cbp_ppc.s

MPEG4的VC代码

#    Copyright (C) 2002 Guillaume Morin <[e-mail]>, Alc魐e
#
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#    $Id: cbp_ppc.s,v 1.10 2002/11/17 00:57:57 edgomez Exp $
#    $Source: /xvid/xvidcore/src/bitstream/ppc_asm/cbp_ppc.s,v $
#    $Date: 2002/11/17 00:57:57 $
#    $Author: edgomez $
#
#    This is my first PPC ASM attempt. So I might do nasty things.
#    Please send any comments to <[e-mail]>


# Returns a field of bits that indicates non zero ac blocks
# for this macro block
#
# uint32_t calc_cbp_c(const int16_t codes[6][64])
#{
#	uint32_t i, j;
#	uint32_t cbp = 0;
#
#	for (i = 0; i < 6; i++) {
#		for (j = 1; j < 61; j+=4) {
#			if (codes[i][j]  |codes[i][j+1]|
#			    codes[i][j+2]|codes[i][j+3]) {
#				cbp |= 1 << (5 - i);
#				break;
#			}
#		}
#
#		if(codes[i][j]|codes[i][j+1]|codes[i][j+2])
#			cbp |= 1 << (5 - i);
#
#	}
#
#	return cbp;
#
#}

.data
.skip:
	.word 0,-1
.align 4 

.text
.global calc_cbp_ppc
calc_cbp_ppc:
	# r9 will contain coeffs addr
	mr %r9,%r3
	# r8 is the loop counter (rows)
	li %r8,5
	# r3 contains the result, therefore we set it to 0
	li %r3,0
.loop:
	# CTR is the loop2 counter
	li %r4,16
	mtctr %r4
	# r6 is coeff pointer for this line
	mr %r6,%r9
	lis %r7,.skip@ha
	addi %r7,%r7,.skip@l
	lwz %r7,0(%r7)
.loop2:
	# coeffs is a matrix of 16 bits cells
	lwz %r4,0(%r6)
	and %r4,%r4,%r7
	li %r7,-1

	lwz %r5,4(%r6)
	# or. updates CR0
	or. %r4,%r5,%r4
	# testing bit 2 (is zero) of CR0
	bf 2,.cbp
	addi %r6,%r6,8
	bdnz .loop2
	b .newline
.cbp:
	li %r4,1
	slw %r4,%r4,%r8
	or %r3,%r3,%r4
.newline:
	addi %r9,%r9,128
	# updates CR0, blabla
	subic. %r8,%r8,1
	bf 0,.loop
	blr