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;//
;//
;// File Name: armVCM4P10_UnpackBlock4x4_s.s
;// OpenMAX DL: v1.0.2
;// Revision: 9641
;// Date: Thursday, February 7, 2008
;//
;// (c) Copyright 2007-2008 ARM Limited. All Rights Reserved.
;//
;//
;//
INCLUDE omxtypes_s.h
INCLUDE armCOMM_s.h
;// Define the processor variants supported by this file
M_VARIANTS ARM1136JS
IF ARM1136JS
;//--------------------------------------
;// Input Arguments and their scope/usage
;//--------------------------------------
ppSrc RN 0 ;// Persistent variable
pDst RN 1 ;// Persistent variable
;//--------------------------------
;// Variables and their scope/usage
;//--------------------------------
pSrc RN 2 ;// Persistent variables
Flag RN 3
Value RN 4
Value2 RN 5
strOffset RN 6
cstOffset RN 7
M_START armVCM4P10_UnpackBlock4x4, r7
LDR pSrc, [ppSrc] ;// Load pSrc
MOV cstOffset, #31 ;// To be used in the loop, to compute offset
;//-----------------------------------------------------------------------
; Firstly, fill all the coefficient values on the <pDst> buffer by zero
;//-----------------------------------------------------------------------
MOV Value, #0 ;// Initialize the zero value
MOV Value2, #0 ;// Initialize the zero value
LDRB Flag, [pSrc], #1 ;// Preload <Flag> before <unpackLoop>
STRD Value, [pDst, #0] ;// pDst[0] = pDst[1] = pDst[2] = pDst[3] = 0
STRD Value, [pDst, #8] ;// pDst[4] = pDst[5] = pDst[6] = pDst[7] = 0
STRD Value, [pDst, #16] ;// pDst[8] = pDst[9] = pDst[10] = pDst[11] = 0
STRD Value, [pDst, #24] ;// pDst[12] = pDst[13] = pDst[14] = pDst[15] = 0
;//----------------------------------------------------------------------------
;// The loop below parses and unpacks the input stream. The C-model has
;// a somewhat complicated logic for sign extension. But in the v6 version,
;// that can be easily taken care by loading the data from <pSrc> stream as
;// SIGNED byte/halfword. So, based on the first TST instruction, 8-bits or
;// 16-bits are read.
;//
;// Next, to compute the offset, where the unpacked value needs to be stored,
;// we modify the computation to perform [(Flag & 15) < 1] as [(Flag < 1) & 31]
;// This results in a saving of one cycle.
;//----------------------------------------------------------------------------
unpackLoop
TST Flag, #0x10 ;// Computing (Flag & 0x10)
LDRSBNE Value2,[pSrc,#1] ;// Load byte wise to avoid unaligned access
LDRBNE Value, [pSrc], #2
AND strOffset, cstOffset, Flag, LSL #1 ;// strOffset = (Flag & 15) < 1;
LDRSBEQ Value, [pSrc], #1 ;// Value = (OMX_U8) *pSrc++
ORRNE Value,Value,Value2, LSL #8 ;// Value = (OMX_U16) *pSrc++
TST Flag, #0x20 ;// Computing (Flag & 0x20) to check, if we're done
LDRBEQ Flag, [pSrc], #1 ;// Flag = (OMX_U8) *pSrc++, for next iteration
STRH Value, [pDst, strOffset] ;// Store <Value> at offset <strOffset>
BEQ unpackLoop ;// Branch to the loop beginning
STR pSrc, [ppSrc] ;// Update the bitstream pointer
M_END
ENDIF
END
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