gfx/2d/ImageScalingSSE2.cpp@97036ab72558
gfx/2d/ImageScalingSSE2.cpp
Tue, 06 Jan 2015 21:39:09 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Tue, 06 Jan 2015 21:39:09 +0100
- branch
- TOR_BUG_9701
- changeset 8
- 97036ab72558
- permissions
- -rw-r--r--
Conditionally force memory storage according to privacy.thirdparty.isolate;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.
1 /* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
2 * This Source Code Form is subject to the terms of the Mozilla Public
3 * License, v. 2.0. If a copy of the MPL was not distributed with this
4 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
6 #include "ImageScaling.h"
7 #include "mozilla/Attributes.h"
9 #include "SSEHelpers.h"
11 /* The functions below use the following system for averaging 4 pixels:
12 *
13 * The first observation is that a half-adder is implemented as follows:
14 * R = S + 2C or in the case of a and b (a ^ b) + ((a & b) << 1);
15 *
16 * This can be trivially extended to three pixels by observaring that when
17 * doing (a ^ b ^ c) as the sum, the carry is simply the bitwise-or of the
18 * carries of the individual numbers, since the sum of 3 bits can only ever
19 * have a carry of one.
20 *
21 * We then observe that the average is then ((carry << 1) + sum) >> 1, or,
22 * assuming eliminating overflows and underflows, carry + (sum >> 1).
23 *
24 * We now average our existing sum with the fourth number, so we get:
25 * sum2 = (sum + d) >> 1 or (sum >> 1) + (d >> 1).
26 *
27 * We now observe that our sum has been moved into place relative to the
28 * carry, so we can now average with the carry to get the final 4 input
29 * average: avg = (sum2 + carry) >> 1;
30 *
31 * Or to reverse the proof:
32 * avg = ((sum >> 1) + carry + d >> 1) >> 1
33 * avg = ((a + b + c) >> 1 + d >> 1) >> 1
34 * avg = ((a + b + c + d) >> 2)
35 *
36 * An additional fact used in the SSE versions is the concept that we can
37 * trivially convert a rounded average to a truncated average:
38 *
39 * We have:
40 * f(a, b) = (a + b + 1) >> 1
41 *
42 * And want:
43 * g(a, b) = (a + b) >> 1
44 *
45 * Observe:
46 * ~f(~a, ~b) == ~((~a + ~b + 1) >> 1)
47 * == ~((-a - 1 + -b - 1 + 1) >> 1)
48 * == ~((-a - 1 + -b) >> 1)
49 * == ~((-(a + b) - 1) >> 1)
50 * == ~((~(a + b)) >> 1)
51 * == (a + b) >> 1
52 * == g(a, b)
53 */
55 MOZ_ALWAYS_INLINE __m128i _mm_not_si128(__m128i arg)
56 {
57 __m128i minusone = _mm_set1_epi32(0xffffffff);
58 return _mm_xor_si128(arg, minusone);
59 }
61 /* We have to pass pointers here, MSVC does not allow passing more than 3
62 * __m128i arguments on the stack. And it does not allow 16-byte aligned
63 * stack variables. This inlines properly on MSVC 2010. It does -not- inline
64 * with just the inline directive.
65 */
66 MOZ_ALWAYS_INLINE __m128i avg_sse2_8x2(__m128i *a, __m128i *b, __m128i *c, __m128i *d)
67 {
68 #define shuf1 _MM_SHUFFLE(2, 0, 2, 0)
69 #define shuf2 _MM_SHUFFLE(3, 1, 3, 1)
71 // This cannot be an inline function as the __Imm argument to _mm_shuffle_ps
72 // needs to be a compile time constant.
