rustc: native on znver2 CPU picks znver1 for target-cpu

[jpds]

I have a Ryzen 7 PRO 4750U on my laptop which gcc sees as march=znver2:

$ gcc -march=native -Q --help=target
The following options are target specific:
  -m128bit-long-double                  [enabled]
  -m16                                  [disabled]
  -m32                                  [disabled]
  -m3dnow                               [disabled]
  -m3dnowa                              [disabled]
  -m64                                  [enabled]
  -m80387                               [enabled]
  -m8bit-idiv                           [disabled]
  -m96bit-long-double                   [disabled]
  -mabi=                                sysv
  -mabm                                 [enabled]
  -maccumulate-outgoing-args            [disabled]
  -maddress-mode=                       long
  -madx                                 [enabled]
  -maes                                 [enabled]
  -malign-data=                         compat
  -malign-double                        [disabled]
  -malign-functions=                    0
  -malign-jumps=                        0
  -malign-loops=                        0
  -malign-stringops                     [enabled]
  -mandroid                             [disabled]
  -march=                               znver2
...

However, rustc sees this CPU as march=znver1:

$ rustc --print target-cpus
Available CPUs for this target:
    native         - Select the CPU of the current host (currently znver1).

Meta

rustc --version --verbose:

rustc 1.53.0 (53cb7b09b 2021-06-17)
binary: rustc
commit-hash: 53cb7b09b00cbea8754ffb78e7e3cb521cb8af4b
commit-date: 2021-06-17
host: x86_64-unknown-linux-gnu
release: 1.53.0
LLVM version: 12.0.1

[jpds]

Appears to be LLVM related:

$ echo | clang -E - -march=native -###
clang version 12.0.0
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/lib/llvm/12/bin
 (in-process)
 "/usr/lib/llvm/12/bin/clang-12" "-cc1" "-triple" "x86_64-pc-linux-gnu" "-E" "-disable-free" "-disable-llvm-verifier" "-discard-value-names" "-main-file-name" "-" "-mrelocation-model" "static" "-mframe-pointer=all" "-fmath-errno" "-fno-rounding-math" "-mconstructor-aliases" "-munwind-tables" "-target-cpu" "znver1" "-target-feature" "+sse2" "-target-feature" "-tsxldtrk" "-target-feature" "+cx16" "-target-feature" "+sahf" "-target-feature" "-tbm" "-target-feature" "-avx512ifma" "-target-feature" "+sha" "-target-feature" "-gfni" "-target-feature" "-fma4" "-target-feature" "-vpclmulqdq" "-target-feature" "+prfchw" "-target-feature" "+bmi2" "-target-feature" "-cldemote" "-target-feature" "+fsgsbase" "-target-feature" "-ptwrite" "-target-feature" "-amx-tile" "-target-feature" "-uintr" "-target-feature" "+popcnt" "-target-feature" "-widekl" "-target-feature" "+aes" "-target-feature" "-avx512bitalg" "-target-feature" "-movdiri" "-target-feature" "+xsaves" "-target-feature" "-avx512er" "-target-feature" "-avxvnni" "-target-feature" "-avx512vnni" "-target-feature" "-amx-bf16" "-target-feature" "-avx512vpopcntdq" "-target-feature" "-pconfig" "-target-feature" "+clwb" "-target-feature" "-avx512f" "-target-feature" "+xsavec" "-target-feature" "+clzero" "-target-feature" "-pku" "-target-feature" "+mmx" "-target-feature" "-lwp" "-target-feature" "+rdpid" "-target-feature" "-xop" "-target-feature" "+rdseed" "-target-feature" "-waitpkg" "-target-feature" "-kl" "-target-feature" "-movdir64b" "-target-feature" "+sse4a" "-target-feature" "-avx512bw" "-target-feature" "+clflushopt" "-target-feature" "+xsave" "-target-feature" "-avx512vbmi2" "-target-feature" "+64bit" "-target-feature" "-avx512vl" "-target-feature" "-serialize" "-target-feature" "-hreset" "-target-feature" "-invpcid" "-target-feature" "-avx512cd" "-target-feature" "+avx" "-target-feature" "-vaes" "-target-feature" "-avx512bf16" "-target-feature" "+cx8" "-target-feature" "+fma" "-target-feature" "-rtm" "-target-feature" "+bmi" "-target-feature" "-enqcmd" "-target-feature" "+rdrnd" "-target-feature" "+mwaitx" "-target-feature" "+sse4.1" "-target-feature" "+sse4.2" "-target-feature" "+avx2" "-target-feature" "+fxsr" "-target-feature" "+wbnoinvd" "-target-feature" "+sse" "-target-feature" "+lzcnt" "-target-feature" "+pclmul" "-target-feature" "-prefetchwt1" "-target-feature" "+f16c" "-target-feature" "+ssse3" "-target-feature" "-sgx" "-target-feature" "-shstk" "-target-feature" "+cmov" "-target-feature" "-avx512vbmi" "-target-feature" "-amx-int8" "-target-feature" "+movbe" "-target-feature" "-avx512vp2intersect" "-target-feature" "+xsaveopt" "-target-feature" "-avx512dq" "-target-feature" "+adx" "-target-feature" "-avx512pf" "-target-feature" "+sse3" "-fno-split-dwarf-inlining" "-debugger-tuning=gdb" "-resource-dir" "/usr/lib/llvm/12/bin/../../../../lib/clang/12.0.0" "-internal-isystem" "/usr/local/include" "-internal-isystem" "/usr/lib/llvm/12/bin/../../../../lib/clang/12.0.0/include" "-internal-externc-isystem" "/include" "-internal-externc-isystem" "/usr/include" "-fdebug-compilation-dir" "/home/jpds" "-ferror-limit" "19" "-fgnuc-version=4.2.1" "-fcolor-diagnostics" "-o" "-" "-x" "c" "-"

