mirror of
https://github.com/emmanuel-marty/lzsa.git
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Optimizations to all the 8088 assembly code. UNTESTED
This commit is contained in:
Krister Nordvall
parent
8075b5ab68
commit
0ec6a3748e
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@ -1,4 +1,4 @@
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; lzsa1fta.asm time-efficient decompressor implementation for 8088
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; LZSA1FTA.ASM time-efficient decompressor implementation for 8088
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; Turbo Assembler IDEAL mode dialect; can also be assembled with NASM.
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;
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; Usual DOS assembler SMALL model assumptions apply. This code:
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@ -8,6 +8,7 @@
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; - Trashes all data and segment registers
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;
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; Copyright (C) 2019 Jim Leonard, Emmanuel Marty
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; Additional optimizations by Krister Nordvall
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;
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; This software is provided 'as-is', without any express or implied
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; warranty. In no event will the authors be held liable for any damages
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@ -77,29 +78,29 @@ lzsa1_start:
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jnc @@got_literals_exact ;if no overflow, we have full count
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je @@big_literals
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@@mid_literals:
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;@@mid_literals:
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lodsb ;grab single extra length byte
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inc ah ;add 256
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; inc ah ;add 256
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xchg cx,ax ;with longer counts, we can save some time
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shr cx,1 ;by doing a word copy instead of a byte copy.
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rcr cl,1 ;by doing a word copy instead of a byte copy.
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rep movsw ;We don't need to account for overlap because
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adc cx,0 ;source for literals isn't the output buffer.
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rep movsb
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jmp @@check_offset_size
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; adc cx,0 ;source for literals isn't the output buffer.
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adc cx,cx ; rcl cx,1 might be even faster on 8088
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jmp @@copy_odd_byte
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@@big_literals:
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lodsw ;grab 16-bit extra length
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xchg cx,ax ;with longer counts, we can save some time
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shr cx,1 ;by doing a word copy instead of a byte copy.
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rep movsw
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adc cx,0
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rep movsb
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jmp @@check_offset_size
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adc cx,cx ; rcl cx,1 might be even faster on 8088
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jmp @@copy_odd_byte
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@@got_literals:
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segcs xlat ;shift literals length into place
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@@got_literals_exact:
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xchg cx,ax
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@@copy_odd_byte:
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rep movsb ;copy cx literals from ds:si to es:di
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@@check_offset_size:
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@ -122,8 +123,16 @@ lzsa1_start:
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lodsw ;grab 16-bit length
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xchg cx,ax ;get ready to do a long copy
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jcxz @@done_decompressing ;wait, is it the EOD marker? Exit if so
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jmp @@copy_len_preset ;otherwise, do the copy
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; jcxz @@done_decompressing ;wait, is it the EOD marker? Exit if so
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; jmp @@copy_len_preset ;otherwise, do the copy
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inc cx
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loop @@copy_len_preset
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;@@done_decompressing:
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pop ax ;retrieve the original decompression offset
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xchg di,ax ;compute decompressed size
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sub ax,di
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ret ;done decompressing, exit to caller
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@@get_long_offset:
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lodsw ;Get 2-byte match offset
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@ -143,12 +152,6 @@ lzsa1_start:
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mov ds,bp ;restore ds
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jmp @@decode_token ;go decode another token
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@@done_decompressing:
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pop ax ;retrieve the original decompression offset
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xchg di,ax ;compute decompressed size
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sub ax,di
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ret ;done decompressing, exit to caller
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;With a confirmed longer match length, we have an opportunity to optimize for
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;the case where a single byte is repeated long enough that we can benefit
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;from rep movsw to perform the run (instead of rep movsb).
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@ -175,7 +178,7 @@ lzsa1_start:
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;This won't affect 8088 that much, but it speeds up 8086 and higher.
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shr cx,1
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rep movsw
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adc cx,0
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adc cx,cx ; rcl cx,1 might be even faster on 8088
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rep movsb
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mov si,bp ;restore si
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pop ds
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@ -189,7 +192,7 @@ lzsa1_start:
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mov ah,al
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shr cx,1
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rep stosw ;perform word run
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adc cx,0
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adc cx,cx ; rcl cx,1 might be even faster on 8088
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rep stosb ;finish word run
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mov si,bp ;restore si
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pop ds
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@ -199,7 +202,8 @@ lzsa1_start:
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lodsw ;load first word of run
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shr cx,1
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rep stosw ;perform word run
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adc cx,0 ;despite 2-byte offset, compressor might
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; adc cx,0 ;despite 2-byte offset, compressor might
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adc cx,cx ; rcl cx,1 might be even faster on 8088
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rep stosb ;output odd length. better safe than sorry.
