AaronBallman wrote: > > > For SystemZ the correct value is 256. > > > > > > Thanks! Double-checking: for both constructive and destructive? > > Yes, for both. Every SystemZ model (supported by GCC/LLVM) has a L1 cache > line size of 256 bytes.
Excellent, thank you! > > > In general I agree it makes sense to look at the GCC implementation as a > > > source of reasonable values. Also, I think there probably should be no > > > generic default value at all - it there is no platform-specific value > > > known, it seems better to not define those values rather than define them > > > to some incorrect value ... > > > > > > On the one hand, I agree. But then libc++ will still have to pick default > > values to expose (these are `constexpr size_t` variables in libc++ rather > > than macros or `std::optional` values), so that just moves the problem > > elsewhere. Also, as best I can tell, that doesn't seem to be how GCC > > behaves (at least, from trying various GCC flavors on Compiler Explorer). > > Looks like GCC's libstdc++ will simply not provide those variables either if > GCC does not know those values for the current target: > > ``` > #ifdef __cpp_lib_hardware_interference_size // C++ >= 17 && > defined(gcc_dest_sz) > inline constexpr size_t hardware_destructive_interference_size = > __GCC_DESTRUCTIVE_SIZE; > inline constexpr size_t hardware_constructive_interference_size = > __GCC_CONSTRUCTIVE_SIZE; > #endif // __cpp_lib_hardware_interference_size > ``` @ldionne do you have a preference? I can always skip defining the predefined macros unless a target has opted into providing that information. https://github.com/llvm/llvm-project/pull/89446 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
