detect x86-64 ABI version on Linux, using /proc/cpuinfo

detect-x86-64-abi-version.sh

#!/bin/bash

# Note on hybrid CPUs (P-cores/E-cores):
# Linux /proc/cpuinfo reports only features common to ALL cores.
# This script will correctly detect the lowest ISA level supported
# across all core types, which matches glibc's behavior.

get_x86_64_abi_version() {
    local FLAGS
    local DETECTED_LEVEL
    local LEVEL
    local FEATURES
    local FEATURE
    local MISSING_FEATURE=0

    FLAGS=$(sed -n -e '/flags		:/{s///;p;q}' /proc/cpuinfo) || return
    DETECTED_LEVEL=0
    while IFS=: read -r LEVEL FEATURES; do
        for FEATURE in $FEATURES; do
            case "$FLAGS" in
                *" $FEATURE "*)
                    continue
                ;;
                *)
                    if [ $MISSING_FEATURE -eq 0 ]; then
                        echo "missing features for x86-64-v$LEVEL:" >&2
                        MISSING_FEATURE=1
                    fi
                    echo "- $FEATURE" >&2
                ;;
            esac
        done
        if [ $MISSING_FEATURE -eq 1 ]; then
            break
        fi
        DETECTED_LEVEL=$LEVEL
    done <<EOF
1:lm cmov cx8 fpu fxsr mmx syscall sse sse2
2:cx16 lahf_lm popcnt pni sse4_1 sse4_2 ssse3
3:avx avx2 bmi1 bmi2 f16c fma abm movbe xsave
4:avx512f avx512bw avx512cd avx512dq avx512vl
EOF
    # level definitions: "level_number:features"
    # each level includes features beyond the previous level
    # note: 'lm' = Long Mode (64-bit), 'pni' = SSE3, 'abm' = LZCNT

    echo "$DETECTED_LEVEL"

}

ABI_VERSION=$(get_x86_64_abi_version)
if [ -n "$ABI_VERSION" ]; then
    echo "result: x86-64-v$ABI_VERSION"
    exit 0
else
    echo 'failed to detect x86-64 ABI version' >&2
    exit 1
fi

% ./detect.sh
missing features for x86-64-v4:
- avx512f
- avx512bw
- avx512cd
- avx512dq
- avx512vl
result: x86-64-v3