71 lines
2.2 KiB
Markdown
71 lines
2.2 KiB
Markdown
# Design
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## Parsing
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- First we tokenize the input (syntax check)
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- Then we interpret the input (semantics check)
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- Then we execute the input
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## Notation
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- `[operation][number type]`, e.g. `divi` for divide (div) integer
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- `%[register]` for addressing registers
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- `$[value]` for using literals/immediate values
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- `;` for end of statement (mandatory)
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- `[label]:` for labels
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- `#[text]` for comments: any text is ignored till a newline (`\n`) is found
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- Elements must be separated by whitespace character
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- Good: `add $2 $5 %A;`
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- Bad: `add $2$5%A;`
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## Examples
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Divide register A by 5 and store the result in register A:
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`divi %A $5 %A;`
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Increment B until it is 10:
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```
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# Set B to zero
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addi $0 $0 %B;
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loop:
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addi $1 %B %B;
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lti %B $10;
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jmp loop;
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```
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## Reserved symbols
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The following whitespace characters are used to separate symbols:
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- space (` `)
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- tab (`\t`)
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- return carriage (`\r`)
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- newline (`\n`)
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The following characters are used as identifiers:
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- dollar (`$`) for immediate (literal) values
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- percentage (`%`) for register identifiers
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- colon (`:`) for jump labels
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- semicolon (`;`) for statement termination
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- hash (`#`) for comments
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All symbols are reserved keywords and can therefore NOT be used as labels.
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## Symbols
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### Operands
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- `addi` add the first to the second argument and store the result in the third argument
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- `subi` subtract the first from the second argument and store the result in the third argument
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- `divi` divide the first by the second argument and store the result in the third argument
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- `muli` multiply the first by the second argument and store the result in the third argument
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- `shli` shift left the first argument by the number of positions given by the second argument and store the result in the third argument
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- `shri` shift right the first argument by the number of positions given by the second argument and store the result in the third argument
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### Control Flow
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- `jmp` jump to the label given by the first argument
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- `lti` execute next statement if argument 1 is less than argument 2 else skip the next statement
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- `gti` execute next statement if argument 1 is greater than argument 2 else skip the next statement
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- `eqi` execute the next statement if argument 1 is equal to argument 2 else skip the next statement
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