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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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