swr: Refactor checks for compiler feature flags
Encapsulate the test for which flags are needed to get a compiler to support certain features. Along with this, give various options to try for AVX and AVX2 support. Ideally we want to use specific instruction set feature flags, like -mavx2 for instance instead of -march=haswell, but the flags required for certain compilers are different. This allows, for AVX2 for instance, GCC to use -mavx2 -mfma -mbmi2 -mf16c while the Intel compiler which doesn't support those flags can fall back to using -march=core-avx2. This addresses a bug where the Intel compiler will silently ignore the AVX2 instruction feature flags and then potentially fail to build. v2: Pass preprocessor-check argument as true-state instead of false-state for clarity. v3: Reduce AVX2 define test to just __AVX2__. Additional defines suchas __FMA__, __BMI2__, and __F16C__ appear to be inconsistently defined w.r.t thier availability. v4: Fix C++11 flags being added globally and add more logic to swr_require_cxx_feature_flags Cc: <mesa-stable@lists.freedesktop.org> Reviewed-by:Tim Rowley <timothy.o.rowley@intel.com> Tested-by:
Tim Rowley <timothy.o.rowley@Intel.com> Signed-off-by:
Chuck Atkins <chuck.atkins@kitware.com>