Add Armv8.0 Neon 6-tap filter path for convolve_horiz_scale
The filter values used in the scaling algorithm are specified in the
documentation of the inter-prediction process (chapter 7.11.3.4. [1]).
These filter values are defined in the av1_interp_filter_params_list
in filter.h. An important characteristic of these filters, except the
MULTITAP_SHARP filter, is that at indices 0 and 7 the values are 0.
Add an implementation for horizontal filtering that specialises on
6-tap filters. This way we avoid redundant work associated with 8-tap
filters. This approach is not applicable for the DotProd and I8MM
version of this horizontal filtering, given that the dot product
instructions accumulate the result of 4 multiplications.
[1]https://aomediacodec.github.io/av1-spec/av1-spec.pdf
Change-Id: I09fcc138289c3b9ee39099b6cdab740e7049260c
diff --git a/av1/common/arm/av1_convolve_scale_neon.c b/av1/common/arm/av1_convolve_scale_neon.c
index a972a19..88d126e 100644
--- a/av1/common/arm/av1_convolve_scale_neon.c
+++ b/av1/common/arm/av1_convolve_scale_neon.c
@@ -68,12 +68,12 @@
return vshrq_n_s16(sum, ROUND0_BITS - 1);
}
-static INLINE void convolve_horiz_scale_neon(const uint8_t *src, int src_stride,
- int16_t *dst, int dst_stride,
- int w, int h,
- const int16_t *x_filter,
- const int subpel_x_qn,
- const int x_step_qn) {
+static INLINE void convolve_horiz_scale_8tap_neon(const uint8_t *src,
+ int src_stride, int16_t *dst,
+ int dst_stride, int w, int h,
+ const int16_t *x_filter,
+ const int subpel_x_qn,
+ const int x_step_qn) {
DECLARE_ALIGNED(16, int16_t, temp[8 * 8]);
const int bd = 8;
@@ -191,6 +191,166 @@
}
}
+static INLINE int16x4_t convolve6_4_h(const int16x4_t s0, const int16x4_t s1,
+ const int16x4_t s2, const int16x4_t s3,
+ const int16x4_t s4, const int16x4_t s5,
+ const int16x8_t filter,
+ const int32x4_t horiz_const) {
+ int16x4_t filter_lo = vget_low_s16(filter);
+ int16x4_t filter_hi = vget_high_s16(filter);
+
+ int32x4_t sum = horiz_const;
+ // Filter values at indices 0 and 7 are 0.
+ sum = vmlal_lane_s16(sum, s0, filter_lo, 1);
+ sum = vmlal_lane_s16(sum, s1, filter_lo, 2);
+ sum = vmlal_lane_s16(sum, s2, filter_lo, 3);
+ sum = vmlal_lane_s16(sum, s3, filter_hi, 0);
+ sum = vmlal_lane_s16(sum, s4, filter_hi, 1);
+ sum = vmlal_lane_s16(sum, s5, filter_hi, 2);
+
+ return vshrn_n_s32(sum, ROUND0_BITS);
+}
+
+static INLINE int16x8_t convolve6_8_h(const int16x8_t s0, const int16x8_t s1,
+ const int16x8_t s2, const int16x8_t s3,
+ const int16x8_t s4, const int16x8_t s5,
+ const int16x8_t filter,
+ const int16x8_t horiz_const) {
+ int16x4_t filter_lo = vget_low_s16(filter);
+ int16x4_t filter_hi = vget_high_s16(filter);
+
+ int16x8_t sum = horiz_const;
+ // Filter values at indices 0 and 7 are 0.
+ sum = vmlaq_lane_s16(sum, s0, filter_lo, 1);
+ sum = vmlaq_lane_s16(sum, s1, filter_lo, 2);
+ sum = vmlaq_lane_s16(sum, s2, filter_lo, 3);
+ sum = vmlaq_lane_s16(sum, s3, filter_hi, 0);
+ sum = vmlaq_lane_s16(sum, s4, filter_hi, 1);
+ sum = vmlaq_lane_s16(sum, s5, filter_hi, 2);
+
+ // We halved the filter values so -1 from right shift.
+ return vshrq_n_s16(sum, ROUND0_BITS - 1);
+}
+
+static INLINE void convolve_horiz_scale_6tap_neon(const uint8_t *src,
+ int src_stride, int16_t *dst,
+ int dst_stride, int w, int h,
+ const int16_t *x_filter,
+ const int subpel_x_qn,
+ const int x_step_qn) {
+ DECLARE_ALIGNED(16, int16_t, temp[8 * 8]);
+ const int bd = 8;
+
+ if (w == 4) {
+ // The shim of 1 << (ROUND0_BITS - 1) enables us to use non-rounding shifts.
+ const int32x4_t horiz_offset =
+ vdupq_n_s32((1 << (bd + FILTER_BITS - 1)) + (1 << (ROUND0_BITS - 1)));
+
+ do {
+ int x_qn = subpel_x_qn;
+
+ // Process a 4x4 tile.
