LoadClosure as pseudo op#6789

youknowone

Summary by CodeRabbit

Refactor
- Optimized internal bytecode instruction handling for closure variable loading, improving the compiler's variable scope management and frame initialization during runtime.

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coderabbitai

📝 Walkthrough

Walkthrough

The PR migrates the LoadClosure opcode from the concrete Instruction enum to the PseudoInstruction enum, updating bytecode emission, IR lowering, decoding logic, instruction metadata, and VM frame execution paths to accommodate this structural change.

Changes

Cohort / File(s)	Summary
Bytecode Definition and Conversion `crates/compiler-core/src/bytecode/instruction.rs`	Moves `LoadClosure(Arg<NameIdx>)` from `Instruction` to `PseudoInstruction` (discriminant 268); updates `TryFrom` bounds and removes `LoadClosure` handling from `Instruction` paths; removes stack effects and formatting for `LoadClosure` from `Instruction`, adds stack effect of 1 to `PseudoInstruction`.
Code Generation and IR Lowering `crates/codegen/src/compile.rs`, `crates/codegen/src/ir.rs`	Updates closure variable emission to use `PseudoInstruction::LoadClosure` instead of `Instruction::LoadClosure`; adds IR lowering to convert `PseudoInstruction::LoadClosure` to `LOAD_FAST` with index adjusted by varnames count.
Opcode Metadata `crates/stdlib/src/opcode.rs`	Removes `LoadClosure(_)` from the `has_free` instruction pattern match, no longer treating it as a free-variable instruction.
Frame Execution and Locals `crates/vm/src/frame.rs`	Restructures frame locals initialization to combine varnames, cellvars, and freevars into a single `fastlocals` array with pre-filled cell objects; removes the `Instruction::LoadClosure` execution path from frame dispatch.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~22 minutes

Possibly related PRs

Bytecode instrumented placeholder #6741: Directly migrates the same LoadClosure opcode out of Instruction into PseudoInstruction with coordinated enum and handling updates.
LoadClassDeref -> LoadFromDictOrDeref #6692: Performs analogous opcode migration (e.g., LoadClassDeref) affecting bytecode enums, codegen, IR, and frame execution.
Pseudo ops #6678: Refactors the broader pseudo-instruction pipeline with similar opcode relocation and IR lowering patterns.

Suggested reviewers

ShaharNaveh

Poem

🐰 A closure hops from Instruction's gate,
To Pseudo's burrow, a lighter fate!
Fastlocals swell with cells in place,
No more dispatch—just stack-bound grace.

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: moving LoadClosure from a regular Instruction to a PseudoInstruction, which is the primary focus across all modified files.

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✨ Finishing touches

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github-actions

Code has been automatically formatted

The code in this PR has been formatted using:

python scripts/generate_opcode_metadata.py
Please pull the latest changes before pushing again:

git pull origin LoadClosure

youknowone force-pushed the LoadClosure branch from 59f2bde to 430ed08 Compare January 18, 2026 15:39

LoadClosure as pseudo op

8fb5bdb

youknowone force-pushed the LoadClosure branch from 5311565 to 8fb5bdb Compare January 18, 2026 16:20

youknowone marked this pull request as ready for review January 18, 2026 17:37

youknowone deleted the LoadClosure branch January 18, 2026 17:45

This was referenced Jan 29, 2026

More Load instructions #6886

Merged

Split stack_effect into pushed & popped #6893

Merged

Use stack_effect_info for getting pop&push count #6913

Merged

This was referenced Mar 2, 2026

Bytecode enum named oparg #7294

Merged

Remove cells_frees duplicate storage from Frame #7351

Closed

coderabbitai Bot mentioned this pull request Mar 25, 2026

Bytecode parity #7504

Merged

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LoadClosure as pseudo op#6789