LoongArch64: Enable cmake cross-compilation

[XiWeiGu]

Refer to the following instructions：

cmake ../ -DCMAKE_TOOLCHAIN_FILE=toolchain.cmake 
                -DTARGET=LOONGSON3R5
                -DDYNAMIC_ARCH=1
                -DCMAKE_C_COMPILER=${CROSS_TARGET}-gcc 
                -DCMAKE_Fortran_COMPILER=${CROSS_TARGET}-gfortran 

Contents of toolchain.cmake:

set(CMAKE_SYSTEM_NAME Linux)
set(CMAKE_SYSTEM_PROCESSOR loongarch64)

[azuresky01]

@XiWeiGu @martin-frbg

This PR still uses old core names since it was issued before the Rename core PR #4900 was merged. I just did some tests and find that we should rename those old core names to new ones to avoid cmake errors. See below.

System details: Loongson 3A6000 CPU, Debian sid, kernel 6.11.0, gcc 14.2.0, gfortran 14.2.0, cmake 3.30.4.

cmake commands: CC=gcc FC=gfortran cmake -B build -DBUILD_TESTING=OFF -DUSE_OPENMP=1 -DDYNAMIC_ARCH=1 and then cmake --build build.

The result:

...
-- Compiling a 64-bit binary.
-- Reading vars from /home/loongson/test/build/kernel/loongarch64/KERNEL...
-- Reading vars from /home/loongson/test/build/kernel/loongarch64/KERNEL.LOONGSON2K1000...
CMake Error at cmake/utils.cmake:23 (file):
  file STRINGS file
  "/home/loongson/test/build/kernel/loongarch64/KERNEL.LOONGSON2K1000" cannot
  be read.
Call Stack (most recent call first):
  kernel/CMakeLists.txt:13 (ParseMakefileVars)
  kernel/CMakeLists.txt:1365 (build_core)


-- -- -- -- -- -- -- -- -- -- -- -- -- --
-- Targeting the LOONGSON3R5 architecture.
-- GEMM multithread threshold set to 4.
-- Multi-threading enabled with 8 threads.
-- Running getarch
-- GETARCH results:
CORE=LA464
LIBCORE=la464
NUM_CORES=8
MAKEFLAGS += -j 8

-- Compiling a 64-bit binary.
-- Reading vars from /home/loongson/test/build/kernel/loongarch64/KERNEL...
-- Reading vars from /home/loongson/test/build/kernel/loongarch64/KERNEL.LOONGSON3R5...
CMake Error at cmake/utils.cmake:23 (file):
  file STRINGS file
  "/home/loongson/test/build/kernel/loongarch64/KERNEL.LOONGSON3R5" cannot be
  read.
Call Stack (most recent call first):
  kernel/CMakeLists.txt:13 (ParseMakefileVars)
  kernel/CMakeLists.txt:1365 (build_core)


LOONGSONGENERIC
LOONGSON2K1000
LOONGSON3R5
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD - Success
-- Found Threads: TRUE
-- Generating openblas_config.h in include/openblas
-- Generating f77blas.h in include/openblas
-- Generating cblas.h in include/openblas
-- Copying LAPACKE header files to include/openblas
-- Configuring incomplete, errors occurred!

I then rename "LOONGSONGENERIC LOONGSON2K1000 LOONGSON3R5 " at line 98 in cmake/arch.cmake:

OpenBLAS/cmake/arch.cmake

Lines 97 to 99 in 624e9d1

	if (LOONGARCH64)
	set(DYNAMIC_CORE LOONGSONGENERIC LOONGSON2K1000 LOONGSON3R5)
	endif ()

to new core names "LA64_GENERIC LA264 LA464", and also rename old core names at lines 1352,1367,1383 in cmake/prebuild.cmake:

OpenBLAS/cmake/prebuild.cmake

Lines 1352 to 1383 in 624e9d1

	elseif ("${TCORE}" STREQUAL "LOONGSONGENERIC")
	file(APPEND ${TARGET_CONF_TEMP}
	"#define DTB_DEFAULT_ENTRIES 64\n")
	set(SGEMM_UNROLL_M 2)
	set(SGEMM_UNROLL_N 8)
	set(DGEMM_UNROLL_M 2)
	set(DGEMM_UNROLL_N 8)
	set(CGEMM_UNROLL_M 1)
	set(CGEMM_UNROLL_N 4)
	set(ZGEMM_UNROLL_M 1)
	set(ZGEMM_UNROLL_N 4)
	set(CGEMM3M_UNROLL_M 2)
	set(CGEMM3M_UNROLL_N 8)
	set(ZGEMM3M_UNROLL_M 2)
	set(ZGEMM3M_UNROLL_N 8)
	elseif ("${TCORE}" STREQUAL "LOONGSON2K1000")
	file(APPEND ${TARGET_CONF_TEMP}
	"#define DTB_DEFAULT_ENTRIES 64\n")
	set(HAVE_LSX 1)
	set(SGEMM_UNROLL_M 2)
	set(SGEMM_UNROLL_N 8)
	set(DGEMM_UNROLL_M 8)
	set(DGEMM_UNROLL_N 4)
	set(CGEMM_UNROLL_M 8)
	set(CGEMM_UNROLL_N 4)
	set(ZGEMM_UNROLL_M 4)
	set(ZGEMM_UNROLL_N 4)
	set(CGEMM3M_UNROLL_M 2)
	set(CGEMM3M_UNROLL_N 8)
	set(ZGEMM3M_UNROLL_M 8)
	set(ZGEMM3M_UNROLL_N 4)
	elseif ("${TCORE}" STREQUAL "LOONGSON3R5")

to "LA64_GENERIC", "LA264", and "LA464" correspondingly.

After these changes I observe that cmake errors for LOONGSON2K1000 and LOONGSON3R5 disappear. But a new cmake error appears:

...
CMake Error at cmake/utils.cmake:23 (file):
  file STRINGS file
  "/home/loongson/test/build/kernel/loongarch64/KERNEL.LA64_GENERIC" cannot be
  read.
Call Stack (most recent call first):
  kernel/CMakeLists.txt:13 (ParseMakefileVars)
  kernel/CMakeLists.txt:1365 (build_core)
...

since there is no file called "kernel/loongarch64/KERNEL.LA64_GENERIC":

Rename the file "kernel/loongarch64/KERNEL.LOONGSONGENERIC" to "kernel/loongarch64/KERNEL.LA64_GENERIC" the above cmake error disappears and the compilation works well.

[XiWeiGu]

Yes, the #4904 was revised based on the old core name, and a patch is still needed to fix the cmake build after the core name revision.

[martin-frbg]

My fault for merging these in the wrong order, sorry. I'll try to fix this later today