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Delay clearing high part of literals count until we really have to in 6809 LZSA1 depacker

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Doug Masten
2020-06-27 00:44:31 -05:00
parent fde15d3fb0
commit 39e11422ec
1 changed files with 2 additions and 2 deletions
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4
asm/6809/unlzsa1.s
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@@ -66,13 +66,12 @@ lz1token ldb ,x+ ; load next token into B: O|LLL|MMMM
andb #$70 ; isolate LLL (embedded literals count) in B andb #$70 ; isolate LLL (embedded literals count) in B
beq lz1nolt ; skip if no literals beq lz1nolt ; skip if no literals
clra ; clear A (high part of literals count)
cmpb #$70 ; LITERALS_RUN_LEN? cmpb #$70 ; LITERALS_RUN_LEN?
bne lz1declt ; if not, we have the complete count, go unshift bne lz1declt ; if not, we have the complete count, go unshift
ldb ,x+ ; load extra literals count byte ldb ,x+ ; load extra literals count byte
addb #$07 ; add LITERALS_RUN_LEN addb #$07 ; add LITERALS_RUN_LEN
bcc lz1gotlt ; if no overflow, we got the complete count, copy bcc lz1gotla ; if no overflow, we got the complete count, copy
bne lz1midlt bne lz1midlt
ldb ,x+ ; load low 8 bits of little-endian literals count ldb ,x+ ; load low 8 bits of little-endian literals count
@@ -87,6 +86,7 @@ lz1declt lsrb ; shift literals count into place
lsrb lsrb
lsrb lsrb
lsrb lsrb
lz1gotla clra ; clear A (high part of literals count)
lz1gotlt tfr x,u lz1gotlt tfr x,u
tfr d,x ; transfer 16-bit count into X tfr d,x ; transfer 16-bit count into X