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131 lines
9.8 KiB
131 lines
9.8 KiB
;* ======================================================================== *;
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;* TEXAS INSTRUMENTS, INC. *;
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;* *;
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;* DSPLIB DSP Signal Processing Library *;
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;* *;
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;* Release: Revision 1.04b *;
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;* CVS Revision: 1.8 Mon Jul 28 13:15:23 2003 (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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* DSP_maxidx *
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* *
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* REVISION DATE *
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* 23-Jul-2003 *
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* *
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* USAGE *
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* This routine is C callable, and has the following C prototype: *
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* *
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* int DSP_maxidx(const short *x, int nx); *
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* *
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* x = pointer to input data *
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* nx = number of samples *
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* return = max index *
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* *
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* DESCRIPTION *
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* This routine finds the maximum value of the vector x[ ] and *
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* returns the index of that value. *
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* *
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* The input array is treated as 16 separate "columns" that are *
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* interleaved throughout the array. If values in different *
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* columns are equal to the maximum value, then the element in *
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* the leftmost column is returned. If two values within a *
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* column are equal to the maximum, then the one with the lower *
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* index is returned. *
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* *
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* Column takes precedence over index. *
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* *
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* int DSP_maxidx(const short *x, int nx) *
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* { *
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* int col, idx; *
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* short max_val; *
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* int max_idx; *
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* *
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* max_val = x[0]; *
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* max_idx = 0; *
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* *
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* for (col = 0; col < 16; col++) *
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* for (idx = col; idx < nx; idx += 16) *
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* if (x[idx] > max_val) *
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* { *
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* max_val = x[idx]; *
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* max_idx = idx; *
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* } *
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* *
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* return max_idx; *
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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 some restrictions, as *
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* noted below. *
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* *
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* TECHNIQUES *
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* The code is unrolled 16 times to enable the full bandwidth of *
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* LDDW and MAX2 instructions to be utilized. This splits the *
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* search into 16 subranges. The global maximum is then found *
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* from the list of maximums of the subsranges. *
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* *
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* Then using this offset from the subranges, the global maximum *
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* and the index of it are found using a simple match. *
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* *
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* For common maximums in multiple ranges, the index will be *
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* different to the above C code. *
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* *
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* ASSUMPTIONS *
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* The input data are stored on double-word aligned boundaries. *
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* nx must be a multiple of 16 and >= 48 *
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* *
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* MEMORY NOTE *
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* There are no bank conflicts in this code. *
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* *
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* This code is ENDIAN NEUTRAL. *
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* *
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* This code requires 40 bytes of stack space for a temporary *
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* buffer. *
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* *
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* NOTES *
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* Interupts are disabled for the duration of this function. *
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* *
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* CYCLES *
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* 5/16 * nx + 42 *
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* For nx = 128, cycles = 82. *
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* *
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* CODESIZE *
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* 388 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 _DSP_maxidx
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* ========================================================================= *
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* End of file: dsp_maxidx.h64 *
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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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