[docs] Add llvm & clang release notes for LoongArch

Reviewed By: rengolin

Differential Revision: https://reviews.llvm.org/D141750

Author: SixWeining

clang/docs/ReleaseNotes.rst

@@ -802,6 +802,19 @@ CUDA Support in Clang
 - Clang now supports CUDA SDK up to 11.8
 - Added support for targeting sm_{87,89,90} GPUs.
 
+LoongArch Support in Clang
+--------------------------
+- Clang now supports LoongArch. Along with the backend, clang is able to build a
+  large corpus of Linux applications. Test-suite 100% pass.
+- Support basic option ``-march=`` which is used to select the target
+  architecture, i.e. the basic set of ISA modules to be enabled. Possible values
+  are ``loongarch64`` and ``la464``.
+- Support basic option ``-mabi=`` which is used to select the base ABI type.
+  Possible values are ``lp64d``, ``lp64f``, ``lp64s``, ``ilp32d``, ``ilp32f``
+  and ``ilp32s``.
+- Support extended options: ``-msoft-float``, ``-msingle-float``, ``-mdouble-float`` and ``mfpu=``.
+  See `LoongArch toolchain conventions <https://loongson.github.io/LoongArch-Documentation/LoongArch-toolchain-conventions-EN.html>`_.
+
 RISC-V Support in Clang
 -----------------------
 - ``sifive-7-rv32`` and ``sifive-7-rv64`` are no longer supported for ``-mcpu``.

llvm/docs/ReleaseNotes.rst

@@ -47,6 +47,8 @@ Non-comprehensive list of changes in this release
    is not a constant in coroutines. This decision may cause unnecessary
    performance regressions and we plan to fix it in later versions.
 
+*  The LoongArch target is promoted to "official" (see below for more details).
+
 * ...
 
 Update on required toolchains to build LLVM
@@ -154,6 +156,19 @@ Changes to the Hexagon Backend
 
 * ...
 
+Changes to the LoongArch Backend
+--------------------------------
+
+* The LoongArch target is no longer "experimental"! It's now built by default,
+  rather than needing to be enabled with ``LLVM_EXPERIMENTAL_TARGETS_TO_BUILD``.
+
+* The backend has full codegen support for the base (both integer and
+  floating-point) instruction set and it conforms to psABI v2. Testing has been
+  performed with Linux, including native compilation of a large corpus of Linux
+  applications.
+
+* Support GHC calling convention.
+
 Changes to the MIPS Backend
 ---------------------------
 
@@ -279,9 +294,13 @@ Changes to the LLVM tools
 Changes to LLDB
 ---------------------------------
 
+* Initial support for debugging Linux LoongArch 64-bit binaries.
+
 Changes to Sanitizers
 ---------------------
 
+* Many Sanitizers (asan, fuzzer, lsan, safestack, scudo, tsan, ubsan) have
+  support for Linux LoongArch 64-bit variant. Some of them may be rudimentary.
 
 Other Changes
 -------------