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z80_unpacker: optimisations: 0B, -13T in decode_bit (stays 177B)

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This commit is contained in:
Peter Helcmanovsky (Ped)
2022-09-15 01:25:57 +02:00
parent aa3fad4d80
commit 3fa9e0fa12
1 changed files with 3 additions and 3 deletions
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6
z80_unpacker/unpack.asm
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@@ -12,7 +12,7 @@
;; upkr.unpack
;; IN: IX = packed data, DE' (shadow DE) = destination
;; OUT: IX = after packed data
;; modifies: all registers except IY, requires 14 bytes of stack space
;; modifies: all registers except IY, requires 10 bytes of stack space
;;
OPT push reset --syntax=abf
@@ -206,7 +206,6 @@ decode_bit:
cp l ; CF = bit = prob-1 < (upkr_state & 255) <=> prob <= (upkr_state & 255)
inc a
; ** adjust state
push af
push bc
ld c,l ; C = (upkr_state & 255); (preserving the value)
push af
@@ -243,7 +242,8 @@ decode_bit:
add a,e ; A = prob_offset + prob - ((prob + 8) >> 4)
pop bc
ld (bc),a ; update probs[context_index]
pop af ; restore resulting CF = bit
add a,d ; bit=0: A = 23..249, D = 240 -> CF=1 || bit=1: D=0 -> CF=0
ccf ; resulting CF = bit restored
pop de
ret