Made bitblt work in 32bpp mode

Reviewed-on: TCShenanigans/symphony_stdlib#19

CONTRIBUTING.md

@@ -16,10 +16,22 @@ All functions in the standard library should follow the following outline:
 ; Arguments: <which register contains what argument>
 ; Result: <what is the result, and where is it stored>
 ; Clobbers: <list of registers that are clobbered>
+; Globals: <list of globals are accessed. OPTIONAL>
+; Errors: <list of any status codes returned in flags. OPTIONAL>
 <label>: <;SHOULD BE INLINED>
     <CODE>
 
 ```
 
 Functions should be in the appropriate asm file, if you are unsure where functionality fits make a seperate file and ask in the pull request
-Functions that are provided for convenience/reference but should be inlined in production code should be marked with `;SHOULD BE INLINED` after their label
+Functions that are provided for convenience/reference but should be inlined in production code should be marked with `;SHOULD BE INLINED` after their label.
+
+If the function returns a status code in flags, the preamble should list all it might return.
+
+## Globals
+
+Any function that uses global variables should document this in the preamble comment, see above.
+
+A file/module should check on intialisation that the address `globals.MAGIC_ADDRESS` contains the 16 bit value `globals.MAGIC_VALUE`, to ensure that the user has properly included [[src/start.asm]] and reservered the global variable area.
+
+No opinion is offered on whether modules can assume globals variables are initialised to zero.

README.md

@@ -3,7 +3,7 @@
 This is a standard library for symphony.
 It is both intended as a practical toolkit to develop more complex software as well as a teaching resource.
 
-If you just want to use the standard library [[src/stdlib.asm]] is your main header, include it after your code.
+If you just want to use the standard library [[src/stdlib.asm]] is your main header, include it after your code. Some modules also require [[src/start.asm]] at the very start of the program.
 
 If you are using it as a learning resource have a look at the [teaching folder](teaching).
 
@@ -20,7 +20,7 @@ If you are intersted in contributing have a look at [[CONTRIBUTING.md]]
 | preserved | sp, r8 - r12 |
 | scratch | flags, r1 - r7 |
 | arguments | r1 - r7 |
-| result | r1-r7 |
+| result | flags, r1 - r7 |
 | return address | r13 |
 
 Arguments not fitting into the 7 registers should be passed on the top of the stack, meaning they should be the last values pushed before the function call.
@@ -32,9 +32,14 @@ Should a function return more values than fit into the 7 registers, the caller h
 This reduces the amount of argument registers to 6 and all arguments above that shall go on the stack, the pointer to the result stack shall **always** be passed in an argument register.
 This register points at the highest available address for results, with the 8th result being stored there, the 9th below it and so on.
 
+Some functions return a success/failure status code in flags. A set low bit will indicate some error condition, the function may return more than one possible value to report different errors. A flags value of 0 is set on success. No other even values are used. This can be checked with `je` or `jne` immediatly on return to the caller. All other functions clobber flags.
+
 ### Stack
 Grows downwards from 0xXXFE_0000 (so top of memory -0x1_0000).
 
+### Globals
+Global variables are stored near the bottom of RAM in the address range 0x0010..0x0100. Programs should `include src/start` as the first line before their own code and before other includes, or otherwise reserve this space, the first instruction should be a jump to user code.
+
 ### Types
 
 #### String

isa/README.md

@@ -0,0 +1,43 @@
+Symphony ISA specs for use in stdlib
+
+# `default.isa`
+The stock game ISA. Production code must comply to this. Taken from `symphony_11_functions` in game version 2.1.330A
+
+# `test.isa`
+ISA with additional instructions. These additional instructions may be used in
+the tests directory only. Some of these instructions require hardware changes.
+
+## Labels in more instructions
+
+`cmp`, `load`, and `store` instructions (but not `pload` and `pstore`) now also accept labels.
+
+## `qcall %a(label)`
+Performs a jump-and-link function call, with label size up to 32 bits.
+
+_HARDWARE:_ Store PC+4 in the result register when in jump mode.
+
+## `li %a(register) %b:U32(immediate | label)`
+Loads an immediate up to 32 bits long
+
+_HARDWARE:_ No requirements
+
+## `halt%c(condition)`
+Halts if `flags` matches the condition.
+
+_HARDWARE:_ Halt if instruction bit 31 is set AND the condition block is true.
+
+```
+condition
+""     1000
+".all" 1000
+".e"   0001
+".ne"  1001
+".b"   0010
+".ae"  1010
+".be"  0011
+".a"   1011
+".l"   0100
+".ge"  1100
+".le"  0101
+".g"   1101
+```

isa/default.isa

@@ -0,0 +1,316 @@
+[settings]
+name = "Symphony"
+
+[fields]
+
+register
+zr 0000
+r1 0001
+r2 0010
+r3 0011
+r4 0100
+r5 0101
+r6 0110
+r7 0111
+r8 1000
+r9 1001
+r10 1010
+r11 1011
+r12 1100
+r13 1101
+sp 1110
+flags 1111
+
+[instructions]
+
+nop
+00000000 00000000 00000000 00000000
+# (31337_88272577071256, `Does nothing.`)
+
+in %a(register)
+00000001 aaaa0000 00000000 00000000
+# (31337_44524771082050, `Loads an input and stores it in %a.`)
+
+out %b(register)
+00000010 00000000 0000bbbb 00000000
+# (31337_18254089726214, `Sends %b to output.`)
+
+out %a:U16(immediate)
+00010010 00000000 aaaaaaaa aaaaaaaa
+# (31337_15915531259935, `Sends %a to output.`)
+
+keyboard %a(register)
+00000011 aaaa0000 00000000 00000000
+# (31337_27868418224252, `Loads keyboard input and stores it to %a.`)
+
+screen %a(register), %b(register)
+00000100 0000aaaa 0000bbbb 00000000
+# (31337_39857449355186, `Stores the value of %b in screen setting %a.`)
+
+screen %a(register), %b:U16(immediate)
+00010100 0000aaaa bbbbbbbb bbbbbbbb
+# (31337_12835125621741, `Stores the value of %b in screen setting %a.`)
+
+time_0 %a(register)
+00000101 aaaa0000 00000000 00000000
+# (31337_72551400437977, `Loads the lower four bytes of the time value and stores it to %a.`)
+
+time_1 %a(register)
+00000110 aaaa0000 00000000 00000000
+# (31337_68219187873304, `Loads the upper four bytes of the time value and stores it to %a.`)
+
+counter %a(register)
+00000111 aaaa0000 00000000 00000000
+# (31337_67376584796076, `Loads the counter value and stores it to %a.`)
+
+
+
+nand %a(register), %b(register), %c(register)
+00100000 aaaabbbb 0000cccc 00000000
+# (31337_86705346481666, `NAND %b and %c and stores the result in %a.`)
+
+or %a(register), %b(register), %c(register)
+00100001 aaaabbbb 0000cccc 00000000
+# (31337_40732211165530, `OR %b and %c and stores the result in %a.`)
+
+and %a(register), %b(register), %c(register)
+00100010 aaaabbbb 0000cccc 00000000
+# (31337_85679146831122, `AND %b and %c and stores the result in %a.`)
+
+nor %a(register), %b(register), %c(register)
+00100011 aaaabbbb 0000cccc 00000000
+# (31337_37333076617857, `NOR %b and %c and stores the result in %a.`)
+
+add %a(register), %b(register), %c(register)
+00100100 aaaabbbb 0000cccc 00000000
+# (31337_51030225266712, `ADD %b and %c and stores the result in %a.`)
+
+sub %a(register), %b(register), %c(register)
+00100101 aaaabbbb 0000cccc 00000000
+# (31337_28652904157569, `SUB %b and %c and stores the result in %a.`)
+
+xor %a(register), %b(register), %c(register)
+00100110 aaaabbbb 0000cccc 00000000
+# (31337_46967848572964, `XOR %b and %c and stores the result in %a.`)
+
+lsl %a(register), %b(register), %c(register)
+00100111 aaaabbbb 0000cccc 00000000
+# (31337_13576771671264, `Logical shifts left %b by %c and stores the result in %a.`)
+
+lsr %a(register), %b(register), %c(register)
+00101000 aaaabbbb 0000cccc 00000000
+# (31337_67019902294705, `Logical shifts right %b by %c and stores the result in %a.`)
