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thumb load/store register offset

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This commit is contained in:
Matthew Berry 2020-10-10 20:38:15 -07:00
parent dfb833a351
commit 9b1f73e741
2 changed files with 17 additions and 1 deletions
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16
src/crab/thumb/load_store_register_offset.cr Normal file
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@ -0,0 +1,16 @@
module THUMB
def thumb_load_store_register_offset(instr : Word) : Nil
load_and_byte_quantity = bits(instr, 10..11)
ro = bits(instr, 6..8)
rb = bits(instr, 3..5)
rd = bits(instr, 0..2)
address = @r[rb] &+ @r[ro]
case load_and_byte_quantity
when 0b00 then @gba.bus[address] = @r[rd]
when 0b01 then @gba.bus[address] = 0xFF_u8 & @r[rd]
when 0b10 then @r[rd] = @gba.bus.read_word address
when 0b11 then @r[rd] = 0xFFFFFFFF_u32 & @gba.bus[address]
end
end
end

2
src/crab/thumb/thumb.cr
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@ -31,7 +31,7 @@ module THUMB
elsif idx & 0b11110010 == 0b01010010
lut[idx] = ->thumb_load_store_sign_extended(Word)
elsif idx & 0b11110010 == 0b01010000
# load/store with register offset
lut[idx] = ->thumb_load_store_register_offset(Word)
elsif idx & 0b11111000 == 0b01001000
lut[idx] = ->thumb_pc_relative_load(Word)
elsif idx & 0b11111100 == 0b01000100