Makefile flags:
CC_FLAGS ?= -m64 -Ofast -Wall -Wextra -mtune=native \
-funroll-loops -ftree-vectorize -fstrict-aliasing \
-fno-semantic-interposition -fvect-cost-model=unlimited \
-fno-trapping-math -fipa-ra -flto -fassociative-math \
-mavx2 -mbmi2 -madx -fwrapv \
-fomit-frame-pointer -fpredictive-commoning -fgcse-sm -fgcse-las \
-fmodulo-sched -fmodulo-sched-allow-regmoves -funsafe-math-optimizations
I'm having ridiculous speeds with these flags. Fastest CPU s*it out here.

Carefully monitor the temperature of the processor. I don't know what settings you have in the system.
For example:
sudo tuned-adm profile latency-performance
sudo cpufreq-set -r -g performance
OR
GOVERNOR="performance" in "/etc/init.d/cpufrequtils"
or you have liquorix kernel
(MX Linux “ahs”)......
If they are all on unlimited like root in linux - you can burn the processor.