+
+asr %a(register), %b(register), %c(register)
+00101001 aaaabbbb 0000cccc 00000000
+# (31337_42626144645228, `Arithmetic shift right %b by %c and stores the result in %a.`)
+
+cmp %a(register), %b(register)
+00101010 1111aaaa 0000bbbb 00000000
+# (31337_54565380946620, `Compares %a and %b and stores the result in the 'flags' register.`)
+
+
+nand %a(register), %b(register), %c:U16(immediate | label)
+00110000 aaaabbbb cccccccc cccccccc
+# (31337_75302656449127, `NAND %b and %c and stores the result in %a.`)
+
+or %a(register), %b(register), %c:U16(immediate | label)
+00110001 aaaabbbb cccccccc cccccccc
+# (31337_30574433901064, `OR %b and %c and stores the result in %a.`)
+
+nor %a(register), %b(register), %c:U16(immediate | label)
+00110011 aaaabbbb cccccccc cccccccc
+# (31337_46087142860391, `NOR %b and %c and stores the result in %a.`)
+
+and %a(register), %b(register), %c:U16(immediate | label)
+00110010 aaaabbbb cccccccc cccccccc
+# (31337_86713121915282, `AND %b and %c and stores the result in %a.`)
+
+add %a(register), %b(register), %c:U16(immediate | label)
+00110100 aaaabbbb cccccccc cccccccc
+# (31337_23349431010010, `ADD %b and %c and stores the result in %a.`)
+
+sub %a(register), %b(register), %c:U16(immediate | label)
+00110101 aaaabbbb cccccccc cccccccc
+# (31337_67495552371225, `SUB %b and %c and stores the result in %a.`)
+
+xor %a(register), %b(register), %c:U16(immediate | label)
+00110110 aaaabbbb cccccccc cccccccc
+# (31337_66785854415645, `XOR %b and %c and stores the result in %a.`)
+
+lsl %a(register), %b(register), %c:U16(immediate | label)
+00110111 aaaabbbb cccccccc cccccccc
+# (31337_54577249258785, `Logical shifts left %b by %c and stores the result in %a.`)
+
+lsr %a(register), %b(register), %c:U16(immediate | label)
+00111000 aaaabbbb cccccccc cccccccc
+# (31337_16685334571248, `Logical shifts right %b by %c and stores the result in %a.`)
+
+asr %a(register), %b(register), %c:U16(immediate | label)
+00111001 aaaabbbb cccccccc cccccccc
+# (31337_55551510150818, `Arithmetic shifts right %b and %c and stores the result in %a.`)
+
+cmp %a(register), %b:U16(immediate)
+00111010 1111aaaa bbbbbbbb bbbbbbbb
+# (31337_37102964808364, `Compares %a and %b and stores the result in the 'flags' register.`)
+
+
+jmp %a(register)
+01001000 00001111 0000aaaa 00000000
+# (31337_74148826866592, `Jumps to %a.`)
+
+
+jmp %a:U16(immediate | label)
+01011000 00001111 aaaaaaaa aaaaaaaa
+# (31337_90876214388280, `Jumps to %a.`)
+
+je %a:U16(immediate | label)
+01010001 00001111 aaaaaaaa aaaaaaaa
+# (31337_88180305667389, `Jumps to %a if the values were equal (reading results from 'flags').`)
+
+jne %a:U16(immediate | label)
+01011001 00001111 aaaaaaaa aaaaaaaa
+# (31337_67178948469318, `Jumps to %a if the values were not equal (reading results from 'flags').`)
+
+
+jb %a:U16(immediate | label)
+01010010 00001111 aaaaaaaa aaaaaaaa
+# (31337_31763492459833, `Jumps to %a if the first value was below (unsigned) the second (reading results from 'flags').`)
+
+jae %a:U16(immediate | label)
+01011010 00001111 aaaaaaaa aaaaaaaa
+# (31337_82087388048746, `Jumps to %a if the first value was above (unsigned) or equal to the second (reading results from 'flags').`)
+
+jbe %a:U16(immediate | label)
+01010011 00001111 aaaaaaaa aaaaaaaa
+# (31337_26183125927881, `Jumps to %a if the First value was below (unsigned) or equal to the second (reading results from 'flags').`)
+
+ja %a:U16(immediate | label)
+01011011 00001111 aaaaaaaa aaaaaaaa
+# (31337_11626177279992, `Jumps to %a if the first value was above (unsigned) the second (reading results from 'flags').`)
+
+
+jl %a:U16(immediate | label)
+01010100 00001111 aaaaaaaa aaaaaaaa
+# (31337_71637103729391, `Jumps to %a if the first value was less (signed) than the second (reading results from 'flags').`)
+
+jge %a:U16(immediate | label)
+01011100 00001111 aaaaaaaa aaaaaaaa
+# (31337_53499765587663, `Jumps to %a if the first value was greater (signed) or equal to the second (reading results from 'flags').`)
+
+jle %a:U16(immediate | label)
+01010101 00001111 aaaaaaaa aaaaaaaa
+# (31337_77040234358389, `Jumps to %a if the first value was less (signed) or equal to the second (reading results from 'flags').`)
+
+jg %a:U16(immediate | label)
+01011101 00001111 aaaaaaaa aaaaaaaa
+# (31337_71317192057126, `Jumps to %a if the first value was greater (signed) than the second (reading results from 'flags').`)
+
+
+
+load_8 %dest(register), [%adr(register)]
+01100000 dddd0000 0000aaaa 00000000
+# (31337_57200935026773, `Loads address %adr from main memory and stores it to %dest.`)
+
+load_8 %dest(register), [%adr:U16(immediate)]
+01110000 dddd0000 aaaaaaaa aaaaaaaa
+# (31337_57200935026773, `Loads address %adr from main memory and stores it to %dest.`)
+
+load_16 %dest(register), [%adr(register)]
+01100001 dddd0000 0000aaaa 00000000
+# (31337_57200935026773, `Loads address %adr from main memory and stores it to %dest.`)
+
+load_16 %dest(register), [%adr:U16(immediate)]
+01110001 dddd0000 aaaaaaaa aaaaaaaa
+# (31337_57200935026773, `Loads address %adr from main memory and stores it to %dest.`)
+
+load_32 %dest(register), [%adr(register)]
+01100010 dddd0000 0000aaaa 00000000
+# (31337_57200935026773, `Loads address %adr from main memory and stores it to %dest.`)
+
+load_32 %dest(register), [%adr:U16(immediate)]
+01110010 dddd0000 aaaaaaaa aaaaaaaa
+# (31337_57200935026773, `Loads address %adr from main memory and stores it to %dest.`)
+
+pload %dest(register), [%adr(register)]
+01100011 dddd0000 0000aaaa 00000000
+# (31337_89257021109854, `Loads address %adr from persistent memory and stores it to %dest.`)
+
+pload %dest(register), [%adr:U16(immediate)]
+01110011 dddd0000 aaaaaaaa aaaaaaaa
+# (31337_89257021109854, `Loads address %adr from persistent memory and stores it to %dest.`)
+
+store_8 [%adr(register)], %value(register)
+01100100 0000vvvv 0000aaaa 00000000
+# (31337_61040780958703, `Stores %value to address %adr in main memory.`)
+
+store_8 [%adr:U16(immediate)], %value(register)
+01110100 0000vvvv aaaaaaaa aaaaaaaa
+# (31337_61040780958703, `Stores %value to address %adr in main memory.`)
+
+store_16 [%adr(register)], %value(register)
+01100101 0000vvvv 0000aaaa 00000000
+# (31337_61040780958703, `Stores %value to address %adr in main memory.`)
+
+store_16 [%adr:U16(immediate)], %value(register)
+01110101 0000vvvv aaaaaaaa aaaaaaaa
+# (31337_61040780958703, `Stores %value to address %adr in main memory.`)
+
+store_32 [%adr(register)], %value(register)
+01100110 0000vvvv 0000aaaa 00000000
+# (31337_61040780958703, `Stores %value to address %adr in main memory.`)
+
+store_32 [%adr:U16(immediate)], %value(register)
+01110110 0000vvvv aaaaaaaa aaaaaaaa
+# (31337_61040780958703, `Stores %value to address %adr in main memory.`)
+
+pstore [%adr(register)], %value(register)
+01100111 0000vvvv 0000aaaa 00000000
+# (31337_13110303123442, `Stores %value to address %adr in persistent memory.`)
+
+pstore [%adr:U16(immediate)], %value(register)
+01110111 0000vvvv aaaaaaaa aaaaaaaa
+# (31337_13110303123442, `Stores %value to address %adr in persistent memory.`)
+
+
+mov %a(register), %b(register)
+00100001 aaaa0000 0000bbbb 00000000
+# (31337_53941960758392, `Moves a value to %a from %b.`)
+
+mov %a(register), %b:U16(immediate | label)
+00110001 aaaa0000 bbbbbbbb bbbbbbbb
+# (31337_34859363394334, `Moves a value to %a.`)
+
+neg %a(register), %b(register)
+00100101 aaaa0000 0000bbbb 00000000
+# (31337_72894099288447, `Negates a %b and stores it in %a.`)
+
+neg %a(register), %b:U16(immediate | label)
+00110101 aaaa0000 bbbbbbbb bbbbbbbb
+# (31337_57504570243305, `Negates a value and stores it in %a.`)
+
+not %a(register), %b(register)
+00100011 aaaa0000 0000bbbb 00000000
+# (31337_55357258069734, `Toggles the bits of %b and stores it in %a.`)
