On Thu, Oct 10, 2024 at 11:13:22AM +0200, Paolo Bonzini wrote:
> Just detect compiler support and always enable the optimizations if
> it is avilable; warn if the user did request AVX2/AVX512 use via
> -Dx86_version= but the intrinsics are not available.
>
> Suggested-by: Richard Henderson <richard.hender...@linaro.org>
> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
> ---
> meson.build | 30 +++++++++++++++++++-----------
> meson_options.txt | 4 ----
> scripts/meson-buildoptions.sh | 6 ------
> 3 files changed, 19 insertions(+), 21 deletions(-)
>
> diff --git a/meson.build b/meson.build
> index e4b2af138da..b4418d54e0a 100644
> --- a/meson.build
> +++ b/meson.build
> @@ -2955,22 +2955,16 @@ config_host_data.set('CONFIG_ASM_HWPROBE_H',
> cc.has_header_symbol('asm/hwprobe.h',
> 'RISCV_HWPROBE_EXT_ZBA'))
>
> -config_host_data.set('CONFIG_AVX2_OPT', get_option('avx2') \
> - .require(have_cpuid_h, error_message: 'cpuid.h not available, cannot
> enable AVX2') \
> - .require(cc.links('''
> - #include <cpuid.h>
> +if have_cpuid_h
> + have_avx2 = cc.links('''
> #include <immintrin.h>
> static int __attribute__((target("avx2"))) bar(void *a) {
> __m256i x = *(__m256i *)a;
> return _mm256_testz_si256(x, x);
> }
> int main(int argc, char *argv[]) { return bar(argv[argc - 1]); }
> - '''), error_message: 'AVX2 not available').allowed())
> -
> -config_host_data.set('CONFIG_AVX512BW_OPT', get_option('avx512bw') \
> - .require(have_cpuid_h, error_message: 'cpuid.h not available, cannot
> enable AVX512BW') \
> - .require(cc.links('''
> - #include <cpuid.h>
> + ''')
> + have_avx512bw = cc.links('''
> #include <immintrin.h>
> static int __attribute__((target("avx512bw"))) bar(void *a) {
> __m512i *x = a;
> @@ -2978,7 +2972,21 @@ config_host_data.set('CONFIG_AVX512BW_OPT',
> get_option('avx512bw') \
> return res[1];
> }
> int main(int argc, char *argv[]) { return bar(argv[0]); }
> - '''), error_message: 'AVX512BW not available').allowed())
> + ''')
> + if get_option('x86_version') >= '3' and not have_avx2
> + warning('Cannot enable AVX optimizations due to missing intrinsics')
> + elif get_option('x86_version') >= '4' and not have_avx512bw
> + warning('Cannot enable AVX512 optimizations due to missing intrinsics')
> + endif
Should these perhaps be error() rather than warning() ?
We only support GCC & CLang. If both GCC 7.4.0 and CLang 10.0 (our
min versions) have the intrinsics, then I'd say this is an impossible
scenario if x86_version is large, and thus would deserve error()
> +else
> + have_avx2 = false
> + have_avx512bw = false
> + if get_option('x86_version') >= '3'
> + warning('Cannot enable AVX optimizations due to missing cpuid.h')
> + endif
> +endif
> +config_host_data.set('CONFIG_AVX2_OPT', have_avx2)
> +config_host_data.set('CONFIG_AVX512BW_OPT', have_avx512bw)
>
> # For both AArch64 and AArch32, detect if builtins are available.
> config_host_data.set('CONFIG_ARM_AES_BUILTIN', cc.compiles('''
> diff --git a/meson_options.txt b/meson_options.txt
> index 5a5c2300261..d5abf5193f5 100644
> --- a/meson_options.txt
> +++ b/meson_options.txt
> @@ -119,10 +119,6 @@ option('tpm', type : 'feature', value : 'auto',
> option('membarrier', type: 'feature', value: 'disabled',
> description: 'membarrier system call (for Linux 4.14+ or Windows')
>
> -option('avx2', type: 'feature', value: 'auto',
> - description: 'AVX2 optimizations')
> -option('avx512bw', type: 'feature', value: 'auto',
> - description: 'AVX512BW optimizations')
> option('keyring', type: 'feature', value: 'auto',
> description: 'Linux keyring support')
> option('libkeyutils', type: 'feature', value: 'auto',
> diff --git a/scripts/meson-buildoptions.sh b/scripts/meson-buildoptions.sh
> index 6d08605b771..dc796f48bad 100644
> --- a/scripts/meson-buildoptions.sh
> +++ b/scripts/meson-buildoptions.sh
> @@ -94,8 +94,6 @@ meson_options_help() {
> printf "%s\n" ' alsa ALSA sound support'
> printf "%s\n" ' attr attr/xattr support'
> printf "%s\n" ' auth-pam PAM access control'
> - printf "%s\n" ' avx2 AVX2 optimizations'
> - printf "%s\n" ' avx512bw AVX512BW optimizations'
> printf "%s\n" ' blkio libblkio block device driver'
> printf "%s\n" ' bochs bochs image format support'
> printf "%s\n" ' bpf eBPF support'
> @@ -238,10 +236,6 @@ _meson_option_parse() {
> --audio-drv-list=*) quote_sh "-Daudio_drv_list=$2" ;;
> --enable-auth-pam) printf "%s" -Dauth_pam=enabled ;;
> --disable-auth-pam) printf "%s" -Dauth_pam=disabled ;;
> - --enable-avx2) printf "%s" -Davx2=enabled ;;
> - --disable-avx2) printf "%s" -Davx2=disabled ;;
> - --enable-avx512bw) printf "%s" -Davx512bw=enabled ;;
> - --disable-avx512bw) printf "%s" -Davx512bw=disabled ;;
> --enable-gcov) printf "%s" -Db_coverage=true ;;
> --disable-gcov) printf "%s" -Db_coverage=false ;;
> --enable-lto) printf "%s" -Db_lto=true ;;
> --
> 2.46.2
>
>
With regards,
Daniel
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