On Fri, 15 Aug 2025 02:47:01 +1200 "[email protected]" <[email protected]> wrote:
> > In principle this sort of thing should be OK. But maybe __BMI1__ is > > defined and so the generic fallback isn't present, or maybe the CPUID > > check is incorrect for your CPU? I'll check the former when I have a > Locally there is no indication these simple checks are being performed. > This indicates __BMI1__ is incorrectly defined. > (Or perhaps there is no runtime detection going on and what we are > seeing is output from intrinsics compiled for a platform that supports > the popcnt instruction.) I have two 64-bit laptops, both running Debian unstable. On the newish one, which has an Intel(R) Core(TM) i7-5600U CPU, the mtxrun works fine (no "illegal instruction"). On the ancient one, which has an Intel(R) Core(TM)2 Duo CPU T9300, it fails right away. According to x86-64-level <https://github.com/HenrikBengtsson/x86-64-level>, it's a level-1 CPU. Here is its cpuinfo, in case it's useful: processor : 0 vendor_id : GenuineIntel cpu family : 6 model : 23 model name : Intel(R) Core(TM)2 Duo CPU T9300 @ 2.50GHz stepping : 6 microcode : 0x60f cpu MHz : 1197.124 cache size : 6144 KB physical id : 0 siblings : 2 core id : 0 cpu cores : 2 apicid : 0 initial apicid : 0 fpu : yes fpu_exception : yes cpuid level : 10 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ht tm pbe syscall nx lm constant_tsc arch_perfmon pebs bts rep_good nopl cpuid aperfmperf pni dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm sse4_1 lahf_lm pti tpr_shadow flexpriority vpid dtherm ida vnmi vmx flags : vnmi flexpriority tsc_offset vtpr vapic bugs : cpu_meltdown spectre_v1 spectre_v2 spec_store_bypass l1tf mds swapgs itlb_multihit mmio_unknown bogomips : 4988.01 clflush size : 64 cache_alignment : 64 address sizes : 36 bits physical, 48 bits virtual power management: processor : 1 vendor_id : GenuineIntel cpu family : 6 model : 23 model name : Intel(R) Core(TM)2 Duo CPU T9300 @ 2.50GHz stepping : 6 microcode : 0x60f cpu MHz : 1197.124 cache size : 6144 KB physical id : 0 siblings : 2 core id : 1 cpu cores : 2 apicid : 1 initial apicid : 1 fpu : yes fpu_exception : yes cpuid level : 10 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ht tm pbe syscall nx lm constant_tsc arch_perfmon pebs bts rep_good nopl cpuid aperfmperf pni dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm sse4_1 lahf_lm pti tpr_shadow flexpriority vpid dtherm ida vnmi vmx flags : vnmi flexpriority tsc_offset vtpr vapic bugs : cpu_meltdown spectre_v1 spectre_v2 spec_store_bypass l1tf mds swapgs itlb_multihit mmio_unknown bogomips : 4988.01 clflush size : 64 cache_alignment : 64 address sizes : 36 bits physical, 48 bits virtual power management: -- -Sanjoy