+
+not %a(register), %b:U16(immediate | label)
+00110011 aaaa0000 bbbbbbbb bbbbbbbb
+# (31337_40508048121543, `Toggles the bits of a value and stores it in %a.`)
+
+
+push %a(register)
+00110101 11101110 00000000 00000100   01100110 0000aaaa 00001110 00000000
+# (31337_28545157055801, `Pushes %a onto the stack. This instruction is a synonym for:   sub sp, sp, 4   store_32 [sp], %a`)
+
+pop %a(register)
+01100010 aaaa0000 00001110 00000000   00110100 11101110 00000000 00000100
+# (31337_54469754973269, `Pops %a off the stack. This instruction is a synonym for:   load_32 %a, [sp]   add sp, sp, 4`)
+
+call %a(label)
+00000111 11110000 00000000 00000000   00110100 11111111 00000000 00010100   00110101 11101110 00000000 00000100   01100110 00001111 00001110 00000000   01011000 00001111 aaaaaaaa aaaaaaaa
+# (31337_57788320241950, `Calls %a. Overwrites the flag register. This instruction is a synonym for:   counter flags   add flags, flags, 20   sub sp, sp, 4   store_32 [sp], flags   jmp %a`)
+
+ret
+01100010 11110000 00001110 00000000   00110100 11101110 00000000 00000100   01001000 00001111 00001111 00000000
+# (31337_48332460366102, `Returns from the last function call. Overwrites the flag register. This instruction is a synonym for:   load_32 flags, [sp]   add sp, sp, 4   jmp flags`)
+

isa/test.isa

@@ -0,0 +1,361 @@
+[settings]
+name = "Symphony"
+
+[fields]
+
+register
+zr 0000
+r1 0001
+r2 0010
+r3 0011
+r4 0100
+r5 0101
+r6 0110
+r7 0111
+r8 1000
+r9 1001
+r10 1010
+r11 1011
+r12 1100
+r13 1101
+sp 1110
+flags 1111
+
+condition
+""     1000
+".all" 1000
+".e"   0001
+".ne"  1001
+".b"   0010
+".ae"  1010
+".be"  0011
+".a"   1011
+".l"   0100
+".ge"  1100
+".le"  0101
+".g"   1101
+
+[instructions]
+
+nop
+00000000 00000000 00000000 00000000
+# (31337_88272577071256, `Does nothing.`)
+
+in %a(register)
+00000001 aaaa0000 00000000 00000000
+# (31337_44524771082050, `Loads an input and stores it in %a.`)
+
+out %b(register)
+00000010 00000000 0000bbbb 00000000
+# (31337_18254089726214, `Sends %b to output.`)
+
+out %a:U16(immediate)
+00010010 00000000 aaaaaaaa aaaaaaaa
+# (31337_15915531259935, `Sends %a to output.`)
+
+keyboard %a(register)
+00000011 aaaa0000 00000000 00000000
+# (31337_27868418224252, `Loads keyboard input and stores it to %a.`)
+
+screen %a(register), %b(register)
+00000100 0000aaaa 0000bbbb 00000000
+# (31337_39857449355186, `Stores the value of %b in screen setting %a.`)
+
+screen %a(register), %b:U16(immediate)
+00010100 0000aaaa bbbbbbbb bbbbbbbb
+# (31337_12835125621741, `Stores the value of %b in screen setting %a.`)
+
+time_0 %a(register)
+00000101 aaaa0000 00000000 00000000
+# (31337_72551400437977, `Loads the lower four bytes of the time value and stores it to %a.`)
+
+time_1 %a(register)
+00000110 aaaa0000 00000000 00000000
+# (31337_68219187873304, `Loads the upper four bytes of the time value and stores it to %a.`)
+
+counter %a(register)
+00000111 aaaa0000 00000000 00000000
+# (31337_67376584796076, `Loads the counter value and stores it to %a.`)
+
+
+
+nand %a(register), %b(register), %c(register)
+00100000 aaaabbbb 0000cccc 00000000
+# (31337_86705346481666, `NAND %b and %c and stores the result in %a.`)
+
+or %a(register), %b(register), %c(register)
+00100001 aaaabbbb 0000cccc 00000000
+# (31337_40732211165530, `OR %b and %c and stores the result in %a.`)
+
+and %a(register), %b(register), %c(register)
+00100010 aaaabbbb 0000cccc 00000000
+# (31337_85679146831122, `AND %b and %c and stores the result in %a.`)
+
+nor %a(register), %b(register), %c(register)
+00100011 aaaabbbb 0000cccc 00000000
+# (31337_37333076617857, `NOR %b and %c and stores the result in %a.`)
+
+add %a(register), %b(register), %c(register)
+00100100 aaaabbbb 0000cccc 00000000
+# (31337_51030225266712, `ADD %b and %c and stores the result in %a.`)
+
+sub %a(register), %b(register), %c(register)
+00100101 aaaabbbb 0000cccc 00000000
+# (31337_28652904157569, `SUB %b and %c and stores the result in %a.`)
+
+xor %a(register), %b(register), %c(register)
+00100110 aaaabbbb 0000cccc 00000000
+# (31337_46967848572964, `XOR %b and %c and stores the result in %a.`)
+
+lsl %a(register), %b(register), %c(register)
+00100111 aaaabbbb 0000cccc 00000000
+# (31337_13576771671264, `Logical shifts left %b by %c and stores the result in %a.`)
+
+lsr %a(register), %b(register), %c(register)
+00101000 aaaabbbb 0000cccc 00000000
+# (31337_67019902294705, `Logical shifts right %b by %c and stores the result in %a.`)
+
+asr %a(register), %b(register), %c(register)
+00101001 aaaabbbb 0000cccc 00000000
+# (31337_42626144645228, `Arithmetic shift right %b by %c and stores the result in %a.`)
+
+cmp %a(register), %b(register)
+00101010 1111aaaa 0000bbbb 00000000
+# (31337_54565380946620, `Compares %a and %b and stores the result in the 'flags' register.`)
+
+
+nand %a(register), %b(register), %c:U16(immediate | label)
+00110000 aaaabbbb cccccccc cccccccc
+# (31337_75302656449127, `NAND %b and %c and stores the result in %a.`)
+
+or %a(register), %b(register), %c:U16(immediate | label)
+00110001 aaaabbbb cccccccc cccccccc
+# (31337_30574433901064, `OR %b and %c and stores the result in %a.`)
+
+nor %a(register), %b(register), %c:U16(immediate | label)
+00110011 aaaabbbb cccccccc cccccccc
+# (31337_46087142860391, `NOR %b and %c and stores the result in %a.`)
+
+and %a(register), %b(register), %c:U16(immediate | label)
+00110010 aaaabbbb cccccccc cccccccc
+# (31337_86713121915282, `AND %b and %c and stores the result in %a.`)
+
+add %a(register), %b(register), %c:U16(immediate | label)
+00110100 aaaabbbb cccccccc cccccccc
+# (31337_23349431010010, `ADD %b and %c and stores the result in %a.`)
+
+sub %a(register), %b(register), %c:U16(immediate | label)
+00110101 aaaabbbb cccccccc cccccccc
+# (31337_67495552371225, `SUB %b and %c and stores the result in %a.`)
+
+xor %a(register), %b(register), %c:U16(immediate | label)
+00110110 aaaabbbb cccccccc cccccccc
+# (31337_66785854415645, `XOR %b and %c and stores the result in %a.`)
+
+lsl %a(register), %b(register), %c:U16(immediate | label)
+00110111 aaaabbbb cccccccc cccccccc
+# (31337_54577249258785, `Logical shifts left %b by %c and stores the result in %a.`)
+
+lsr %a(register), %b(register), %c:U16(immediate | label)
+00111000 aaaabbbb cccccccc cccccccc
+# (31337_16685334571248, `Logical shifts right %b by %c and stores the result in %a.`)
+
+asr %a(register), %b(register), %c:U16(immediate | label)
+00111001 aaaabbbb cccccccc cccccccc
+# (31337_55551510150818, `Arithmetic shifts right %b and %c and stores the result in %a.`)
+
+cmp %a(register), %b:U16(immediate | label)
+00111010 1111aaaa bbbbbbbb bbbbbbbb
+# (31337_37102964808364, `Compares %a and %b and stores the result in the 'flags' register.`)
+
+
+jmp %a(register)
+01001000 00001111 0000aaaa 00000000
+# (31337_74148826866592, `Jumps to %a.`)
+
+
+jmp %a:U16(immediate | label)
+01011000 00001111 aaaaaaaa aaaaaaaa
+# (31337_90876214388280, `Jumps to %a.`)
+
+je %a:U16(immediate | label)
+01010001 00001111 aaaaaaaa aaaaaaaa
+# (31337_88180305667389, `Jumps to %a if the values were equal (reading results from 'flags').`)
+
+jne %a:U16(immediate | label)
+01011001 00001111 aaaaaaaa aaaaaaaa
+# (31337_67178948469318, `Jumps to %a if the values were not equal (reading results from 'flags').`)
+
+
+jb %a:U16(immediate | label)
+01010010 00001111 aaaaaaaa aaaaaaaa
+# (31337_31763492459833, `Jumps to %a if the first value was below (unsigned) the second (reading results from 'flags').`)
+
+jae %a:U16(immediate | label)
+01011010 00001111 aaaaaaaa aaaaaaaa
+# (31337_82087388048746, `Jumps to %a if the first value was above (unsigned) or equal to the second (reading results from 'flags').`)
+
+jbe %a:U16(immediate | label)
+01010011 00001111 aaaaaaaa aaaaaaaa
