Add Neon I8MM horiz 2x1 scale spec. impl for convolve_2d_scale
AV1 has a limit on the scale ratio, specifically, the reference
resolution cannot be more than 2 times the source resolution in any
dimension. Given that the algorithm uses higher precision
(1/1024-pel) for the step size (chapter 7.11.3.4. [1]), the
horizontal scaling function can be easily optimised for this specific
case. The indices of the source pixel to be interpolated are
calculated using the (subpel_qn + x * step) >> 1024 equation, which
can be simplified if step is a multiple of 1024.
Add implementation that specialises on x_step_qn equals to 2048, that
gives an uplift of around 28% when a 2x1 scaling is applied.
[1]https://aomediacodec.github.io/av1-spec/av1-spec.pdf
Change-Id: I87b0730d0a75c534813f154555cbdb473b445438
diff --git a/av1/common/arm/av1_convolve_scale_neon_i8mm.c b/av1/common/arm/av1_convolve_scale_neon_i8mm.c
index ab215ca..42de38f 100644
--- a/av1/common/arm/av1_convolve_scale_neon_i8mm.c
+++ b/av1/common/arm/av1_convolve_scale_neon_i8mm.c
@@ -19,6 +19,13 @@
#include "aom_dsp/arm/transpose_neon.h"
#include "av1/common/arm/convolve_scale_neon.h"
+// clang-format off
+DECLARE_ALIGNED(16, static const uint8_t, kScale2DotProdPermuteTbl[32]) = {
+ 0, 1, 2, 3, 2, 3, 4, 5, 4, 5, 6, 7, 6, 7, 8, 9,
+ 4, 5, 6, 7, 6, 7, 8, 9, 8, 9, 10, 11, 10, 11, 12, 13
+};
+// clang-format on
+
static INLINE int16x4_t convolve8_4_h(const uint8x8_t s0, const uint8x8_t s1,
const uint8x8_t s2, const uint8x8_t s3,
const int8x8_t filter,
@@ -160,6 +167,128 @@
}
}
+static INLINE int16x4_t convolve8_4_h_scale_2(uint8x16_t samples,
+ const int8x8_t filters,
+ const int32x4_t horiz_const,
+ const uint8x16x2_t permute_tbl) {
+ // Permute samples ready for dot product.
+ // { 0, 1, 2, 3, 2, 3, 4, 5, 4, 5, 6, 7, 6, 7, 8, 9 }
+ // { 4, 5, 6, 7, 6, 7, 8, 9, 8, 9, 10, 11, 10, 11, 12, 13 }
+ uint8x16_t perm_samples[2] = { vqtbl1q_u8(samples, permute_tbl.val[0]),
+ vqtbl1q_u8(samples, permute_tbl.val[1]) };
+
+ int32x4_t sum = vusdotq_lane_s32(horiz_const, perm_samples[0], filters, 0);
+ sum = vusdotq_lane_s32(sum, perm_samples[1], filters, 1);
+
+ // We halved the filter values so -1 from right shift.
+ return vshrn_n_s32(sum, ROUND0_BITS - 1);
+}
+
+static INLINE int16x8_t convolve8_8_h_scale_2(uint8x16_t samples[2],
+ const int8x8_t filters,
+ const int32x4_t horiz_const,
+ const uint8x16x2_t permute_tbl) {
+ // Permute samples ready for dot product.
+ // { 0, 1, 2, 3, 2, 3, 4, 5, 4, 5, 6, 7, 6, 7, 8, 9 }
+ // { 4, 5, 6, 7, 6, 7, 8, 9, 8, 9, 10, 11, 10, 11, 12, 13 }
+ uint8x16_t perm_samples[4] = { vqtbl1q_u8(samples[0], permute_tbl.val[0]),
+ vqtbl1q_u8(samples[0], permute_tbl.val[1]),
+ vqtbl1q_u8(samples[1], permute_tbl.val[0]),
+ vqtbl1q_u8(samples[1], permute_tbl.val[1]) };
+
+ // First 4 output values.
+ int32x4_t sum0123 =
+ vusdotq_lane_s32(horiz_const, perm_samples[0], filters, 0);
+ sum0123 = vusdotq_lane_s32(sum0123, perm_samples[1], filters, 1);
+
+ // Second 4 output values.
+ int32x4_t sum4567 =
+ vusdotq_lane_s32(horiz_const, perm_samples[2], filters, 0);
+ sum4567 = vusdotq_lane_s32(sum4567, perm_samples[3], filters, 1);
+
+ // We halved the filter values so -1 from right shift.
+ return vcombine_s16(vshrn_n_s32(sum0123, ROUND0_BITS - 1),
+ vshrn_n_s32(sum4567, ROUND0_BITS - 1));
+}
+
+static INLINE void convolve_horiz_scale_2_neon_i8mm(
+ const uint8_t *src, int src_stride, int16_t *dst, int dst_stride, int w,
+ int h, const int16_t *x_filter) {
+ const int bd = 8;
+ // A shim of 1 << (ROUND0_BITS - 1) enables us to use non-rounding
+ // shifts - which are generally faster than rounding shifts on modern CPUs.