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mov si,bp ;restore si
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pop ds
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@ -1,6 +1,5 @@
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; lzsa2fta.asm time-efficient decompressor implementation for 808x CPUs.
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; LZSA1JMP.ASM time-efficient decompressor implementation for 808x CPUs.
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; Turbo Assembler IDEAL mode dialect.
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; (Is supposed to also assemble with NASM's IDEAL mode support, but YMMV.)
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;
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; This code assembles to about 3K of lookup tables and unrolled code,
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; but the tradeoff for that size is the absolute fastest decompressor
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@ -15,7 +14,7 @@
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; - Trashes all data and segment registers
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;
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; Copyright (C) 2019 Jim Leonard, Emmanuel Marty
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; Additional speed optimizations by Pavel Zagrebin
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; Additional speed optimizations by Pavel Zagrebin, Krister Nordvall
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;
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; This software is provided 'as-is', without any express or implied
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; warranty. In no event will the authors be held liable for any damages
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@ -295,14 +294,27 @@ MACRO do_match_copy
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jmp decode_token
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ENDM
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MACRO do_literal_copy
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MACRO do_literal_copy_shr
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LOCAL even
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; Copies a literal sequence using words.
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; Meant for longer lengths; for 128 bytes or less, use REP MOVSB.
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; requirements: cx=length, ds:si=compdata, es:di=output
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; must leave cx=0 at exit
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shr cx,1
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jnc even
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jnc even
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movsb
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even:
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rep movsw
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ENDM
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MACRO do_literal_copy_rcr
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LOCAL even
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; Copies a literal sequence using words.
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; Meant for longer lengths; for 128 bytes or less, use REP MOVSB.
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; requirements: (cf << 8 | cl)=length, ds:si=compdata, es:di=output
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; must leave cx=0 at exit
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rcr cl,1
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jnc even
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movsb
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even:
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rep movsw
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@ -403,21 +415,22 @@ lit_ext_mat_len_1b:
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; jz @@val249_3 ;if zf & cf, 249: get 16-bit literal length
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jc @@val250_3 ;if cf, 250: get extra literal length byte
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xchg cx,ax ;otherwise, we have our literal length
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do_literal_copy ;this might be better as rep movsw !!! benchmark
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do_literal_copy_shr ;this might be better as rep movsw !!! benchmark
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get_byte_match_offset
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copy_small_match_len
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@@val250_3:
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jz @@val249_3
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jz @@val249_3
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lodsb ;ah=0; grab single extra length byte
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inc ah ;ax=256+length byte
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; inc ah ;ax=256+length byte
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; Instead of 'inc ah' (2 bytes), use the CF in do_literal_copy_rcr
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xchg cx,ax
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do_literal_copy
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do_literal_copy_rcr
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get_byte_match_offset
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copy_small_match_len
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@@val249_3:
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lodsw ;grab 16-bit length
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xchg cx,ax
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do_literal_copy
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do_literal_copy_shr
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get_byte_match_offset
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copy_small_match_len
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@ -430,21 +443,22 @@ lit_ext_mat_ext_1b:
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; jz @@val249_4 ;if zf & cf, 249: get 16-bit literal length
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jc @@val250_4 ;if cf, 250: get extra literal length byte
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xchg cx,ax ;otherwise, we have our literal length
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do_literal_copy ;this might be better as rep movsw !!! benchmark
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do_literal_copy_shr ;this might be better as rep movsw !!! benchmark
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get_byte_match_offset
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copy_large_match_len
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@@val250_4:
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jz @@val249_4
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jz @@val249_4
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lodsb ;ah=0; grab single extra length byte
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inc ah ;ax=256+length byte
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; inc ah ;ax=256+length byte
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; Instead of 'inc ah' (2 bytes), use the CF in do_literal_copy_rcr
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xchg cx,ax
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do_literal_copy
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do_literal_copy_rcr
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get_byte_match_offset
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copy_large_match_len
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@@val249_4:
