#!/bin/sh
# x86-64-level: print the x86-64 microarchitecture level (x86-64-v1 to
# x86-64-v4) of this machine's processor, as Linux reports it.
#
# Documentation: https://x86-64.net/check/
# SPDX-License-Identifier: MIT
#
# Usage: x86-64-level [-q] [-v]
#   -q  print only the level number (1 to 4)
#   -v  also list the features missing for the next level
#
# X86_64_LEVEL_CPUINFO names a file to read instead of /proc/cpuinfo.
set -eu

# Linux flag names of the features each level adds, following the x86-64
# psABI. OSFXSR and OSXSAVE have no flags; Linux clears the AVX family
# flags when the OS has not enabled XSAVE, so the lists below cover them.
LEVEL1="cmov cx8 fpu fxsr mmx syscall sse sse2"
LEVEL2="cx16 lahf_lm popcnt pni sse4_1 sse4_2 ssse3"
LEVEL3="avx avx2 bmi1 bmi2 f16c fma abm movbe xsave"
LEVEL4="avx512f avx512bw avx512cd avx512dq avx512vl"

quiet=0
verbose=0
for arg in "$@"; do
	case $arg in
	-q) quiet=1 ;;
	-v) verbose=1 ;;
	-h | --help)
		sed -n '2,13s/^# \{0,1\}//p' "$0"
		exit 0
		;;
	*)
		echo "x86-64-level: unknown option: $arg" >&2
		exit 2
		;;
	esac
done

cpuinfo=${X86_64_LEVEL_CPUINFO:-/proc/cpuinfo}
if [ ! -r "$cpuinfo" ]; then
	echo "x86-64-level: cannot read $cpuinfo (this script needs Linux)" >&2
	exit 1
fi

# All CPUs report the same flags; the first "flags" line is enough.
flags=$(sed -n 's/^flags[[:space:]]*:[[:space:]]*//p' "$cpuinfo" | head -n 1)
if [ -z "$flags" ]; then
	echo "x86-64-level: no x86 flags line in $cpuinfo" >&2
	exit 1
fi

missing() {
	for flag in $1; do
		case " $flags " in
		*" $flag "*) ;;
		*) printf ' %s' "$flag" ;;
		esac
	done
}

level=0
lack=
for n in 1 2 3 4; do
	eval "wanted=\$LEVEL$n"
	lack=$(missing "$wanted")
	[ -n "$lack" ] && break
	level=$n
done

if [ "$level" -eq 0 ]; then
	echo "x86-64-level: not even the x86-64 baseline; missing:$lack" >&2
	exit 1
fi

if [ "$quiet" -eq 1 ]; then
	echo "$level"
else
	echo "x86-64-v$level"
fi
if [ "$verbose" -eq 1 ] && [ "$level" -lt 4 ]; then
	echo "missing for x86-64-v$((level + 1)):$lack"
fi