wasm: Generic add,sub saturate
BUG=webp:352
Change-Id: I2640df736ea852ca5adcb5048550e26475c777ef
diff --git a/src/dsp/dec_wasm.c b/src/dsp/dec_wasm.c
index ad9d08f..14f1da2 100644
--- a/src/dsp/dec_wasm.c
+++ b/src/dsp/dec_wasm.c
@@ -131,6 +131,20 @@
return final;
}
+// int16 to int8 with saturation.
+static WEBP_INLINE int8x16 int16x8_to_int8x16_sat(const int16x8 x) {
+ const int16x8 k7f = splat_int16(0x007f);
+ const int16x8 kff80 = splat_int16(0xff80);
+ const int16x8 s1 = (x < k7f);
+ const int16x8 a = (s1 & x) | (~s1 & k7f);
+ const int16x8 s2 = (a > kff80);
+ const int16x8 a2 = (s2 & a) | (~s2 & kff80);
+ const int8x16 final = (int8x16)__builtin_shufflevector(
+ (int8x16)a2, (int8x16)a2, 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24,
+ 26, 28, 30);
+ return final;
+}
+
//------------------------------------------------------------------------------
// Transforms (Paragraph 14.4)
@@ -317,26 +331,83 @@
{i8x16,i16x8}.{add,sub}_saturate_[su].
*/
+// For testing purposes.
+// #define ENABLE_X86_BUILTIN_ADDSUB_SAT
+
static WEBP_INLINE uint8x16 uint8x16_add_sat(const uint8x16 a,
const uint8x16 b) {
- // TODO(slavarnway): add generic implementation for non-x86
+#if ENABLE_X86_BUILTIN_ADDSUB_SAT
return (uint8x16)__builtin_ia32_paddusb128(a, b);
+#else
+ // Generic implementation for non-x86
+ const uint8x16 zero = splat_uint8(0);
+ const uint16x8 a_lo = _unpacklo_epi8(a, zero);
+ const uint16x8 a_hi = _unpackhi_epi8(a, zero);
+ const uint16x8 b_lo = _unpacklo_epi8(b, zero);
+ const uint16x8 b_hi = _unpackhi_epi8(b, zero);
+ const uint16x8 sum_lo = a_lo + b_lo;
+ const uint16x8 sum_hi = a_hi + b_hi;
+ const uint8x16 usat_lo = int16x8_to_uint8x16_sat(sum_lo);
+ const uint8x16 usat_hi = int16x8_to_uint8x16_sat(sum_hi);
+ return _unpacklo_epi64(usat_lo, usat_hi);
+#endif
}
static WEBP_INLINE int8x16 int8x16_add_sat(const int8x16 a, const int8x16 b) {
- // TODO(slavarnway): add generic implementation for non-x86
+#if ENABLE_X86_BUILTIN_ADDSUB_SAT
return (int8x16)__builtin_ia32_paddsb128(a, b);
+#else
+ // Generic implementation for non-x86
+ const int8x16 zero = splat_uint8(0);
+ const int16x8 eight = splat_int16(8);
+ const int16x8 a_lo = _unpacklo_epi8(zero, a) >> eight;
+ const int16x8 a_hi = _unpackhi_epi8(zero, a) >> eight;
+ const int16x8 b_lo = _unpacklo_epi8(zero, b) >> eight;
+ const int16x8 b_hi = _unpackhi_epi8(zero, b) >> eight;
+ const int16x8 sum_lo = a_lo + b_lo;
+ const int16x8 sum_hi = a_hi + b_hi;
+ const int8x16 sat_lo = int16x8_to_int8x16_sat(sum_lo);
+ const int8x16 sat_hi = int16x8_to_int8x16_sat(sum_hi);
+ return _unpacklo_epi64(sat_lo, sat_hi);
+#endif
}
static WEBP_INLINE uint8x16 uint8x16_sub_sat(const uint8x16 a,
const uint8x16 b) {
- // TODO(slavarnway): add generic implementation for non-x86
+#if ENABLE_X86_BUILTIN_ADDSUB_SAT
return (uint8x16)__builtin_ia32_psubusb128(a, b);
+#else
+ // Generic implementation for non-x86
+ const uint8x16 zero = splat_uint8(0);
+ const uint16x8 a_lo = _unpacklo_epi8(a, zero);
+ const uint16x8 a_hi = _unpackhi_epi8(a, zero);
+ const uint16x8 b_lo = _unpacklo_epi8(b, zero);
+ const uint16x8 b_hi = _unpackhi_epi8(b, zero);
+ const uint16x8 diff_lo = a_lo - b_lo;
+ const uint16x8 diff_hi = a_hi - b_hi;
+ const uint8x16 usat_lo = int16x8_to_uint8x16_sat(diff_lo);
+ const uint8x16 usat_hi = int16x8_to_uint8x16_sat(diff_hi);
+ return _unpacklo_epi64(usat_lo, usat_hi);
+#endif
}
static WEBP_INLINE int8x16 int8x16_sub_sat(const int8x16 a, const int8x16 b) {
- // TODO(slavarnway): add generic implementation for non-x86
+#if ENABLE_X86_BUILTIN_ADDSUB_SAT
return (int8x16)__builtin_ia32_psubsb128(a, b);
+#else
+ // Generic implementation for non-x86
+ const int8x16 zero = splat_uint8(0);
+ const int16x8 eight = splat_int16(8);
+ const int16x8 a_lo = _unpacklo_epi8(zero, a) >> eight;
+ const int16x8 a_hi = _unpackhi_epi8(zero, a) >> eight;
+ const int16x8 b_lo = _unpacklo_epi8(zero, b) >> eight;
+ const int16x8 b_hi = _unpackhi_epi8(zero, b) >> eight;
+ const int16x8 diff_lo = a_lo - b_lo;
+ const int16x8 diff_hi = a_hi - b_hi;
+ const int8x16 sat_lo = int16x8_to_int8x16_sat(diff_lo);
+ const int8x16 sat_hi = int16x8_to_int8x16_sat(diff_hi);
+ return _unpacklo_epi64(sat_lo, sat_hi);
+#endif
}
static WEBP_INLINE uint8x16 _max_u8x16(const uint8x16 a, const uint8x16 b) {
