swscale/output: Altivec-optimize float yuv2plane1

This function wouldn't benefit from VSX instructions, so I put it
under altivec.

./ffmpeg_g -f rawvideo -pix_fmt rgb24 -s hd1080 -i /dev/zero -pix_fmt grayf32le \
-f null -vframes 100 -v error -nostats -

3743 UNITS in planar1,   65495 runs,     41 skips

-cpuflags 0

23511 UNITS in planar1,   65530 runs,      6 skips

grayf32be

4647 UNITS in planar1,   65449 runs,     87 skips

-cpuflags 0

28608 UNITS in planar1,   65530 runs,      6 skips

The native speedup is 6.28133, and the bswapping one 6.15623.
Fate passes, each format tested with an image to video conversion.
Signed-off-by: Lauri Kasanen <cand@gmx.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libswscale/ppc/swscale_altivec.c

@@ -31,7 +31,8 @@
 #include "yuv2rgb_altivec.h"
 #include "libavutil/ppc/util_altivec.h"
 
-#if HAVE_ALTIVEC && HAVE_BIGENDIAN
+#if HAVE_ALTIVEC
+#if HAVE_BIGENDIAN
 #define vzero vec_splat_s32(0)
 
 #define  GET_LS(a,b,c,s) {\
@@ -102,7 +103,137 @@
 #include "swscale_ppc_template.c"
 #undef FUNC
 
