eREGS Stack machine & Interpreter

This is just an old, simple toy project and consists of a simple stack language and an interpreter for integer arithmetic.

The instruction set consists of the following instructions:

Instruction	Description
push	Pushes element to the top of the stack
pop	Pops (retrieves) top element from stack
add	Pops 2 top most elements from stack, performs an addition and pushed result back to the stack
sub	Same as for "add", but performs subtraction
mul	Same as for "add", but performs multiplication
div	Same as for "add", but performs division (checks for division by 0)
cmpl	Checks 2 top most stack elements (true, if Arg1 < Arg2, 0 otherwise)
cmpg	Checks 2 top most stack elements (true, if Arg1 > Arg2, 0 otherwise)
cmple	Checks 2 top most stack elements (true, if Arg1 <= Arg2, 0 otherwise)
cmpge	Checks 2 top most stack elements (true, if Arg1 >= Arg2, 0 otherwise)
cmpeq	Checks 2 top most stack elements (true, if Arg1 == Arg2, 0 otherwise)
cmpne	Checks 2 top most stack elements (true, if Arg1 != Arg2, 0 otherwise)
print	Pops top element from stack and prints its value
jmp	Unconditional jump to label
jfalse	Conditional jump to label
L	Label (used for go to markers)
r	Register definition (for variables)
shl	Binary left shift
shr	Binary right shift
rol	Binary rotate left
ror	Binary rotate right
not	Binary NOT
and	Binary AND
xor	Binary Exclusive Or
mod	Modulo

For a detailed description on eREGS you may check the documentation located in the doc directory (german only).

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Compilation

Just run make all to compile the interpreter.

🛑 (This is just a spontaneously uploaded git repository and the Makefile may not work properly as of now).

Requirements

• Make
• Yacc
• Flex

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Running the interpreter

Just run ./bin/eregs <eREGS SOURCEFILE> to run the interpreter.

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Example Code

A "eREGS" source code may use up to 32 registers and 999 labels (jump markers).

C commentary style // for single line comments and /* for multiline comments */ are also supported.

The following example shows how to compute the average of the two numbers 22 and 48 in a not so obvious way 😈.

push $22
push $48
xor 
pop r1
push $1
push r1
shr
pop r1
push $22
push $48
and
push r1
add
print

See the examples directory for more examples on how to use the eREGS stack language.