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https://github.com/emmanuel-marty/lzsa.git
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Additional minor speedups
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mobygamer
parent
9a180a59f9
commit
638c33b432
@ -27,12 +27,22 @@
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IDEAL
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P8086
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MODEL SMALL
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CODESEG
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SEGMENT CODE para public
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ASSUME cs:CODE, ds:CODE
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PUBLIC lzsa1_decompress_speed
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; ---------------------------------------------------------------------------
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; Decompress raw LZSA1 block
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; inputs:
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; * ds:si: raw LZSA1 block
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; * es:di: output buffer
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; output:
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; * ax: decompressed size
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; ---------------------------------------------------------------------------
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; Must declare this in the code segment:
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SHR4table:
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DB 00h,00h,00h,00h,00h,00h,00h,00h,00h,00h,00h,00h,00h,00h,00h,00h
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@ -44,27 +54,18 @@ SHR4table:
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DB 06h,06h,06h,06h,06h,06h,06h,06h,06h,06h,06h,06h,06h,06h,06h,06h
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DB 07h,07h,07h,07h,07h,07h,07h,07h,07h,07h,07h,07h,07h,07h,07h,07h
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; ---------------------------------------------------------------------------
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; Decompress raw LZSA1 block
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; inputs:
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; * ds:si: raw LZSA1 block
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; * es:di: output buffer
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; output:
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; * ax: decompressed size
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; ---------------------------------------------------------------------------
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PROC lzsa1_decompress_speed NEAR
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lzsa1_start:
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push di ;remember decompression offset
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cld ;ensure string ops move forward
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mov bx,offset SHR4table ;table lookup faster than bitops if op > 3
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mov bx,offset SHR4table
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xor cx,cx
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@@decode_token:
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mov ax,cx ;clear ah (cx = 0 from match copy's rep movsb)
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xchg cx,ax ;clear ah (cx = 0 from match copy's rep movsb)
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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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mov dx,ax ;copy our token to dl for later MMMM handling
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and al,070H ;isolate literals length in token (LLL)
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jz @@check_offset_size ;if LLL=0, we have no literals; goto match
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@ -74,16 +75,7 @@ lzsa1_start:
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lodsb ;grab extra length byte
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add al,07H ;add LITERALS_RUN_LEN
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jnc @@got_literals_exact ;if no overflow, we have full count
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jne @@mid_literals
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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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je @@big_literals
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@@mid_literals:
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lodsb ;grab single extra length byte
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@ -95,11 +87,21 @@ lzsa1_start:
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rep movsb
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jmp @@check_offset_size
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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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@@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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rep movsb ;copy cx literals from ds:si to es:di
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@@check_offset_size:
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test dl,dl ;check match offset size in token (O bit)
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js @@get_long_offset ;load absolute 16-bit match offset
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@ -110,9 +112,7 @@ lzsa1_start:
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@@get_match_length:
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xchg dx,ax ;dx: match offset ax: original token
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and al,0FH ;isolate match length in token (MMMM)
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add al,3 ;add MIN_MATCH_SIZE
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cmp al,012H ;MATCH_RUN_LEN?
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cmp al,0FH ;MATCH_RUN_LEN?
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jne @@got_matchlen_short ;no, we have the full match length from the token, go copy
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lodsb ;grab extra length byte
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@ -126,6 +126,7 @@ lzsa1_start:
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jmp @@copy_len_preset ;otherwise, do the copy
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@@got_matchlen_short:
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add al,3 ;add MIN_MATCH_SIZE
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xchg cx,ax ;copy match length into cx
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mov bp,ds ;save ds
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mov ax,es
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@ -207,7 +208,7 @@ lzsa1_start:
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ENDP lzsa1_decompress_speed
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ENDS
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ENDS CODE
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END
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@ -234,5 +235,17 @@ END
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; reverse 16-bit len compar shuttle 102000 alice 59263 robotron 364460 --- rb
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; jcxz for EOD detection no change to speed, but is 1 byte shorter +++
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; force movsw for literals shuttle 107183 alice 62555 robotron 379524 --- rb
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; defer shr4 until necessry shuttle 102069 alice 60236 robotron 364096 --- rb
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; skip literals if LLL=0 shuttle 98655 alice 57849 robotron 363358 --- rb
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; defer shr4 until necessry shuttle 102069 alice 60236 robotron 364096 ---
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; skip literals if LLL=0 shuttle 98655 alice 57849 robotron 363358 ---
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; fall through to mid_liter shuttle 98595 alice 57789 robotron 361998 +++
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; == jumptable experiments begin ==
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; jumptable for small copys shuttle 101594 alice 61078 robotron 386018 ---
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; start:xchg instead of mov shuttle 100948 alice 60467 robotron 381112 +++
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; use table for LLL=0 check shuttle 106972 alice 63333 robotron 388304 --- rb
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; jmptbl to fallthrough mov shuttle 102532 alice 60760 robotron 383070 ---
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; cpy fallthrough check_ofs shuttle 98939 alice 58917 robotron 371019 +**
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; single jumptable jump shuttle 97528 alice 57264 robotron 362194 ++*
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; conditional check for L=7 shuttle 98610 alice 58521 robotron 368153 --- rb
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; rip out the jumptable :-/ shuttle 97616 alice 57128 robotron 360697 +++
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; defer add MIN_MATCH_SIZE shuttle 97250 alice 57004 robotron 361191 ++?
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; cache constants in regs shuttle 104681 alice 59939 robotron 380125 --- rb
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