-#endif /* HAVE_ALTIVEC && HAVE_BIGENDIAN */
+#undef vzero
+
+#endif /* HAVE_BIGENDIAN */
+
+#define output_pixel(pos, val, bias, signedness) \
+    if (big_endian) { \
+        AV_WB16(pos, bias + av_clip_ ## signedness ## 16(val >> shift)); \
+    } else { \
+        AV_WL16(pos, bias + av_clip_ ## signedness ## 16(val >> shift)); \
+    }
+
+static void
+yuv2plane1_float_u(const int32_t *src, float *dest, int dstW, int start)
+{
+    static const int big_endian = HAVE_BIGENDIAN;
+    static const int shift = 3;
+    static const float float_mult = 1.0f / 65535.0f;
+    int i, val;
+    uint16_t val_uint;
+
+    for (i = start; i < dstW; ++i){
+        val = src[i] + (1 << (shift - 1));
+        output_pixel(&val_uint, val, 0, uint);
+        dest[i] = float_mult * (float)val_uint;
+    }
+}
+
+static void
+yuv2plane1_float_bswap_u(const int32_t *src, uint32_t *dest, int dstW, int start)
+{
+    static const int big_endian = HAVE_BIGENDIAN;
+    static const int shift = 3;
+    static const float float_mult = 1.0f / 65535.0f;
+    int i, val;
+    uint16_t val_uint;
+
+    for (i = start; i < dstW; ++i){
+        val = src[i] + (1 << (shift - 1));
+        output_pixel(&val_uint, val, 0, uint);
+        dest[i] = av_bswap32(av_float2int(float_mult * (float)val_uint));
+    }
+}
+
+static void yuv2plane1_float_altivec(const int32_t *src, float *dest, int dstW)
+{
+    const int dst_u = -(uintptr_t)dest & 3;
+    const int shift = 3;
+    const int add = (1 << (shift - 1));
+    const int clip = (1 << 16) - 1;
+    const float fmult = 1.0f / 65535.0f;
+    const vector uint32_t vadd = (vector uint32_t) {add, add, add, add};
+    const vector uint32_t vshift = (vector uint32_t) vec_splat_u32(shift);
+    const vector uint32_t vlargest = (vector uint32_t) {clip, clip, clip, clip};
+    const vector float vmul = (vector float) {fmult, fmult, fmult, fmult};
+    const vector float vzero = (vector float) {0, 0, 0, 0};
+    vector uint32_t v;
+    vector float vd;
+    int i;
+
+    yuv2plane1_float_u(src, dest, dst_u, 0);
+
+    for (i = dst_u; i < dstW - 3; i += 4) {
+        v = vec_ld(0, (const uint32_t *) &src[i]);
+        v = vec_add(v, vadd);
+        v = vec_sr(v, vshift);
+        v = vec_min(v, vlargest);
+
+        vd = vec_ctf(v, 0);
+        vd = vec_madd(vd, vmul, vzero);
+
+        vec_st(vd, 0, &dest[i]);
+    }
+
+    yuv2plane1_float_u(src, dest, dstW, i);
+}
+
+static void yuv2plane1_float_bswap_altivec(const int32_t *src, uint32_t *dest, int dstW)
+{
+    const int dst_u = -(uintptr_t)dest & 3;
+    const int shift = 3;
+    const int add = (1 << (shift - 1));
+    const int clip = (1 << 16) - 1;
+    const float fmult = 1.0f / 65535.0f;
+    const vector uint32_t vadd = (vector uint32_t) {add, add, add, add};
+    const vector uint32_t vshift = (vector uint32_t) vec_splat_u32(shift);
+    const vector uint32_t vlargest = (vector uint32_t) {clip, clip, clip, clip};
+    const vector float vmul = (vector float) {fmult, fmult, fmult, fmult};
+    const vector float vzero = (vector float) {0, 0, 0, 0};
+    const vector uint32_t vswapbig = (vector uint32_t) {16, 16, 16, 16};
+    const vector uint16_t vswapsmall = vec_splat_u16(8);
+    vector uint32_t v;
+    vector float vd;
+    int i;
+
+    yuv2plane1_float_bswap_u(src, dest, dst_u, 0);
+
+    for (i = dst_u; i < dstW - 3; i += 4) {
+        v = vec_ld(0, (const uint32_t *) &src[i]);
+        v = vec_add(v, vadd);
+        v = vec_sr(v, vshift);
+        v = vec_min(v, vlargest);
+
+        vd = vec_ctf(v, 0);
+        vd = vec_madd(vd, vmul, vzero);
+
+        vd = (vector float) vec_rl((vector uint32_t) vd, vswapbig);
+        vd = (vector float) vec_rl((vector uint16_t) vd, vswapsmall);
+
+        vec_st(vd, 0, (float *) &dest[i]);
+    }
+
+    yuv2plane1_float_bswap_u(src, dest, dstW, i);
+}
+
+#define yuv2plane1_float(template, dest_type, BE_LE) \
+static void yuv2plane1_float ## BE_LE ## _altivec(const int16_t *src, uint8_t *dest, \
+                                                  int dstW, \
+                                                  const uint8_t *dither, int offset) \
+{ \
+    template((const int32_t *)src, (dest_type *)dest, dstW); \
+}
+
+#if HAVE_BIGENDIAN
+yuv2plane1_float(yuv2plane1_float_altivec,       float,    BE)
+yuv2plane1_float(yuv2plane1_float_bswap_altivec, uint32_t, LE)
+#else
+yuv2plane1_float(yuv2plane1_float_altivec,       float,    LE)
+yuv2plane1_float(yuv2plane1_float_bswap_altivec, uint32_t, BE)
+#endif
+
+#endif /* HAVE_ALTIVEC */
 
 av_cold void ff_sws_init_swscale_ppc(SwsContext *c)
 {
@@ -124,6 +255,12 @@ av_cold void ff_sws_init_swscale_ppc(SwsContext *c)
     }
 #endif
 
+    if (dstFormat == AV_PIX_FMT_GRAYF32BE) {
+        c->yuv2plane1 = yuv2plane1_floatBE_altivec;
+    } else if (dstFormat == AV_PIX_FMT_GRAYF32LE) {
+        c->yuv2plane1 = yuv2plane1_floatLE_altivec;
+    }
+
     /* The following list of supported dstFormat values should
      * match what's found in the body of ff_yuv2packedX_altivec() */
     if (!(c->flags & (SWS_BITEXACT | SWS_FULL_CHR_H_INT)) && !c->needAlpha) {