p1es/assembler.rb

$bytes = []

def zero_fill(pos)
	while ($bytes.length <= pos) do
		$bytes.push(0)
	end
end

def word(i)
	$bytes.push((i & 0x000000ff),
		(i & 0x0000ff00) >> 8,
		(i & 0x00ff0000) >> 16,
		(i & 0xff000000) >> 24)
end

def string(s)
	$bytes.push *s.bytes
	while (($bytes.length % 4) != 0) do
		$bytes.push 0
	end
end




# # # INSTRUCTIONS # # #
def jmp(addr)
	# TODO: this probs wont show up since we have < 3mb of ram but
	# we can't jump to an address with a different 4 most significant bits
	raise "jmp addr must be 4 byte aligned" if addr % 4 != 0
	op = 0b0000_1000_0000_0000_0000_0000_0000_0000
	op = op | ((addr >> 2) & 0b11_11111111_11111111_11111111)
	word op
end

def jal(addr)
	# TODO: same problem as jmp
	raise "jmp addr must be 4 byte aligned" if addr % 4 != 0
	op = 0b0000_1100_0000_0000_0000_0000_0000_0000
	op = op | ((addr >> 2) & 0b11_11111111_11111111_11111111)
	word op
end

# load upper immediate
# NOTE: val will be shifted left by 16
def lui(val, dest)
	#      oooooo ----- ttttt iiiiiiiiiiiiiiii
	op = 0b001111_00000_00000_0000000000000000
	op |= 0xffff & val
	op |= (0b11111 & dest) << 16
	word op
end

# shift right logical
def srl(src, amt, dest)
	#      oooooo ----- sssss ddddd hhhhh oooooo
	op = 0b000000_00000_00000_00000_00000_000010
	op |= (src & 0b11111) << 16
	op |= (amt & 0b11111) << 6
	op |= (dest & 0b11111) << 11
	word op
end

# or immediate
def ori(src, bits, dest)
	#      oooooo sssss ddddd iiiiiiii iiiiiiii
	op = 0b001101_00000_00000_00000000_00000000
	op |= (src & 0b11111) << 21
	op |= (bits & 0xffff)
	op |= (dest & 0x11111) << 16
	word op
end




# # # PSEUDO-INSTRUCTIONS # # #
def nop
	word 0x00000000
end




# this is a terrible idea and im doing it
#$labels = {}
#def method_missing(m, *args)
#	puts m.to_s
#	super
#end


# # # CONSTANTS # # #
$base_addr = 0x80010000 # 0x10000 # 0x80010000
$file_size = 0x800
$gp0 = 0x1F801810

# # # EXE HEADER # # #
string "PS-X EXE"
zero_fill 0x00f
word $base_addr # initial pc
word 0x00000000 # initial GP/R28
word $base_addr # destintation address in RAM
word $file_size # file size excluding header (must be N * 0x800)
word 0x00000000 # Unknown/Unused
word 0x00000000 # Unknown/Unused
word 0x00000000 # Memfill start address
word 0x00000000 # Memfill size in bytes
word 0x801ffff0 # Initial SP/R29 & FP/R30 Base
word 0x00000000 # Initial SP/R29 & FP/R30 Offs
zero_fill 0x4b # Reserved for A(43h) Function
# Ascii marker would go here
zero_fill 0x7ff
$exe_header = $bytes[0..]
$bytes = []




# # # PROGRAM CODE # # #
nop ; jmp $base_addr + 16 ; nop ; word 0xdeadbeef

# ops should always be in format of
# src [args] -> dest

lui $gp0 >> 16, 1
ori 1, $gp0, 1

nop ; nop ; nop ; nop
nop ; nop ; nop ; nop
nop ; nop ; nop ; nop
nop ; nop ; nop ; nop

jmp $base_addr
nop







string "this is a test lol"




zero_fill $file_size - 1

f = File.new "LOADTHIS.EXE", "wb"
f.write $exe_header.pack("C*")
f.write $bytes.pack("C*")
f.close