[babl] avx2-int8: add gamma u8 -> linear float conversions

[Ell <ell src gnome org>]

commit 57bd10c3f114a2f785ca6325204f035665d2892e
Author: Ell <ell_se yahoo com>
Date:   Sun Apr 12 17:42:16 2020 +0300

    avx2-int8: add gamma u8 -> linear float conversions
    
    Add AVX2 conversions from u8 Y', Y'A, R'G'B, and R'G'B'A to float
    Y, YA, RGB, and RGBA, respectively.  The conversions use an LUT
    together with the AVX2 gather instructions to process 8 values a
     once.  Depending on the formats and cache utilization, the new
    conversions are between 1.25x to 2.2x faster than the existing
    conversions.

 extensions/avx2-int8-tables.h | 517 ++++++++++++++++++++++++++++++++++++++++++
 extensions/avx2-int8.c        | 184 +++++++++++++++
 2 files changed, 701 insertions(+)
---
diff --git a/extensions/avx2-int8-tables.h b/extensions/avx2-int8-tables.h
index 8e3c6fb2a..cfc5208bc 100644
--- a/extensions/avx2-int8-tables.h
+++ b/extensions/avx2-int8-tables.h
@@ -4098,3 +4098,520 @@ static const int32_t linear_to_gamma[65536] =
 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255
 };
+
+static const float gamma_to_linear[512] =
+{
+0x0p+0,
+0x1.3e45677c176f7p-12,
+0x1.3e45677c176f7p-11,
+0x1.dd681b3a23272p-11,
+0x1.3e45677c176f7p-10,
+0x1.8dd6c15b1d4b4p-10,
+0x1.dd681b3a23272p-10,
+0x1.167cba8c94818p-9,
+0x1.3e45677c176f7p-9,
+0x1.660e146b9a5d5p-9,
+0x1.8dd6c15b1d4b4p-9,
+0x1.b6a31b5259c99p-9,
+0x1.e1e31d70c99ddp-9,
+0x1.07c38bf8583a9p-8,
+0x1.1fcc2beed6421p-8,
+0x1.390ffaf95e279p-8,
+0x1.53936cc7bc928p-8,
+0x1.6f5addb50c915p-8,
+0x1.8c6a94031b561p-8,
+0x1.aac6c0fb97351p-8,
+0x1.ca7381f9f602bp-8,
+0x1.eb74e160978dp-8,
+0x1.06e76bbda92b8p-7,
+0x1.18c2a5a8a8044p-7,
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+0x1.3e8b7b3bde965p-7,
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+0x1.3333333333333p-1,
+0x1.3535353535353p-1,
+0x1.3737373737373p-1,
+0x1.3939393939394p-1,
+0x1.3b3b3b3b3b3b4p-1,
+0x1.3d3d3d3d3d3d4p-1,
+0x1.3f3f3f3f3f3f4p-1,
+0x1.4141414141414p-1,
+0x1.4343434343434p-1,
+0x1.4545454545454p-1,
+0x1.4747474747474p-1,
+0x1.4949494949495p-1,
+0x1.4b4b4b4b4b4b5p-1,
+0x1.4d4d4d4d4d4d5p-1,
+0x1.4f4f4f4f4f4f5p-1,
+0x1.5151515151515p-1,
+0x1.5353535353535p-1,
