Merge pull request #4924 from XiWeiGu/la64_readme

LoongArch64: Update README.md

Author: martin-frbg

README.md

@@ -221,6 +221,26 @@ e.g.:
     HOSTCC=gcc HOSTFC=gfortran -j
   ```
 
+#### LOONGARCH64
+
+- **LA64_GENERIC**: Optimized Level-3, Level-2 and Level-1 BLAS with scalar instruction
+  ```sh
+  make HOSTCC=gcc TARGET=LA64_GENERIC CC=loongarch64-unknown-linux-gnu-gcc FC=loongarch64-unknown-linux-gnu-gfortran USE_SIMPLE_THREADED_LEVEL3=1
+  ```
+  The old-style TARGET=LOONGSONGENERIC is still supported
+
+- **LA264**: Optimized Level-3, Level-2 and Level-1 BLAS with LSX instruction
+  ```sh
+  make HOSTCC=gcc TARGET=LA264 CC=loongarch64-unknown-linux-gnu-gcc FC=loongarch64-unknown-linux-gnu-gfortran USE_SIMPLE_THREADED_LEVEL3=1
+  ```
+  The old-style TARGET=LOONGSON2K1000 is still supported
+
+- **LA464**: Optimized Level-3, Level-2 and Level-1 BLAS with LASX instruction
+  ```sh
+  make HOSTCC=gcc TARGET=LA464 CC=loongarch64-unknown-linux-gnu-gcc FC=loongarch64-unknown-linux-gnu-gfortran USE_SIMPLE_THREADED_LEVEL3=1
+  ```
+  The old-style TARGET=LOONGSON3R5 is still supported
+
 ### Support for multiple targets in a single library
 
 OpenBLAS can be built for multiple targets with runtime detection of the target cpu by specifiying `DYNAMIC_ARCH=1` in Makefile.rule, on the gmake command line or as `-DDYNAMIC_ARCH=TRUE` in cmake.
@@ -238,6 +258,8 @@ on **ZARCH** it comprises Z13 and Z14 as well as generic zarch support.
 
 On **riscv64**, DYNAMIC_ARCH enables support for riscv64_zvl128b and riscv64_zvl256b in addition to generic riscv64 support.  A compiler that supports RVV 1.0 is required to build OpenBLAS for riscv64 when DYNAMIC_ARCH is enabled.
 
+On **LoongArch64**, it comprises LA264 and LA464 as well as generic LoongArch64 support.
+
 The `TARGET` option can be used in conjunction with `DYNAMIC_ARCH=1` to specify which cpu model should be assumed for all the
 common code in the library, usually you will want to set this to the oldest model you expect to encounter.
 Please note that it is not possible to combine support for different architectures, so no combined 32 and 64 bit or x86_64 and arm64 in the same library.