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lodsw ;grab 16-bit length
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xchg cx,ax
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do_literal_copy
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do_literal_copy_shr
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get_byte_match_offset
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copy_large_match_len
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@ -494,21 +508,22 @@ lit_ext_mat_len_2b:
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; jz @@val249_7 ;if zf & cf, 249: get 16-bit literal length
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jc @@val250_7 ;if cf, 250: get extra literal length byte
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xchg cx,ax ;otherwise, we have our literal length
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do_literal_copy ;this might be better as rep movsw !!! benchmark
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do_literal_copy_shr ;this might be better as rep movsw !!! benchmark
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get_word_match_offset
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copy_small_match_len
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@@val250_7:
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jz @@val249_7
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jz @@val249_7
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lodsb ;ah=0; grab single extra length byte
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inc ah ;ax=256+length byte
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; inc ah ;ax=256+length byte
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; Instead of 'inc ah' (2 bytes), use the CF in do_literal_copy_rcr
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xchg cx,ax
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do_literal_copy
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do_literal_copy_rcr
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get_word_match_offset
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copy_small_match_len
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@@val249_7:
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lodsw ;grab 16-bit length
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xchg cx,ax
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do_literal_copy
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do_literal_copy_shr
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get_word_match_offset
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copy_small_match_len
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@ -521,21 +536,22 @@ lit_ext_mat_ext_2b:
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; jz @@val249_8 ;if zf & cf, 249: get 16-bit literal length
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jc @@val250_8 ;if cf, 250: get extra literal length byte
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xchg cx,ax ;otherwise, we have our literal length
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do_literal_copy ;this might be better as rep movsw !!! benchmark
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do_literal_copy_shr ;this might be better as rep movsw !!! benchmark
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get_word_match_offset
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copy_large_match_len
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@@val250_8:
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jz @@val249_8
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jz @@val249_8
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lodsb ;ah=0; grab single extra length byte
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inc ah ;ax=256+length byte
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; inc ah ;ax=256+length byte
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; Instead of 'inc ah' (2 bytes), use the CF in do_literal_copy_rcr
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xchg cx,ax
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do_literal_copy
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do_literal_copy_rcr
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get_word_match_offset
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copy_large_match_len
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@@val249_8:
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lodsw ;grab 16-bit length
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xchg cx,ax
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do_literal_copy
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do_literal_copy_shr
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get_word_match_offset
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copy_large_match_len
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@ -1,4 +1,4 @@
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; lzsa2fta.asm - LZSA v2 time-efficient decompressor implementation for 8088
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; LZSA2FTA.ASM - LZSA v2 time-efficient decompressor implementation for 8088
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; Turbo Assembler IDEAL mode dialect; can also be assembled with NASM.
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;
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; Usual DOS assembler SMALL model assumptions apply. This code:
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@ -8,6 +8,7 @@
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; - Trashes all data and segment registers
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;
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; Copyright (C) 2019 Jim Leonard, Emmanuel Marty
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; Additional optimizations by Krister Nordvall
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;
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; This software is provided 'as-is', without any express or implied
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; warranty. In no event will the authors be held liable for any damages
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@ -72,7 +73,7 @@ lzsa2_speed_start:
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mov bx,0100H ;bx used by get_nybble
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@@decode_token:
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mov ax,cx ;clear ah - cx is zero (and must stay that way)
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xchg cx,ax ;clear ah - cx is zero
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lodsb ;read token byte: XYZ|LL|MMMM
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mov dx,ax ;keep copy of token in dl
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@ -101,28 +102,32 @@ lzsa2_speed_start:
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xchg cx,ax
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shr cx,1
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rep movsw
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adc cx,0
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adc cx,cx
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rep movsb
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jmp @@check_offset
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@@got_literals:
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xchg cx,ax
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rep movsb ;copy cx literals from ds:si to es:di
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jmp @@check_offset
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; jmp @@check_offset
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db 0B8h ; Opcode byte for MOV AX, <immed> (faster than jumping)
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;LZSA2 likes to produce tiny literals of 1 or 2 bytes. Handle them here.