+0x1.5555555555555p-1,
+0x1.5757575757575p-1,
+0x1.5959595959596p-1,
+0x1.5b5b5b5b5b5b6p-1,
+0x1.5d5d5d5d5d5d6p-1,
+0x1.5f5f5f5f5f5f6p-1,
+0x1.6161616161616p-1,
+0x1.6363636363636p-1,
+0x1.6565656565656p-1,
+0x1.6767676767676p-1,
+0x1.6969696969697p-1,
+0x1.6b6b6b6b6b6b7p-1,
+0x1.6d6d6d6d6d6d7p-1,
+0x1.6f6f6f6f6f6f7p-1,
+0x1.7171717171717p-1,
+0x1.7373737373737p-1,
+0x1.7575757575757p-1,
+0x1.7777777777777p-1,
+0x1.7979797979798p-1,
+0x1.7b7b7b7b7b7b8p-1,
+0x1.7d7d7d7d7d7d8p-1,
+0x1.7f7f7f7f7f7f8p-1,
+0x1.8181818181818p-1,
+0x1.8383838383838p-1,
+0x1.8585858585858p-1,
+0x1.8787878787878p-1,
+0x1.8989898989899p-1,
+0x1.8b8b8b8b8b8b9p-1,
+0x1.8d8d8d8d8d8d9p-1,
+0x1.8f8f8f8f8f8f9p-1,
+0x1.9191919191919p-1,
+0x1.9393939393939p-1,
+0x1.9595959595959p-1,
+0x1.9797979797979p-1,
+0x1.999999999999ap-1,
+0x1.9b9b9b9b9b9bap-1,
+0x1.9d9d9d9d9d9dap-1,
+0x1.9f9f9f9f9f9fap-1,
+0x1.a1a1a1a1a1a1ap-1,
+0x1.a3a3a3a3a3a3ap-1,
+0x1.a5a5a5a5a5a5ap-1,
+0x1.a7a7a7a7a7a7ap-1,
+0x1.a9a9a9a9a9a9bp-1,
+0x1.ababababababbp-1,
+0x1.adadadadadadbp-1,
+0x1.afafafafafafbp-1,
+0x1.b1b1b1b1b1b1bp-1,
+0x1.b3b3b3b3b3b3bp-1,
+0x1.b5b5b5b5b5b5bp-1,
+0x1.b7b7b7b7b7b7bp-1,
+0x1.b9b9b9b9b9b9cp-1,
+0x1.bbbbbbbbbbbbcp-1,
+0x1.bdbdbdbdbdbdcp-1,
+0x1.bfbfbfbfbfbfcp-1,
+0x1.c1c1c1c1c1c1cp-1,
+0x1.c3c3c3c3c3c3cp-1,
+0x1.c5c5c5c5c5c5cp-1,
+0x1.c7c7c7c7c7c7cp-1,
+0x1.c9c9c9c9c9c9dp-1,
+0x1.cbcbcbcbcbcbdp-1,
+0x1.cdcdcdcdcdcddp-1,
+0x1.cfcfcfcfcfcfdp-1,
+0x1.d1d1d1d1d1d1dp-1,
+0x1.d3d3d3d3d3d3dp-1,
+0x1.d5d5d5d5d5d5dp-1,
+0x1.d7d7d7d7d7d7dp-1,
+0x1.d9d9d9d9d9d9ep-1,
+0x1.dbdbdbdbdbdbep-1,
+0x1.ddddddddddddep-1,
+0x1.dfdfdfdfdfdfep-1,
+0x1.e1e1e1e1e1e1ep-1,
+0x1.e3e3e3e3e3e3ep-1,
+0x1.e5e5e5e5e5e5ep-1,
+0x1.e7e7e7e7e7e7ep-1,
+0x1.e9e9e9e9e9e9fp-1,
+0x1.ebebebebebebfp-1,
+0x1.ededededededfp-1,
+0x1.efefefefefeffp-1,
+0x1.f1f1f1f1f1f1fp-1,
+0x1.f3f3f3f3f3f3fp-1,
+0x1.f5f5f5f5f5f5fp-1,
+0x1.f7f7f7f7f7f7fp-1,
+0x1.f9f9f9f9f9fap-1,
+0x1.fbfbfbfbfbfcp-1,
+0x1.fdfdfdfdfdfep-1,
+0x1p+0
+};
diff --git a/extensions/avx2-int8.c b/extensions/avx2-int8.c
index b6d516566..a3ded4d7a 100644
--- a/extensions/avx2-int8.c
+++ b/extensions/avx2-int8.c
@@ -338,6 +338,184 @@ conv_rgbaF_linear_rgba8_gamma (const Babl  *conversion,
 #undef CVT1
 #undef CVTA1
 
