[Buildroot] [PATCH v8 20/28] xbmc: Allow compilation with uClibc

[Yann E. MORIN <yann.morin.1998@free.fr>]

Bernd, All,

On 2014-05-17 17:57 +0200, Bernd Kuhls spake thusly:
> - Add dependencies needed by xbmc on BR2_LARGEFILE, BR2_INET_IPV6 &
>   BR2_USE_WCHAR after the removal of BR2_TOOLCHAIN_USES_GLIBC
> - Add xbmc-0002-mathutil.patch to fix ARM compilation

I was just wondering how important building on uClibc would be.

XBMC is already a large chunk of a beast, so the benefit of switching to
uClibc would be minimal size-wise, no?

Remember that uClibc was initially made for systems with storage size
constrains, which is surely not the case for a device where XBMC is
expected to run in the first place.

That being said, I don't much care about XBMC+uClibc, but the small
runtime speed benefits alone might be worth the patch anyway.

Regards,
Yann E. MORIN.

> Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
> ---
>  package/xbmc/Config.in                |   15 ++-
>  package/xbmc/xbmc-0002-mathutil.patch |  213 +++++++++++++++++++++++++++++++++
>  2 files changed, 222 insertions(+), 6 deletions(-)
>  create mode 100644 package/xbmc/xbmc-0002-mathutil.patch
> 
> diff --git a/package/xbmc/Config.in b/package/xbmc/Config.in
> index 0f45f5c..f001209 100644
> --- a/package/xbmc/Config.in
> +++ b/package/xbmc/Config.in
> @@ -1,11 +1,10 @@
> -comment "xbmc needs an (e)glibc toolchain w/ C++, threads"
> -	depends on !BR2_TOOLCHAIN_USES_GLIBC || !BR2_INSTALL_LIBSTDCPP || !BR2_TOOLCHAIN_HAS_THREADS
> +comment "xbmc needs a toolchain w/ C++, IPv6, largefile, threads, wchar"
> +	depends on BR2_arm || BR2_i386 || BR2_x86_64
> +	depends on !BR2_INET_IPV6 || !BR2_INSTALL_LIBSTDCPP || !BR2_LARGEFILE || !BR2_TOOLCHAIN_HAS_THREADS || !BR2_USE_WCHAR
>  
>  comment "xbmc requires an OpenGL ES and EGL backend"
> +	depends on BR2_arm || BR2_i386 || BR2_x86_64
>  	depends on !BR2_PACKAGE_HAS_LIBEGL || !BR2_PACKAGE_HAS_LIBGLES
> -	depends on BR2_TOOLCHAIN_USES_GLIBC
> -	depends on BR2_INSTALL_LIBSTDCPP
> -	depends on BR2_TOOLCHAIN_HAS_THREADS
>  
>  menuconfig BR2_PACKAGE_XBMC
>  	bool "xbmc"
> @@ -57,10 +56,14 @@ menuconfig BR2_PACKAGE_XBMC
>  	select BR2_PACKAGE_TINYXML
>  	select BR2_PACKAGE_YAJL
>  	select BR2_PACKAGE_ZLIB
> -	depends on BR2_TOOLCHAIN_USES_GLIBC
> +	depends on BR2_INET_IPV6
>  	depends on BR2_INSTALL_LIBSTDCPP
> +	depends on BR2_LARGEFILE
>  	depends on BR2_TOOLCHAIN_HAS_THREADS
>  	depends on BR2_PACKAGE_HAS_LIBEGL && BR2_PACKAGE_HAS_LIBGLES
> +	depends on BR2_USE_MMU # python
> +	depends on BR2_USE_WCHAR
> +	depends on BR2_arm || BR2_i386 || BR2_x86_64
>  	help
>  	  XBMC is an award-winning free and open source (GPL) software
>  	  media player and entertainment hub for digital media.
> diff --git a/package/xbmc/xbmc-0002-mathutil.patch b/package/xbmc/xbmc-0002-mathutil.patch
> new file mode 100644
> index 0000000..33f91eb
> --- /dev/null
> +++ b/package/xbmc/xbmc-0002-mathutil.patch
> @@ -0,0 +1,213 @@
> +Taken from upstream PR: https://github.com/xbmc/xbmc/pull/3760
> +
> +Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
> +
> +
> +From 7388e8be7cd5e78100532ebf0dba15dccb7b03f8 Mon Sep 17 00:00:00 2001
> +From: Ben Avison <bavison@riscosopen.org>
> +Date: Tue, 3 Dec 2013 15:51:39 +0000
> +Subject: [PATCH] Faster and simpler portable implementation of
> + MathUtils::round_int().
> +
> +Much as I like a bit of inline assembler, I have also removed the ARM versions
> +of MathUtils::truncate_int() and MathUtils::round_int(). The former was just
> +how any sane compiler should have assembled a cast from double to signed int
> +anyway. The latter was a much too complicated way to achieve the desired
> +effect, and was switched out in most ARM builds anyway in favour of the old
> +portable implementation that used floor().
> +
> +Verified that MathUtils::test() still passes, and that GCC is now able to
> +inline MathUtils::round_int(), where it didn't previously.
> +
> +I tested on a Raspberry Pi with the default theme, displaying the front page
> +with the RSS ticker enabled. This saturates the CPU, so I'm measuring the
> +improvement using the debug window's FPS figure. This patch improves this from
> +~50.8 FPS to ~52.6 FPS.
> +---