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@@lit2b:movsb
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@@lit1b:movsb
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@@check_offset:
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test dl,dl ;check match offset mode in token (X bit)
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js @@rep_match_or_large_offset
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; test dl,dl ;check match offset mode in token (X bit)
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; js @@rep_match_or_large_offset
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cmp dl,040H ;check if this is a 5 or 9-bit offset (Y bit)
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jnb @@offset_9_bit
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; cmp dl,040H ;check if this is a 5 or 9-bit offset (Y bit)
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; jnb @@offset_9_bit
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test dl,0C0h
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js @@rep_match_or_large_offset
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jnz @@offset_9_bit
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;5 bit offset:
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xchg cx,ax ;clear ah - cx is zero from prior rep movs
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mov al,020H ;shift Z (offset bit 4) in place
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and al,dl
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shl al,1
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@ -131,12 +136,12 @@ lzsa2_speed_start:
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or al,cl ;merge nybble
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rol al,1
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xor al,0E1H ;set offset bits 7-5 to 1
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dec ah ;set offset bits 15-8 to 1
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cbw ;set offset bits 15-8 to 1
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jmp @@get_match_length
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@@rep_match_or_16_bit:
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test dl,020H ;test bit Z (offset bit 8)
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jne @@repeat_match ;rep-match
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jnz @@repeat_match ;rep-match
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;16 bit offset:
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lodsw ;Get 2-byte match offset
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@ -145,18 +150,18 @@ lzsa2_speed_start:
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@@offset_9_bit:
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;9 bit offset:
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xchg cx,ax ;clear ah - cx is zero from prior rep movs
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lodsb ;get 8 bit offset from stream in A
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dec ah ;set offset bits 15-8 to 1
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mov ah,0FFh ;set offset bits 15-8 to 1
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test dl,020H ;test bit Z (offset bit 8)
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je @@get_match_length
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jz @@get_match_length
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dec ah ;clear bit 8 if Z bit is clear
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jmp @@get_match_length
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@@rep_match_or_large_offset:
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cmp dl,0c0H ;check if this is a 13-bit offset
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; cmp dl,0c0H ;check if this is a 13-bit offset
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;or a 16-bit offset/rep match (Y bit)
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jnb @@rep_match_or_16_bit
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; jnb @@rep_match_or_16_bit
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jpe @@rep_match_or_16_bit
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;13 bit offset:
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mov ah,020H ;shift Z (offset bit 12) in place
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@ -188,7 +193,7 @@ lzsa2_speed_start:
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lodsb ;grab extra length byte
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add al,018H ;overflow?
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jnc @@got_matchlen_big ;if not, we have entire (big) length
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je @@done_decompressing ; detect EOD code
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jz @@done_decompressing ; detect EOD code
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lodsw ;grab 16-bit length
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@ -217,7 +222,7 @@ ENDIF
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;This won't affect 8088 that much, but it speeds up 8086 and higher.
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shr cx,1
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rep movsw
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adc cx,0
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adc cx,cx
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rep movsb
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xchg si,ax
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mov ds,dx ;restore ds:si
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@ -254,7 +259,7 @@ ENDIF
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mov ah,al
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shr cx,1
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rep stosw ;perform word run
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adc cx,0
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adc cx,cx
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rep stosb ;finish word run
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pop si
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mov ds,dx
