Julia v1.8.0-rc1: support for znver3 (even though underlying LLVM13 supports is) is missing

[LebedevRI]

This is with the official https://julialang-s3.julialang.org/bin/linux/x64/1.8/julia-1.8.0-rc1-linux-x86_64.tar.gz

$ /opt/julia/bin/julia --cpu-target znver2 
               _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.8.0-rc1 (2022-05-27)
 _/ |\__'_|_|_|\__'_|  |  Official https://julialang.org/ release
|__/                   |

julia> exit()
$ /opt/julia/bin/julia --cpu-target native
               _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.8.0-rc1 (2022-05-27)
 _/ |\__'_|_|_|\__'_|  |  Official https://julialang.org/ release
|__/                   |

julia> exit()
$ /opt/julia/bin/julia --cpu-target znver3 
ERROR: Your CPU does not support the CX16 instruction, which is required by this version of Julia!  This is often due to running inside of a virtualized environment.  Please read https://docs.julialang.org/en/v1/devdocs/sysimg/ for more.
$ lscpu
Architecture:            x86_64
  CPU op-mode(s):        32-bit, 64-bit
  Address sizes:         48 bits physical, 48 bits virtual
  Byte Order:            Little Endian
CPU(s):                  32
  On-line CPU(s) list:   0-31
Vendor ID:               AuthenticAMD
  Model name:            AMD Ryzen 9 5950X 16-Core Processor
    CPU family:          25
    Model:               33
    Thread(s) per core:  2
    Core(s) per socket:  16
    Socket(s):           1
    Stepping:            0
    Frequency boost:     disabled
    CPU(s) scaling MHz:  67%
    CPU max MHz:         6017.8462
    CPU min MHz:         2200.0000
    BogoMIPS:            8050.09
    Flags:               fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm constant_tsc rep_good nopl nonstop_tsc cpuid extd_apicid aperfmperf rapl pni pclmulqdq monitor ssse
                         3 fma cx16 sse4_1 sse4_2 movbe popcnt aes xsave avx f16c rdrand lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs skinit wdt tce topoext perfctr_core perfctr_nb bpext perfctr_llc mwaitx cpb cat_l3 cdp_l3 hw_p
                         state ssbd mba ibrs ibpb stibp vmmcall fsgsbase bmi1 avx2 smep bmi2 erms invpcid cqm rdt_a rdseed adx smap clflushopt clwb sha_ni xsaveopt xsavec xgetbv1 xsaves cqm_llc cqm_occup_llc cqm_mbm_total cqm_mbm_local clzero irperf xsaveerptr rdpru wbn
                         oinvd arat npt lbrv svm_lock nrip_save tsc_scale vmcb_clean flushbyasid decodeassists pausefilter pfthreshold avic v_vmsave_vmload vgif v_spec_ctrl umip pku ospke vaes vpclmulqdq rdpid overflow_recov succor smca fsrm
Virtualization features: 
  Virtualization:        AMD-V
Caches (sum of all):     
  L1d:                   512 KiB (16 instances)
  L1i:                   512 KiB (16 instances)
  L2:                    8 MiB (16 instances)
  L3:                    64 MiB (2 instances)
NUMA:                    
  NUMA node(s):          1
  NUMA node0 CPU(s):     0-31
Vulnerabilities:         
  Itlb multihit:         Not affected
  L1tf:                  Not affected
  Mds:                   Not affected
  Meltdown:              Not affected
  Spec store bypass:     Mitigation; Speculative Store Bypass disabled via prctl
  Spectre v1:            Mitigation; usercopy/swapgs barriers and __user pointer sanitization
  Spectre v2:            Mitigation; Retpolines, IBPB conditional, IBRS_FW, STIBP always-on, RSB filling
  Srbds:                 Not affected
  Tsx async abort:       Not affected

[vtjnash]

This also means Julia doesn't recognize the name znver3 (we only list features up to znver2). Perhaps we should improve the error message to clarify that?

[LebedevRI]

This also means Julia doesn't recognize the name znver3 (we only list features up to znver2).

o_O
And yet,

 /opt/julia/bin/julia --cpu-target help
Available CPUs for this target:
<...>
  znver3         - Select the znver3 processor.

Since Julia v1.8 is LLVM13-based, which already had good Zen3 support,
i would really expect this to work.

Does this mean --cpu-target native also picks wrong CPU?

I'm actually surprised that the target CPU is not emitted in LLVM IR metadata, similarly to how clang/halide does it.

[gbaraldi]

One has to do something similar to #44696 but for zen 3.

[LebedevRI]

One has to do something similar to #44696 but for zen 3.

Okay, thank you for the hint, done: #45663
I've verified that (with the right JULIA_CPU_TARGET in Make.inc, to actually result in usable sysmage),
--cpu-target native / --cpu-target znver3 now work for me.

Thanks.