+#define CVT1(src, dst) \
+  (*dst++ = gamma_to_linear[*src++])
+
+#define CVTA1(src, dst) \
+  (*dst++ = gamma_to_linear[*src++ + 256])
+
+static inline void
+conv_y8_gamma_yF_linear (const Babl    *conversion,
+                         const uint8_t *src,
+                         float         *dst,
+                         long           samples)
+{
+  const __m128i *src_vec;
+  __v8sf        *dst_vec;
+
+  while ((uintptr_t) dst % 32 && samples > 0)
+    {
+      CVT1 (src, dst);
+
+      samples--;
+    }
+
+  src_vec = (const __m128i *) src;
+  dst_vec = (__v8sf        *) dst;
+
+  while (samples >= 16)
+    {
+      __m128i i8_01;
+      __m256i i32_0;
+
+      i8_01 = _mm_loadu_si128 (src_vec++);
+
+      i32_0      = _mm256_cvtepu8_epi32 (i8_01);
+      *dst_vec++ = _mm256_i32gather_ps (gamma_to_linear, i32_0, 4);
+
+      i8_01 = _mm_shuffle_epi32 (i8_01, _MM_SHUFFLE (1, 0, 3, 2));
+
+      i32_0      = _mm256_cvtepu8_epi32 (i8_01);
+      *dst_vec++ = _mm256_i32gather_ps (gamma_to_linear, i32_0, 4);
+
+      samples -= 16;
+    }
+
+  src = (const uint8_t *) src_vec;
+  dst = (float         *) dst_vec;
+
+  while (samples > 0)
+    {
+      CVT1 (src, dst);
+
+      samples--;
+    }
+}
+
+static inline void
+conv_ya8_gamma_yaF_linear (const Babl    *conversion,
+                           const uint8_t *src,
+                           float         *dst,
+                           long           samples)
+{
+  const __m128i *src_vec;
+  __v8sf        *dst_vec;
+  const __m256i  offset = _mm256_setr_epi32 (0, 256, 0, 256,
+                                             0, 256, 0, 256);
+
+  while ((uintptr_t) dst % 32 && samples > 0)
+    {
+      CVT1  (src, dst);
+      CVTA1 (src, dst);
+
+      samples--;
+    }
+
+  src_vec = (const __m128i *) src;
+  dst_vec = (__v8sf        *) dst;
+
+  while (samples >= 8)
+    {
+      __m128i i8_01;
+      __m256i i32_0;
+
+      i8_01 = _mm_loadu_si128 (src_vec++);
+
+      i32_0       = _mm256_cvtepu8_epi32 (i8_01);
+      i32_0      += offset;
+      *dst_vec++  = _mm256_i32gather_ps (gamma_to_linear, i32_0, 4);
+
+      i8_01 = _mm_shuffle_epi32 (i8_01, _MM_SHUFFLE (1, 0, 3, 2));
+
+      i32_0       = _mm256_cvtepu8_epi32 (i8_01);
+      i32_0      += offset;
+      *dst_vec++  = _mm256_i32gather_ps (gamma_to_linear, i32_0, 4);
+
+      samples -= 8;
+    }
+
+  src = (const uint8_t *) src_vec;
+  dst = (float         *) dst_vec;
+
+  while (samples > 0)
+    {
+      CVT1  (src, dst);
+      CVTA1 (src, dst);
+
+      samples--;
+    }
+}
+
+static inline void
+conv_rgb8_gamma_rgbF_linear (const Babl    *conversion,
+                             const uint8_t *src,
+                             float         *dst,
+                             long           samples)
+{
+  conv_y8_gamma_yF_linear (conversion, src, dst, 3 * samples);
+}
+
+static inline void
+conv_rgba8_gamma_rgbaF_linear (const Babl    *conversion,
+                               const uint8_t *src,
+                               float         *dst,
+                               long           samples)
+{
+  const __m128i *src_vec;
+  __v8sf        *dst_vec;
+  const __m256i  offset = _mm256_setr_epi32 (0, 0, 0, 256,
+                                             0, 0, 0, 256);
+
+  while ((uintptr_t) dst % 32 && samples > 0)
+    {
+      CVT1  (src, dst);
+      CVT1  (src, dst);
+      CVT1  (src, dst);
+      CVTA1 (src, dst);
+
+      samples--;
+    }
+
+  src_vec = (const __m128i *) src;
+  dst_vec = (__v8sf        *) dst;
+
+  while (samples >= 4)
+    {
+      __m128i i8_01;
+      __m256i i32_0;
+
+      i8_01 = _mm_loadu_si128 (src_vec++);
+
+      i32_0       = _mm256_cvtepu8_epi32 (i8_01);
+      i32_0      += offset;
+      *dst_vec++  = _mm256_i32gather_ps (gamma_to_linear, i32_0, 4);
+
+      i8_01 = _mm_shuffle_epi32 (i8_01, _MM_SHUFFLE (1, 0, 3, 2));
+
+      i32_0       = _mm256_cvtepu8_epi32 (i8_01);
+      i32_0      += offset;
+      *dst_vec++  = _mm256_i32gather_ps (gamma_to_linear, i32_0, 4);
+
+      samples -= 4;
+    }
+
+  src = (const uint8_t *) src_vec;
+  dst = (float         *) dst_vec;
+
+  while (samples > 0)
+    {
+      CVT1  (src, dst);
+      CVT1  (src, dst);
+      CVT1  (src, dst);
+      CVTA1 (src, dst);
+
+      samples--;
+    }
+}
+
+#undef CVT1
+#undef CVTA1
+
 #endif /* defined(USE_AVX2) */
 
 int init (void);
@@ -407,6 +585,12 @@ init (void)
                            dst ## _gamma,                             \
                            "linear",                                  \
                            conv_ ## src ## _linear_ ## dst ## _gamma, \
+                           NULL);                                     \
+                                                                      \
+      babl_conversion_new (dst ## _gamma,                             \
+                           src ## _linear,                            \
+                           "linear",                                  \
+                           conv_ ## dst ## _gamma_ ## src ## _linear, \
                            NULL);                                     \
     }                                                                 \
   while (0)