perf(codegen): call shared constructor symbol instead of inlining per new-site (~2.5x faster, smaller IR)

[proggeramlug]

What

The inlined constructor body (field-init stores etc.) was the dominant per-new-site IR after the allocator — ~136 IR lines per site on a class with super + fields. Default to calling the already-emitted standalone <Class>_constructor symbol instead of inlining the ctor body at every new site, so it's emitted once. PERRY_INLINE_CTOR=1 opts back into inlining.

Restricted to classes with their own constructor and an emitted standalone symbol: no-own-ctor subclasses (class C extends B {}) stay on the inline path (the symbol-call path doesn't reproduce the inline leaf-keys/shape setup); without the symbol the call would be a no-op. Classes with super(...) / rest params round-trip correctly.

Win on both axes

8M construct-heavy allocation loop (new P(i, i+1) with this.x/this.y), -O2:

	inline ctor (old)	call ctor (new)
8M loop	5609 ms	2251 ms (~2.5× faster)
IR / new site	baseline	−136 lines

Same root cause as the allocator outline (#5294): inlining ~136 lines of ctor body at every site bloated the hot loop, hurting icache / register allocation / LLVM-opt far more than a call costs. Calling the shared symbol is smaller IR and multiples faster.

Tests

cargo test -p perry-codegen --tests green on the default (call) path. Output matches the previous inline baseline for super, rest params, and arrays of instances (including the unrelated, pre-existing no-own-ctor by-name-read quirk, which is identical on both paths and untouched here).

Context

Second of the codegen size-optimizations from compiling a real 13MB app — together with #5294 (allocator), per-new IR drops ~181 lines/site, shrinking large-bundle IR substantially while improving runtime speed.

Summary by CodeRabbit

• Chore
  • Added support for the PERRY_INLINE_CTOR environment variable to control constructor execution routing.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: f47a8214-0e69-4218-9ffe-865004141c27

📥 Commits

Reviewing files that changed from the base of the PR and between f0bbc2d and ff0bbc8.

📒 Files selected for processing (1)

• crates/perry-codegen/src/lower_call/new.rs

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📝 Walkthrough

Walkthrough

In lower_new, a force_ctor_call boolean flag is introduced, enabled by default unless the PERRY_INLINE_CTOR environment variable is set. This flag is added as a third OR branch to the existing redirect condition (alongside class_stack recursion detection and ctor_alias_collision), routing constructor calls through the standalone *_constructor symbol by default.

Changes

Constructor Dispatch Control Flag

Layer / File(s)	Summary
force_ctor_call flag and redirect condition crates/perry-codegen/src/lower_call/new.rs	Adds force_ctor_call defaulting to true unless PERRY_INLINE_CTOR is set; expands the redirect if to class_stack recursion || ctor_alias_collision || force_ctor_call, making constructor symbol dispatch the default and inline the opt-in path.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Possibly related PRs

• PerryTS/perry#5171: Modifies the same constructor dispatch logic in lower_call/new.rs, changing walk-stop and parameter wiring for explicit zero-arg imported constructors at the same call-resolution level.

Poem

🐇 A flag hops in, small but bright,
PERRY_INLINE_CTOR sets the light.
By default the symbol gets the call,
No inlining needed, one rule for all.
The rabbit grins — less surprise in store! ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately summarizes the main change: switching from inlining constructor bodies to calling a shared constructor symbol, with quantified performance benefits (~2.5x faster, smaller IR).
Description check	✅ Passed	The description covers the 'What' section explaining the change, includes quantified performance results and IR reduction, mentions testing, and provides context. However, it lacks explicit checklist items completion markers and doesn't follow the template's structured sections perfectly.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch perf/codegen-outline-ctor

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