> + xbmc/utils/MathUtils.h | 129 +++++++++++++++++++++++--------------------------
> + 1 file changed, 61 insertions(+), 68 deletions(-)
> +
> +diff --git a/xbmc/utils/MathUtils.h b/xbmc/utils/MathUtils.h
> +index 96af9f4..0dae77d 100644
> +--- a/xbmc/utils/MathUtils.h
> ++++ b/xbmc/utils/MathUtils.h
> +@@ -34,17 +34,13 @@
> + 
> + #if defined(__ppc__) || \
> +     defined(__powerpc__) || \
> +-   (defined(TARGET_DARWIN_IOS) && defined(__llvm__)) || \
> +-   (defined(TARGET_ANDROID) && defined(__arm__)) || \
> +-    defined(TARGET_RASPBERRY_PI)
> ++    defined(__arm__)
> +   #define DISABLE_MATHUTILS_ASM_ROUND_INT
> + #endif
> + 
> + #if defined(__ppc__) || \
> +     defined(__powerpc__) || \
> +-   (defined(TARGET_DARWIN) && defined(__llvm__)) || \
> +-   (defined(TARGET_ANDROID) && defined(__arm__)) || \
> +-    defined(TARGET_RASPBERRY_PI)
> ++    defined(__arm__)
> +   #define DISABLE_MATHUTILS_ASM_TRUNCATE_INT
> + #endif
> + 
> +@@ -73,60 +69,63 @@
> +   {
> +     assert(x > static_cast<double>(INT_MIN / 2) - 1.0);
> +     assert(x < static_cast<double>(INT_MAX / 2) + 1.0);
> +-    const float round_to_nearest = 0.5f;
> +-    int i;
> + 
> + #if defined(DISABLE_MATHUTILS_ASM_ROUND_INT)
> +-    i = floor(x + round_to_nearest);
> +-
> +-#elif defined(__arm__)
> +-    // From 'ARM-v7-M Architecture Reference Manual' page A7-569:
> +-    //  "The floating-point to integer operation (vcvt) [normally] uses the Round towards Zero rounding mode"
> +-    // Because of this...we must use some less-than-straightforward logic to perform this operation without
> +-    //  changing the rounding mode flags
> +-
> +-    /* The assembly below implements the following logic:
> +-     if (x < 0)
> +-       inc = -0.5f
> +-     else
> +-       inc = 0.5f
> +-     int_val = trunc(x+inc);
> +-     err = x - int_val;
> +-     if (err == 0.5f)
> +-       int_val++;
> +-     return int_val;
> +-    */
> ++    /* This implementation warrants some further explanation.
> ++     *
> ++     * First, a couple of notes on rounding:
> ++     * 1) C casts from float/double to integer round towards zero.
> ++     * 2) Float/double additions are rounded according to the normal rules,
> ++     *    in other words: on some architectures, it's fixed at compile-time,
> ++     *    and on others it can be set using fesetround()). The following
> ++     *    analysis assumes round-to-nearest with ties rounding to even. This
> ++     *    is a fairly sensible choice, and is the default with ARM VFP.
> ++     *
> ++     * What this function wants is round-to-nearest with ties rounding to
> ++     * +infinity. This isn't an IEEE rounding mode, even if we could guarantee
> ++     * that all architectures supported fesetround(), which they don't. Instead,
> ++     * this adds an offset of 2147483648.5 (= 0x80000000.8p0), then casts to
> ++     * an unsigned int (crucially, all possible inputs are now in a range where
> ++     * round to zero acts the same as round to -infinity) and then subtracts
> ++     * 0x80000000 in the integer domain. The 0.5 component of the offset
> ++     * converts what is effectively a round down into a round to nearest, with
> ++     * ties rounding up, as desired.
> ++     *
> ++     * There is a catch, that because there is a double rounding, there is a
> ++     * small region where the input falls just *below* a tie, where the addition
> ++     * of the offset causes a round *up* to an exact integer, due to the finite
> ++     * level of precision available in floating point. You need to be aware of
> ++     * this when calling this function, although at present it is not believed
> ++     * that XBMC ever attempts to round numbers in this window.
> ++     *
> ++     * It is worth proving the size of the affected window. Recall that double
> ++     * precision employs a mantissa of 52 bits.
> ++     * 1) For all inputs -0.5 <= x <= INT_MAX
> ++     *    Once the offset is applied, the most significant binary digit in the
> ++     *    floating-point representation is +2^31.
> ++     *    At this magnitude, the smallest step representable in double precision
> ++     *    is 2^31 / 2^52 = 0.000000476837158203125
> ++     *    So the size of the range which is rounded up due to the addition is
