Support short type

[hhhh1300]

Add short data type support

This PR implements support for the short data type (#282).

Changes Made

• Parser & Type System: Extended parser with TYPE_short cases for all operations
• ARM/RISC-V Architecture: Added halfword instructions.
• Test Coverage: Expanded test suite with comprehensive short type validation

Testing

• All tests pass on both Stage 0 and Stage 2

---

Summary by cubic

Add full support for the short (2-byte) type across the parser, type system, and ARM/RISC-V codegen, with correct halfword loads/stores, truncation, and sign extension. Expanded tests cover variables, pointers, arrays, casts, and sizeof.

• New Features
  • Parser/type system: added TYPE_short and TY_short (2 bytes); handled dereference, lvalues, compound literals, pointer arithmetic, and sizeof.
  • ARM: implemented halfword transfers (__lh LDRSH, __sh), SXTH sign extension, fixed OP_trunc via shifts, updated OP_read/write and ELF offsets.
  • RISC-V: added lh/sh operations, fixed OP_trunc using shift pairs, implemented sign extension for byte/short, updated ELF offsets.
  • Tests: added short cases for assignment and arithmetic, pointers and deref, arrays, compound literals, function params/returns, casts, and sizeof.

[cubic-dev-ai]

1 issue found across 7 files

Prompt for AI agents (all 1 issues)

Understand the root cause of the following 1 issues and fix them.


<file name="tests/driver.sh">

<violation number="1" location="tests/driver.sh:5061">
The new cast_tests array is never executed because there is no run_* invocation for it, so these added tests never run. Please add the corresponding runner call so the short casts are actually tested.</violation>
</file>

---

Since this is your first cubic review, here's how it works:

• cubic automatically reviews your code and comments on bugs and improvements
• Teach cubic by replying to its comments. cubic learns from your replies and gets better over time
• Ask questions if you need clarification on any suggestion

_{React with 👍 or 👎 to teach cubic. Mention @cubic-dev-ai to give feedback, ask questions, or re-run the review.}

[jserv]

Once you are confident that you have addressed the reviewers’ suggestions, simply click the "Resolve conversation" button in the GitHub web interface.

[ChAoSUnItY]

I think you missed to change logic in reg-alloc.c as well, some stack alignment are done there.

Hint: look at OP_allocat usages in reg-alloc.c, you should also consider TY_short cases there.

[DrXiao]

Does the proposed changes enable shecc to parse short int ?

If so, add some test cases to validate.

[hhhh1300]

This PR doesn't enable short int. I think this may require further changes on parser.c.

It causes "Unexpected token" error when parsing short int.

[visitorckw]

Please rebase your branch to keep the git history clean.

[jserv]

Check https://cbea.ms/git-commit/ carefully and enforce the rules.

[DrXiao]

I think these changes look good.

[jserv]

Thank @hhhh1300 for contributing!