+# (31337_26183125927881, `Jumps to %a if the First value was below (unsigned) or equal to the second (reading results from 'flags').`)
+
+ja %a:U16(immediate | label)
+01011011 00001111 aaaaaaaa aaaaaaaa
+# (31337_11626177279992, `Jumps to %a if the first value was above (unsigned) the second (reading results from 'flags').`)
+
+
+jl %a:U16(immediate | label)
+01010100 00001111 aaaaaaaa aaaaaaaa
+# (31337_71637103729391, `Jumps to %a if the first value was less (signed) than the second (reading results from 'flags').`)
+
+jge %a:U16(immediate | label)
+01011100 00001111 aaaaaaaa aaaaaaaa
+# (31337_53499765587663, `Jumps to %a if the first value was greater (signed) or equal to the second (reading results from 'flags').`)
+
+jle %a:U16(immediate | label)
+01010101 00001111 aaaaaaaa aaaaaaaa
+# (31337_77040234358389, `Jumps to %a if the first value was less (signed) or equal to the second (reading results from 'flags').`)
+
+jg %a:U16(immediate | label)
+01011101 00001111 aaaaaaaa aaaaaaaa
+# (31337_71317192057126, `Jumps to %a if the first value was greater (signed) than the second (reading results from 'flags').`)
+
+
+
+load_8 %dest(register), [%adr(register)]
+01100000 dddd0000 0000aaaa 00000000
+# (31337_57200935026773, `Loads address %adr from main memory and stores it to %dest.`)
+
+load_8 %dest(register), [%adr:U16(immediate | label)]
+01110000 dddd0000 aaaaaaaa aaaaaaaa
+# (31337_57200935026773, `Loads address %adr from main memory and stores it to %dest.`)
+
+load_16 %dest(register), [%adr(register)]
+01100001 dddd0000 0000aaaa 00000000
+# (31337_57200935026773, `Loads address %adr from main memory and stores it to %dest.`)
+
+load_16 %dest(register), [%adr:U16(immediate | label)]
+01110001 dddd0000 aaaaaaaa aaaaaaaa
+# (31337_57200935026773, `Loads address %adr from main memory and stores it to %dest.`)
+
+load_32 %dest(register), [%adr(register)]
+01100010 dddd0000 0000aaaa 00000000
+# (31337_57200935026773, `Loads address %adr from main memory and stores it to %dest.`)
+
+load_32 %dest(register), [%adr:U16(immediate | label)]
+01110010 dddd0000 aaaaaaaa aaaaaaaa
+# (31337_57200935026773, `Loads address %adr from main memory and stores it to %dest.`)
+
+pload %dest(register), [%adr(register)]
+01100011 dddd0000 0000aaaa 00000000
+# (31337_89257021109854, `Loads address %adr from persistent memory and stores it to %dest.`)
+
+pload %dest(register), [%adr:U16(immediate)]
+01110011 dddd0000 aaaaaaaa aaaaaaaa
+# (31337_89257021109854, `Loads address %adr from persistent memory and stores it to %dest.`)
+
+store_8 [%adr(register)], %value(register)
+01100100 0000vvvv 0000aaaa 00000000
+# (31337_61040780958703, `Stores %value to address %adr in main memory.`)
+
+store_8 [%adr:U16(immediate | label)], %value(register)
+01110100 0000vvvv aaaaaaaa aaaaaaaa
+# (31337_61040780958703, `Stores %value to address %adr in main memory.`)
+
+store_16 [%adr(register)], %value(register)
+01100101 0000vvvv 0000aaaa 00000000
+# (31337_61040780958703, `Stores %value to address %adr in main memory.`)
+
+store_16 [%adr:U16(immediate | label)], %value(register)
+01110101 0000vvvv aaaaaaaa aaaaaaaa
+# (31337_61040780958703, `Stores %value to address %adr in main memory.`)
+
+store_32 [%adr(register)], %value(register)
+01100110 0000vvvv 0000aaaa 00000000
+# (31337_61040780958703, `Stores %value to address %adr in main memory.`)
+
+store_32 [%adr:U16(immediate | label)], %value(register)
+01110110 0000vvvv aaaaaaaa aaaaaaaa
+# (31337_61040780958703, `Stores %value to address %adr in main memory.`)
+
+pstore [%adr(register)], %value(register)
+01100111 0000vvvv 0000aaaa 00000000
+# (31337_13110303123442, `Stores %value to address %adr in persistent memory.`)
+
+pstore [%adr:U16(immediate)], %value(register)
+01110111 0000vvvv aaaaaaaa aaaaaaaa
+# (31337_13110303123442, `Stores %value to address %adr in persistent memory.`)
+
+
+mov %a(register), %b(register)
+00100001 aaaa0000 0000bbbb 00000000
+# (31337_53941960758392, `Moves a value to %a from %b.`)
+
+mov %a(register), %b:U16(immediate | label)
+00110001 aaaa0000 bbbbbbbb bbbbbbbb
+# (31337_34859363394334, `Moves a value to %a.`)
+
+neg %a(register), %b(register)
+00100101 aaaa0000 0000bbbb 00000000
+# (31337_72894099288447, `Negates a %b and stores it in %a.`)
+
+neg %a(register), %b:U16(immediate | label)
+00110101 aaaa0000 bbbbbbbb bbbbbbbb
+# (31337_57504570243305, `Negates a value and stores it in %a.`)
+
+not %a(register), %b(register)
+00100011 aaaa0000 0000bbbb 00000000
+# (31337_55357258069734, `Toggles the bits of %b and stores it in %a.`)
+
+not %a(register), %b:U16(immediate | label)
+00110011 aaaa0000 bbbbbbbb bbbbbbbb
+# (31337_40508048121543, `Toggles the bits of a value and stores it in %a.`)
+
+
+push %a(register)
+00110101 11101110 00000000 00000100   01100110 0000aaaa 00001110 00000000
+# (31337_28545157055801, `Pushes %a onto the stack. This instruction is a synonym for:   sub sp, sp, 4   store_32 [sp], %a`)
+
+pop %a(register)
+01100010 aaaa0000 00001110 00000000   00110100 11101110 00000000 00000100
+# (31337_54469754973269, `Pops %a off the stack. This instruction is a synonym for:   load_32 %a, [sp]   add sp, sp, 4`)
+
+call %a(label)
+00000111 11110000 00000000 00000000   00110100 11111111 00000000 00010100   00110101 11101110 00000000 00000100   01100110 00001111 00001110 00000000   01011000 00001111 aaaaaaaa aaaaaaaa
+# (31337_57788320241950, `Calls %a. Overwrites the flag register. This instruction is a synonym for:   counter flags   add flags, flags, 20   sub sp, sp, 4   store_32 [sp], flags   jmp %a`)
+
+ret
+01100010 11110000 00001110 00000000   00110100 11101110 00000000 00000100   01001000 00001111 00001111 00000000
+# (31337_48332460366102, `Returns from the last function call. Overwrites the flag register. This instruction is a synonym for:   load_32 flags, [sp]   add sp, sp, 4   jmp flags`)
+
+
+li %r(register), %a:S33(immediate | label)
+; assert(0 - 0x80000000 <= %a, "%a is too low")
+; assert(%a <= 0xffffffff, "%a is too high")
+%s = trailing_zeros(%a)
+%sa = %a >> %s
+%nota = %a ^ 0xffffffff
+when %a <=u 0xffff   : 00110001 %r[3:0]0000 %a[15:0]                                                 ; First 64k
+when %nota <=u 0xffff: 00110001 %r[3:0]0000 %nota[15:0]    00100011 %r[3:0]0000 0000%r[3:0] 00000000 ; Last 64k
+when %sa <=u 0xffff  : 00110001 %r[3:0]0000 %sa[15:0]      00110111 %r[3:0]%r[3:0] 00000000 %s[7:0]  ; Aligned
+00110001 %r[3:0]0000 %a[31:16]   00110111 %r[3:0]%r[3:0] 00000000 00010000   00110001 %r[3:0]%r[3:0] %a[15:0]          ; Any 32-bit
+# Load 32-bit immediate %a into %r
+
+qcall %a:U32(label)
+; assert(0 - 0x80000000 <= %a, "%a is too low")
+; assert(%a <= 0xffffffff, "%a is too high")
+%r = 13
+%f = 15
+%s = trailing_zeros(%a)
+%sa = %a >> %s
+%nota = %a ^ 0xffffffff
+when %a <=u 0xffff   : 01011000 %r[3:0]ffff %a[15:0]                                                                                              ; First 64k
+when %nota <=u 0xffff: 00110001 %r[3:0]0000 %nota[15:0]    00100011 %r[3:0]0000 0000%r[3:0] 00000000    01001000 %r[3:0]ffff 0000%r[3:0] 00000000 ; Last 64k
+when %sa <=u 0xffff  : 00110001 %r[3:0]0000 %sa[15:0]      00110111 %r[3:0]%r[3:0] 00000000 %s[7:0]     01001000 %r[3:0]ffff 0000%r[3:0] 00000000 ; Aligned
+00110001 %r[3:0]0000 %a[31:16]   00110111 %r[3:0]%r[3:0] 00000000 00010000   00110001 %r[3:0]%r[3:0] %a[15:0]    01001000 %r[3:0]ffff 0000%r[3:0] 00000000 ; Any 32-bit
+# Jump and link to 32-bit label
+
+halt%c(condition)
+1000cccc 00001111 00000000 00000000
+# Halt on condition %c
+

src/errno.asm

@@ -0,0 +1,28 @@
+; Error numbers should be 16 bit ODD numbers, so they can be loaded as immediates
+; and can be checked with:
+;
+;   qcall falible_function
+;   jne falible_ok ; Jump no error
+;       ; handle error
+;   falible_ok:
+;   ; Happy path
+;   ; ...
