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zasm: optimize handleRST a little bit
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@ -559,16 +559,14 @@ handleLDrr:
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handleRST:
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ld a, (INS_CURARG1+1)
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; verify that A is either 0x08, 0x10, 0x18, 0x20, 0x28, 0x30 or 0x38.
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; Good news: they're all multiples of 8.
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; to verify that we're within range, we to 8-bit rotation. If any of
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; the first 3 bytes are set (thus not a multiple of 8), the cp 8
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; later will yield NC because those bits will now be upwards.
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rrca \ rrca \ rrca
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cp 8
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jr nc, .error
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; good, we have a proper arg. Now let's get those 3 bits in position
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rlca \ rlca \ rlca
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or 0b11000111
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; Good news: the relevant bits (bits 5:3) are already in place. We only
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; have to verify that they're surrounded by zeroes.
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ld c, 0b11000111
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and c
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jr nz, .error
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; We're in range. good.
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ld a, (INS_CURARG1+1)
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or c
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ld (INS_UPCODE), a
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ld c, 1
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ret
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