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Cleanup readme and add license for going public

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Tijmen van Nesselrooij
2019-11-24 11:27:38 +01:00
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LICENSE.md Normal file
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Copyright 2019 Tijmen van Nesselrooij
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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README.md
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# About
This is an exploratory project into virtual machines and assembly language. By
no means is this ready for production use or particularly well maintained. The
language is inspired by x86 and ARM assembly and does very little hand holding.
Checkout the `bin/example.wasm` example source to get an overview of the
language, or keep on reading!
# Design
## Parsing
## From Text To Runtime Behaviour
- First we tokenize the input (syntax check)
- Then we interpret the input (semantics check)
- Then we execute the input
In order to turn the source text into executable code we use 3 passes:
- Pass 1: tokenization (syntax check)
- Pass 2: interpretation (semantics check)
- Pass 3: execution (runtime check)
After pass 2 ties to the source code are lost, meaning that any error occurring
afterwards can be a bit cryptic as to where it originated.
## Notation
@@ -41,7 +54,7 @@ seti %A [$1024];
```
Remember not to use spaces inside the `[` brackets.
## Reserved symbols
## Reserved Symbols
The following whitespace characters are used to separate symbols:
- space (` `)
@@ -55,37 +68,62 @@ The following characters are used as identifiers:
- colon (`:`) for jump labels
- semicolon (`;`) for statement termination
- hash (`#`) for comments
- square brackets (`[` and `]`) for addressing memory
All symbols are reserved keywords and can therefore NOT be used as labels.
## Memory Model
The stack, with which you interact through pop/push operations, grows from
memory location 0 to the end of the memory. There is no strict checking on
whether your own memory operations through `[]` affect the stack: this is a
feature, not a bug. Keep in mind that the stack can underflow and overflow
and that the memory uses byte units (8 bits), whereas the registers are all
32 bits wide. This means that reading from location `$900` overlaps with 3
bytes when reading from location `$901` (the first byte of `$901` is the
second byte of location `$900`).
## Symbols
All symbols are reserved keywords and can therefore NOT be used as labels.
There is currently no strict checking, so be careful.
## Directives
- `DECLARE` declares the first label argument to equal the second, immediate value, argument and is used to declare a constant for the virtual machine.
- `DECLARE` declares the first label argument to equal the second, immediate
value, argument and is used to declare a constant for the virtual machine.
### Operands
- `addi` add the first to the second argument and store the result in the third argument
- `subi` subtract the first from the second argument and store the result in the third argument
- `divi` divide the first by the second argument and store the result in the third argument
- `muli` multiply the first by the second argument and store the result in the third argument
- `shli` shift left the first argument by the number of positions given by the second argument and store the result in the third argument
- `shri` shift right the first argument by the number of positions given by the second argument and store the result in the third argument
- `addi` add the first to the second argument and store the result in the third
argument
- `subi` subtract the first from the second argument and store the result in
the third argument
- `divi` divide the first by the second argument and store the result in the
third argument
- `muli` multiply the first by the second argument and store the result in the
third argument
- `shli` shift left the first argument by the number of positions given by the
second argument and store the result in the third argument
- `shri` shift right the first argument by the number of positions given by the
second argument and store the result in the third argument
- `seti` set the first register argument to the second argument
- `int` calls the interrupt specified by the first (integer) argument
### Control Flow
- `jmp` jump to the label given by the first argument
- `lti` execute next statement if argument 1 is less than argument 2 else skip the next statement
- `gti` execute next statement if argument 1 is greater than argument 2 else skip the next statement
- `eqi` execute the next statement if argument 1 is equal to argument 2 else skip the next statement
- `lti` execute next statement if argument 1 is less than argument 2 else skip
the next statement
- `gti` execute next statement if argument 1 is greater than argument 2 else
skip the next statement
- `eqi` execute the next statement if argument 1 is equal to argument 2 else
skip the next statement
## Memory
- `popi` pops the first value on the stack into the register specified as the first argument
- `pushi` pushes the value on the stack from the register or immediate value as the first argument
- `popi` pops the first value on the stack into the register specified as the
first argument
- `pushi` pushes the value on the stack from the register or immediate value as
the first argument
## Interupts
@@ -93,4 +131,5 @@ All symbols are reserved keywords and can therefore NOT be used as labels.
- `0` put value of register A as ASCII character on stdout
- `1` put value of register A as decimal integer on stdout
- `2` put value of register A as hexadecimal integer on stdout
- `3` put the string pointed at by register A for the amount of characters defined by register B on stdout
- `3` put the string pointed at by register A for the amount of characters
defined by register B on stdout