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Firefox still treats SSE2 as its SIMD assumed-present baseline. Does GCC introduce multiversioned AVX functions on its own initiative?
by hsivonen 8y ago
Firefox still treats SSE2 as its SIMD assumed-present baseline. Does GCC introduce multiversioned AVX functions on its own initiative?
- nkurz 8y agoDoes GCC introduce multiversioned AVX functions on its own initiative? Yes, this seems like one reasonable approach. The current approach of compiling to a "least common denominator" and then updating this denominator every decade or so seems insufficient. Instead of interpreting the absence of a "-march=" flag to mean optimize for nothing, maybe it can mean that multiple optimizations are automatically compiled and the appropriate one is selected at runtime. Alternatively, maybe we need to move away from the idea of compiling a single binary that runs on all platforms, and encourage greater use of platform specific compilations.
- hubicka 8y agoYou need to explicitly ask for it via attribute, no automatic multiversioning is done (yet) and it would be more for -Ofast than usual -O2 builds I guess.