mm512_mask_dpbf16_ps fails on emulated Saphire Rapids

[mr-c]

https://github.com/simd-everywhere/simde/actions/runs/6627841500/job/18003657630#step:10:958

[mr-c]

And on a AMD EPYC 9454 (zen4) processor that has avx512_bf16 :-(

[mr-c]

mr-c@eee2676 has regenerated test cases that pass using real hardware, but now the non-native path fails.

I went through the implementation of simde_mm512_dpbf16_ps and the two masking variants in great detail, but I can't find anything wrong with their implementations versus the Intel documentation: https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_dpbf16_ps&ig_expand=2671

[mr-c]

The next step would be to take the failing test case and see exactly what is happening differently from the native hardware versus the emulated version, at the bit level.

[ajraymond]

@mr-c I wanted to try troubleshooting this one, but I cannot reproduce it. Is this still an issue?

$ CFLAGS="-mavx512bf16" CXXFLAGS="-mavx512bf16" meson setup ..
The Meson build system
Version: 1.7.0
Source dir: <...>/simde
Build dir: <...>/simde/build
Build type: native build
Project name: SIMDe
Project version: 0.8.4
C compiler for the host machine: ccache cc (gcc 14.2.0 "cc (Debian 14.2.0-19) 14.2.0")
C linker for the host machine: cc ld.bfd 2.44
C++ compiler for the host machine: ccache c++ (gcc 14.2.0 "c++ (Debian 14.2.0-19) 14.2.0")
C++ linker for the host machine: c++ ld.bfd 2.44
Host machine cpu family: x86_64
Host machine cpu: x86_64
Library m found: YES
Compiler for C supports arguments -fopenmp-simd: YES
Compiler for C++ supports arguments -fopenmp-simd: YES
Library m found: YES
Found pkg-config: YES (/usr/bin/pkg-config) 1.8.1
Build targets in project: 2010

Found ninja-1.12.1 at /usr/bin/ninja

$ sde64 --version
Intel(R) Software Development Emulator.  Version:  9.58.0 external (0)
Copyright (C) 2008-2025, Intel Corporation. All rights reserved.

$ sde64 -spr -- meson test --print-errorlogs x86/avx512/dpbf16/*
ninja: Entering directory `<...>/simde/build'
ninja: no work to do.
1/4 x86/avx512/dpbf16/native/c          OK              0.60s   9 subtests passed
2/4 x86/avx512/dpbf16/emul/c            OK              0.97s   9 subtests passed
3/4 x86/avx512/dpbf16/emul/cpp          OK              0.68s   9 subtests passed
4/4 x86/avx512/dpbf16/native/cpp        OK              0.60s   9 subtests passed

Ok:                 4
Expected Fail:      0
Fail:               0
Unexpected Pass:    0
Skipped:            0
Timeout:            0

Full log written to <...>/simde/build/meson-logs/testlog.txt

[mr-c]

@ajraymond the latest work on this is at #1276

Try testing with CFLAGS="-march=x86-64-v4 -mcx16 -mxsave -mpclmul -mfsgsbase -mrdrnd -mhle -mrdseed -maes -mclflushopt -mxsavec -mxsaves -msgx -mpku -msha -mrdpid -mavx512vpopcntdq -mavx512ifma -mavx512vbmi -mavx512vnni -mavx512vbmi2 -mavx512bitalg -mvpclmulqdq -mgfni -mvaes -mpconfig -mwbnoinvd -mclwb -mmovdiri -mmovdir64b -menqcmd -mcldemote -mptwrite -mwaitpkg -mserialize -mtsxldtrk -muintr -mavxvnni -mavx512fp16 -mavx512bf16" CXXFLAGS="-march=x86-64-v4 -mcx16 -mxsave -mpclmul -mfsgsbase -mrdrnd -mhle -mrdseed -maes -mclflushopt -mxsavec -mxsaves -msgx -mpku -msha -mrdpid -mavx512vpopcntdq -mavx512ifma -mavx512vbmi -mavx512vnni -mavx512vbmi2 -mavx512bitalg -mvpclmulqdq -mgfni -mvaes -mpconfig -mwbnoinvd -mclwb -mmovdiri -mmovdir64b -menqcmd -mcldemote -mptwrite -mwaitpkg -mserialize -mtsxldtrk -muintr -mavxvnni -mavx512fp16 -mavx512bf16" meson setup ..

(as from b150db2#diff-b803fcb7f17ed9235f1e5cb1fcd2f5d3b2838429d4368ae4c57ce4436577f03fR121 )