1/*
2 * Copyright 2013 The Android Open Source Project
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8
9#include "SkBitmap.h"
10#include "SkColorPriv.h"
11#include "SkBlurImage_opts.h"
12#include "SkRect.h"
13
14#include <arm_neon.h>
15
16namespace {
17
18enum BlurDirection {
19    kX, kY
20};
21
22/**
23 * Helper function to load 2 pixels from diffent rows to a 8x8 NEON register
24 * and also pre-load pixels for future read
25 */
26template<BlurDirection srcDirection>
27inline uint8x8_t load_2_pixels(const SkPMColor* src, int srcStride) {
28    if (srcDirection == kX) {
29        uint32x2_t temp = vdup_n_u32(0);
30        // 10% faster by adding these 2 prefetches
31        SK_PREFETCH(src + 16);
32        SK_PREFETCH(src + srcStride + 16);
33        return vreinterpret_u8_u32(vld1_lane_u32(src + srcStride, vld1_lane_u32(src, temp, 0), 1));
34     } else {
35         return vld1_u8((uint8_t*)src);
36     }
37}
38
39/**
40 * Helper function to store the low 8-bits from a 16x8 NEON register to 2 rows
41 */
42template<BlurDirection dstDirection>
43inline void store_2_pixels(uint16x8_t result16x8, SkPMColor* dst, int dstStride) {
44    if (dstDirection == kX) {
45        uint32x2_t temp = vreinterpret_u32_u8(vmovn_u16(result16x8));
46        vst1_lane_u32(dst, temp, 0);
47        vst1_lane_u32(dst + dstStride, temp, 1);
48    } else {
49        uint8x8_t temp = vmovn_u16(result16x8);
50        vst1_u8((uint8_t*)dst, temp);
51    }
52}
53
54/**
55 * fast path for kernel size less than 128
56 */
57template<BlurDirection srcDirection, BlurDirection dstDirection>
58void SkDoubleRowBoxBlur_NEON(const SkPMColor** src, int srcStride, SkPMColor** dst, int kernelSize,
59                        int leftOffset, int rightOffset, int width, int* height)
60{
61    const int rightBorder = SkMin32(rightOffset + 1, width);
62    const int srcStrideX = srcDirection == kX ? 1 : srcStride;
63    const int dstStrideX = dstDirection == kX ? 1 : *height;
64    const int srcStrideY = srcDirection == kX ? srcStride : 1;
65    const int dstStrideY = dstDirection == kX ? width : 1;
66    const uint16x8_t scale = vdupq_n_u16((1 << 15) / kernelSize);
67
68    for (; *height >= 2; *height -= 2) {
69        uint16x8_t sum = vdupq_n_u16(0);
70        const SkPMColor* p = *src;
71        for (int i = 0; i < rightBorder; i++) {
72            sum = vaddw_u8(sum,
73                load_2_pixels<srcDirection>(p, srcStride));
74            p += srcStrideX;
75        }
76
77        const SkPMColor* sptr = *src;
78        SkPMColor* dptr = *dst;
79        for (int x = 0; x < width; x++) {
80            // val = (sum * scale * 2 + 0x8000) >> 16
81            uint16x8_t resultPixels = vreinterpretq_u16_s16(vqrdmulhq_s16(
82                vreinterpretq_s16_u16(sum), vreinterpretq_s16_u16(scale)));
83            store_2_pixels<dstDirection>(resultPixels, dptr, width);
84
85            if (x >= leftOffset) {
86                sum = vsubw_u8(sum,
87                    load_2_pixels<srcDirection>(sptr - leftOffset * srcStrideX, srcStride));
88            }
89            if (x + rightOffset + 1 < width) {
90                sum = vaddw_u8(sum,
91                    load_2_pixels<srcDirection>(sptr + (rightOffset + 1) * srcStrideX, srcStride));
92            }
93            sptr += srcStrideX;
94            dptr += dstStrideX;
95        }
96        *src += srcStrideY * 2;
97        *dst += dstStrideY * 2;
98    }
99}
100
101
102/**
103 * Helper function to spread the components of a 32-bit integer into the
104 * lower 8 bits of each 16-bit element of a NEON register.