+; OR
+;   qcall falible_function
+;   je handle_error ; Jump if error
+;   ; Happy path
+;   ; ...
+;   handle_error:
+;       ; handle error
+
+pub const OK                   = 0x0000
+pub const SCREEN_INVALID_MODE  = 0x0001
+pub const SCREEN_INVALID_WIDTH = 0x0003
+pub const SCREEN_FB_TOO_SMALL  = 0x0005
+pub const SCREEN_OUTSIDE_FB    = 0x0007
+pub const BUFFER_DEPTH_MISMATCH= 0x0009
+
+pub const MAGIC_BAD            = 0x8001
+
+; Extended error codes, these would require loading a 32 bit value.
+pub const EXT_OK              = 0x00000000

src/globals.asm

@@ -0,0 +1,30 @@
+; Addresses of global variables
+
+pub const MAGIC_ADDRESS_LONG = 0x0c       ; U32 Location of the magic value
+pub const MAGIC_VALUE_LONG   = 0xb301534c ; U32 Full 32 bits of the magic value
+pub const MAGIC_ADDRESS      = 0x0e       ; U16 Location of the low 16 bits of magic value
+pub const MAGIC_VALUE        = 0x534c     ; U16 Low 16 bits of the magic value
+
+; If not double buffering these point to the same buffer
+; If double buffering they must the same size
+pub const FB_DISPLAY_PTR     = 0x10       ; U32 Currently displayed buffer
+pub const FB_DISPLAY_STRIDE  = 0x14       ; U16 Bytes in each row of the displayed buffer
+pub const FB_DISPLAY_DEPTH   = 0x16       ; U16 Bits per pixel of the display buffer
+pub const FB_DRAW_PTR        = 0x18       ; U32 Draw to this buffer
+pub const FB_DRAW_STRIDE     = 0x1c       ; U16 Bytes in each row of the draw buffer == FB_DISPLAY_STRIDE
+pub const FB_DRAW_DEPTH      = 0x1e       ; U16 Bits per pixel of the draw buffer == FB_DISPLAY_DEPTH
+pub const FB_SIZE_BYTE       = 0x20       ; U32 In bytes
+pub const FB_WIDTH_PX        = 0x24       ; U16 Width of screen in pixels
+pub const FB_HEIGHT_PX       = 0x26       ; U16 Height of screen in pixels
+
+; Log2 of width in pixels, e.g.
+; * 10 => 1024 * 768
+; *  8 =>  256 * 192
+pub const FB_LOG_WIDTH       = 0x28       ; U8
+pub const FB_LOG_STRIDE      = 0x29       ; U8 Log2 of FB_xxx_STRIDE in bytes
+
+pub const FB_BYTES_PER_PIXEL = 0x2a       ; U8 Specialisations should hardcode this
+; Log2 of bytes per pixel
+; * 0 => 8 bits per pixel
+; * 2 => 32 bits per pixel
+pub const FB_LOG_BPP         = 0x2b       ; U8 Specialisations should hardcode this

src/graphics.asm

@@ -0,0 +1,268 @@
+include errno
+
+; Performs a Bitblock transfer, copying a section of the Source to the Destination, applying a given Mode operation
+; Arguments:
+; r1 - Destination Buffer pointer
+; r2 - Source Buffer pointer
+; r3 - X destination coordinate
+; r4 - Y destination coordinate
+; r5 - X source coordinate
+; r6 - Y source coordinate
+; r7 - Mode:
+;    000 - SRCCOPY (copies source over destination)
+;    001 - XOR
+;    010 - AND
+;    011 - NOT
+;    100 - OR
+;    101 - reserved
+;    110 - reserved
+;    111 - SRCALPHA (copies source over destination if: source != 0 (for 8bpp), source.alpha != 0 (for 32bpp))
+; Stack argument 1: Width
+; Stack argument 2: Height
+; Result: None
+; Clobbers: r1, r2, r3, r4, r5, r6, r7
+; Errors: BUFFER_DEPTH_MISMATCH - if the buffers have different bit depths
+pub bitblit:
+    push r8
+    push r9
+    ; Checking if the bit depths are correct
+    add r8, r1, 6 ; r8 = pointer to destination depth
+    load_16 r8, [r8] ; r8 = dest depth
+    add r9, r2, 6 ; r9 = pointer to source depth
+    load_16 r9, [r9] ; r9 = src depth
+    cmp r8, r9
+    je bitblit_depth_good
+        ; Bit depths differ - error
+        pop r9
+        pop r8
+        add sp, sp, 8 ; Removing the stack Arguments
+        mov flags, errno.BUFFER_DEPTH_MISMATCH
+        jmp r13
+    bitblit_depth_good:
+    push r8
+    push r10
+    push r11
+    push r12
+    push r13
+	push r7
+	mov r7, r8
+	lsr r7, r7, 4
+
+    add r10, r1, 4 ; r10 = pointer to destination stride
+    load_16 r10, [r10] ; r10 = destination stride
+	lsl r10, r10, r7
+	
+    add r11, r2, 4 ; r11 = pointer to source stride
+    load_16 r11, [r11] ; r11 = source stride
+	lsl r11, r11, r7
+	
+	add sp, sp, 32
+    load_32 r8, [sp] ; r8 = height
+    add sp, sp, 4
+    load_32 r9, [sp] ; r9 = width
+    lsl r9, r9, r7
+    sub sp, sp, 36
+
+
+    ; Calculating destination index
+    push r10
+    mov r12, 0
+    bitblit_destination_index:
+        cmp r4, zr
+        je bitblit_after_destination_index
+        mov flags, r4
+        jne bitblit_destination_index_afteradd
+        add r12, r12, r10
+        bitblit_destination_index_afteradd:
+        lsr r4, r4, 1
+        lsl r10, r10, 1
+        jmp bitblit_destination_index
+    bitblit_after_destination_index:
+    add r4, r4, r12 ; Now r4 is dest_y * dest_stride
+    load_32 r1, [r1] ; r1 = destination data pointer
+    add r1, r1, r4 ; Now r1 is dest_pointer + dest_y * dest_stride
+    lsl r3, r3, r7
+    add r1, r1, r3 ; Now r1 is dest_pointer + dest_y * dest_stride + dest_x
+	pop r10
+
+	push r11
+    ; Calculating source index
+    mov r12, 0
+    bitblit_source_index:
+        cmp r6, zr
+        je bitblit_after_source_index
+        mov flags, r6
+        jne bitblit_source_index_afteradd
+        add r12, r12, r11
+        bitblit_source_index_afteradd:
+        lsr r6, r6, 1
+        lsl r11, r11, 1
+        jmp bitblit_source_index
+    bitblit_after_source_index:
+    add r6, r6, r12 ; Now r6 is src_y * src_stride
+    load_32 r2, [r2] ; r2 = source data pointer
+    add r2, r2, r6 ; Now r2 is src_pointer + src_y * src_stride
+    lsl r5, r5, r7
+    add r2, r2, r5 ; Now r2 is src_pointer + src_y * src_stride + src_x
+	pop r11
+	
+	pop r7
+
+    ; r3, r4, r5, r6 are now free
+
+    mov r3, bitblit_mode
+    mov r12, bitblit_end_mode
+    lsl r7, r7, 3 ; 2 instructions per mode
+    add r12, r7, r12
+    add r7, r7, r3
+    
+    ; r1 is line dest pointer (or bit depth)
+    ; r2 is line src pointer (or temp)
+    ; r3 is width iterator
+    ; r4 is current dest pointer
+    ; r5 is current src pointer
+    ; r6 is current src value
+    ; r7 is 32bit mode jump table destination
+    ; r8 is height iterator
+    ; r9 is width of bitblit
+    ; r10 is dest stride
+    ; r11 is src stride
+    ; r12 is 8bit mode jump table destination
+    ; r13 is current dest value
+
+	bitblit_copy_height:
+		cmp r8, zr
+		je bitblit_finish
+		
+	    bitblit_copy_line:
+	        mov r3, 0
+	        mov r4, r1 ; r4 = dest
+	        mov r5, r2 ; r5 = src
+            push r1
+            add r1, sp, 20 ; Pointing to bit depth saved on stack
+            load_32 r1, [r1] ; r1 = bit depth
+            push r2
+	        bitblit_copy_line_loop: ; Main loop that copies 4 bytes at a time
+	        	add r3, r3, 4
+	        	cmp r9, r3
+	            jb bitblit_copy_line_end
+	            load_32 r6, [r5] ; r6 = [src]