[ehuss]

I believe a patch to support detection of Renior is already up at https://reviews.llvm.org/D96220.

[KaneGreen]

AMD Custom APU 0405, which is the CPU used on Steam Deck, has the same issue.
This CPU should be Zen 2, but the rustc considers it as Zen 1 (znver1)

rustc 1.68.2 (9eb3afe9e 2023-03-27)
binary: rustc
commit-hash: 9eb3afe9ebe9c7d2b84b71002d44f4a0edac95e0
commit-date: 2023-03-27
host: x86_64-unknown-linux-gnu
release: 1.68.2
LLVM version: 15.0.6

[truboxl]

I believe this is fixed in llvm/llvm-project@a15532d which needs at least LLVM 18.1 (tested on Steam Deck OLED)

(deck@steamdeck ~)$ . "$HOME/.cargo/env"
(deck@steamdeck ~)$ rustc --version --verbose
rustc 1.80.0 (051478957 2024-07-21)
binary: rustc
commit-hash: 051478957371ee0084a7c0913941d2a8c4757bb9
commit-date: 2024-07-21
host: x86_64-unknown-linux-gnu
release: 1.80.0
LLVM version: 18.1.7
(deck@steamdeck ~)$ rustc --print target-cpus | grep native
    native                  - Select the CPU of the current host (currently znver2).
(deck@steamdeck ~)$ lscpu
Architecture:            x86_64
  CPU op-mode(s):        32-bit, 64-bit
  Address sizes:         44 bits physical, 48 bits virtual
  Byte Order:            Little Endian
CPU(s):                  8
  On-line CPU(s) list:   0-7
Vendor ID:               AuthenticAMD
  Model name:            AMD Custom APU 0932
    CPU family:          23
    Model:               145
    Thread(s) per core:  2
    Core(s) per socket:  4
    Socket(s):           1
    Stepping:            0
    Frequency boost:     enabled
    CPU(s) scaling MHz:  48%
    CPU max MHz:         3500.0000
    CPU min MHz:         1700.0000
    BogoMIPS:            5602.13
    Flags:               fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse ss
                         e2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm constant_tsc rep_good nopl nonstop_tsc cpuid
                          extd_apicid aperfmperf rapl pni pclmulqdq monitor ssse3 fma cx16 sse4_1 sse4_2 movbe popcnt ae
                         s xsave avx f16c rdrand lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowpr
                         efetch osvw ibs skinit wdt tce topoext perfctr_core perfctr_nb bpext perfctr_llc mwaitx cpb cat
                         _l3 cdp_l3 hw_pstate ssbd mba ibrs ibpb stibp vmmcall fsgsbase bmi1 avx2 smep bmi2 cqm rdt_a rd
                         seed adx smap clflushopt clwb sha_ni xsaveopt xsavec xgetbv1 cqm_llc cqm_occup_llc cqm_mbm_tota
                         l cqm_mbm_local clzero irperf xsaveerptr rdpru wbnoinvd cppc arat npt lbrv svm_lock nrip_save t
                         sc_scale vmcb_clean flushbyasid decodeassists pausefilter pfthreshold avic v_vmsave_vmload vgif
                          v_spec_ctrl umip rdpid overflow_recov succor smca sev sev_es
Virtualization features:
  Virtualization:        AMD-V
Caches (sum of all):
  L1d:                   128 KiB (4 instances)
  L1i:                   128 KiB (4 instances)
  L2:                    2 MiB (4 instances)
  L3:                    4 MiB (1 instance)
NUMA:
  NUMA node(s):          1
  NUMA node0 CPU(s):     0-7
Vulnerabilities:
  Gather data sampling:  Not affected
  Itlb multihit:         Not affected
  L1tf:                  Not affected
  Mds:                   Not affected
  Meltdown:              Not affected
  Mmio stale data:       Not affected
  Retbleed:              Mitigation; untrained return thunk; SMT enabled with STIBP protection
  Spec rstack overflow:  Mitigation; safe RET
  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, STIBP always-on, RSB filling, PBRSB-eIBRS Not affecte
                         d
  Srbds:                 Not affected
  Tsx async abort:       Not affected
(deck@steamdeck ~)$ uname -a
Linux steamdeck 6.1.52-valve16-1-neptune-61 #1 SMP PREEMPT_DYNAMIC Tue, 06 Feb 2024 00:51:49 +0000 x86_64 GNU/Linux