Yocto project is transitioning x86_64 builds to build for x86-64-v3 (e.g. enabling AVX, AVX2, BMI1, BMI2, F16C, FMA, LZCNT, MOVBE, XSAVE). Presumably, something in the instructions enabled by that target (AVX, AVX2, BMI1, BMI2, F16C, FMA, LZCNT, MOVBE, XSAVE) distorts the floating point results slightly in libm math functions: memcheck/tests/vcpu_fnfns.stdout.diff ************ --- vcpu_fnfns.stdout.exp 2018-03-09 12:34:56.000000000 +0000 +++ vcpu_fnfns.stdout.out 2022-12-25 14:43:29.195000000 +0000 @@ -305,7 +305,7 @@ cosF( -3.0170e-01) = +9.5483e-01 cosF( -2.0180e-01) = +9.7971e-01 cosF( -1.0190e-01) = +9.9481e-01 - cosF( -1.9999e-03) = +1.0000e-00 + cosF( -1.9999e-03) = +1.0000e+00 cosF( +9.7900e-02) = +9.9521e-01 cosF( +1.9780e-01) = +9.8050e-01 cosF( +2.9770e-01) = +9.5601e-01 @@ -536,7 +536,7 @@ logD(+9.9999999900000e-02) = -2.3025850939940e+00 logD(+1.9999999980000e-01) = -1.6094379134341e+00 logD(+2.9999999970000e-01) = -1.2039728053259e+00 - logD(+3.9999999960000e-01) = -9.1629073287415e-01 + logD(+3.9999999960000e-01) = -9.1629073287416e-01 logD(+4.9999999950000e-01) = -6.9314718155995e-01 logD(+5.9999999940000e-01) = -5.1082562476599e-01 logD(+6.9999999930000e-01) = -3.5667494493873e-01 More detailed information about the feature level targets in gcc is here: https://www.phoronix.com/news/GCC-11-x86-64-Feature-Levels
Confirmed. But also seems to be fixed with the patch from https://bugs.kde.org/show_bug.cgi?id=481127
commit a5693c1203c3a26443af13182a8082c2e9152f6c Author: Mark Wielaard <mark@klomp.org> Date: Sat Apr 13 14:33:19 2024 +0200 amd64: Implement VFMADD213 for Iop_MAddF32 and Iop_MAddF64 Speed up F32 and F64 FMA on amd64. Add priv/host_amd64_maddf.c implementing h_amd64_calc_MAddF32_fma4 and h_amd64_calc_MAddF64_fma4 to be used instead of the generic variants h_generic_calc_MAddF32 and h_generic_calc_MAddF64 when host has VEX_HWCAPS_AMD64_FMA4. Add fma3 and fma4 detection m_machine.c (machine_get_hwcaps). This patch also fixes the memcheck/tests/vcpu_fnfns and none/tests/amd64/fma testcases when run on a x86-64-v3 system. Patch contributed by Grazvydas Ignotas <notasas@gmail.com> and Bruno Lathuilière <bruno.lathuiliere@edf.fr> https://bugs.kde.org/show_bug.cgi?id=481127 https://bugs.kde.org/show_bug.cgi?id=463463 https://bugs.kde.org/show_bug.cgi?id=463458