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@ -266,7 +271,7 @@ IF HANDLE_WORD_RUN
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lodsw ;load first word of run
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shr cx,1
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rep stosw ;perform word run
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adc cx,0 ;despite 2-byte offset, compressor might
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adc cx,cx ;despite 2-byte offset, compressor might
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rep stosb ;output odd length. better safe than sorry.
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pop si
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mov ds,dx
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@ -1,6 +1,7 @@
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; decompress_small.S - space-efficient decompressor implementation for 8088
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;
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; Copyright (C) 2019 Emmanuel Marty
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; Additional optimizations by Krister Nordvall
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;
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; This software is provided 'as-is', without any express or implied
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; warranty. In no event will the authors be held liable for any damages
|
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@ -37,10 +38,10 @@ lzsa1_decompress:
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xor cx,cx
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.decode_token:
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mov ax,cx ; clear ah - cx is zero from above or from after rep movsb in .copy_match
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xchg cx,ax ; clear ah - cx is zero from above or from after rep movsb in .copy_match
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lodsb ; read token byte: O|LLL|MMMM
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mov dx,ax ; keep token in dl
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and al,070H ; isolate literals length in token (LLL)
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mov cl,4
|
||||
shr al,cl ; shift literals length into place
|
||||
|
|
@ -51,7 +52,7 @@ lzsa1_decompress:
|
|||
lodsb ; grab extra length byte
|
||||
add al,07H ; add LITERALS_RUN_LEN
|
||||
jnc .got_literals ; if no overflow, we have the full literals count, go copy
|
||||
jne .mid_literals
|
||||
jnz .mid_literals
|
||||
|
||||
lodsw ; grab 16-bit extra length
|
||||
db 81H ; mask inc ah/lodsb
|
||||
|
|
@ -88,11 +89,11 @@ lzsa1_decompress:
|
|||
lodsb ; grab extra length byte
|
||||
add al,012H ; add MIN_MATCH_SIZE + MATCH_RUN_LEN
|
||||
jnc .got_matchlen ; if no overflow, we have the entire length
|
||||
jne .mid_matchlen
|
||||
jnz .mid_matchlen
|
||||
|
||||
lodsw ; grab 16-bit length
|
||||
test ax,ax ; bail if we hit EOD
|
||||
je short .done_decompressing
|
||||
jz short .done_decompressing
|
||||
|
||||
db 81H ; mask inc ah/lodsb
|
||||
; (*like jmp short .got_literals but faster)
|
||||
|
|
@ -103,7 +104,7 @@ lzsa1_decompress:
|
|||
.got_matchlen:
|
||||
xchg cx,ax ; copy match length into cx
|
||||
push ds ; save ds:si (current pointer to compressed data)
|
||||
xchg si,ax
|
||||
xchg si,ax
|
||||
push es
|
||||
pop ds
|
||||
mov si,di ; ds:si now points at back reference in output data
|
||||
|
|
|
|||
|
|
@ -1,6 +1,7 @@
|
|||
; decompress_small.S - space-efficient decompressor implementation for 8088
|
||||
;
|
||||
; Copyright (C) 2019 Emmanuel Marty
|
||||
; Additional optimizations by Krister Nordvall
|
||||
;
|
||||
; This software is provided 'as-is', without any express or implied
|
||||
; warranty. In no event will the authors be held liable for any damages
|
||||
|
|
@ -39,10 +40,10 @@ lzsa2_decompress:
|
|||
xor bp,bp
|
||||
|
||||
.decode_token:
|
||||
mov ax,cx ; clear ah - cx is zero from above or from after rep movsb in .copy_match
|
||||
xchg cx,ax ; clear ah - cx is zero from above or from after rep movsb in .copy_match
|
||||
lodsb ; read token byte: XYZ|LL|MMMM
|
||||
mov dx,ax ; keep token in dl
|
||||
|
||||
|
||||
and al,018H ; isolate literals length in token (LL)
|
||||
mov cl,3
|
||||
shr al,cl ; shift literals length into place
|
||||
|
|
@ -51,7 +52,7 @@ lzsa2_decompress:
|
|||
jne .got_literals ; no, we have the full literals count from the token, go copy
|
||||
|
||||
call .get_nibble ; get extra literals length nibble
|
||||
add al,cl ; add len from token to nibble
|
||||
add al,cl ; add len from token to nibble
|
||||
cmp al,012H ; LITERALS_RUN_LEN_V2 + 15 ?
|
||||
jne .got_literals ; if not, we have the full literals count, go copy
|
||||
|
||||
|
|
@ -82,7 +83,7 @@ lzsa2_decompress:
|
|||
lodsb ; get 8 bit offset from stream in A
|
||||
dec ah ; set offset bits 15-8 to 1
|
||||
test dl,020H ; test bit Z (offset bit 8)
|
||||
je .get_match_length
|
||||
jz .get_match_length
|
||||
.dec_offset_top:
|
||||
dec ah ; clear bit 8 if Z bit is clear
|
||||
; or set offset bits 15-8 to 1
|
||||
|
|
@ -102,7 +103,7 @@ lzsa2_decompress:
|
|||
|
||||
.rep_match_or_16_bit:
|
||||
test dl,020H ; test bit Z (offset bit 8)
|
||||
jne .repeat_match ; rep-match
|
||||
jnz .repeat_match ; rep-match
|
||||
|
||||
; 16 bit offset
|
||||
lodsb ; Get 2-byte match offset
|
||||
|
|
@ -122,7 +123,7 @@ lzsa2_decompress:
|
|||
jne .got_matchlen ; no, we have the full match length from the token, go copy
|
||||
|
||||
call .get_nibble ; get extra literals length nibble
|
||||
add al,cl ; add len from token to nibble
|
||||
add al,cl ; add len from token to nibble
|
||||
cmp al,018H ; MIN_MATCH_SIZE_V2 + MATCH_RUN_LEN_V2 + 15?
|
||||
jne .got_matchlen ; no, we have the full match length from the token, go copy
|
||||
|
||||
|
|
@ -136,7 +137,7 @@ lzsa2_decompress:
|
|||
.got_matchlen:
|
||||
xchg cx,ax ; copy match length into cx
|
||||
push ds ; save ds:si (current pointer to compressed data)
|
||||
xchg si,ax
|
||||
xchg si,ax
|
||||
push es
|
||||
pop ds
|
||||
lea si,[bp+di] ; ds:si now points at back reference in output data
|
||||
|
|
@ -163,7 +164,7 @@ lzsa2_decompress:
|
|||
.get_nibble:
|
||||
neg bh ; nibble ready?
