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optimize dos stub size to save 2 bytes (discovered by qkumba)

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This commit is contained in:
5684185+vsariola@users.noreply.github.com
2023-01-26 20:16:28 +02:00
committed by exoticorn
parent 2eb8f230ba
commit f502bf4e28
3 changed files with 13 additions and 16 deletions
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7
dos_unpacker/unpack_x86_16_DOS.asm
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@@ -105,15 +105,14 @@ upkr_decode_bit:
dec dx
jns upkr_load_bit
movzx ax, byte [bx] ; u16 prob = upkr_probs[context_index]
neg byte [bx]
push ax ; save prob, tmp = prob
cmp dl, al ; int bit = (upkr_state & 255) < prob ? 1 : 0; (carry = bit)
pushf ; save bit flags
jc .bit ; (skip if bit)
neg al ; tmp = 256 - tmp;
xchg [bx], al ; tmp = 256 - tmp;
.bit:
mov [bx], al ; upkr_probs[context_index] = tmp + (256 - tmp + 8) >> 4;
neg byte [bx]
shr byte [bx], 4
shr byte [bx], 4 ; upkr_probs[context_index] = tmp + (256 - tmp + 8) >> 4;
adc [bx], al
mul dh ; upkr_state = tmp * (upkr_state >> 8) + (upkr_state & 255);
mov dh, 0