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160 lines
12 KiB
160 lines
12 KiB
3 years ago
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;* ======================================================================== *;
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;* TEXAS INSTRUMENTS, INC. *;
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;* *;
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;* IMGLIB DSP Image/Video Processing Library *;
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;* *;
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;* Release: Revision 1.04b *;
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;* CVS Revision: 1.8 Sun Sep 29 03:32:23 2002 (UTC) *;
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;* Snapshot date: 23-Oct-2003 *;
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;* *;
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;* This library contains proprietary intellectual property of Texas *;
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;* Instruments, Inc. The library and its source code are protected by *;
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;* various copyrights, and portions may also be protected by patents or *;
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;* other legal protections. *;
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;* *;
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;* This software is licensed for use with Texas Instruments TMS320 *;
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;* family DSPs. This license was provided to you prior to installing *;
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;* the software. You may review this license by consulting the file *;
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;* TI_license.PDF which accompanies the files in this library. *;
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;* ------------------------------------------------------------------------ *;
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;* Copyright (C) 2003 Texas Instruments, Incorporated. *;
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;* All Rights Reserved. *;
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;* ======================================================================== *;
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;* ======================================================================== *;
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;* Assembler compatibility shim for assembling 4.30 and later code on *;
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;* tools prior to 4.30. *;
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;* ======================================================================== *;
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;* ======================================================================== *;
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;* End of assembler compatibility shim. *;
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;* ======================================================================== *;
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* ========================================================================= *
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* TEXAS INSTRUMENTS, INC. *
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* *
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* NAME *
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* IMG_histogram *
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* *
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* REVISION DATE *
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* 26-May-2000 *
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* *
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* USAGE *
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* This routine is C-callable and can be called as: *
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* *
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* void IMG_histogram *
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* ( *
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* const unsigned char *restrict img, /* incoming image */ *
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* int n, /* number of pixels */ *
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* short accumulate, /* weighting factor */ *
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* short *restrict t_hist, /* temporary array */ *
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* short *restrict hist /* IMG_histogram. */ *
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* ); *
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* *
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* *
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* DESCRIPTION *
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* This code takes a IMG_histogram of an array of n, 8 bit inputs. It *
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* returns the IMG_histogram of 256 bins at 16 bit precision. It can *
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* either add or subtract to an existing IMG_histogram, using the *
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* 'accumulate' control. *
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* *
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* It requires some temporary storage for 4 temporary histograms, *
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* which are later summed together. *
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* *
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* void IMG_histogram *
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* ( *
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* const unsigned char *restrict img, /* incoming image */ *
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* int n, /* number of pixels */ *
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* short accumulate, /* weighting factor */ *
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* short *restrict t_hist, /* temporary array */ *
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* short *restrict hist /* IMG_histogram. */ *
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* ) *
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* { *
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* int pixel, j; *
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* for (j = 0; j < n; j++) *
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* { *
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* pixel = (int) img[j]; *
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* hist[pixel] += accumulate; *
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* } *
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* } *
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* *
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* The above C code is a general implementation without *
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* restrictions. The assembly code has various restrictions, as *
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* noted below. *
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* *
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* ASSUMPTIONS *
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* It is assumed that the temporary array of data, t_hist is *
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* initialised to zero. The input array of image data must be *
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* aligned to a 4 byte boundary and n must be a multiple of 8. The *
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* maximum number of pixels that can be profiled in each bin is *
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* 65535 in the main IMG_histogram. *
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* *
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* MEMORY NOTE *
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* No bank conflicts occur. *
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* *
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* The main IMG_histogram loop accesses two banks on 8 of 9 cycles, *
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* and four banks on the 9th cycle. The summing loop accesses *
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* 128 bits every cycle. *
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* *
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* TECHNIQUES *
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* This code operates on four interleaved IMG_histogram bins. The loop *
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* is divided into two halves: The "even" half operates on the *
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* even-numbered words from the input image, and the "odd" half *
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* operates on odd words. Each half processes four pixels at a *
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* time, and both halves operate on the same four sets of IMG_histogram *
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* bins. This introduces a memory dependency on the IMG_histogram bins *
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* which ordinarily would degrade performance. To break the memory *
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* depenencies, the two halves forward their results to each other *
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* via the register file, bypassing memory. *
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* *
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* Exact memory access ordering obviates the need to predicate *
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* stores The algorithm is ordered as follows: *
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* *
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* 1. Load from IMG_histogram for even half *
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* 2. Store odd_bin to IMG_histogram for odd half (previous itn.) *
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* 3. if data_even == previous data_odd increment even_bin by 2 *
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* else increment even_bin by 1, forward to odd *
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* 4. Load from IMG_histogram for odd half (current itn.) *
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* 5. Store even_bin to IMG_histogram for even half *
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* 6. if data_odd == previous data_even increment odd_bin by 2 *
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* else increment odd_bin by 1, forward to even *
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* 7. goto 1. *
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* *
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* With this particular ordering, forwarding is necessary between *
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* even/odd halves when pixels in adjacent halves need to be *
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* placed in the same bin. *
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* *
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* The store is never predicated and occurs speculatively *
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* as it will be overwritten by the next value containing the *
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* extra forwarded value. *
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* *
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* The four histograms are interleaved with each bin spaced four *
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* half-words apart and each IMG_histogram starting in a different *
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* memory bank. This allows the four IMG_histogram accesses to proceed *
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* in any order without worrying about bank conflicts. The *
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* diagram below illustrates this: (addresses are halfword *
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* offsets) *
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* *
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* 0 1 2 3 4 5 6 ... *
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* | hst 0 | hst 1 | hst 2 | hst 3 | hst 0 | hst 1 | ... ... *
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* | bin 0 | bin 0 | bin 0 | bin 0 | bin 1 | bin 1 | ... ... *
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* *
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* These are then summed together at the end in blocks of 4 *
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* *
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* CYCLES *
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* 9 * n/8 + 228 *
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* *
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* CODESIZE *
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* 552 bytes *
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* *
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* ------------------------------------------------------------------------- *
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* Copyright (c) 2003 Texas Instruments, Incorporated. *
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* All Rights Reserved. *
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* ========================================================================= *
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.global _IMG_histogram
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* ========================================================================= *
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* End of file: img_histogram.h64 *
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* ------------------------------------------------------------------------- *
|
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|
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* Copyright (c) 2003 Texas Instruments, Incorporated. *
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* All Rights Reserved. *
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* ========================================================================= *
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