www.pudn.com > scaling.rar > pix_expand_h.h62
* ========================================================================= *
* TEXAS INSTRUMENTS, INC. *
* *
* NAME *
* pix_expand *
*S *
*S REVISION HISTORY *
*S 15-Oct-2000 Rewrote from scratch . . . . . . . . . J. Zbiciak *
* *
* USAGE *
* This routine is C-callable and can be called as: *
* *
* void pix_expand_asm *
* ( *
* int n, /* # of elements */ *
* const unsigned char *restrict in_data, /* Input data */ *
* short *restrict out_data /* Output data */ *
* ) *
* *
* *
* DESCRIPTION *
* The code takes an array of bytes and promotes them to half-words *
* by zero-extension. *
* *
* This is the C equivalent of the assembly code, without *
* restrictions. The assembly code has restrictions, as noted below. *
* *
* void pix_expand *
* ( *
* int n, *
* const unsigned char *restrict in_data, *
* short *restrict out_data *
* ) *
* { *
* int i; *
* *
* for (i = 0; i < n; i++) *
* out_data[i] = in_data[i]; *
* } *
* *
* ASSUMPTIONS *
* Input and output arrays must be double-word (8-byte) aligned. *
* *
* The input must be at least 16 elements long and contain a *
* multiple of 16 elements. *
* *
* NOTE *
* Interrupts are masked during the entire duration of this *
* function, as the entire function occurs within branch delay slots. *
* *
* MEMORY NOTE *
* No bank conflicts occur. This is a LITTLE ENDIAN implementation. *
* *
* TECHNIQUES *
* The loop is unrolled 16 times, loading bytes with LDDW. It uses *
* UNPKHU4 and UNPKLU4 to unpack the data and store the results with *
* STDW. *
* *
* To shave a few extra cycles from the function, the return branch *
* is issued from within the kernel. *
* *
* CYCLES *
* cycles = 3 * (n / 16) + 15. *
* For n = 1072, cycles = 216. *
* *
* CODESIZE *
* 100 bytes. *
* *
* ------------------------------------------------------------------------- *
* Copyright (c) 2000 Texas Instruments, Incorporated. *
* All Rights Reserved. *
* ========================================================================= *
.sect ".opt_pix_expand"
.global _pix_expand_asm
* ========================================================================= *
* End of file: pix_expand_h.h62 *
* ------------------------------------------------------------------------- *
* Copyright (c) 2000 Texas Instruments, Incorporated. *
* All Rights Reserved. *
* ========================================================================= *