StrawberryVM

A fantasy virtual machine with limits on resources.
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TODO

• Basic instructions
• Addition implementation
• Loading from a file
• Text to binary
• Assembler
• Refactoring
• Turing completion
• TCC support

Instruction Set

Opcode	Name	Arguments	Description
0x00	Nop	None	No operation.
0x10	Push	u8	Pushes an 8-bit immediate onto the stack.
0x11	Pop	Register	Pops the top of the stack into the specified register.
0x12	PushReg	Register	Pushes the value of the specified register onto the stack.
0x13	Mov	Register, Register	Copies the value from the second register to the first.
0x20	Add	Register, Register	Adds the second register to the first and stores the result in the first.
0x21	Sub	Register, Register	Subtracts the second register from the first and stores the result in the first.
0x22	Shl	Register, Register	Shifts left the first register by the amount contained in the second.
0x23	Shr	Register, Register	Shifts right the first register by the amount contained in the second.
0x24	And	Register, Register	Bitwise AND between registers, result in first.
0x25	Or	Register, Register	Bitwise OR between registers, result in first.
0x26	Xor	Register, Register	Bitwise XOR between registers, result in first.
0x27	Not	Register	Bitwise NOT on a register.
0x28	Mul	Register, Register	Multiply two registers; result in first.
0x29	Div	Register, Register	Divide two registers; result in first.
0x30	Cmp	Register, Register	Compare two registers and set flags (Compare, Negative, Overflow).
0x31	Jmp	i8	Jump by signed offset (in instructions / 16-bit words) relative to the instruction pointer.
0x32	Je	i8	Jump by signed offset (in instructions / 16-bit words) if last compare indicated equality.
0x33	Jne	i8	Jump by signed offset (in instructions / 16-bit words) if last compare indicated inequality.
0x40	Load	Register, Register	Load a u16 from memory at address in second register into first.
0x41	Store	Register, Register	Store a u16 from first register into memory at address in second.
0x50	Signal	u8	Host call sending an 8-bit signal value (used for logging / halting).

Note: Push and Signal accept 8-bit immediates. Jmp/Je/Jne take signed 8-bit offsets measured in instructions (each instruction is 16 bits / 2 bytes). Instruction encoding packs the opcode in the low byte and operands in the high byte(s).

Registers

• General purpose: A, B, C, D
• Special: SP (stack pointer), PC (program counter), BP (base pointer), FL (flags)

Flags (in FL):

• Compare = 1 (set when equal)
• Negative = 2 (set on negative result)
• Overflow = 4 (set on arithmetic overflow)

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Reserved symbols

Symbol	Use
$	Hexadecimal value
%	Binary value
^	Label value

Credits

This project is following along with the live streams by TomMarksTalksCode and this project would not have been possible without him. He can also be found on GitHub and on his website.