CMake set release flags properly #2138
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Depending on architecture and compiler, CMake may prepend flags into global flags. While this may work for general CMake projects, the use of arch/configure.defaults allows for specific control of flag options where additional unintended optimization flags may negatively impact compilation, performance, or even model validity.
amstokely
approved these changes
Dec 10, 2024
mgduda
approved these changes
Dec 20, 2024
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TYPE: bug fix
KEYWORDS: cmake, flags, optimization
SOURCE: internal
DESCRIPTION OF CHANGES:
Problem:
To feed initial flags into the cmake build, a toolchain file is used.
However, for particular build configurations, namely release and debug, despite the configuration being "Release" and "Debug", respectively, the corresponding
CMAKE_<LANG>_FLAGS_<CONFIG>_INIThas the configuration name capitalized.Additionally, these initial flags supplement the starting flags and do not override any inherited flags that CMake automatically appends. This can cause issues with certain compilers where subsequent flags that normally should supersede previously listed options are ignored. As an example, using nvfortran/pgi the following will cause forced optimization, which is not viable for some files within WRF :
https://forums.developer.nvidia.com/t/nvfortran-reducing-optimation-level-by-multiple-on-does-not-work/191825
https://forums.developer.nvidia.com/t/how-to-override-pgccs-optimization-flag/136275
Finally, certain files do not have optimization overridden even if it were to work correctly
Solution:
Ensure correct variable name in toolchain file to provide initial starting flags, and wipe CMake-injected release flags to avoid significant deviation from provided optimization flags. Add proper directory scope to files that need these reduced optimizations.
TESTS CONDUCTED:
RELEASE NOTE: Override CMake-injected optimization flags in favor of the flags set by the build system and provided stanza information.