diff --git a/clang/docs/LanguageExtensions.rst b/clang/docs/LanguageExtensions.rst
--- a/clang/docs/LanguageExtensions.rst
+++ b/clang/docs/LanguageExtensions.rst
@@ -526,6 +526,7 @@
 * 64-bit ARM (AArch64)
 * AMDGPU
 * SPIR
+* RISC-V
 
 ``_Float16`` will be supported on more targets as they define ABIs for it.
 
@@ -535,13 +536,18 @@
 
 The ``__bf16`` type is only available when supported in hardware.
 
-``__fp16`` is a storage and interchange format only.  This means that values of
+``__fp16`` is a storage and interchange format only on most targets.  This means that values of
 ``__fp16`` are immediately promoted to (at least) ``float`` when used in arithmetic
 operations, so that e.g. the result of adding two ``__fp16`` values has type ``float``.
 The behavior of ``__fp16`` is specified by the ARM C Language Extensions (`ACLE <http://infocenter.arm.com/help/topic/com.arm.doc.ihi0053d/IHI0053D_acle_2_1.pdf>`_).
 Clang uses the ``binary16`` format from IEEE 754-2008 for ``__fp16``, not the ARM
 alternative format.
 
+On RISC-V, the evaluation format of ``__fp16`` will depend on the presence of
+the ``Zfh``  (half-precision) extension. ``__fp16`` will perform arithmetic
+without promotion when the Zfh extension is enabled, and promoted to float
+otherwise.
+
 ``_Float16`` is an interchange floating-point type.  This means that, just like arithmetic on
 ``float`` or ``double``, arithmetic on ``_Float16`` operands is formally performed in the
 ``_Float16`` type, so that e.g. the result of adding two ``_Float16`` values has type