+	            load_32 r13, [r4] ; r13 = [dest]
+	            jmp r7
+	            bitblit_mode:
+	                nop ; SRCCOPY
+	                jmp bitblit_save_bits
+	                xor r6, r6, r13 ; XOR
+	                jmp bitblit_save_bits
+	                and r6, r6, r13 ; AND
+	                jmp bitblit_save_bits
+	                not r6, r6 ; NOT
+	                jmp bitblit_save_bits
+	                or r6, r6, r13 ; OR
+	                jmp bitblit_save_bits
+	                nop ; reserved
+	                jmp bitblit_save_bits
+	                nop ; reserved
+	                jmp bitblit_save_bits
+	                cmp r1, 8 ; SRCALPHA
+	                jne bitblit_srcalpha_32 ; If bit depth is 32, we jump to alpha checking
+                    ; If bit depth is 8, we need to repack this value
+                    mov r2, 0 ; our mask
+                    
+                    lsr flags, r6, 24
+                    cmp flags, zr
+                    jne bitblit_srcalpha_8_1
+                    or r2, r2, 0xFF
+                    bitblit_srcalpha_8_1:
+                    lsl r2, r2, 8
+
+                    lsr flags, r6, 16
+                    and flags, flags, 0xFF
+                    cmp flags, zr
+                    jne bitblit_srcalpha_8_2
+                    or r2, r2, 0xFF
+                    bitblit_srcalpha_8_2:
+                    lsl r2, r2, 8
+
+                    lsr flags, r6, 8
+                    and flags, flags, 0xFF
+                    cmp flags, zr
+                    jne bitblit_srcalpha_8_3
+                    or r2, r2, 0xFF
+                    bitblit_srcalpha_8_3:
+                    lsl r2, r2, 8
+
+                    and flags, r6, 0xFF
+                    cmp flags, zr
+                    jne bitblit_srcalpha_8_4
+                    or r2, r2, 0xFF
+                    bitblit_srcalpha_8_4:
+
+                    and r13, r13, r2
+                    not r2, r2
+                    and r6, r6, r2
+                    or r6, r6, r13
+
+                    jmp bitblit_save_bits
+                    bitblit_srcalpha_32:
+                    and flags, r6, 0xFF
+                    cmp flags, zr
+                    jne bitblit_save_bits ; If alpha channel is not zero, we save the value
+                    mov r6, r13 ; If it was zero, we take [dest], i.e. don't overwrite
+	            bitblit_save_bits:
+	                store_32 [r4], r6
+	                cmp r9, r3
+	            	je bitblit_copy_line_finish
+	                add r4, r4, 4
+	                add r5, r5, 4
+	                jmp bitblit_copy_line_loop
+	        bitblit_copy_line_end: ; Now we need to handle up to 3 bytes that were not copied
+				sub r3, r3, 4
+				bitblit_copy_line_end_loop:
+					load_8 r6, [r5] ; r6 = [src]
+		            load_8 r13, [r4] ; r13 = [dest]
+		            jmp r12
+		            bitblit_end_mode:
+		                nop ; SRCCOPY
+		                jmp bitblit_save_bits_end
+		                xor r6, r6, r13 ; XOR
+		                jmp bitblit_save_bits_end
+		                and r6, r6, r13 ; AND
+		                jmp bitblit_save_bits_end
+		                not r6, r6 ; NOT
+		                jmp bitblit_save_bits_end
+		                or r6, r6, r13 ; OR
+		                jmp bitblit_save_bits_end
+		                nop ; reserved
+		                jmp bitblit_save_bits_end
+		                nop ; reserved
+		                jmp bitblit_save_bits_end
+		                cmp r6, zr ; SRCALPHA (will happen only in 8bpp)
+		                jne bitblit_save_bits_end
+                        mov r6, r13 ; [src] = 0, so we take [dest], i.e. don't overwrite
+		            bitblit_save_bits_end:
+		                store_8 [r4], r6
+		                add r3, r3, 1
+		                add r4, r4, 1
+		                add r5, r5, 1
+		                cmp r9, r3
+		                ja bitblit_copy_line_end_loop
+				
+		bitblit_copy_line_finish:
+        pop r2
+        pop r1
+	    add r1, r1, r10
+	    add r2, r2, r11 ; Moving dest & src to next line
+		sub r8, r8, 1
+		jmp bitblit_copy_height
+    bitblit_finish:
+        pop r13
+        pop r12
+        pop r11
+        pop r10
+        add sp, sp, 4 ; Bit depth skip
+        pop r9
+        pop r8
+        add sp, sp, 8
+        mov flags, errno.OK
+        jmp r13

src/imath.asm

@@ -4,22 +4,53 @@
 ; r2 - The second value
 ; Result:
 ; r1 - The lower 32 bits of the result
-; Clobbers: r2, r3, r4, r5
+; Clobbers: r2, r3, r4, r5, r6
 pub mul_low:
-	mov r3, 0 ; result
-	mov r4, 31 ; loop counter
-	
-	mul_low_loop:
-		asr r5, r2, 31
-		and r5, r5, r1
-		lsl r5, r5, r4
-		add r3, r3, r5
-		lsl r2, r2, 1
-		sub r4, r4, 1
-		cmp r4, 0
-		jge mul_low_loop
-	mov r1, r3
+	cmp r1, r2
+	jbe mul_low_noswap
+	xor r1, r2, r1
+	xor r2, r1, r2
+	xor r1, r2, r1
+	; Passthrough
+
+; Multiplies r1 and r2, returning the lower part of the result
+; This method assumes r1 is smaller than r2, which results in faster execution
+; Arguments:
+; r1 - The first value
+; r2 - The second value
+; Result:
+; r1 - The lower 32 bits of the result
+; Clobbers: r2, r3, r4, r5, r6
+pub mul_low_noswap:
+	mov r4, 0 ; r4 has the result
+	mov r6, mul_loop_end
+	add r3, r2, r2
 	
+	mul_loop:
+		and r5, r1, 14 ; Taking the first four bits, discarding the odd
+		lsl r5, r5, 1 ; 0000 - 0, 0001 - 2, 0010 - 4, 0011 - 8, etc.
+		sub r5, r6, r5
+		jmp r5
+		
+		add r4, r4, r3
+		add r4, r4, r3
+		add r4, r4, r3
+		add r4, r4, r3
+		add r4, r4, r3
+		add r4, r4, r3
+		add r4, r4, r3
+		mul_loop_end:
+			mov flags, r1
+			jne mul_skip_one
+			add r4, r4, r2
+			mul_skip_one:
+			lsl r2, r2, 4
+			lsl r3, r3, 4
+			lsr r1, r1, 4
+			cmp r1, zr
+			jne mul_loop
+
+	mov r1, r4
 	jmp r13
 
 ; Calculates the absolute value of the value provided in the r1 register

src/mem.asm

@@ -0,0 +1,174 @@
+; int compare(uint8_t* a, uint8_t* b, size_t count);
+;   Compares two memory segment of equal length lexicographically.
+;
+; Arguments:
+; - `r1`: A pointer to the first memory segment.
+; - `r2`: A pointer to the second memory segment.
+; - `r3`: The size of both memory segments.
+; Results:
+; - `r1`:
+;   -  `0` if both segments are equal.
+;   - `<0` if the first segment is less than the second segment.
+;   - `>0` if the first segment is greater than the second segment.
+;
+pub compare:
+    ; Exclusive end point of the first segment.
+    add r3, r3, r1
+    sub r3, r3, 4
+_compare__loop:
+    load_32 r4, [r1]
+    add r1, r1, 4
+    load_32 r5, [r2]
+    add r2, r2, 4
+    ; Comparing two sequences of 4 bytes lexicographically is equivalent to
+    ; comparing the corresponding big endian 32 bit words.