73 #define shuffle_si128(arga, argb, imm) \
74 _mm_castps_si128(_mm_shuffle_ps(_mm_castsi128_ps((arga)), _mm_castsi128_ps((argb)), (imm)));
76 __m128i t = shuffle_si128(*a, *b, shuf1);
77 *b = shuffle_si128(*a, *b, shuf2);
78 *a = t;
79 t = shuffle_si128(*c, *d, shuf1);
80 *d = shuffle_si128(*c, *d, shuf2);
81 *c = t;
83 #undef shuf1
84 #undef shuf2
85 #undef shuffle_si128
87 __m128i sum = _mm_xor_si128(*a, _mm_xor_si128(*b, *c));
89 __m128i carry = _mm_or_si128(_mm_and_si128(*a, *b), _mm_or_si128(_mm_and_si128(*a, *c), _mm_and_si128(*b, *c)));
91 sum = _mm_avg_epu8(_mm_not_si128(sum), _mm_not_si128(*d));
93 return _mm_not_si128(_mm_avg_epu8(sum, _mm_not_si128(carry)));
94 }
96 MOZ_ALWAYS_INLINE __m128i avg_sse2_4x2_4x1(__m128i a, __m128i b)
97 {
98 return _mm_not_si128(_mm_avg_epu8(_mm_not_si128(a), _mm_not_si128(b)));
99 }
101 MOZ_ALWAYS_INLINE __m128i avg_sse2_8x1_4x1(__m128i a, __m128i b)
102 {
103 __m128i t = _mm_castps_si128(_mm_shuffle_ps(_mm_castsi128_ps(a), _mm_castsi128_ps(b), _MM_SHUFFLE(3, 1, 3, 1)));
104 b = _mm_castps_si128(_mm_shuffle_ps(_mm_castsi128_ps(a), _mm_castsi128_ps(b), _MM_SHUFFLE(2, 0, 2, 0)));
105 a = t;
107 return _mm_not_si128(_mm_avg_epu8(_mm_not_si128(a), _mm_not_si128(b)));
108 }
110 MOZ_ALWAYS_INLINE uint32_t Avg2x2(uint32_t a, uint32_t b, uint32_t c, uint32_t d)
111 {
112 uint32_t sum = a ^ b ^ c;
113 uint32_t carry = (a & b) | (a & c) | (b & c);
115 uint32_t mask = 0xfefefefe;
117 // Not having a byte based average instruction means we should mask to avoid
118 // underflow.
119 sum = (((sum ^ d) & mask) >> 1) + (sum & d);
121 return (((sum ^ carry) & mask) >> 1) + (sum & carry);
122 }
124 // Simple 2 pixel average version of the function above.
125 MOZ_ALWAYS_INLINE uint32_t Avg2(uint32_t a, uint32_t b)
126 {
127 uint32_t sum = a ^ b;
128 uint32_t carry = (a & b);
130 uint32_t mask = 0xfefefefe;
132 return ((sum & mask) >> 1) + carry;
133 }
135 namespace mozilla {
136 namespace gfx {
138 void
139 ImageHalfScaler::HalfImage2D_SSE2(uint8_t *aSource, int32_t aSourceStride,
140 const IntSize &aSourceSize, uint8_t *aDest,
141 uint32_t aDestStride)
142 {
143 const int Bpp = 4;
145 for (int y = 0; y < aSourceSize.height; y += 2) {
146 __m128i *storage = (__m128i*)(aDest + (y / 2) * aDestStride);
147 int x = 0;
148 // Run a loop depending on alignment.
