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59109f3293
Current blitters-test program had difficulties detecting a bug in
over_n_8888_8888_ca implementation for MIPS DSPr2:
http://lists.freedesktop.org/archives/pixman/2013-March/002645.html
In order to hit the buggy code path, two consecutive mask values had
to be equal to 0xFFFFFFFF because of loop unrolling. The current
blitters-test generates random images in such a way that each byte
has 25% probability for having 0xFF value. Hence each 32-bit mask
value has ~0.4% probability for 0xFFFFFFFF. Because we are testing
many compositing operations with many pixels, encountering at least
one 0xFFFFFFFF mask value reasonably fast is not a problem. If a
bug related to 0xFFFFFFFF mask value is artificialy introduced into
over_n_8888_8888_ca generic C function, it gets detected on 675591
iteration in blitters-test (out of 2000000).
However two consecutive 0xFFFFFFFF mask values are much less likely
to be generated, so the bug was missed by blitters-test.
This patch addresses the problem by also randomly setting the 32-bit
values in images to either 0xFFFFFFFF or 0x00000000 (also with 25%
probability). It allows to have larger clusters of consecutive 0x00
or 0xFF bytes in images which may have special shortcuts for handling
them in unrolled or SIMD optimized code.
172 lines
6.0 KiB
C
172 lines
6.0 KiB
C
/*
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* Copyright © 2012 Siarhei Siamashka <siarhei.siamashka@gmail.com>
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*
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* Based on the public domain implementation of small noncryptographic PRNG
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* authored by Bob Jenkins: http://burtleburtle.net/bob/rand/smallprng.html
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice (including the next
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* paragraph) shall be included in all copies or substantial portions of the
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* Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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* DEALINGS IN THE SOFTWARE.
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*/
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#ifndef __UTILS_PRNG_H__
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#define __UTILS_PRNG_H__
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/*
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* This file provides a fast SIMD-optimized noncryptographic PRNG (pseudorandom
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* number generator), with the output good enough to pass "Big Crush" tests
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* from TestU01 (http://en.wikipedia.org/wiki/TestU01).
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*
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* SIMD code uses http://gcc.gnu.org/onlinedocs/gcc/Vector-Extensions.html
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* which is a GCC specific extension. There is also a slower alternative
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* code path, which should work with any C compiler.
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*
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* The "prng_t" structure keeps the internal state of the random number
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* generator. It is possible to have multiple instances of the random number
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* generator active at the same time, in this case each of them needs to have
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* its own "prng_t". All the functions take a pointer to "prng_t"
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* as the first argument.
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*
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* Functions:
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*
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* ----------------------------------------------------------------------------
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* void prng_srand_r (prng_t *prng, uint32_t seed);
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*
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* Initialize the pseudorandom number generator. The sequence of preudorandom
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* numbers is deterministic and only depends on "seed". Any two generators
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* initialized with the same seed will produce exactly the same sequence.
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*
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* ----------------------------------------------------------------------------
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* uint32_t prng_rand_r (prng_t *prng);
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*
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* Generate a single uniformly distributed 32-bit pseudorandom value.
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*
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* ----------------------------------------------------------------------------
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* void prng_randmemset_r (prng_t *prng,
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* void *buffer,
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* size_t size,
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* prng_randmemset_flags_t flags);
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*
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* Fills the memory buffer "buffer" with "size" bytes of pseudorandom data.
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* The "flags" argument may be used to tweak some statistics properties:
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* RANDMEMSET_MORE_00 - set ~25% of bytes to 0x00
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* RANDMEMSET_MORE_FF - set ~25% of bytes to 0xFF
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* The flags can be combined. This allows a bit better simulation of typical
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* pixel data, which normally contains a lot of fully transparent or fully
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* opaque pixels.
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*/
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#ifdef HAVE_CONFIG_H
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#include <config.h>
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#endif
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#include "pixman-private.h"
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/*****************************************************************************/
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#if defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 7))
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#define GCC_VECTOR_EXTENSIONS_SUPPORTED
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typedef uint32_t uint32x4 __attribute__ ((vector_size(16)));
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typedef uint8_t uint8x16 __attribute__ ((vector_size(16)));
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#endif
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typedef struct
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{
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uint32_t a, b, c, d;
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} smallprng_t;
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typedef struct
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{
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#ifdef GCC_VECTOR_EXTENSIONS_SUPPORTED
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uint32x4 a, b, c, d;
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#else
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smallprng_t p1, p2, p3, p4;
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#endif
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smallprng_t p0;
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} prng_t;
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typedef union
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{
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uint8_t b[16];
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uint32_t w[4];
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#ifdef GCC_VECTOR_EXTENSIONS_SUPPORTED
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uint8x16 vb;
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uint32x4 vw;
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#endif
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} prng_rand_128_data_t;
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/*****************************************************************************/
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static force_inline uint32_t
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smallprng_rand_r (smallprng_t *x)
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{
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uint32_t e = x->a - ((x->b << 27) + (x->b >> (32 - 27)));
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x->a = x->b ^ ((x->c << 17) ^ (x->c >> (32 - 17)));
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x->b = x->c + x->d;
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x->c = x->d + e;
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x->d = e + x->a;
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return x->d;
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}
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/* Generate 4 bytes (32-bits) of random data */
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static force_inline uint32_t
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prng_rand_r (prng_t *x)
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{
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return smallprng_rand_r (&x->p0);
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}
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/* Generate 16 bytes (128-bits) of random data */
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static force_inline void
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prng_rand_128_r (prng_t *x, prng_rand_128_data_t *data)
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{
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#ifdef GCC_VECTOR_EXTENSIONS_SUPPORTED
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uint32x4 e = x->a - ((x->b << 27) + (x->b >> (32 - 27)));
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x->a = x->b ^ ((x->c << 17) ^ (x->c >> (32 - 17)));
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x->b = x->c + x->d;
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x->c = x->d + e;
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x->d = e + x->a;
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data->vw = x->d;
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#else
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data->w[0] = smallprng_rand_r (&x->p1);
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data->w[1] = smallprng_rand_r (&x->p2);
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data->w[2] = smallprng_rand_r (&x->p3);
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data->w[3] = smallprng_rand_r (&x->p4);
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#endif
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}
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typedef enum
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{
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RANDMEMSET_MORE_00 = 1, /* ~25% chance for 0x00 bytes */
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RANDMEMSET_MORE_FF = 2, /* ~25% chance for 0xFF bytes */
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RANDMEMSET_MORE_00000000 = 4, /* ~25% chance for 0x00000000 clusters */
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RANDMEMSET_MORE_FFFFFFFF = 8, /* ~25% chance for 0xFFFFFFFF clusters */
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RANDMEMSET_MORE_00_AND_FF = (RANDMEMSET_MORE_00 | RANDMEMSET_MORE_00000000 |
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RANDMEMSET_MORE_FF | RANDMEMSET_MORE_FFFFFFFF)
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} prng_randmemset_flags_t;
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/* Set the 32-bit seed for PRNG */
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void prng_srand_r (prng_t *prng, uint32_t seed);
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/* Fill memory buffer with random data */
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void prng_randmemset_r (prng_t *prng,
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void *buffer,
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size_t size,
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prng_randmemset_flags_t flags);
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#endif
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