pengfei added a comment. In D131134#3715079 <https://reviews.llvm.org/D131134#3715079>, @craig.topper wrote:
> In D131134#3715062 <https://reviews.llvm.org/D131134#3715062>, @pengfei wrote: > >> In D131134#3715024 <https://reviews.llvm.org/D131134#3715024>, @pengfei >> wrote: >> >>> In D131134#3714860 <https://reviews.llvm.org/D131134#3714860>, >>> @craig.topper wrote: >>> >>>> Yes AMX is only supported in 64-bit mode but I doubt CPUID checks which >>>> mode the program is running in. >>> >>> I guess `HasAMXSave` is `false` on 32-bit mode >>> https://github.com/llvm/llvm-project/blob/main/llvm/lib/Support/Host.cpp#L1800. >>> But I don't have the environment to check it. >> >> I found it. The `XFEATURE_MASK_XTILE` in Kernel is the same as `HasAMXSave` >> in compiler: >> https://lwn.net/ml/linux-kernel/20210710130313.5072-20-chang.seok....@intel.com/ >> So these features bits are `true` only on 64-bit mode. > > Is it cleared when running a 32-bit binary on a 64-bit kernel? No, a 32-bit binary gets the same CR0 as 64-bit on a 64-bit kernel. Actually, it's compiler to get the CR0 rather than the binary it builds. It should be rare to run 32-bit compiler on 64-bit kernel. So you are right. No matter 32 or 64 bits compiler, when it builds a binary with `-m32` on 64-bit kernel with `-march=native`, it always sets AMX features. Maybe we should reset them to false when compile for 32-bit? Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D131134/new/ https://reviews.llvm.org/D131134 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
