[SCM] ffmpeg/master: Add patch to fix random FTBFS on i386 caused by float precision issues

[jcowgill at users.alioth.debian.org]

The following commit has been merged in the master branch:
commit ee19a5f6d1c96e27d9c0e1d30e4fcadc44bd9703
Author: James Cowgill <jcowgill at debian.org>
Date:   Sat Nov 18 19:33:23 2017 +0000

    Add patch to fix random FTBFS on i386 caused by float precision issues
    
    Closes: #882075

diff --git a/debian/patches/0005-float-dsp-i386.patch b/debian/patches/0005-float-dsp-i386.patch
new file mode 100644
index 0000000..f373167
--- /dev/null
+++ b/debian/patches/0005-float-dsp-i386.patch
@@ -0,0 +1,57 @@
+Description: Workaround checkasm failures on i386 by forcing x87 FPU precision
+ On i386, the float_dsp.vector_dmul test randomly fails if the x87 FPU
+ calculates a slightly different result compared to the optimized SSE routines.
+ .
+ Workaround these failures by setting the x87 FPCW register to round all results
+ to double precision.
+Author: James Cowgill <jcowgill at debian.org>
+Bug-Debian: https://bugs.debian.org/882075
+---
+This patch header follows DEP-3: http://dep.debian.net/deps/dep3/
+--- a/tests/checkasm/float_dsp.c
++++ b/tests/checkasm/float_dsp.c
+@@ -154,6 +154,20 @@ static void test_vector_fmac_scalar(cons
+     bench_new(odst, src0, src1[0], LEN);
+ }
+ 
++#if defined(__i386__) && !defined(__SSE_MATH__)
++static inline unsigned short get_x86_fpcw(void)
++{
++    unsigned short fpcw;
++    __asm__ volatile ("fstcw %0":"=m"(fpcw));
++    return fpcw;
++}
++
++static inline void set_x86_fpcw(unsigned short fpcw)
++{
++    __asm__ volatile ("fldcw %0"::"m"(fpcw));
++}
++#endif
++
+ static void test_vector_dmul_scalar(const double *src0, const double *src1)
+ {
+     LOCAL_ALIGNED_32(double, cdst, [LEN]);
+@@ -162,8 +176,23 @@ static void test_vector_dmul_scalar(cons
+ 
+     declare_func(void, double *dst, const double *src, double mul, int len);
+ 
++#if defined(__i386__) && !defined(__SSE_MATH__)
++    /*
++     * On x86, if the C code computes the multiplcations using the x87 FPU, and
++     * the optimized version computes them using SSE, results may be different.
++     *
++     * Workaround this by forcing the x87 FPU to round to double precision by
++     * setting the FPCW register.
++     */
++
++    unsigned short old_fpcw = get_x86_fpcw();
++    set_x86_fpcw(0x27F);
++#endif
+     call_ref(cdst, src0, src1[0], LEN);
+     call_new(odst, src0, src1[0], LEN);
++#if defined(__i386__) && !defined(__SSE_MATH__)
++    set_x86_fpcw(old_fpcw);
++#endif
+     for (i = 0; i < LEN; i++) {
+         if (!double_near_abs_eps(cdst[i], odst[i], DBL_EPSILON)) {
+             fprintf(stderr, "%d: %- .12f - %- .12f = % .12g\n", i,
diff --git a/debian/patches/series b/debian/patches/series
index dd8059d..7b10f1c 100644
--- a/debian/patches/series
+++ b/debian/patches/series
@@ -2,3 +2,4 @@
 0002-arm-Check-for-have_vfp_vm-instead-of-have_vfpv3.patch
 0003-lavc-reset-codec-on-receiving-packet-after-EOF-in-co.patch
 0004-avformat-dashenc-fix-min_seg_duration-option-size.patch
+0005-float-dsp-i386.patch

-- 
ffmpeg packaging