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simplify register rotates a little bit

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Matthew Berry 2021-05-02 19:08:06 -07:00
parent 655bd67855
commit b8a7fc1428
1 changed files with 4 additions and 5 deletions
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9
src/crab/arm/arm.cr
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@ -72,14 +72,13 @@ module ARM
def rotate_register(instr : Word, carry_out : Pointer(Bool), allow_register_shifts : Bool) : Word def rotate_register(instr : Word, carry_out : Pointer(Bool), allow_register_shifts : Bool) : Word
reg = bits(instr, 0..3) reg = bits(instr, 0..3)
shift_type = bits(instr, 5..6) shift_type = bits(instr, 5..6)
if allow_register_shifts && bit?(instr, 4) immediate = !(allow_register_shifts && bit?(instr, 4))
if immediate
shift_amount = bits(instr, 7..11)
else
shift_register = bits(instr, 8..11) shift_register = bits(instr, 8..11)
# todo weird logic if bottom byte of reg > 31 # todo weird logic if bottom byte of reg > 31
shift_amount = @r[shift_register] & 0xFF shift_amount = @r[shift_register] & 0xFF
immediate = false
else
shift_amount = bits(instr, 7..11)
immediate = true
end end
case shift_type case shift_type
when 0b00 then lsl(@r[reg], shift_amount, carry_out) when 0b00 then lsl(@r[reg], shift_amount, carry_out)