|
||||
jns .has_nibble
|
||||
|
||||
|
||||
xchg bx,ax
|
||||
lodsb ; load two nibbles
|
||||
xchg bx,ax
|
||||
|
|
|
|||
|
|
@ -8,6 +8,7 @@
|
|||
; - Trashes all data and segment registers
|
||||
;
|
||||
; Copyright (C) 2019 Jim Leonard, Emmanuel Marty
|
||||
; Additional optimizations by Krister Nordvall
|
||||
;
|
||||
; This software is provided 'as-is', without any express or implied
|
||||
; warranty. In no event will the authors be held liable for any damages
|
||||
|
|
@ -71,27 +72,27 @@ lzsa1_decompress_speed:
|
|||
|
||||
.mid_literals:
|
||||
lodsb ;grab single extra length byte
|
||||
inc ah ;add 256
|
||||
; inc ah ;add 256
|
||||
xchg cx,ax ;with longer counts, we can save some time
|
||||
shr cx,1 ;by doing a word copy instead of a byte copy.
|
||||
rcr cl,1 ;by doing a word copy instead of a byte copy.
|
||||
rep movsw ;We don't need to account for overlap because
|
||||
adc cx,0 ;source for literals isn't the output buffer.
|
||||
rep movsb
|
||||
jmp .check_offset_size
|
||||
; adc cx,0 ;source for literals isn't the output buffer.
|
||||
adc cx,cx ; rcl cx,1 might be even faster on 8088
|
||||
jmp .copy_odd_byte
|
||||
|
||||
.big_literals:
|
||||
lodsw ;grab 16-bit extra length
|
||||
xchg cx,ax ;with longer counts, we can save some time
|
||||
shr cx,1 ;by doing a word copy instead of a byte copy.
|
||||
rep movsw
|
||||
adc cx,0
|
||||
rep movsb
|
||||
jmp .check_offset_size
|
||||
adc cx,cx ; rcl cx,1 might be even faster on 8088
|
||||
jmp .copy_odd_byte
|
||||
|
||||
.got_literals:
|
||||
cs xlat ;shift literals length into place
|
||||
cs xlat ;shift literals length into place
|
||||
.got_literals_exact:
|
||||
xchg cx,ax
|
||||
.copy_odd_byte:
|
||||
rep movsb ;copy cx literals from ds:si to es:di
|
||||
|
||||
.check_offset_size:
|
||||
|
|
@ -114,8 +115,16 @@ lzsa1_decompress_speed:
|
|||
|
||||
lodsw ;grab 16-bit length
|
||||
xchg cx,ax ;get ready to do a long copy
|
||||
jcxz .done_decompressing ;wait, is it the EOD marker? Exit if so
|
||||
jmp .copy_len_preset ;otherwise, do the copy
|
||||
; jcxz .done_decompressing ;wait, is it the EOD marker? Exit if so
|
||||
; jmp .copy_len_preset ;otherwise, do the copy
|
||||
inc cx
|
||||
loop .copy_len_preset
|
||||
|
||||
;.done_decompressing:
|
||||
pop ax ;retrieve the original decompression offset
|
||||
xchg di,ax ;compute decompressed size
|
||||
sub ax,di
|
||||
ret ;done decompressing, exit to caller
|
||||
|
||||
.get_long_offset:
|
||||
lodsw ;Get 2-byte match offset
|
||||
|
|
@ -135,12 +144,6 @@ lzsa1_decompress_speed:
|
|||
mov ds,bp ;restore ds
|
||||
jmp .decode_token ;go decode another token
|
||||
|
||||
.done_decompressing:
|
||||
pop ax ;retrieve the original decompression offset
|
||||
xchg di,ax ;compute decompressed size
|
||||
sub ax,di
|
||||
ret ;done decompressing, exit to caller
|
||||
|
||||
;With a confirmed longer match length, we have an opportunity to optimize for
|
||||
;the case where a single byte is repeated long enough that we can benefit
|
||||
;from rep movsw to perform the run (instead of rep movsb).
|
||||
|
|
@ -167,7 +170,7 @@ lzsa1_decompress_speed:
|
|||
;This won't affect 8088 that much, but it speeds up 8086 and higher.