+ // The additional -1 is needed because we are halving the filter values.
+ const int32x4_t horiz_offset =
+ vdupq_n_s32((1 << (bd + FILTER_BITS - 2)) + (1 << (ROUND0_BITS - 2)));
+
+ const uint8x16x2_t permute_tbl = vld1q_u8_x2(kScale2DotProdPermuteTbl);
+ // Filter values are all even so halve them to fit in int8_t.
+ const int8x8_t filter = vshrn_n_s16(vld1q_s16(x_filter), 1);
+
+ if (w == 4) {
+ do {
+ const uint8_t *s = src;
+ int16_t *d = dst;
+ int width = w;
+
+ do {
+ uint8x16_t s0, s1, s2, s3;
+ load_u8_16x4(s, src_stride, &s0, &s1, &s2, &s3);
+
+ int16x4_t d0 =
+ convolve8_4_h_scale_2(s0, filter, horiz_offset, permute_tbl);
+ int16x4_t d1 =
+ convolve8_4_h_scale_2(s1, filter, horiz_offset, permute_tbl);
+ int16x4_t d2 =
+ convolve8_4_h_scale_2(s2, filter, horiz_offset, permute_tbl);
+ int16x4_t d3 =
+ convolve8_4_h_scale_2(s3, filter, horiz_offset, permute_tbl);
+
+ store_s16_4x4(d, dst_stride, d0, d1, d2, d3);
+
+ s += 8;
+ d += 4;
+ width -= 4;
+ } while (width != 0);
+
+ dst += 4 * dst_stride;
+ src += 4 * src_stride;
+ h -= 4;
+ } while (h > 0);
+ } else {
+ do {
+ const uint8_t *s = src;
+ int16_t *d = dst;
+ int width = w;
+
+ do {
+ uint8x16_t s0[2], s1[2], s2[2], s3[2];
+ load_u8_16x4(s, src_stride, &s0[0], &s1[0], &s2[0], &s3[0]);
+ load_u8_16x4(s + 8, src_stride, &s0[1], &s1[1], &s2[1], &s3[1]);
+
+ int16x8_t d0 =
+ convolve8_8_h_scale_2(s0, filter, horiz_offset, permute_tbl);
+ int16x8_t d1 =
+ convolve8_8_h_scale_2(s1, filter, horiz_offset, permute_tbl);
+ int16x8_t d2 =
+ convolve8_8_h_scale_2(s2, filter, horiz_offset, permute_tbl);
+ int16x8_t d3 =
+ convolve8_8_h_scale_2(s3, filter, horiz_offset, permute_tbl);
+
+ store_s16_8x4(d, dst_stride, d0, d1, d2, d3);
+
+ s += 16;
+ d += 8;
+ width -= 8;
+ } while (width != 0);
+
+ dst += 4 * dst_stride;
+ src += 4 * src_stride;
+ h -= 4;
+ } while (h > 0);
+ }
+}
+
void av1_convolve_2d_scale_neon_i8mm(const uint8_t *src, int src_stride,
uint8_t *dst, int dst_stride, int w, int h,
const InterpFilterParams *filter_params_x,
@@ -191,9 +320,29 @@
const ptrdiff_t vert_offset = (filter_params_y->taps / 2 - 1) * src_stride;
// Horizontal filter
- convolve_horiz_scale_neon_i8mm(
- 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 (x_step_qn != 2 * (1 << SCALE_SUBPEL_BITS)) {
+ convolve_horiz_scale_neon_i8mm(
+ 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 {
+ assert(subpel_x_qn < (1 << SCALE_SUBPEL_BITS));
+ // The filter index is calculated using the
+ // ((subpel_x_qn + x * x_step_qn) & SCALE_SUBPEL_MASK) >> SCALE_EXTRA_BITS
+ // equation, where the values of x are from 0 to w. If x_step_qn is a
+ // multiple of SCALE_SUBPEL_MASK we can leave it out of the equation.
+ const ptrdiff_t filter_offset =
+ SUBPEL_TAPS * ((subpel_x_qn & SCALE_SUBPEL_MASK) >> SCALE_EXTRA_BITS);
+ const int16_t *x_filter = filter_params_x->filter_ptr + filter_offset;
+
+ // The source index is calculated using the (subpel_x_qn + x * x_step_qn) >>
+ // SCALE_SUBPEL_BITS, where the values of x are from 0 to w. If subpel_x_qn
+ // < (1 << SCALE_SUBPEL_BITS) and x_step_qn % (1 << SCALE_SUBPEL_BITS) == 0,
+ // the source index can be determined using the value x * (x_step_qn /
+ // (1 << SCALE_SUBPEL_BITS)).
+ convolve_horiz_scale_2_neon_i8mm(src - horiz_offset - vert_offset,
+ src_stride, im_block, im_stride, w, im_h,
+ x_filter);
+ }
// Vertical filter
if (filter_params_y->interp_filter == MULTITAP_SHARP) {
