digitalmars.D.bugs - [Issue 20838] New: on modern (x86_64) CPUs, dmd emit cmpxchg8b
- d-bugmail puremagic.com (60/60) May 17 2020 https://issues.dlang.org/show_bug.cgi?id=20838
https://issues.dlang.org/show_bug.cgi?id=20838 Issue ID: 20838 Summary: on modern (x86_64) CPUs, dmd emit cmpxchg8b instead of CMPXCHG16B Product: D Version: D2 Hardware: x86_64 OS: Linux Status: NEW Severity: blocker Priority: P1 Component: dmd Assignee: nobody puremagic.com Reporter: mingwu gmail.com Created attachment 1788 --> https://issues.dlang.org/attachment.cgi?id=1788&action=edit on modern (x86_64) CPUs, dmd emit cmpxchg8b instead of CMPXCHG16B $ cat c.d -------------------------------------------------------------------------------- import std.stdio; import core.atomic; struct N { N* prev; N* next; } shared(N) n; void main() { cas(&n, n, n); writeln(size_t.sizeof*2, N.sizeof); // output 16 16 } -------------------------------------------------------------------------------- $ dmd -m64 c.d $ /usr/bin/obj2asm c.o > c.o.asm $ grep -i xchg c.o.asm cmpxchg8b [R8] However $ grep flags /proc/cpuinfo | head -1 | grep 16 -------------------------------------------------------------------------------- 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 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc art arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc cpuid aperfmperf tsc_known_freq pni pclmulqdq dtes64 monitor ds_cpl vmx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch cpuid_fault epb invpcid_single pti ssbd ibrs ibpb stibp tpr_shadow vnmi flexpriority ept vpid fsgsbase tsc_adjust bmi1 avx2 smep bmi2 erms invpcid mpx rdseed adx smap clflushopt intel_pt xsaveopt xsavec xgetbv1 xsaves dtherm ida arat pln pts hwp hwp_notify hwp_act_window hwp_epp md_clear flush_l1d -------------------------------------------------------------------------------- in particular, the flag cx16 is there: CX16 * Supports CMPXCHG16B instruction https://docs.microsoft.com/en-us/sysinternals/downloads/coreinfo $ uname -a x86_64 x86_64 x86_64 GNU/Linux $ dmd --version DMD64 D Compiler v2.092.0 Copyright (C) 1999-2020 by The D Language Foundation, All Rights Reserved written by Walter Bright --
May 17 2020