RISC-V/AArch64: disable CPU features detection #25901
This PR is the first step in fixing current issues with NEON/RVV, FP16, BF16 and other CPU features on AArch64 and RISC-V platforms.
On AArch64 and RISC-V platforms we usually have the platform set by default in the toolchain when we compile it or in the cmake toolchain file or in CMAKE_CXX_FLAGS by user. Then, there are two ways to set platform options: a) "-mcpu=<some_cpu>" ; b) "-march=<arch description>" (e.g. "rv64gcv"). Furthermore, there are no similar "levels" of optimizations as for x86_64, instead we have features (RVV, FP16,...) which can be enabled or disabled. So, for example, if a user has "rv64gc" set by the toolchain and we want to enable RVV. Then we need to somehow parse their current feature set and append "v" (vector optimizations) to this string. This task is quite hard and the whole procedure is prone to errors.
I propose to use "CPU_BASELINE=DETECT" by default on AArch64 and RISC-V platforms. And somehow remove other features or make them read-only/detect-only, so that OpenCV wouldn't add any extra "-march" flags to the default configuration. We would rely only on the flags provided by the compiler and cmake toolchain file. We can have some predefined configurations in our cmake toolchain files.
Changes made by this PR:
- `CMakeLists.txt`:
- use `CMAKE_CROSSCOMPILING` instead of `CMAKE_TOOLCHAIN_FILE` to detect cross-compilation. This might be useful in cases of native compilation with a toolchain file
- removed obsolete variables `ENABLE_NEON` and `ENABLE_VFPV3`, the first one have been turned ON by default on AArch64 platform which caused setting `CPU_BASELINE=NEON`
- raise minimum cmake version allowed to 3.7 to allow using `CMAKE_CXX_FLAGS_INIT` in toolchain files
- added separate files with arch flags for native compilation on AArch64 and RISC-V, these files will be used in our toolchain files and in regular cmake
- use `DETECT` as default value for `CPU_BASELINE` also allow `NATIVE`, warn user if other values were used (only for AArch64 and RISC-V)
- for each feature listed in `CPU_DISPATCH` check if corresponding `CPU_${opt}_FLAGS_ON` has been provided, warn user if it is empty (only for AArch64 and RISC-V)
- use `CPU_BASELINE_DISABLE` variable to actually turn off macros responsible for corresponding features even if they are enabled by compiler
- removed Aarch64 feature merge procedure (it didn't support `-mcpu` and built-in `-march`)
- reworked AArch64 and two RISC-V cmake toolchain files (does not affect Android/OSX/iOS/Win):
- use `CMAKE_CXX_FLAGS_INIT` to set compiler flags
- use variables `ENABLE_BF16`, `ENABLE_DOTPROD`, `ENABLE_RVV`, `ENABLE_FP16` to control `-march`
- AArch64: removed other compiler and linker flags
- `-fdata-sections`, `-fsigned-char`, `-Wl,--no-undefined`, `-Wl,--gc-sections` - already set by OpenCV
- `-Wa,--noexecstack`, `-Wl,-z,noexecstack`, `-Wl,-z,relro`, `-Wl,-z,now` - can be enabled by OpenCV via `ENABLE_HARDENING`
- `-Wno-psabi` - this option used to disable some warnings on older ARM platforms, shouldn't harm
- ARM: removed same common flags as for AArch64, but left `-mthumb` and `--fix-cortex-a8`, `-z nocopyreloc`
FAILED: lib/libopencv_core.so.13.0
...
ld: error: undefined symbol: __cxa_atexit
Do not try to use --no-undefined on OpenBSD. OpenBSD does not link
shared libraries with libc and thus linkage with --no-undefined is
expected to fail.
* Added NEON support in builds for Windows on ARM
* Fixed `HAVE_CPU_NEON_SUPPORT` display broken during compiler test
* Fixed a build error prior to Visual Studio 2022
* [build][option] Introduce `OPENCV_DISABLE_THREAD_SUPPORT` option.
The option forces the library to build without thread support.
* update handling of OPENCV_DISABLE_THREAD_SUPPORT
- reduce amount of #if conditions
* [to squash] cmake: apply mode vars in toolchains too
Co-authored-by: Alexander Alekhin <alexander.a.alekhin@gmail.com>
* add -Wno-psabi when using GCC 6
* add -Wundef for CUDA 10
* add -Wdeprecated-declarations when using GCC 7
* add -Wstrict-aliasing and -Wtautological-compare for GCC 7
* replace cudaThreadSynchronize with cudaDeviceSynchronize
- builds with CMAKE_SKIP_RPATH=ON should properly find project .so files from <build>/lib directory
- $ORIGIN doesn't work properly in cross-compilation mode
- allow cmake to check sanity of vsx aligned ld/st
- force universal intrinsics v_load_aligned/v_store_aligned
to failback to unaligned ld/st if cmake runtime vsx aligned test fail
* Enabled -Wnarrowing warning
* Fixed type narrowing issues
* Cast python constants
* Use long long for python constants
* Use int for python constants with fallback to long
* Update cv2.cpp
Avoids passing -Wall, which will enable literally every warning in
Clang. Avoids passing -ffunction-sections etc to clang-cl, which each
generate warnings.
* trying to fix the custom AVX2 builder test failures (false alarms)
* fixed compile error with CPU_BASELINE=AVX2 on x86; raised tolerance thresholds in a couple of tests
* fixed compile error with CPU_BASELINE=AVX2 on x86; raised tolerance thresholds in a couple of tests
* fixed compile error with CPU_BASELINE=AVX2 on x86; raised tolerance thresholds in a couple of tests
* seemingly disabled false alarm warning in surf.cpp; increased tolerance thresholds in the tests for SolvePnP and in DNN/ENet
- Recommended compiler checks:
- GCC: CV_GCC
- Clang: CV_CLANG
- fixed problem with CMAKE_CXX_COMPILER_ID=Clang/AppleClang mess on MacOSX
Details: cmake --help-policy CMP0025
- do not declare Clang as GCC compiler
Maksim Shabunin
Brad Smith
Letu Ren
ashadrina
不鱼儿
Alexander Smorkalov
Andrey Senyaev
Alexander Alekhin
Tatsuro Shibamura
Dale Phurrough
Francesco Petrogalli
Peter Würtz
Alexander Alekhin
Tomoaki Teshima
Sayed Adel
Reid Kleckner
Vadim Pisarevsky
Kuang Fangjun
luz.paz