[FFmpeg-devel] [PATCH 1/2] avutil/intmath: use AV_HAS_BUILTIN to detect builtin availability

[Kacper Michajlow]

On Mon, 31 Mar 2025 at 14:03, Kacper Michajłow <kasper93 at gmail.com> wrote:
>
> Fixes use of bultins on clang x86_64-pc-windows-msvc which does not
> define any __GNUC__. Also on other targets __GNUC__ is defined to 4 by
> default, so any feature testing based on version is not really valid.
>
> Signed-off-by: Kacper Michajłow <kasper93 at gmail.com>
> ---
>  libavutil/intmath.h     | 12 +++++-------
>  libavutil/x86/intmath.h |  4 ++--
>  2 files changed, 7 insertions(+), 9 deletions(-)
>
> diff --git a/libavutil/intmath.h b/libavutil/intmath.h
> index 52e11a8d5f..b177a848c6 100644
> --- a/libavutil/intmath.h
> +++ b/libavutil/intmath.h
> @@ -35,7 +35,7 @@
>  #endif
>
>  #if HAVE_FAST_CLZ
> -#if AV_GCC_VERSION_AT_LEAST(3,4)
> +#if AV_GCC_VERSION_AT_LEAST(3,4) || AV_HAS_BUILTIN(__builtin_clz)
>  #ifndef ff_log2
>  #   define ff_log2(x) (31 - __builtin_clz((x)|1))
>  #   ifndef ff_log2_16bit
> @@ -90,18 +90,16 @@ static av_always_inline av_const int ff_log2_16bit_c(unsigned int v)
>   */
>
>  #if HAVE_FAST_CLZ
> -#if AV_GCC_VERSION_AT_LEAST(3,4)
> -#ifndef ff_ctz
> +#if !defined(ff_ctz) && (AV_GCC_VERSION_AT_LEAST(3,4) || AV_HAS_BUILTIN(__builtin_ctz))
>  #define ff_ctz(v) __builtin_ctz(v)
>  #endif
> -#ifndef ff_ctzll
> +#if !defined(ff_ctzll) && (AV_GCC_VERSION_AT_LEAST(3,4) || AV_HAS_BUILTIN(__builtin_ctzll))
>  #define ff_ctzll(v) __builtin_ctzll(v)
>  #endif
> -#ifndef ff_clz
> +#if !defined(ff_clz) && (AV_GCC_VERSION_AT_LEAST(3,4) || AV_HAS_BUILTIN(__builtin_clz))
>  #define ff_clz(v) __builtin_clz(v)
>  #endif
>  #endif
> -#endif
>
>  #ifndef ff_ctz
>  #define ff_ctz ff_ctz_c
> @@ -154,7 +152,7 @@ static av_always_inline av_const unsigned ff_clz_c(unsigned x)
>  }
>  #endif
>
> -#if AV_GCC_VERSION_AT_LEAST(3,4)
> +#if AV_GCC_VERSION_AT_LEAST(3,4) || AV_HAS_BUILTIN(__builtin_parity)
>  #ifndef av_parity
>  #define av_parity __builtin_parity
>  #endif
> diff --git a/libavutil/x86/intmath.h b/libavutil/x86/intmath.h
> index 4893a1f1b4..030ded6b6f 100644
> --- a/libavutil/x86/intmath.h
> +++ b/libavutil/x86/intmath.h
> @@ -66,7 +66,7 @@ static av_always_inline av_const int ff_ctzll_x86(long long v)
>
>  #endif /* HAVE_FAST_CLZ */
>
> -#if defined(__GNUC__)
> +#if defined(__GNUC__) || defined(__clang__)
>
>  /* Our generic version of av_popcount is faster than GCC's built-in on
>   * CPUs that don't support the popcnt instruction.
> @@ -81,7 +81,7 @@ static av_always_inline av_const int ff_ctzll_x86(long long v)
>
>  #if defined(__BMI2__)
>
> -#if AV_GCC_VERSION_AT_LEAST(5,1)
> +#if AV_GCC_VERSION_AT_LEAST(5,1) || AV_HAS_BUILTIN(__builtin_ia32_bzhi_si)
>  #if defined(ASSERT_LEVEL) && ASSERT_LEVEL >= 2
>  #define av_zero_extend av_zero_extend_bmi2
>  static av_always_inline av_const unsigned av_zero_extend_bmi2(unsigned a, unsigned p)
> --
> 2.45.1
>

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