+ for (int r = 0; r < 4; ++r) {
+ const uint8_t *const s = &src[x_qn >> SCALE_SUBPEL_BITS];
+
+ const ptrdiff_t filter_offset =
+ SUBPEL_TAPS * ((x_qn & SCALE_SUBPEL_MASK) >> SCALE_EXTRA_BITS);
+ const int16x8_t filter = vld1q_s16(x_filter + filter_offset);
+
+ uint8x8_t t0, t1, t2, t3;
+ load_u8_8x4(s, src_stride, &t0, &t1, &t2, &t3);
+
+ transpose_elems_inplace_u8_8x4(&t0, &t1, &t2, &t3);
+
+ int16x4_t s0 = vget_low_s16(vreinterpretq_s16_u16(vmovl_u8(t1)));
+ int16x4_t s1 = vget_low_s16(vreinterpretq_s16_u16(vmovl_u8(t2)));
+ int16x4_t s2 = vget_low_s16(vreinterpretq_s16_u16(vmovl_u8(t3)));
+ int16x4_t s3 = vget_high_s16(vreinterpretq_s16_u16(vmovl_u8(t0)));
+ int16x4_t s4 = vget_high_s16(vreinterpretq_s16_u16(vmovl_u8(t1)));
+ int16x4_t s5 = vget_high_s16(vreinterpretq_s16_u16(vmovl_u8(t2)));
+
+ int16x4_t d0 =
+ convolve6_4_h(s0, s1, s2, s3, s4, s5, filter, horiz_offset);
+
+ vst1_s16(&temp[r * 4], d0);
+ x_qn += x_step_qn;
+ }
+
+ // Transpose the 4x4 result tile and store.
+ int16x4_t d0, d1, d2, d3;
+ load_s16_4x4(temp, 4, &d0, &d1, &d2, &d3);
+
+ transpose_elems_inplace_s16_4x4(&d0, &d1, &d2, &d3);
+
+ store_s16_4x4(dst, dst_stride, d0, d1, d2, d3);
+
+ dst += 4 * dst_stride;
+ src += 4 * src_stride;
+ h -= 4;
+ } while (h > 0);
+ } else {
+ // The shim of 1 << (ROUND0_BITS - 1) enables us to use non-rounding shifts.
+ // The additional -1 is needed because we are halving the filter values.
+ const int16x8_t horiz_offset =
+ vdupq_n_s16((1 << (bd + FILTER_BITS - 2)) + (1 << (ROUND0_BITS - 2)));
+
+ do {
+ int x_qn = subpel_x_qn;
+ int16_t *d = dst;
+ int width = w;
+
+ do {
+ // Process an 8x8 tile.
+ for (int r = 0; r < 8; ++r) {
+ const uint8_t *const s = &src[(x_qn >> SCALE_SUBPEL_BITS)];
+
+ const ptrdiff_t filter_offset =
+ SUBPEL_TAPS * ((x_qn & SCALE_SUBPEL_MASK) >> SCALE_EXTRA_BITS);
+ int16x8_t filter = vld1q_s16(x_filter + filter_offset);
+ // Filter values are all even so halve them to allow convolution
+ // kernel computations to stay in 16-bit element types.
+ filter = vshrq_n_s16(filter, 1);
+
+ uint8x8_t t0, t1, t2, t3, t4, t5, t6, t7;
+ load_u8_8x8(s, src_stride, &t0, &t1, &t2, &t3, &t4, &t5, &t6, &t7);
+
+ transpose_elems_u8_8x8(t0, t1, t2, t3, t4, t5, t6, t7, &t0, &t1, &t2,
+ &t3, &t4, &t5, &t6, &t7);
+
+ int16x8_t s0 = vreinterpretq_s16_u16(vmovl_u8(t1));
+ int16x8_t s1 = vreinterpretq_s16_u16(vmovl_u8(t2));
+ int16x8_t s2 = vreinterpretq_s16_u16(vmovl_u8(t3));
+ int16x8_t s3 = vreinterpretq_s16_u16(vmovl_u8(t4));
+ int16x8_t s4 = vreinterpretq_s16_u16(vmovl_u8(t5));
+ int16x8_t s5 = vreinterpretq_s16_u16(vmovl_u8(t6));
+
+ int16x8_t d0 =
+ convolve6_8_h(s0, s1, s2, s3, s4, s5, filter, horiz_offset);
+
+ vst1q_s16(&temp[r * 8], d0);
+
+ x_qn += x_step_qn;
+ }
+
+ // Transpose the 8x8 result tile and store.
+ int16x8_t d0, d1, d2, d3, d4, d5, d6, d7;
+ load_s16_8x8(temp, 8, &d0, &d1, &d2, &d3, &d4, &d5, &d6, &d7);
+
+ transpose_elems_inplace_s16_8x8(&d0, &d1, &d2, &d3, &d4, &d5, &d6, &d7);
+
+ store_s16_8x8(d, dst_stride, d0, d1, d2, d3, d4, d5, d6, d7);
+
+ d += 8;
+ width -= 8;
+ } while (width != 0);
+
+ dst += 8 * dst_stride;
+ src += 8 * src_stride;
+ h -= 8;
+ } while (h > 0);
+ }
+}
+
void av1_convolve_2d_scale_neon(const uint8_t *src, int src_stride,
uint8_t *dst, int dst_stride, int w, int h,
const InterpFilterParams *filter_params_x,
@@ -222,9 +382,15 @@
const ptrdiff_t vert_offset = (filter_params_y->taps / 2 - 1) * src_stride;
// Horizontal filter
- convolve_horiz_scale_neon(
- src - horiz_offset - vert_offset, src_stride, im_block, im_stride, w,
- im_h, filter_params_x->filter_ptr, subpel_x_qn, x_step_qn);
+ if (filter_params_x->interp_filter == MULTITAP_SHARP) {
+ convolve_horiz_scale_8tap_neon(
+ src - horiz_offset - vert_offset, src_stride, im_block, im_stride, w,
+ im_h, filter_params_x->filter_ptr, subpel_x_qn, x_step_qn);
+ } else {
+ convolve_horiz_scale_6tap_neon(
+ src - horiz_offset - vert_offset, src_stride, im_block, im_stride, w,
+ im_h, filter_params_x->filter_ptr, subpel_x_qn, x_step_qn);
+ }
// Vertical filter
if (filter_params_y->interp_filter == MULTITAP_SHARP) {