|
||||
shr cx,1
|
||||
rep movsw
|
||||
adc cx,0
|
||||
adc cx,cx ; rcl cx,1 might be even faster on 8088
|
||||
rep movsb
|
||||
mov si,bp ;restore si
|
||||
pop ds
|
||||
|
|
@ -181,7 +184,7 @@ lzsa1_decompress_speed:
|
|||
mov ah,al
|
||||
shr cx,1
|
||||
rep stosw ;perform word run
|
||||
adc cx,0
|
||||
adc cx,cx ; rcl cx,1 might be even faster on 8088
|
||||
rep stosb ;finish word run
|
||||
mov si,bp ;restore si
|
||||
pop ds
|
||||
|
|
@ -191,7 +194,8 @@ lzsa1_decompress_speed:
|
|||
lodsw ;load first word of run
|
||||
shr cx,1
|
||||
rep stosw ;perform word run
|
||||
adc cx,0 ;despite 2-byte offset, compressor might
|
||||
; adc cx,0 ;despite 2-byte offset, compressor might
|
||||
adc cx,cx ; rcl cx,1 might be even faster on 8088
|
||||
rep stosb ;output odd length. better safe than sorry.
|
||||
mov si,bp ;restore si
|
||||
pop ds
|
||||
|
|
|
|||
|
|
@ -8,6 +8,7 @@
|
|||
; - Trashes all data and segment registers
|
||||
;
|
||||
; Copyright (C) 2019 Jim Leonard, Emmanuel Marty
|
||||
; Additional optimizations by Krister Nordvall
|
||||
;
|
||||
; This software is provided 'as-is', without any express or implied
|
||||
; warranty. In no event will the authors be held liable for any damages
|
||||
|
|
@ -64,17 +65,17 @@ lzsa2_decompress_speed:
|
|||
mov bx,0100H ;bx used by get_nybble
|
||||
|
||||
.decode_token:
|
||||
mov ax,cx ;clear ah - cx is zero (and must stay that way)
|
||||
xchg cx,ax ;clear ah - cx is zero
|
||||
lodsb ;read token byte: XYZ|LL|MMMM
|
||||
mov dx,ax ;keep copy of token in dl
|
||||
|
||||
and al,018H ;isolate literals length in token (LL)
|
||||
jz .check_offset ;no literals? stop decoding, go to matches
|
||||
jz .check_offset ;no literals? stop decoding, go to matches
|
||||
|
||||
;At this point, al can be in three (unshifted) states: 1, 2, or 3.
|
||||
;3 = not done yet.
|
||||
cmp al,(2 << 3) ;LITERALS_RUN_LEN_V2? (original: cmp al,03h)
|
||||
jb .lit1b ;LZSA2 output 1-byte more often, so test first
|
||||
cmp al,(2 << 3) ;LITERALS_RUN_LEN_V2? (original: cmp al,03h)
|
||||
jb .lit1b ;LZSA2 output 1-byte more often, so test first
|
||||
je .lit2b
|
||||
|
||||
mov cl,3
|
||||
|
|
@ -82,7 +83,7 @@ lzsa2_decompress_speed:
|
|||
get_nybble ;cl := get extra literals length nybble
|
||||
add al,cl ;add len from token to nybble
|
||||
cmp al,012H ;LITERALS_RUN_LEN_V2 + 15 ?
|
||||
jne .got_literals ;if not, we have the full literals count
|
||||
jne .got_literals ;if not, we have the full literals count
|
||||
lodsb ;grab extra length byte
|
||||
add al,012H ;overflow?
|
||||
jnc .got_literals_big ;if not, we have a big full literals count
|
||||
|
|
@ -93,28 +94,36 @@ lzsa2_decompress_speed:
|
|||
xchg cx,ax
|
||||
shr cx,1
|
||||
rep movsw
|
||||
adc cx,0
|
||||
adc cx,cx
|
||||
rep movsb
|
||||
jmp .check_offset
|
||||
|
||||
.got_literals:
|
||||
xchg cx,ax
|
||||
rep movsb ;copy cx literals from ds:si to es:di
|
||||
jmp .check_offset
|
||||
; jmp .check_offset
|
||||
db 0B8h ; Opcode byte for MOV AX, <immed> (faster than jumping)
|
||||
|
||||
;LZSA2 likes to produce tiny literals of 1 or 2 bytes. Handle them here.