105 */
106
107static inline uint16x4_t expand(uint32_t a) {
108    // ( ARGB ) -> ( ARGB ARGB ) -> ( A R G B A R G B )
109    uint8x8_t v8 = vreinterpret_u8_u32(vdup_n_u32(a));
110    // ( A R G B A R G B ) -> ( 0A 0R 0G 0B 0A 0R 0G 0B ) -> ( 0A 0R 0G 0B )
111    return vget_low_u16(vmovl_u8(v8));
112}
113
114template<BlurDirection srcDirection, BlurDirection dstDirection>
115void SkBoxBlur_NEON(const SkPMColor* src, int srcStride, SkPMColor* dst, int kernelSize,
116                    int leftOffset, int rightOffset, int width, int height)
117{
118    const int rightBorder = SkMin32(rightOffset + 1, width);
119    const int srcStrideX = srcDirection == kX ? 1 : srcStride;
120    const int dstStrideX = dstDirection == kX ? 1 : height;
121    const int srcStrideY = srcDirection == kX ? srcStride : 1;
122    const int dstStrideY = dstDirection == kX ? width : 1;
123    const uint32x4_t scale = vdupq_n_u32((1 << 24) / kernelSize);
124    const uint32x4_t half = vdupq_n_u32(1 << 23);
125
126    if (kernelSize < 128)
127    {
128        SkDoubleRowBoxBlur_NEON<srcDirection, dstDirection>(&src, srcStride, &dst, kernelSize,
129            leftOffset, rightOffset, width, &height);
130    }
131
132    for (; height > 0; height--) {
133        uint32x4_t sum = vdupq_n_u32(0);
134        const SkPMColor* p = src;
135        for (int i = 0; i < rightBorder; ++i) {
136            sum = vaddw_u16(sum, expand(*p));
137            p += srcStrideX;
138        }
139
140        const SkPMColor* sptr = src;
141        SkPMColor* dptr = dst;
142        for (int x = 0; x < width; ++x) {
143            // ( half+sumA*scale half+sumR*scale half+sumG*scale half+sumB*scale )
144            uint32x4_t result = vmlaq_u32(half, sum, scale);
145
146            // Saturated conversion to 16-bit.
147            // ( AAAA RRRR GGGG BBBB ) -> ( 0A 0R 0G 0B )
148            uint16x4_t result16 = vqshrn_n_u32(result, 16);
149
150            // Saturated conversion to 8-bit.
151            // ( 0A 0R 0G 0B ) -> ( 0A 0R 0G 0B 0A 0R 0G 0B ) -> ( A R G B A R G B )
152            uint8x8_t result8 = vqshrn_n_u16(vcombine_u16(result16, result16), 8);
153
154            // ( A R G B A R G B ) -> ( ARGB ARGB ) -> ( ARGB )
155            // Store low 32 bits to destination.
156            vst1_lane_u32(dptr, vreinterpret_u32_u8(result8), 0);
157
158            if (x >= leftOffset) {
159                const SkPMColor* l = sptr - leftOffset * srcStrideX;
160                sum = vsubw_u16(sum, expand(*l));
161            }
162            if (x + rightOffset + 1 < width) {
163                const SkPMColor* r = sptr + (rightOffset + 1) * srcStrideX;
164                sum = vaddw_u16(sum, expand(*r));
165            }
166            sptr += srcStrideX;
167            if (srcDirection == kX) {
168                SK_PREFETCH(sptr + (rightOffset + 16) * srcStrideX);
169            }
170            dptr += dstStrideX;
171        }
172        src += srcStrideY;
173        dst += dstStrideY;
174    }
175}
176
177} // namespace
178
179bool SkBoxBlurGetPlatformProcs_NEON(SkBoxBlurProc* boxBlurX,
180                                    SkBoxBlurProc* boxBlurY,
181                                    SkBoxBlurProc* boxBlurXY,
182                                    SkBoxBlurProc* boxBlurYX) {
183    *boxBlurX = SkBoxBlur_NEON<kX, kX>;
184    *boxBlurY = SkBoxBlur_NEON<kY, kY>;
185    *boxBlurXY = SkBoxBlur_NEON<kX, kY>;
186    *boxBlurYX = SkBoxBlur_NEON<kY, kX>;
187    return true;
188}
189