfsf2.c
+  extendhfxf2.c
   ffsdi2.c
   ffssi2.c
   ffsti2.c
diff --git a/compiler-rt/lib/builtins/extendhfxf2.c b/compiler-rt/lib/builtins/extendhfxf2.c
new file mode 100644
index 00000000000000..ce70c0eaf87118
--- /dev/null
+++ b/compiler-rt/lib/builtins/extendhfxf2.c
@@ -0,0 +1,18 @@
+//===-- lib/extendhfxf2.c - half -> long double conversion -------------*- C -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#define SRC_HALF
+#define DST_DOUBLE
+#include "fp_extend_impl.inc"
+
+// Use a forwarding definition and noinline to implement a poor man's alias,
+// as there isn't a good cross-platform way of defining one.
+// Long double are expected to be as precise as double.
+COMPILER_RT_ABI NOINLINE long double __extendhfxf2(src_t a) {
+  return (long double)__extendXfYf2__(a);
+}
diff --git a/compiler-rt/lib/builtins/macho_embedded/common.txt b/compiler-rt/lib/builtins/macho_embedded/common.txt
index 819109768f5298..fa99bc239e68f2 100644
--- a/compiler-rt/lib/builtins/macho_embedded/common.txt
+++ b/compiler-rt/lib/builtins/macho_embedded/common.txt
@@ -60,6 +60,7 @@ divsf3
 divsi3
 extendsfdf2
 extendhfsf2
+extendhfxf2
 ffssi2
 fixdfsi
 fixsfsi