|
||||
.lit2b:movsb
|
||||
.lit1b:movsb
|
||||
|
||||
.check_offset:
|
||||
%if 0 ; 9 bytes
|
||||
test dl,dl ;check match offset mode in token (X bit)
|
||||
js .rep_match_or_large_offset
|
||||
|
||||
cmp dl,040H ;check if this is a 5 or 9-bit offset (Y bit)
|
||||
jnb .offset_9_bit
|
||||
%else ; 7 bytes
|
||||
; This is shorter than the above and should be faster overall if
|
||||
; falling through to 5-bit offsets is the most common path.
|
||||
test dl,0C0h
|
||||
js .rep_match_or_large_offset
|
||||
jnz .offset_9_bit
|
||||
%endif ; 0
|
||||
|
||||
;5 bit offset:
|
||||
xchg cx,ax ;clear ah - cx is zero from prior rep movs
|
||||
mov al,020H ;shift Z (offset bit 4) in place
|
||||
and al,dl
|
||||
shl al,1
|
||||
|
|
@ -123,12 +132,12 @@ lzsa2_decompress_speed:
|
|||
or al,cl ;merge nybble
|
||||
rol al,1
|
||||
xor al,0E1H ;set offset bits 7-5 to 1
|
||||
dec ah ;set offset bits 15-8 to 1
|
||||
cbw ;set offset bits 15-8 to 1
|
||||
jmp .get_match_length
|
||||
|
||||
.rep_match_or_16_bit:
|
||||
test dl,020H ;test bit Z (offset bit 8)
|
||||
jne .repeat_match ;rep-match
|
||||
jnz .repeat_match ;rep-match
|
||||
|
||||
;16 bit offset:
|
||||
lodsw ;Get 2-byte match offset
|
||||
|
|
@ -137,18 +146,21 @@ lzsa2_decompress_speed:
|
|||
|
||||
.offset_9_bit:
|
||||
;9 bit offset:
|
||||
xchg cx,ax ;clear ah - cx is zero from prior rep movs
|
||||
lodsb ;get 8 bit offset from stream in A
|
||||
dec ah ;set offset bits 15-8 to 1
|
||||
mov ah,0FFh ;set offset bits 15-8 to 1
|
||||
test dl,020H ;test bit Z (offset bit 8)
|
||||
je .get_match_length
|
||||
jz .get_match_length
|
||||
dec ah ;clear bit 8 if Z bit is clear
|
||||
jmp .get_match_length
|
||||
|
||||
.rep_match_or_large_offset:
|
||||
%if 0
|
||||
cmp dl,0c0H ;check if this is a 13-bit offset
|
||||
;or a 16-bit offset/rep match (Y bit)
|
||||
jnb .rep_match_or_16_bit
|
||||
%else
|
||||
jpe .rep_match_or_16_bit
|
||||
%endif ; 0
|
||||
|
||||
;13 bit offset:
|
||||
mov ah,020H ;shift Z (offset bit 12) in place
|
||||
|
|
@ -180,7 +192,7 @@ lzsa2_decompress_speed:
|
|||
lodsb ;grab extra length byte
|
||||
add al,018H ;overflow?
|
||||
jnc .got_matchlen_big ;if not, we have entire (big) length
|
||||
je .done_decompressing ; detect EOD code
|
||||
jz .done_decompressing ; detect EOD code
|
||||
|
||||
lodsw ;grab 16-bit length
|
||||
|
||||
|
|
@ -209,7 +221,7 @@ lzsa2_decompress_speed:
|
|||
;This won't affect 8088 that much, but it speeds up 8086 and higher.
|
||||
shr cx,1
|
||||
rep movsw
|
||||
adc cx,0
|
||||
adc cx,cx
|
||||
rep movsb
|
||||
xchg si,ax
|
||||
mov ds,dx ;restore ds:si
|
||||
|
|
@ -246,7 +258,7 @@ lzsa2_decompress_speed:
|
|||
mov ah,al
|
||||
shr cx,1
|
||||
rep stosw ;perform word run
|
||||
adc cx,0
|
||||
adc cx,cx
|
||||
rep stosb ;finish word run
|
||||
pop si
|
||||
mov ds,dx
|
||||
|
|
@ -258,7 +270,7 @@ lzsa2_decompress_speed:
|
|||
lodsw ;load first word of run
|
||||
shr cx,1
|
||||
rep stosw ;perform word run
|
||||
adc cx,0 ;despite 2-byte offset, compressor might
|
||||
adc cx,cx ;despite 2-byte offset, compressor might
|
||||
rep stosb ;output odd length. better safe than sorry.
|
||||
pop si
|
||||
mov ds,dx
|
||||
|
|
|
|||
Loading…
Reference in New Issue
Block a user