Support gp relocations for Psy-Q AS 2.5x

[galaxyhaxz]

I'm not sure what version of object files the current tool targets (could be newer or older) but at least with 2.5x of the Psy-Q assembler (1996-1997), it generates gp relocations not supported. They are code 12 for big-endian and code 30 for little-endian. These relocations are handled slightly differently from the other GP type, in this case sdata uses an absolute value whereas sbss goes by symbol name, both reference the section start point.

This adds support for them so that the tool can convert their relevant objects for use on decomp.me. Also note that I'm not a C++ wizard so the code may not be the best, but it works in my testing.

[coderabbitai]

Walkthrough

This change introduces two new relocation types, GPREL16_BE and GPREL16_LE, into the Psyq object parser. The parser’s logic is updated in its parsing, display, and ELF generation methods to correctly handle these types, including their mappings to ELF MIPS relocation types. These modifications ensure that the new relocation types are recognized during file parsing and applied properly during ELF generation.

Changes

File	Summary
tools/.../psyq-obj-parser.cc	- Added enum values GPREL16_BE and GPREL16_LE to the PsyqRelocType enumeration. - Updated the parse method to handle these new relocation types. - Modified displayRelocs to include string representations for the new types. - Enhanced generateElf logic for ELF output and updated type mappings.

Sequence Diagram(s)

sequenceDiagram
    participant User
    participant Parser
    participant Relocation
    participant Display

    User->>Parser: Load object file
    Parser->>Parser: Identify relocation type (including GPREL16_BE/LE)
    Parser->>Relocation: Pass relocation info for ELF generation
    Relocation->>Relocation: Adjust offset & write bytes based on type
    Parser->>Display: Format relocation strings for output
    Display-->>User: Present parsed relocation details

Loading

Poem

Hopping through lines of code so bright,
Two fresh relocation types take flight.
GPREL16_BE and LE join the parade,
In parsing and ELF, their marks are laid.
I, the rabbit, celebrate this byte-filled delight!

---

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📥 Commits

Reviewing files that changed from the base of the PR and between 2b06c4c and 3f77d56.

📒 Files selected for processing (1)

• tools/psyq-obj-parser/psyq-obj-parser.cc (8 hunks)

🧰 Additional context used

🪛 GitHub Check: CodeScene Cloud Delta Analysis (main)

tools/psyq-obj-parser/psyq-obj-parser.cc

[warning] 344-351: ❌ Getting worse: Complex Method
PsyqLnkFile::parse increases in cyclomatic complexity from 55 to 57, threshold = 9. This function has many conditional statements (e.g. if, for, while), leading to lower code health. Avoid adding more conditionals and code to it without refactoring.

---

[warning] 1198-1463: ❌ Getting worse: Complex Method
PsyqLnkFile::Relocation::generateElf increases in cyclomatic complexity from 55 to 62, threshold = 9. This function has many conditional statements (e.g. if, for, while), leading to lower code health. Avoid adding more conditionals and code to it without refactoring.

---

[warning] 1198-1198: ❌ New issue: Complex Conditional
PsyqLnkFile::Relocation::generateElf has 1 complex conditionals with 2 branches, threshold = 2. A complex conditional is an expression inside a branch (e.g. if, for, while) which consists of multiple, logical operators such as AND/OR. The more logical operators in an expression, the more severe the code smell.

---

[warning] 1198-1463: ❌ Getting worse: Complex Method
PsyqLnkFile::Relocation::generateElf increases in cyclomatic complexity from 55 to 62, threshold = 9. This function has many conditional statements (e.g. if, for, while), leading to lower code health. Avoid adding more conditionals and code to it without refactoring.

⏰ Context from checks skipped due to timeout of 90000ms (1)

• GitHub Check: Codacy Static Code Analysis

🔇 Additional comments (7)

tools/psyq-obj-parser/psyq-obj-parser.cc (7)

73-75: Addition of new relocation types for Psy-Q AS 2.5x

The new enum values GPREL16_BE and GPREL16_LE have been correctly added to the PsyqRelocType enum with the appropriate values (12 and 30) as mentioned in the PR description. These values match the relocation codes generated by the Psy-Q assembler version 2.5x.

---

344-351: Handler for new relocation types in the parse method

The appropriate case statements have been added to handle the new relocation types during parsing. The implementation follows the pattern established for other relocation types in the codebase.

🧰 Tools

🪛 GitHub Check: CodeScene Cloud Delta Analysis (main)

[warning] 344-351: ❌ Getting worse: Complex Method
PsyqLnkFile::parse increases in cyclomatic complexity from 55 to 57, threshold = 9. This function has many conditional statements (e.g. if, for, while), leading to lower code health. Avoid adding more conditionals and code to it without refactoring.

---

779-780: Updated relocation type string mapping

The string mappings for the new relocation types have been correctly added to the typeStr map, ensuring proper display in debug/verbose output.

---

1008-1009: Updated ELF relocation type mapping

The new relocation types have been properly mapped to the appropriate ELF MIPS relocation type (R_MIPS_GPREL16).

---

1198-1200: Updated offset adjustment for big-endian relocations

The condition has been extended to include GPREL16_BE in the list of big-endian relocation types that require offset adjustment. This is consistent with the handling of other big-endian relocation types.

🧰 Tools

🪛 GitHub Check: CodeScene Cloud Delta Analysis (main)

[warning] 1198-1463: ❌ Getting worse: Complex Method
PsyqLnkFile::Relocation::generateElf increases in cyclomatic complexity from 55 to 62, threshold = 9. This function has many conditional statements (e.g. if, for, while), leading to lower code health. Avoid adding more conditionals and code to it without refactoring.

---

[warning] 1198-1198: ❌ New issue: Complex Conditional
PsyqLnkFile::Relocation::generateElf has 1 complex conditionals with 2 branches, threshold = 2. A complex conditional is an expression inside a branch (e.g. if, for, while) which consists of multiple, logical operators such as AND/OR. The more logical operators in an expression, the more severe the code smell.

---

1246-1257: Implementation of new relocation handlers in generateElf

The implementation correctly handles both little-endian and big-endian GP relocations:

• For GPREL16_LE, bytes are written in little-endian order (least significant byte first)
• For GPREL16_BE, bytes are written in big-endian order (most significant byte first)

The code follows the established pattern for other relocation types and properly handles the 16-bit offset masking.

---

1454-1463: Handling for SECTION_START in SUB expression

The code adds support for subtractions involving SECTION_START, which is needed for GP relocations that reference the section start point as mentioned in the PR description.

🧰 Tools

🪛 GitHub Check: CodeScene Cloud Delta Analysis (main)

[warning] 1198-1463: ❌ Getting worse: Complex Method
PsyqLnkFile::Relocation::generateElf increases in cyclomatic complexity from 55 to 62, threshold = 9. This function has many conditional statements (e.g. if, for, while), leading to lower code health. Avoid adding more conditionals and code to it without refactoring.

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[nicolasnoble]

Looks good to me :)