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;********************************************************************
;* *
;* THIS FILE IS PART OF THE OggTheora SOFTWARE CODEC SOURCE CODE. *
;* USE, DISTRIBUTION AND REPRODUCTION OF THIS LIBRARY SOURCE IS *
;* GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE *
;* IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING. *
;* *
;* THE Theora SOURCE CODE IS COPYRIGHT (C) 2002-2010 *
;* by the Xiph.Org Foundation and contributors http://www.xiph.org/ *
;* *
;********************************************************************
;
; function:
; last mod: $Id: armbits.s 17481 2010-10-03 22:49:42Z tterribe $
;
;********************************************************************
AREA |.text|, CODE, READONLY
; Explicitly specifying alignment here because some versions of
; gas don't align code correctly. See
; http://lists.gnu.org/archive/html/bug-binutils/2011-06/msg00199.html
; https://bugzilla.mozilla.org/show_bug.cgi?id=920992
ALIGN
EXPORT oc_pack_read_arm
EXPORT oc_pack_read1_arm
EXPORT oc_huff_token_decode_arm
oc_pack_read1_arm PROC
; r0 = oc_pack_buf *_b
ADD r12,r0,#8
LDMIA r12,{r2,r3} ; r2 = window
; Stall... ; r3 = available
; Stall...
SUBS r3,r3,#1 ; r3 = available-1, available<1 => LT
BLT oc_pack_read1_refill
MOV r0,r2,LSR #31 ; r0 = window>>31
MOV r2,r2,LSL #1 ; r2 = window<<=1
STMIA r12,{r2,r3} ; window = r2
; available = r3
MOV PC,r14
ENDP
oc_pack_read_arm PROC
; r0 = oc_pack_buf *_b
; r1 = int _bits
ADD r12,r0,#8
LDMIA r12,{r2,r3} ; r2 = window
; Stall... ; r3 = available
; Stall...
SUBS r3,r3,r1 ; r3 = available-_bits, available<_bits => LT
BLT oc_pack_read_refill
RSB r0,r1,#32 ; r0 = 32-_bits
MOV r0,r2,LSR r0 ; r0 = window>>32-_bits
MOV r2,r2,LSL r1 ; r2 = window<<=_bits
STMIA r12,{r2,r3} ; window = r2
; available = r3
MOV PC,r14
; We need to refill window.
oc_pack_read1_refill
MOV r1,#1
oc_pack_read_refill
STMFD r13!,{r10,r11,r14}
LDMIA r0,{r10,r11} ; r10 = stop
; r11 = ptr
RSB r0,r1,#32 ; r0 = 32-_bits
RSB r3,r3,r0 ; r3 = 32-available
; We can use unsigned compares for both the pointers and for available
; (allowing us to chain condition codes) because available will never be
; larger than 32 (or we wouldn't be here), and thus 32-available will never be
; negative.
CMP r10,r11 ; ptr<stop => HI
CMPHI r3,#7 ; available<=24 => HI
LDRHIB r14,[r11],#1 ; r14 = *ptr++
SUBHI r3,#8 ; available += 8
; (HI) Stall...
ORRHI r2,r14,LSL r3 ; r2 = window|=r14<<32-available
CMPHI r10,r11 ; ptr<stop => HI
CMPHI r3,#7 ; available<=24 => HI
LDRHIB r14,[r11],#1 ; r14 = *ptr++
SUBHI r3,#8 ; available += 8
; (HI) Stall...
ORRHI r2,r14,LSL r3 ; r2 = window|=r14<<32-available
CMPHI r10,r11 ; ptr<stop => HI
CMPHI r3,#7 ; available<=24 => HI
LDRHIB r14,[r11],#1 ; r14 = *ptr++
SUBHI r3,#8 ; available += 8
; (HI) Stall...
ORRHI r2,r14,LSL r3 ; r2 = window|=r14<<32-available
CMPHI r10,r11 ; ptr<stop => HI
CMPHI r3,#7 ; available<=24 => HI
LDRHIB r14,[r11],#1 ; r14 = *ptr++
SUBHI r3,#8 ; available += 8
; (HI) Stall...
ORRHI r2,r14,LSL r3 ; r2 = window|=r14<<32-available
SUBS r3,r0,r3 ; r3 = available-=_bits, available<bits => GT
BLT oc_pack_read_refill_last
MOV r0,r2,LSR r0 ; r0 = window>>32-_bits
MOV r2,r2,LSL r1 ; r2 = window<<=_bits
STR r11,[r12,#-4] ; ptr = r11
STMIA r12,{r2,r3} ; window = r2
; available = r3
LDMFD r13!,{r10,r11,PC}
; Either we wanted to read more than 24 bits and didn't have enough room to
; stuff the last byte into the window, or we hit the end of the packet.
oc_pack_read_refill_last
CMP r11,r10 ; ptr<stop => LO
; If we didn't hit the end of the packet, then pull enough of the next byte to
; to fill up the window.
LDRLOB r14,[r11] ; (LO) r14 = *ptr
; Otherwise, set the EOF flag and pretend we have lots of available bits.
