build: Use try_compile for robust RVV toolchain detection #3905
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The previous RVV detection mechanism was unreliable as it only checked the architecture name string ("riscv64"). This could lead to build failures if the configured C/C++ toolchain, despite targeting riscv64, did not actually support the Vector ('V') extension or the required compiler flags.
This commit replaces the simple string check with a robust `try_compile` test. The new implementation verifies the toolchain's actual capabilities by:
- Compiling a test source file with the `-march=rv64gcv` flag.
- Ensuring the `__riscv_v` macro is defined by the compiler.
This approach correctly handles both native and cross-compilation scenarios, preventing build errors and providing clearer diagnostic messages. Additionally, it cleans up all temporary files used during the check.
Signed-off-by: lyd1992 <[email protected]>
Signed-off-by: ihb2032 <[email protected]>
Refactored the RISC-V backend CMake script to resolve a `g++` error during the main build, which was caused by duplicate compiler flags. - **Removed**: The logic that hard-coded `-march` and `-mabi` flags via `target_compile_options` is now gone. - **Kept**: The `try_compile` test is preserved, but its role is now only to **verify** that the flags passed globally by the user (via `CMAKE_C(XX)_FLAGS`) effectively enable RVV support. - **Reliance**: Compilation of RVV sources now depends entirely on the user's externally specified global build options, which prevents conflicts and parameter errors. - **Improved**: If `MNN_USE_RVV=ON` but the flag verification fails, the configuration now terminates immediately with a `FATAL_ERROR`, providing earlier and clearer feedback. Signed-off-by: lyd1992 <[email protected]> Signed-off-by: ihb2032 <[email protected]>
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Description
This PR significantly improves the reliability of the RISC-V Vector (RVV) feature detection in the CMake build system. It replaces the previous brittle architecture name check with a robust
try_compile-based toolchain validation.Motivation and Context
The existing method for enabling RVV optimizations relied solely on checking if the target architecture string matched
riscv64. This approach is fragile and can cause the build to fail in several common scenarios:The goal of this PR is to prevent these build failures by verifying the compiler's capabilities directly, ensuring a smoother and more reliable experience for developers targeting RISC-V.
Key Changes
if (... MATCHES "riscv64")logic has been replaced with a more intelligenttry_compileblock.-march=rv64gcvflag and defines the__riscv_vmacro, which is the standard-compliant way to verify vector support.STATUSandWARNINGmessages are now provided to inform the user about the result of the toolchain check.CMakeFiles/CMakeTmp) used bytry_compileis now removed after the check, ensuring a clean build directory.How Has This Been Tested?
I have tested this new logic on my development environment:
This change should make the build process much more robust for all developers working with the RISC-V backend.