+    cmp r4, r5
+    jne _compare__break
+    ; Check if there are enough bytes left to continue with the vectorized loop.
+    cmp r1, r3
+    jbe _compare__loop
+    ; `r3 + 4 - r1 = <remaining byte count> = r3 - r1 mod 4`
+    sub flags, r3, r1
+    ; Check if one of the lowest 2 bits is non-zero
+    jbe _compare__rem
+    ; If not, we are done. Both segments are equal.
+    mov r1, 0
+    jmp r13
+_compare__break:
+    ; `flags` is the comparison result in the format of `cmp`. Convert it to the desired format.
+    ; 00 => 0x40000000 > 0
+    ; 01 => 0x00000000 = 0
+    ; 10 => 0xC0000000 < 0
+    xor r1, flags, 1
+    lsl r1, r1, 30
+    jmp r13
+_compare__rem:
+    ; Compute `S = 8*(4 - <remaining byte count>)` and
+    ; [r1] >> S, [r2] >> S
+    mov r3, 8
+    load_32 r4, [r1]
+    sub r3, r3, flags
+    load_32 r5, [r2]
+    lsl r3, r3, 3
+    lsr r4, r4, r3
+    lsr r5, r5, r3
+    ; Compare both values, now with garbage bytes removed.
+    cmp r4, r5
+    jmp _compare__break
+
+
+; void copy(void* src, void* dest, size_t count);
+;   Copies `count` bytes from `src` to `dest`. The two memory segments must not overlap.
+;
+; Arguments:
+; - `r1`: Pointer to the memory segment to be copied.
+; - `r2`: Pointer to the memory segment to be copied into.
+; - `r3`: Byte size of both the `src` and `dest` segments.
+;
+pub copy:
+    ; Exclusive end point of the source segment.
+    add r3, r1, r3
+    ; Last index from where we can safely copy 8 bytes per loop iteration.
+    sub r3, r3, 8
+    jmp _copy__loop_entry
+_copy__loop:
+    ; Copy 8 bytes from `src` to `dest`.
+    load_32 flags, [r1]
+    add r1, r1, 4
+    store_32 [r2], flags
+    add r2, r2, 4
+    load_32 flags, [r1]
+    add r1, r1, 4
+    store_32 [r2], flags
+    add r2, r2, 4
+_copy__loop_entry:
+    ; Check if we can process more data in the vectorized loop.
+    cmp r1, r3
+    jbe _copy__loop
+    ; The remaining amount of bytes `R` is `R = r3 + 8 - r1 = r3 - r1 mod 8`.
+    sub flags, r3, r1
+    ; Test if `R` is not a multiple of `4`, i.e. the lowest 2 bits are non-zero.
+    jbe _copy__rem
+    ; `R` is a multiple of `4`. Special case this.
+    ; Check if `R` is `0`, i.e. the third bit is also 0. In that case, we are already done.
+    ; There are no conditional indirect jumps, so we can't return immediately.
+    jge _copy__ret
+    ; `R = 4`. No need to update `r1` or `r2`, we don't need them anymore.
+    load_32 flags, [r1]
+    store_32 [r2], flags
+_copy__ret:
+    ; Return
+    jmp r13
+_copy__rem:
+    ; Optimize the remaining cases for code size.
+    ; End point of the source segment.
+    add r3, r3, 8
+    ; We already handled the case `R = 0` earlier,
+    ; so no bounds check needed for the first iteration.
+_copy__rem_loop:
+    ; Copy 1 byte.
+    load_8 flags, [r1]
+    add r1, r1, 1
+    store_8 [r2], flags
+    add r2, r2, 1
+    ; Check if we are still within the bounds.
+    cmp r1, r3
+    jb _copy__rem_loop
+    jmp r13
+    
+; void fill32(uint8_t* dest, size_t count, uint32_t value);
+;   Fills `count` bytes in `dest` with `value`. If `count` is not a multiple of 4, 
+;   the least significant bytes of `value` are cut off for the last entry.
+;
+; Arguments:
+; - `r1`: A pointer to the destination segment.
+; - `r2`: The size of the destination segment.
+; - `r3`: The 32 bit value that the segment is filled with.
+;
+pub fill32:
+    ; Exclusive end point of the destination segment.
+    add r2, r1, r2
+    ; Last index from where we can safely write 8 bytes per loop iteration.
+    sub r2, r2, 8
+    jmp _fill32__entry
+_fill32__loop:
+	; Set 8 bytes per loop iteraion.
+    store_32 [r1], r3
+    add r1, r1, 4
+    store_32 [r1], r3
+    add r1, r1, 4
+_fill32__entry:
+    ; Check if we can process more data in the vectorized loop.
+    cmp r1, r2
+    jbe _fill32__loop
+    ; The remaining amount of bytes `R` is `R = r2 + 8 - r1 = r2 - r1 mod 8`.
+    sub flags, r2, r1
+    ; Check if the third bit of the remainder is cleared.
+    jge _fill32__r4
+    ; Otherwise set 4 bytes.
+    store_32 [r1], r3
+    add r1, r1, 4
+_fill32__r4:
+    ; Check if the two least significant bits of the remainder are zero.
+    ja _fill32__ret
+    ; Handle the remaining bytes `R` individually, in reverse order.
+    add r2, r2, 4
+    ; `r1 + 4 - r2 = 4 - R`.
+    sub flags, r1, r2
+    ; Exclusive end point of the destination segment.
+    add r2, r2, 4
+    ; Shift out the least significant `8*(4 - R)` bits of the value.
+    lsl flags, flags, 3
+    lsr r3, r3, flags
+    jmp _fill32__loop2_entry
+_fill32__loop2:
+    sub r2, r2, 1
+    ; Write the least significant byte of the value...
+    store_8 [r2], r3
+    ; and then shift it out.
+    lsr r3, r3, 8
+_fill32__loop2_entry:
+    cmp r1, r2
+    jb _fill32__loop2
+_fill32__ret:
+    jmp r13

src/start.asm

@@ -0,0 +1,19 @@
+;@0 ; Reserve space for globals
+
+; First initialise the stack pointer
+nor sp, zr, 0xffff
+; Jump over the globals to user code
+jmp 0x100
+
+U32 0 ; 4 bytes
+
+; MAGIC_VALUE
+;@0x0c
+U32 0xb301534c
+
+; Pad with zeroes since the @addr feature is currently broken.
+; * https://discord.com/channels/828292123936948244/1545010596246847568
+;
+U1920 0  ; 240 bytes
+
+;@0x100 ; start of user code

src/stdlib.asm

@@ -2,6 +2,8 @@ pub include bit
 pub include imath
 pub include array
 pub include console
+pub include mem
+pub include string_to_int
 
 ; Needs to be last!
 pub include LUTs

src/string_to_int.asm

@@ -0,0 +1,188 @@
+; Internal register assignments:
+; r1 - Partially parsed output integer
+; r2 - Parsing position
+; r3 - Character being parsed
+; r4 - Set to -1 if the input is negative
+
+; Convert string to integer (akin to libc atoi(), strotoi())
+; Arguments:
+; r1 - Pointer to string
+; Result:
+; r1 - Parsed integer
+; r2 - Pointer to first rejected input byte
+; Clobbers:
+; flags
+; r3 - last character read
+; r4 - Negative marker
+; Note: Unless the input is "0", tail-calls into a base-specific specialization.
+pub auto:
+mov r2, r1
+mov r1, 0
+mov r4, 0
+load_8 r3, [r2]
+cmp r3, 0x2D ; '-'
+jne auto_positive
+sub r4, zr, 1           ; Set r4 to -1
+add r2, r2, 1
+auto_positive:
+load_16 r3, [r2]        ; 2-byte prefix "0b", "0o", "0x", etc.
+or r3, r3, 0x20         ; 2nd char to lower case
+add r2, r2, 2
+cmp r3, 0x3062 ; "0b"
+je bin_loop
+cmp r3, 0x306F ; "0o"
+je oct_loop
+cmp r3, 0x3078 ; "0x"
+je hex_loop
+sub r2, r2, 2           ; no matching prefix, move pointer back
+jmp dec_loop
+
+; Epilogue
+done:
+add r1, r1, r4          ; If r4 is -1, negate r1. Else it's 0 and no effect.
