pengfei added a comment. In D155145#4556157 <https://reviews.llvm.org/D155145#4556157>, @anna wrote:
> In D155145#4554786 <https://reviews.llvm.org/D155145#4554786>, @anna wrote: > >>> Can you capture the values of EAX, EBX, ECX, and EDX after the two calls to >>> getX86CpuIDAndInfoEx that have 0x7 as the first argument? Maybe there's a >>> bug in CPUID on Sandy Bridge. >> >> Sure, on the original code before the patch you suggested right? >> The two calls are: >> >> bool HasLeaf7 = >> MaxLevel >= 7 && !getX86CpuIDAndInfoEx(0x7, 0x0, &EAX, &EBX, &ECX, >> &EDX); >> + llvm::errs() << "Before setting fsgsbase the value for EAX: " << EAX >> + << " EBX: " << EBX << " ECX: " << ECX << " EDX: " >> << EDX >> + << "\n"; >> >> Features["fsgsbase"] = HasLeaf7 && ((EBX >> 0) & 1); >> .... >> bool HasLeaf7Subleaf1 = >> MaxLevel >= 7 && !getX86CpuIDAndInfoEx(0x7, 0x1, &EAX, &EBX, &ECX, >> &EDX); >> + llvm::errs() << "Before setting sha512 the value for EAX: " << EAX >> + << " EBX: " << EBX << " ECX: " << ECX << " EDX: " >> << EDX >> + << "\n"; >> Features["sha512"] = HasLeaf7Subleaf1 && ((EAX >> 0) & 1); >> ... >> we set avxvnniint16 after this >> >> Takes a while to get a build on this machine, should have the output soon. > > @craig.topper here is the output: > > Before setting fsgsbase the value for EAX: 0 EBX: 0 ECX: 0 EDX: 2617246720 > // this is after the HasLeaf7 calculation > Before setting sha512 the value for EAX: 0 EBX: 0 ECX: 0 EDX: 2617246720 > // this is after the HasLeaf7Subleaf1 calculation > > So, with your patch `HasLeaf7Subleaf1` is 0 as EAX is 0. Pls let me know if > you need any additional diagnostics output (we actually lose access to the > machine on friday, since it is being retired!). > >> The documentation says that invalid subleaves of leaf 7 should return all >> 0s. So we thought it was safe to check the bits of sub leaf 1 even if eax >> from subleaf 0 doesn't say subleaf 1 is supported. > > This means the CPUID doesn't satisfy the documentation since EDX != 0 for > SubLeaf1? The identical EDX value looks dubious to me. Could you compile and run above code and paste the result here? Thanks! Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D155145/new/ https://reviews.llvm.org/D155145 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
