C++: Add basic Aarch64 Neon IR test

[jketema]

This is just to check that the produced IR looks sensible, which it does.

[Copilot]

Pull Request Overview

This PR adds a simple ARM64 NEON test to verify that the extractor produces sensible IR for basic vector operations.

• Implements three NEON-based functions (vadd_u8, vaddl_u8, arm_add) in arm.cpp
• Updates raw_ir.expected, aliased_ir.expected, and PrintAST.expected to include the IR and AST outputs for the new functions

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
cpp/ql/test/library-tests/ir/ir/arm.cpp	New test file defining basic AArch64 NEON functions
cpp/ql/test/library-tests/ir/ir/raw_ir.expected	Added expected raw IR for the new NEON functions
cpp/ql/test/library-tests/ir/ir/aliased_ir.expected	Added expected aliased IR for the new NEON functions
cpp/ql/test/library-tests/ir/ir/PrintAST.expected	Added expected AST dump for the new NEON functions

Comments suppressed due to low confidence (4)

cpp/ql/test/library-tests/ir/ir/arm.cpp:1

• [nitpick] Add a brief file-level comment explaining that this file defines basic ARM64 NEON functions used for IR extraction tests.

// semmle-extractor-options: --edg --target --edg linux_arm64

cpp/ql/test/library-tests/ir/ir/arm.cpp:3

• Avoid defining identifiers with double leading underscores, which are reserved by the language. Consider using a non-reserved name.

typedef __Uint8x8_t uint8x8_t;

cpp/ql/test/library-tests/ir/ir/arm.cpp:6

• [nitpick] Unify function signature formatting by removing the space before the parenthesis to match the style used elsewhere (e.g., vaddl_u8 and arm_add).

uint8x8_t vadd_u8 (uint8x8_t __a, uint8x8_t __b)

cpp/ql/test/library-tests/ir/ir/arm.cpp:21

• [nitpick] Indentation is inconsistent: this block is indented with 4 spaces while other functions use 2. Consider standardizing the indentation style.

    uint8x8_t c = vadd_u8(a, b);

[IdrissRio]

Both the IR and AST generated look good to me.