149 if (!(uintptr_t(aSource + (y * aSourceStride)) % 16) &&
150 !(uintptr_t(aSource + ((y + 1) * aSourceStride)) % 16)) {
151 for (; x < (aSourceSize.width - 7); x += 8) {
152 __m128i *upperRow = (__m128i*)(aSource + (y * aSourceStride + x * Bpp));
153 __m128i *lowerRow = (__m128i*)(aSource + ((y + 1) * aSourceStride + x * Bpp));
155 __m128i a = _mm_load_si128(upperRow);
156 __m128i b = _mm_load_si128(upperRow + 1);
157 __m128i c = _mm_load_si128(lowerRow);
158 __m128i d = _mm_load_si128(lowerRow + 1);
160 *storage++ = avg_sse2_8x2(&a, &b, &c, &d);
161 }
162 } else if (!(uintptr_t(aSource + (y * aSourceStride)) % 16)) {
163 for (; x < (aSourceSize.width - 7); x += 8) {
164 __m128i *upperRow = (__m128i*)(aSource + (y * aSourceStride + x * Bpp));
165 __m128i *lowerRow = (__m128i*)(aSource + ((y + 1) * aSourceStride + x * Bpp));
167 __m128i a = _mm_load_si128(upperRow);
168 __m128i b = _mm_load_si128(upperRow + 1);
169 __m128i c = loadUnaligned128(lowerRow);
170 __m128i d = loadUnaligned128(lowerRow + 1);
172 *storage++ = avg_sse2_8x2(&a, &b, &c, &d);
173 }
174 } else if (!(uintptr_t(aSource + ((y + 1) * aSourceStride)) % 16)) {
175 for (; x < (aSourceSize.width - 7); x += 8) {
176 __m128i *upperRow = (__m128i*)(aSource + (y * aSourceStride + x * Bpp));
177 __m128i *lowerRow = (__m128i*)(aSource + ((y + 1) * aSourceStride + x * Bpp));
179 __m128i a = loadUnaligned128((__m128i*)upperRow);
180 __m128i b = loadUnaligned128((__m128i*)upperRow + 1);
181 __m128i c = _mm_load_si128((__m128i*)lowerRow);
182 __m128i d = _mm_load_si128((__m128i*)lowerRow + 1);
184 *storage++ = avg_sse2_8x2(&a, &b, &c, &d);
185 }
186 } else {
187 for (; x < (aSourceSize.width - 7); x += 8) {
188 __m128i *upperRow = (__m128i*)(aSource + (y * aSourceStride + x * Bpp));
189 __m128i *lowerRow = (__m128i*)(aSource + ((y + 1) * aSourceStride + x * Bpp));
191 __m128i a = loadUnaligned128(upperRow);
192 __m128i b = loadUnaligned128(upperRow + 1);
193 __m128i c = loadUnaligned128(lowerRow);
194 __m128i d = loadUnaligned128(lowerRow + 1);
196 *storage++ = avg_sse2_8x2(&a, &b, &c, &d);
197 }
198 }
200 uint32_t *unalignedStorage = (uint32_t*)storage;
201 // Take care of the final pixels, we know there's an even number of pixels
202 // in the source rectangle. We use a 2x2 'simd' implementation for this.
203 //
204 // Potentially we only have to do this in the last row since overflowing
205 // 8 pixels in an earlier row would appear to be harmless as it doesn't
206 // touch invalid memory. Even when reading and writing to the same surface.
207 // in practice we only do this when doing an additional downscale pass, and
208 // in this situation we have unused stride to write into harmlessly.
209 // I do not believe the additional code complexity would be worth it though.
210 for (; x < aSourceSize.width; x += 2) {
211 uint8_t *upperRow = aSource + (y * aSourceStride + x * Bpp);
212 uint8_t *lowerRow = aSource + ((y + 1) * aSourceStride + x * Bpp);
214 *unalignedStorage++ = Avg2x2(*(uint32_t*)upperRow, *((uint32_t*)upperRow + 1),
215 *(uint32_t*)lowerRow, *((uint32_t*)lowerRow + 1));
216 }
217 }
218 }
220 void
221 ImageHalfScaler::HalfImageVertical_SSE2(uint8_t *aSource, int32_t aSourceStride,
222 const IntSize &aSourceSize, uint8_t *aDest,
223 uint32_t aDestStride)
224 {
225 for (int y = 0; y < aSourceSize.height; y += 2) {
226 __m128i *storage = (__m128i*)(aDest + (y / 2) * aDestStride);
227 int x = 0;
228 // Run a loop depending on alignment.
229 if (!(uintptr_t(aSource + (y * aSourceStride)) % 16) &&
230 !(uintptr_t(aSource + ((y + 1) * aSourceStride)) % 16)) {
231 for (; x < (aSourceSize.width - 3); x += 4) {
232 uint8_t *upperRow = aSource + (y * aSourceStride + x * 4);
233 uint8_t *lowerRow = aSource + ((y + 1) * aSourceStride + x * 4);
235 __m128i a = _mm_load_si128((__m128i*)upperRow);
236 __m128i b = _mm_load_si128((__m128i*)lowerRow);
238 *storage++ = avg_sse2_4x2_4x1(a, b);
239 }
240 } else if (!(uintptr_t(aSource + (y * aSourceStride)) % 16)) {
241 // This line doesn't align well.
