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Merged
sacckey merged 1 commit into from
Feb 16, 2025
Merged

Optimize Rubyboy::Bus #25

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137 changes: 78 additions & 59 deletions lib/rubyboy/bus.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -11,74 +11,93 @@ def initialize(ppu, rom, ram, mbc, timer, interrupt, joypad, apu)
@apu = apu
@interrupt = interrupt
@timer = timer
end

def read_byte(addr)
case addr >> 12
when 0x0, 0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0xa, 0xb
return @mbc.read_byte(addr)
when 0x8, 0x9
return @ppu.read_byte(addr)
when 0xc
return @ram.wram1[addr - 0xc000]
when 0xd
return @ram.wram2[addr - 0xd000]
when 0xf
case addr >> 8
when 0xfe
return @ppu.read_byte(addr) if addr <= 0xfe9f
when 0xff
last_byte = addr & 0xFF

@read_methods = Array.new(0x10000)
@write_methods = Array.new(0x10000)
case last_byte
when 0x00
return @joypad.read_byte(addr)
when 0x04, 0x05, 0x06, 0x07
return @timer.read_byte(addr)
when 0x0f
return @interrupt.read_byte(addr)
when 0x46
return @ppu.read_byte(addr)
when 0xff
return @interrupt.read_byte(addr)
end

set_methods
end
return @apu.read_byte(addr) if last_byte <= 0x26 && last_byte >= 0x10
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@sacckey sacckey Feb 16, 2025

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Just a minor detail, but since it was originally written as when 0xff10..0xff26, it might be more readable to write it starting with the smaller value, like if last_byte >= 0x10 && last_byte <= 0x26.

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@byroot byroot Feb 16, 2025

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It was done this way for performance reasons. Almost all values are >= 0x10 few <= 0x26, so it avoid a comparison in most cases.

If Ruby had a very advanced optimizing compiler that wouldn't be needed, but it's not the case yet.

But if you fell very strongly about it, I can change that.

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@sacckey sacckey Feb 16, 2025

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I see, got it!

I don't have a strong opinion, so it's fine as is.


def set_methods
0x10000.times do |addr|
case addr
when 0x0000..0x7fff
@read_methods[addr] = -> { @mbc.read_byte(addr) }
@write_methods[addr] = ->(value) { @mbc.write_byte(addr, value) }
when 0x8000..0x9fff
@read_methods[addr] = -> { @ppu.read_byte(addr) }
@write_methods[addr] = ->(value) { @ppu.write_byte(addr, value) }
when 0xa000..0xbfff
@read_methods[addr] = -> { @mbc.read_byte(addr) }
@write_methods[addr] = ->(value) { @mbc.write_byte(addr, value) }
when 0xc000..0xcfff
@read_methods[addr] = -> { @ram.wram1[addr - 0xc000] }
@write_methods[addr] = ->(value) { @ram.wram1[addr - 0xc000] = value }
when 0xd000..0xdfff
@read_methods[addr] = -> { @ram.wram2[addr - 0xd000] }
@write_methods[addr] = ->(value) { @ram.wram2[addr - 0xd000] = value }
when 0xfe00..0xfe9f
@read_methods[addr] = -> { @ppu.read_byte(addr) }
@write_methods[addr] = ->(value) { @ppu.write_byte(addr, value) }
when 0xff00
@read_methods[addr] = -> { @joypad.read_byte(addr) }
@write_methods[addr] = ->(value) { @joypad.write_byte(addr, value) }
when 0xff04..0xff07
@read_methods[addr] = -> { @timer.read_byte(addr) }
@write_methods[addr] = ->(value) { @timer.write_byte(addr, value) }
when 0xff0f
@read_methods[addr] = -> { @interrupt.read_byte(addr) }
@write_methods[addr] = ->(value) { @interrupt.write_byte(addr, value) }
when 0xff10..0xff26
@read_methods[addr] = -> { @apu.read_byte(addr) }
@write_methods[addr] = ->(value) { @apu.write_byte(addr, value) }
when 0xff30..0xff3f
@read_methods[addr] = -> { @apu.read_byte(addr) }
@write_methods[addr] = ->(value) { @apu.write_byte(addr, value) }
when 0xff46
@read_methods[addr] = -> { @ppu.read_byte(addr) }
@write_methods[addr] = ->(value) { 0xa0.times { |i| write_byte(0xfe00 + i, read_byte((value << 8) + i)) } }
when 0xff40..0xff4b
@read_methods[addr] = -> { @ppu.read_byte(addr) }
@write_methods[addr] = ->(value) { @ppu.write_byte(addr, value) }
when 0xff80..0xfffe
@read_methods[addr] = -> { @ram.hram[addr - 0xff80] }
@write_methods[addr] = ->(value) { @ram.hram[addr - 0xff80] = value }
when 0xffff
@read_methods[addr] = -> { @interrupt.read_byte(addr) }
@write_methods[addr] = ->(value) { @interrupt.write_byte(addr, value) }
else
@read_methods[addr] = -> { 0xff }
@write_methods[addr] = ->(_value) {}
return @apu.read_byte(addr) if last_byte <= 0x3f && last_byte >= 0x30

return @ppu.read_byte(addr) if last_byte <= 0x4b && last_byte >= 0x40

return @ram.hram[addr - 0xff80] if last_byte <= 0xfe && last_byte >= 0x80
end
end
end

def read_byte(addr)
@read_methods[addr].call
0xff
end

def write_byte(addr, value)
@write_methods[addr].call(value)
case addr >> 12
when 0x0, 0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0xa, 0xb
return @mbc.write_byte(addr, value)
when 0x8, 0x9
return @ppu.write_byte(addr, value)
when 0xc
return @ram.wram1[addr - 0xc000] = value
when 0xd
return @ram.wram2[addr - 0xd000] = value
when 0xf
case addr >> 8
when 0xfe
return @ppu.write_byte(addr, value) if addr <= 0xfe9f
when 0xff
last_byte = addr & 0xFF

case last_byte
when 0x00
return @joypad.write_byte(addr, value)
when 0x04, 0x05, 0x06, 0x07
return @timer.write_byte(addr, value)
when 0x0f
return @interrupt.write_byte(addr, value)
when 0x46
0xa0.times { |i| write_byte(0xfe00 + i, read_byte((value << 8) + i)) }
return
when 0xff
return @interrupt.write_byte(addr, value)
end

return @apu.write_byte(addr, value) if last_byte <= 0x26 && last_byte >= 0x10

return @apu.write_byte(addr, value) if last_byte <= 0x3f && last_byte >= 0x30

return @ppu.write_byte(addr, value) if last_byte <= 0x4b && last_byte >= 0x40

return @ram.hram[addr - 0xff80] = value if last_byte <= 0xfe && last_byte >= 0x80
end
end

nil
end

def read_word(addr)
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