> ++     *    half the size of this step, or 0.0000002384185791015625
> ++     *
> ++     * 2) For all inputs INT_MIN/2 < x < -0.5
> ++     *    Once the offset is applied, the most significant binary digit in the
> ++     *    floating-point representation is +2^30.
> ++     *    At this magnitude, the smallest step representable in double precision
> ++     *    is 2^30 / 2^52 = 0.0000002384185791015625
> ++     *    So the size of the range which is rounded up due to the addition is
> ++     *    half the size of this step, or 0.00000011920928955078125
> ++     *
> ++     * 3) For all inputs INT_MIN <= x <= INT_MIN/2
> ++     *    The representation once the offset is applied has equal or greater
> ++     *    precision than the input, so the addition does not cause rounding.
> ++     */
> ++    return ((unsigned int) (x + 0x80000000.8p0)) - 0x80000000;
> + 
> +-    __asm__ __volatile__ (
> +-#if defined(__ARM_PCS_VFP)
> +-      "fconstd d1,#%G[rnd_val]     \n\t" // Copy round_to_nearest into a working register (d1 = 0.5)
> + #else
> +-      "vmov.F64 d1,%[rnd_val]      \n\t"
> +-#endif
> +-      "fcmpezd %P[value]           \n\t" // Check value against zero (value == 0?)
> +-      "fmstat                      \n\t" // Copy the floating-point status flags into the general-purpose status flags
> +-      "it mi                       \n\t"
> +-      "vnegmi.F64 d1, d1           \n\t" // if N-flag is set, negate round_to_nearest (if (value < 0) d1 = -1 * d1)
> +-      "vadd.F64 d1,%P[value],d1    \n\t" // Add round_to_nearest to value, store result in working register (d1 += value)
> +-      "vcvt.S32.F64 s3,d1          \n\t" // Truncate(round towards zero) (s3 = (int)d1)
> +-      "vmov %[result],s3           \n\t" // Store the integer result in a general-purpose register (result = s3)
> +-      "vcvt.F64.S32 d1,s3          \n\t" // Convert back to floating-point (d1 = (double)s3)
> +-      "vsub.F64 d1,%P[value],d1    \n\t" // Calculate the error (d1 = value - d1)
> +-#if defined(__ARM_PCS_VFP)
> +-      "fconstd d2,#%G[rnd_val]     \n\t" // d2 = 0.5;
> +-#else
> +-      "vmov.F64 d2,%[rnd_val]      \n\t"
> +-#endif
> +-      "fcmped d1, d2               \n\t" // (d1 == 0.5?)
> +-      "fmstat                      \n\t" // Copy the floating-point status flags into the general-purpose status flags
> +-      "it eq                       \n\t"
> +-      "addeq %[result],#1          \n\t" // (if (d1 == d2) result++;)
> +-      : [result] "=r"(i)                                  // Outputs
> +-      : [rnd_val] "Dv" (round_to_nearest), [value] "w"(x) // Inputs
> +-      : "d1", "d2", "s3"                                  // Clobbers
> +-    );
> +-
> +-#elif defined(__SSE2__)
> ++    const float round_to_nearest = 0.5f;
> ++    int i;
> ++#if defined(__SSE2__)
> +     const float round_dn_to_nearest = 0.4999999f;
> +     i = (x > 0) ? _mm_cvttsd_si32(_mm_set_sd(x + round_to_nearest)) : _mm_cvttsd_si32(_mm_set_sd(x - round_dn_to_nearest));
> + 
> +@@ -150,8 +149,8 @@
> +     );
> + 
> + #endif
> +-
> +     return i;
> ++#endif
> +   }
> + 
> +   /*! \brief Truncate to nearest integer.
> +@@ -165,20 +164,13 @@
> +   {
> +     assert(x > static_cast<double>(INT_MIN / 2) - 1.0);
> +     assert(x < static_cast<double>(INT_MAX / 2) + 1.0);
> +-    int i;
> + 
> + #if defined(DISABLE_MATHUTILS_ASM_TRUNCATE_INT)
> +-    return i = (int)x;
> +-
> +-#elif defined(__arm__)
> +-    __asm__ __volatile__ (
> +-      "vcvt.S32.F64 %[result],%P[value]   \n\t" // Truncate(round towards zero) and store the result
> +-      : [result] "=w"(i)                        // Outputs
> +-      : [value] "w"(x)                          // Inputs
> +-    );
> +-    return i;
> ++    return x;
> + 
> +-#elif defined(TARGET_WINDOWS)
> ++#else
> ++    int i;
> ++#if defined(TARGET_WINDOWS)
> +     const float round_towards_m_i = -0.5f;
> +     __asm
> +     {
> +@@ -204,6 +196,7 @@
> +     if (x < 0)
> +       i = -i;
> +     return (i);
> ++#endif
> +   }
> + 
> +   inline int64_t abs(int64_t a)
> +-- 
> +1.9.1
> +
> -- 
> 1.7.10.4
> 
> _______________________________________________
> buildroot mailing list
> buildroot at busybox.net
> http://lists.busybox.net/mailman/listinfo/buildroot

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