+xor r1, r1, r4
+mov flags, 0            ; No error
+jmp r13
+
+; Convert decimal string to integer
+; Arguments:
+; r1 - Pointer to string
+; Result:
+; r1 - Parsed integer
+; r2 - Pointer to first rejected input byte
+; Clobbers:
+; flags
+; r3 - last character read
+; r4 - Negative marker
+pub dec:
+mov r2, r1
+mov r1, 0
+mov r4, 0
+load_8 r3, [r2]
+cmp r3, 0x2D ; '-'
+jne dec_positive
+sub r4, zr, 1           ; Set r4 to -1
+add r2, r2, 1
+dec_loop:
+load_8 r3, [r2]
+dec_positive:
+sub r3, r3, 0x30 ; '0'
+cmp r3, 9
+ja done
+add r2, r2, 1
+lsl flags, r1, 2        ; Use flags to help multiply by 10
+add r1, r1, flags
+lsl r1, r1, 1
+add r1, r1, r3
+jmp dec_loop
+
+; Convert binary string to integer
+; Arguments:
+; r1 - Pointer to string
+; Result:
+; r1 - Parsed integer
+; r2 - Pointer to first rejected input byte
+; Clobbers:
+; flags
+; r3 - last character read
+; r4 - Negative marker
+pub bin:
+mov r2, r1
+mov r1, 0
+mov r4, 0
+load_8 r3, [r2]
+cmp r3, 0x2D ; '-'
+jne bin_positive
+sub r4, zr, 1           ; Set r4 to -1
+add r2, r2, 1
+bin_positive:
+load_16 r3, [r2]        ; check for prefix
+or r3, r3, 0x20         ; 2nd char to lower case
+cmp r3, 0x3062 ; "0b"
+jne bin_loop
+add r2, r2, 2
+bin_loop:
+load_8 r3, [r2]
+sub r3, r3, 0x30 ; '0'
+cmp r3, 1
+ja done
+add r2, r2, 1
+lsl r1, r1, 1
+add r1, r1, r3
+jmp bin_loop
+
+; Convert octal string to integer
+; Arguments:
+; r1 - Pointer to string
+; Result:
+; r1 - Parsed integer
+; r2 - Pointer to first rejected input byte
+; Clobbers:
+; flags
+; r3 - last character read
+; r4 - Negative marker
+pub oct:
+mov r2, r1
+mov r1, 0
+mov r4, 0
+load_8 r3, [r2]
+cmp r3, 0x2D ; '-'
+jne oct_positive
+sub r4, zr, 1           ; Set r4 to -1
+add r2, r2, 1
+oct_positive:
+load_16 r3, [r2]        ; check for prefix
+or r3, r3, 0x20         ; 2nd char to lower case
+cmp r3, 0x306F ; "0o"
+jne oct_loop
+add r2, r2, 2
+oct_loop:
+load_8 r3, [r2]
+sub r3, r3, 0x30 ; '0'
+cmp r3, 7
+ja done
+add r2, r2, 1
+lsl r1, r1, 3
+add r1, r1, r3
+jmp oct_loop
+
+; Convert hexadecimal string to integer
+; Arguments:
+; r1 - Pointer to string
+; Result:
+; r1 - Parsed integer
+; r2 - Pointer to first rejected input byte
+; Clobbers:
+; flags
+; r3 - last character read
+; r4 - Negative marker
+pub hex:
+mov r2, r1
+mov r1, 0
+mov r4, 0
+load_8 r3, [r2]
+cmp r3, 0x2D ; '-'
+jne hex_positive
+sub r4, zr, 1           ; Set r4 to -1
+add r2, r2, 1
+hex_positive:
+load_16 r3, [r2]        ; check for prefix
+or r3, r3, 0x20         ; 2nd char to lower case
+cmp r3, 0x3078 ; "0x"
+jne hex_loop
+add r2, r2, 2
+hex_loop:
+load_8 r3, [r2]
+sub r3, r3, 0x30 ; '0'
+cmp r3, 10
+jb hex_add
+sub r3, r3, 0x11 ; 'A' - '0'
+and r3, r3, 0xdf        ; to lower case
+cmp r3, 5               ; 0-5: 6 letters
+ja done
+add r3, r3, 10          ; Adjust for digits below
+hex_add:
+add r2, r2, 1
+lsl r1, r1, 4
+add r1, r1, r3
+jmp hex_loop

src/unsafe_mem.asm

@@ -0,0 +1,77 @@
+; int compare(uint8_t* a, uint8_t* b, size_t count);
+;   Compares two memory segment of equal length lexicographically.
+;   Temporarily modifies the byte at address `a + count`.
+;
+; Arguments:
+; - `r1`: A pointer to the first memory segment.
+; - `r2`: A pointer to the second memory segment.
+; - `r3`: The size of both memory segments.
+; Results:
+; - `r1`:
+;   -  `0` if both segments are equal.
+;   - `<0` if the first segment is less than the second segment.
+;   - `>0` if the first segment is greater than the second segment.
+pub compare:
+    cmp r1, r2
+    je _compare__is_eq
+    ; Exclusive end point of the second segment.
+    add r4, r3, r2
+    ; Exclusive end point of the first segment.
+    add r3, r3, r1
+    load_8 r6, [r3]
+    load_8 flags, [r4]
+    ; Check if the first bytes behind the sequences are equal.
+    cmp flags, r6
+    jne _compare__loop
+    ; Change the byte directly behind the first segment.
+    xor r4, r6, 1
+    ; This would be problematic if someone calls compare with a first segment
+    ; whose end point overlaps the program memory of this function.
+    store_8 [r3], r4
+_compare__loop:
+    load_32 r4, [r1]
+    add r1, r1, 4
+    load_32 r5, [r2]
+    add r2, r2, 4
+    ; Comparing two sequences of 4 bytes lexicographically is equivalent to
+    ; comparing the corresponding big endian 32 bit words.
+    cmp r4, r5
+    je _compare__loop
+    ; We overshot in the loop; decrement r1 again. (Only by 2, we backtrack the rest if necessary later)
+    sub r1, r1, 2
+    ; Restore the byte we changed.
+    store_8 [r3], r6
+    ; We encountered two different words. Figure out what byte they differ on.
+    xor r4, r4, r5
+    ; Store the flags for later, to figure out the return value.
+    mov r5, flags
+    ; Check if at least one of the two most significant bytes is not 0.
+    cmp r4, 0xffff
+    jbe _compare__low2
+    ; If it is, backtrack the remaining 2 indices.
+    ; Shift the most significant bytes to the least significant ones.
+    sub r1, r1, 2
+    lsr r4, r4, 16
+_compare__low2:
+    ; r1 now points to a non-zero 16 bit value.
+    ; If the 16 bit value at r1-2 is in-bounds, then it is 0.
+    ; Check if the most significant byte of the 16 bit value is 0.
+    cmp r4, 0xff
+    ja _compare__low1
+    ; If it is, our target is the least significant byte.
+    add r1, r1, 1
+_compare__low1:
+    ; Otherwise, the target is that non-zero byte.
+    ; Check if the target is out of bounds, i.e. the loop terminated through the "bounds check".
+    cmp r1, r3
+    jae _compare__is_eq
+    ; r5 is the comparison result in the format of `cmp`. Convert it to the desired format.
+    ; 00 => 0x40000000 > 0
+    ; 01 => 0x00000000 = 0
+    ; 10 => 0xC0000000 < 0
+    xor r1, r5, 1
+    lsl r1, r1, 30
+    jmp r13
+_compare__is_eq:
+    mov r1, 0
+    jmp r13

tests/string_to_int_test.asm

@@ -0,0 +1,57 @@
+; test harness for string_to_int
+; Registers:
+; r8 - test address
+; r9 - expected result
+; r10 - actual length
+; r11 - expected length
+li r8, tests
+li r12, end_of_tests
+next_test:
+; Set up arguments and run test
+add r1, r8, 5          ; Start of test string
+mov r13, atoi_test_ret
+jmp stdlib.string_to_int.auto
+atoi_test_ret:
+
+; Load reference data
+load_32 r9, [r8]       ; Expected result
+sub r10, r2, r8
+sub r10, r10, 5        ; Actual string length
+add r11, r8, 4         ; Address of expected length
+load_8 r11, [r11]      ; Expected length
+
+; Verify results
+cmp r1, r9
+incorrect_result: jne incorrect_result
+cmp r10, r11
+incorrect_length: jne incorrect_length
+
+; Next test
+add r8, r8, 0x10
+cmp r8, r12
+jl next_test
+
+; Done
+success: jmp success
+
+include ../src/stdlib
+
+@0x20000
+tests:
+; inlen is the number of input bytes the function is expected to consume
+; addr  result          inlen  instr
+@0x20000 U32 0           U8 0   "\0"
+@0x20010 U32 0           U8 1   "0\0"
+@0x20020 U32 1           U8 1   "1\0"
+@0x20030 U32 2           U8 1   "2:\0"
+@0x20040 U32 42          U8 2   "42\0"
+@0x20050 U32 67          U8 2   "67lol\0"
+@0x20060 U32 0x69a       U8 5   "0x69a@\0"
+@0x20070 U32 0x4B4       U8 5   "0x4B4g\0"
+@0x20080 U32 0o23        U8 4   "0o239\0"
+@0x20090 U32 0b1011      U8 6   "0b1011\0"
+@0x200a0 U32 0b10001     U8 7   "0b100012\0"
+@0x200b0 U32 0xFFFFFFEB  U8 3   "-21\0"       ; Yuk
+@0x200c0
+end_of_tests:
+