242 for (; x < (aSourceSize.width - 3); x += 4) {
243 uint8_t *upperRow = aSource + (y * aSourceStride + x * 4);
244 uint8_t *lowerRow = aSource + ((y + 1) * aSourceStride + x * 4);
246 __m128i a = _mm_load_si128((__m128i*)upperRow);
247 __m128i b = loadUnaligned128((__m128i*)lowerRow);
249 *storage++ = avg_sse2_4x2_4x1(a, b);
250 }
251 } else if (!(uintptr_t(aSource + (y * aSourceStride)) % 16)) {
252 for (; x < (aSourceSize.width - 3); x += 4) {
253 uint8_t *upperRow = aSource + (y * aSourceStride + x * 4);
254 uint8_t *lowerRow = aSource + ((y + 1) * aSourceStride + x * 4);
256 __m128i a = loadUnaligned128((__m128i*)upperRow);
257 __m128i b = _mm_load_si128((__m128i*)lowerRow);
259 *storage++ = avg_sse2_4x2_4x1(a, b);
260 }
261 } else {
262 for (; x < (aSourceSize.width - 3); x += 4) {
263 uint8_t *upperRow = aSource + (y * aSourceStride + x * 4);
264 uint8_t *lowerRow = aSource + ((y + 1) * aSourceStride + x * 4);
266 __m128i a = loadUnaligned128((__m128i*)upperRow);
267 __m128i b = loadUnaligned128((__m128i*)lowerRow);
269 *storage++ = avg_sse2_4x2_4x1(a, b);
270 }
271 }
273 uint32_t *unalignedStorage = (uint32_t*)storage;
274 // Take care of the final pixels, we know there's an even number of pixels
275 // in the source rectangle.
276 //
277 // Similar overflow considerations are valid as in the previous function.
278 for (; x < aSourceSize.width; x++) {
279 uint8_t *upperRow = aSource + (y * aSourceStride + x * 4);
280 uint8_t *lowerRow = aSource + ((y + 1) * aSourceStride + x * 4);
282 *unalignedStorage++ = Avg2(*(uint32_t*)upperRow, *(uint32_t*)lowerRow);
283 }
284 }
285 }
287 void
288 ImageHalfScaler::HalfImageHorizontal_SSE2(uint8_t *aSource, int32_t aSourceStride,
289 const IntSize &aSourceSize, uint8_t *aDest,
290 uint32_t aDestStride)
291 {
292 for (int y = 0; y < aSourceSize.height; y++) {
293 __m128i *storage = (__m128i*)(aDest + (y * aDestStride));
294 int x = 0;
295 // Run a loop depending on alignment.
296 if (!(uintptr_t(aSource + (y * aSourceStride)) % 16)) {
297 for (; x < (aSourceSize.width - 7); x += 8) {
298 __m128i* pixels = (__m128i*)(aSource + (y * aSourceStride + x * 4));
300 __m128i a = _mm_load_si128(pixels);
301 __m128i b = _mm_load_si128(pixels + 1);
303 *storage++ = avg_sse2_8x1_4x1(a, b);
304 }
305 } else {
306 for (; x < (aSourceSize.width - 7); x += 8) {
307 __m128i* pixels = (__m128i*)(aSource + (y * aSourceStride + x * 4));
309 __m128i a = loadUnaligned128(pixels);
310 __m128i b = loadUnaligned128(pixels + 1);
312 *storage++ = avg_sse2_8x1_4x1(a, b);
313 }
314 }
316 uint32_t *unalignedStorage = (uint32_t*)storage;
317 // Take care of the final pixels, we know there's an even number of pixels
318 // in the source rectangle.
319 //
320 // Similar overflow considerations are valid as in the previous function.
321 for (; x < aSourceSize.width; x += 2) {
322 uint32_t *pixels = (uint32_t*)(aSource + (y * aSourceStride + x * 4));
324 *unalignedStorage++ = Avg2(*pixels, *(pixels + 1));
325 }
326 }
327 }
329 }
330 }
