feat(minifier): inline single-use variable past read-only variables

[sapphi-red]

fixes #13912

As long as we know the variable is not re-assigned, the value is same even if we reordered the expression.
By using that fact, we can compress

function wrapper() { var x = foo, y = bar; return [x, y] }

to

function wrapper() { return [foo, bar] }

.

[sapphi-red]

• fix(minifier): don't inline single use variable in conditional logical expressions #14185
• feat(minifier): inline single-use variable past read-only variables #14184 👈 (View in Graphite)
• main

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[codspeed-hq]

CodSpeed Instrumentation Performance Report

Merging #14184 will degrade performances by 8.35%

_{Comparing 09-27-feat_minifier_inline_single-use_variable_past_read-only_variables (6123684) with main (e4e963b)¹}

Summary

❌ 1 regression
✅ 32 untouched
⏩ 4 skipped²

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
❌	minifier[cal.com.tsx]	32.7 ms	35.7 ms	-8.35%

Footnotes

1. No successful run was found on main (6123684) during the generation of this report, so e4e963b was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

2. 4 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[Copilot]

Pull Request Overview

This PR implements an optimization to inline single-use variables past read-only variables in the JavaScript minifier. The change allows variables to be inlined even when they appear after other read-only variables in the declaration order, as long as the variables being moved past are not mutated.

• Adds logic to detect read-only variables that can be safely reordered during inlining
• Includes comprehensive test cases covering various scenarios with read-only and mutable variables
• Updates existing tests to fix compatibility issues with the new optimization

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tasks/track_memory_allocations/allocs_minifier.snap	Updated memory allocation metrics showing improved efficiency
tasks/minsize/minsize.snap	Updated file size metrics showing reduced minified output sizes
crates/oxc_minifier/tests/peephole/inline_single_use_variable.rs	Added comprehensive test cases for the new read-only variable inlining optimization
crates/oxc_minifier/tests/peephole/esbuild.rs	Commented out failing tests and adjusted existing test case to maintain compatibility
crates/oxc_minifier/src/peephole/minimize_statements.rs	Implemented core logic to check for read-only variables and allow inlining past them

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[graphite-app]

Merge activity

• Oct 1, 4:55 AM UTC: Boshen added this pull request to the Graphite merge queue.
• Oct 1, 5:18 AM UTC: Merged by the Graphite merge queue.