Metadata-Version: 2.1
Name: gasm
Version: 1.0.5
Summary: An assembler/dissassembler for the Gheith ISA
Author-email: Michael Goppert <goppert@cs.utexas.edu>
License: MIT License
        
        Copyright (c) 2024 Michael Goppert
        
        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
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Project-URL: Homepage, https://github.com/migopp/gasm
Classifier: Programming Language :: Python :: 3
Requires-Python: >=3.8
Description-Content-Type: text/markdown
License-File: LICENSE

# gasm
The Gheith ISA assembler.

For students in Dr. Gheith's CS 429H course completing pipelining.

## Quick Start

```
python3 -m pip install gasm
```
And, you're good to go. 👍

## Usage

### Assembling:

```
gasm <path to assembly file> <OPTIONAL: path to desired output file>
```

There are relatively few restrictions on the assembly file. The file extension, for example, is entirely unimportant. Designations like `r` for registers and `#` for literals are also not required (and do not impact the assembly process).

However, you may not have labels (this should not matter). You may only have instructions, comments, and memory directives. Take the following as an example:

```
// place at memory location 0
@0
movl r0, #104 // print 'h'
movl r0, #101 // print 'e'
movl r0, #108 // print 'l'
movl r0, #108 // print 'l'
movl r0, #111 // print 'o'
movl r0, #10  // print '\n'
end
```

You may choose to end your assembly with an `end` directive. Doing so, the assembler will provide the hex instruction `ffff` in its place.

### Disassembling:

```
dasm <path to .hex file> <OPTIONAL: path to desired output file>
```

The file you want to disassemble should be valid `.hex`. It may, however, end with an `ffff`, though the instruction is not officially recognized.

### Numerical Literals:

In the case of the `movl` and `movh` instructions, you may use either hex or decimal to represent numerical literals. gasm assumes decimal by default; to use hex, prefix the literal with `0x`:

```
@0
movl r1, #0x21
```

### Character Literals:

gasm supports the use of character literals in place of numerical ones. Suppose you wanted to store the ASCII value for 'a' into `r1`:

```
@0
movl r1, 'a'
```

### Labels:

To assist in creating programs with branches, gasm supports use of labels. Create a label like so:

```
my_first_label:
<instruction 1>
<instruction 2>
...
```

Reference them in `movl` or `movh` with the label name.

```
@0
movl r1, my_first_label
...
```

#### Misaligned Labels

There may also be cases where one wishes to create misaligned labels (as in, `byte_addr + 1`). Here, one may use the `!mis_` prefix to the label.

```
!mis_my_first_label:
...
```

#### Generated Comments

All labels generate a comment in the `.hex` of the form:

```
// [PC: <PC>] <<LABEL>>:
```

### Directive Blocks:

gasm supports a few different directives that are outlined here. Directives start with an `@BEGIN` and end with an `@END`. Directive bounds are placed in comments; use the below example for reference:

```
// @BEGIN <DIRECTIVE NAME>
...
// @END <DIRECTIVE NAME>
```

#### `DATA`

Programs may find it helpful to have a data section occasionally. Now, you can specify that a section of memory contains data instead of instructions with the `DATA` directive.

```
@0
movl r1, #0
movl r2, #33
st r1, r2       // mem[0x21] <= 0
                // should form:
                //
                // @10
                // 0061
                // 0000
                //
movl r3, #32    // get word at 0x10
ld r0, r3       // print ascii('0x61') ('a')

// @BEGIN DATA
@10
ff61            // now, gasm is sure that these
00ff            // are not instructions
// @END DATA
```

#### `MISALIGNMENT`

Some programs may leverage misalignment for one reason or another. As such, gasm supports writing instructions that will be stored in a misaligned fashion with the `MISALIGNED` directive. It is used functionally the same as the `DATA` directive.

```
@0
movl r1, !mis_first_jmp
jnz r1, r1

// @BEGIN MISALIGNED
!mis_first_jmp:
movl r0, #97
movl r0, #98
movl r1, second_jmp
jnz r1, r1
// @END MISALIGNED

second_jmp:
movl r0, #99
end
```

The above code assembles to:

```
@0
8051
e111

// @BEGIN MISALIGNED
// [PC: 0x5] <!mis_first_jmp>:
10ff
2086
e186
1180
ffe1
// @END MISALIGNED

// [PC: 0xe] <second_jmp>:
8630
ffff
```

The misaligned instructions are padded with `ff`; you can verify that the above translation is correct.

Another aspect to note is the use of the `!mis_` label.

### Comments:

You may find it important to comment your `.hex` output for test case quality. gasm supports this functionality, and should maintain your comments when assembling. For example, the above code assembles to:

```
// place at memory location 0
@0
8680	// print 'h'
8650	// print 'e'
86c0	// print 'l'
86c0	// print 'l'
86f0	// print 'o'
80a0	// print '\n'
ffff
```

Note that within `MISALIGNED` blocks, comments are not preserved. There is not a great uniform standard, so you will need to comment this portion of your `.hex` manually.

dasm also supports having comments in the `.hex`, though I chose not to display them because of clutter.
