The extension aims to help the students in studying LC3 assembly language. It is developed by the teaching stuff, mainly Qi Li, for students taking ECE120/220 at University of Illinois at Urbana Champaign.

The extension is developed based on Patt And Patel Introduction To Computing Systems 2nd Edition. Note that if you are using another edition of the book, or you are using a different textbook, you may see some false positive warnings.

This extension does NOT include any analysis for I/O behavior and several new concepts in the 3rd version of LC3, including interrupts and access control violation.

For issues and bug reports, please contact [email protected].

Syntax highlighting for Opcodes, Registers, Numbers and Strings. The highlighting varies based on the VSCode color scheme.

All labels in the file can be autocompleted using VSCode's tab completion.

Also, you can view the example usage of an opcode if you type the opcode and expand the related information window by clicking on the right side of the completion item.

You can quickly navigate to the definition of a label by holding Ctrl and then left-click on a label.

The extension provides a variety of checks on your code, including:

Instructions that are incomplete or illegal generates errors.

This checking is turned off by default to provide better coding experience. This feature will be improved in future versions.

Ranges of immediate values are checked. If they exceed the limit of the specific instruction, an error is generated. For AND and ADD, an additional checking on whether encoding issue occurs is performed. A warning is generated when a positive decimal immediate number is used, but the encoding makes it negative.

If the code reaches HALT inside a subroutine, or a RET inside main code, a warning is generated.

Code before and after .ORIG and .END are shown as errors and warnings respectively.

Code that potentially execute data as instructions are warned.

Shared code between different subroutines is warned.

Label names that are not usable, like X10, R3, 12LABEL are warned.

Duplicated labels cannot appear in the same file. An error is generated for labels that have appeared before.

Having multiple labels at the same memory location is not a fatal issue, but it illustrates structural defect in the code. Thus, a warning is generated.

If a branch instruction contains redundant condition code, a warning is generated.

If a branch instruction is conditional, but the condition is always true, a warning is generated.

Unreachable instructions are the instructions that can never be executed unless one manually set PC to the corresponding address. The problem is caused by the control flow.

Code that has no effect in the program is grayed out. It is recommended to remove dead code for better readability.

Warning: Some code may be marked as dead because they do not have effect in the current scope. It is the programmer's responsibility to decide whether to remove them or not.

Reports the callee-saved registers in a subroutine if they are laid out as consecutive ST's right after the subroutine label, and consecutive LD's right before RET. Any mismatch of saving and restoring registers is warned.

Uncalled subroutine is warned. If you want to write a subroutine before writing the invocation somewhere else, you can prevent this warning by adding a comment ; @SUBROUTINE in the line right above the subroutine label. You can also do so by using the quick fix provided when you hover over the subroutine label.

Consecutive repeated code blocks are recognized as an "unrolled loop", which means a loop may be used in place of the repeated code. It is a good practice to write loops or subroutines to perform repetitive work, rather than copy and paste code.

Version of the LC3 assembler. Note that this option only changes LEA and TRAP behavior.

Controls whether to show all errors.

Controls whether to show all warnings.

Controls whether to generate error message when an illegal instruction is present.

This option is turned off by default to provide better coding experience.

Enables subroutine analysis for calling interfaces and callee-saved registers.

Enables the detection of consecutively repeated code (unrolled loop).

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