MOVHS r14,#1 ; (HS) r14 = 1
ADDLO r10,r3,r1 ; (LO) r10 = available
STRHS r14,[r12,#8] ; (HS) eof = 1
ANDLO r10,r10,#7 ; (LO) r10 = available&7
MOVHS r3,#1<<30 ; (HS) available = OC_LOTS_OF_BITS
ORRLO r2,r14,LSL r10 ; (LO) r2 = window|=*ptr>>(available&7)
MOV r0,r2,LSR r0 ; r0 = window>>32-_bits
MOV r2,r2,LSL r1 ; r2 = window<<=_bits
STR r11,[r12,#-4] ; ptr = r11
STMIA r12,{r2,r3} ; window = r2
; available = r3
LDMFD r13!,{r10,r11,PC}
ENDP
oc_huff_token_decode_arm PROC
; r0 = oc_pack_buf *_b
; r1 = const ogg_int16_t *_tree
STMFD r13!,{r4,r5,r10,r14}
LDRSH r10,[r1] ; r10 = n=_tree[0]
LDMIA r0,{r2-r5} ; r2 = stop
; Stall... ; r3 = ptr
; Stall... ; r4 = window
; r5 = available
CMP r10,r5 ; n>available => GT
BGT oc_huff_token_decode_refill0
RSB r14,r10,#32 ; r14 = 32-n
MOV r14,r4,LSR r14 ; r14 = bits=window>>32-n
ADD r14,r1,r14,LSL #1 ; r14 = _tree+bits
LDRSH r12,[r14,#2] ; r12 = node=_tree[1+bits]
; Stall...
; Stall...
RSBS r14,r12,#0 ; r14 = -node, node>0 => MI
BMI oc_huff_token_decode_continue
MOV r10,r14,LSR #8 ; r10 = n=node>>8
MOV r4,r4,LSL r10 ; r4 = window<<=n
SUB r5,r10 ; r5 = available-=n
STMIB r0,{r3-r5} ; ptr = r3
; window = r4
; available = r5
AND r0,r14,#255 ; r0 = node&255
LDMFD r13!,{r4,r5,r10,pc}
; The first tree node wasn't enough to reach a leaf, read another
oc_huff_token_decode_continue
ADD r12,r1,r12,LSL #1 ; r12 = _tree+node
MOV r4,r4,LSL r10 ; r4 = window<<=n
SUB r5,r5,r10 ; r5 = available-=n
LDRSH r10,[r12],#2 ; r10 = n=_tree[node]
; Stall... ; r12 = _tree+node+1
; Stall...
CMP r10,r5 ; n>available => GT
BGT oc_huff_token_decode_refill
RSB r14,r10,#32 ; r14 = 32-n
MOV r14,r4,LSR r14 ; r14 = bits=window>>32-n
ADD r12,r12,r14 ;
LDRSH r12,[r12,r14] ; r12 = node=_tree[node+1+bits]
; Stall...
; Stall...
RSBS r14,r12,#0 ; r14 = -node, node>0 => MI
BMI oc_huff_token_decode_continue
MOV r10,r14,LSR #8 ; r10 = n=node>>8
MOV r4,r4,LSL r10 ; r4 = window<<=n
SUB r5,r10 ; r5 = available-=n
STMIB r0,{r3-r5} ; ptr = r3
; window = r4
; available = r5
AND r0,r14,#255 ; r0 = node&255
LDMFD r13!,{r4,r5,r10,pc}
oc_huff_token_decode_refill0
ADD r12,r1,#2 ; r12 = _tree+1
oc_huff_token_decode_refill
; We can't possibly need more than 15 bits, so available must be <= 15.
; Therefore we can load at least two bytes without checking it.
CMP r2,r3 ; ptr<stop => HI
LDRHIB r14,[r3],#1 ; r14 = *ptr++
RSBHI r5,r5,#24 ; (HI) available = 32-(available+=8)
RSBLS r5,r5,#32 ; (LS) r5 = 32-available
ORRHI r4,r14,LSL r5 ; r4 = window|=r14<<32-available
CMPHI r2,r3 ; ptr<stop => HI
LDRHIB r14,[r3],#1 ; r14 = *ptr++
SUBHI r5,#8 ; available += 8
; (HI) Stall...
ORRHI r4,r14,LSL r5 ; r4 = window|=r14<<32-available
; We can use unsigned compares for both the pointers and for available
; (allowing us to chain condition codes) because available will never be
; larger than 32 (or we wouldn't be here), and thus 32-available will never be
; negative.
CMPHI r2,r3 ; ptr<stop => HI
CMPHI r5,#7 ; available<=24 => HI
LDRHIB r14,[r3],#1 ; r14 = *ptr++
SUBHI r5,#8 ; available += 8
; (HI) Stall...
ORRHI r4,r14,LSL r5 ; r4 = window|=r14<<32-available
CMP r2,r3 ; ptr<stop => HI
MOVLS r5,#-1<<30 ; (LS) available = OC_LOTS_OF_BITS+32
CMPHI r5,#7 ; (HI) available<=24 => HI
LDRHIB r14,[r3],#1 ; (HI) r14 = *ptr++
SUBHI r5,#8 ; (HI) available += 8
; (HI) Stall...
ORRHI r4,r14,LSL r5 ; (HI) r4 = window|=r14<<32-available
RSB r14,r10,#32 ; r14 = 32-n
MOV r14,r4,LSR r14 ; r14 = bits=window>>32-n
ADD r12,r12,r14 ;
LDRSH r12,[r12,r14] ; r12 = node=_tree[node+1+bits]
RSB r5,r5,#32 ; r5 = available
; Stall...
RSBS r14,r12,#0 ; r14 = -node, node>0 => MI
BMI oc_huff_token_decode_continue
MOV r10,r14,LSR #8 ; r10 = n=node>>8
MOV r4,r4,LSL r10 ; r4 = window<<=n
SUB r5,r10 ; r5 = available-=n
STMIB r0,{r3-r5} ; ptr = r3
; window = r4
; available = r5
AND r0,r14,#255 ; r0 = node&255
LDMFD r13!,{r4,r5,r10,pc}
ENDP
END
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