feat(minifier): apply De Morgan's law to negated comparison chains in jump guards and loop tests#24279
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… jump guards and loop tests (#24279) ### What Terser rewrites `!(a==b||c==d)` into `a!=b&&c!=d`. oxc only removed the `!` when a later pass could consume it for free, such as swapping if-else branches. In guards that end in a jump (`throw`, `return`, `break`) and in loop tests there is nothing to swap, so the negation stayed in the output. ### How `minimize_unary` gets a `LogicalExpression` arm that distributes the `!` over `&&`/`||` chains. It only fires when every comparison in the chain can invert its operator in place (`==`, `!=`, `===`, `!==`; relational operators are excluded because `!(a<b)` is not `a>=b` under NaN) and when flipping `&&`/`||` does not add parentheses. Under those rules the fold always saves bytes and is its own inverse, so shapes that re-negate the test later (branch swaps, `!!` collapses) still reach their old output. DCE mode is untouched; `minimize_unary` only runs in full minify. ### Example Before: ```js export function f(e,t,n,r){if(!(e==t||n==r))throw Error(`x`)}export function g2(e,t,n,r){for(;!(e==t||n==r);)h()} ``` After: ```js export function f(e,t,n,r){if(e!=t&&n!=r)throw Error(`x`)}export function g2(e,t,n,r){for(;e!=t&&n!=r;)h()} ``` ### Size jquery, d3, three, victory, echarts, typescript, react and bundle.min each shrink by 0.01–0.02 kB minified; no fixture grows. jquery's gzip column ticks up 0.01 kB even though its raw output shrank — a compression artifact of an equal-or-smaller input. Arena allocation counts rise slightly (+1 to +11 per fixture) from a transient `!` wrapper that re-negation builds and immediately unwraps.
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### 🚀 Features - 616bfa2 minifier: Remove unreachable code after terminating statements (#24441) (Dunqing) - ddab89a data_structures: Add `likely` and `unlikely` functions (#24368) (overlookmotel) - a3a39f9 react_compiler: Implement enableEmitHookGuards codegen (#24329) (Boshen) - b79eef7 minifier: Apply De Morgan's law to negated comparison chains in jump guards and loop tests (#24279) (Dunqing) - 34ff7b4 minifier: Drop write-only property assignments to unused local bindings by default (#24112) (Dunqing) - 1b829d8 semantic: Record const enums in EnumData (#24268) (Dunqing) - ba0944c semantic: Add `Scoping::set_symbol_span` (#24221) (camc314) ### 🐛 Bug Fixes - 7d33363 minifier: Preserve guaranteed throws from class heritage evaluation (#24349) (Dunqing) - 058a62f semantic: Track ambient contexts in `SemanticBuilder` (#24327) (camc314) - 721eb0b transformer/decorator: Scope accessor class binding (#24330) (camc314) - 1ebdce3 semantic: Allow reserved keywords in ambient declaration types (#24325) (camc314) - 460176a track-memory-allocations: Exclude arena chunks from Sys allocs (#24292) (Dunqing) - af4922b transformer: Clear lowered namespace redeclarations (#24300) (camc314) - ffd2765 semantic: Mark declared computed `MethodDefinition`s as type references (#24296) (camc314) - f17514b isolated-declarations: Emit const readonly fields as types (#24288) (camc314) - 40f769d minifier: Make `__proto__` write tracking execution-order independent (#24280) (Dunqing) - 6371fed transformer: Remove stale enum member bindings (#24272) (camc314) - f05dfab transformer: Correct symbol flags for lowered namespaces (#24271) (Dunqing) - 84eeb55 transformer: Correct symbol flags for lowered enums (#24269) (Dunqing) - c3057da transformer: Preserve generated class binding spans (#24220) (camc314) - 8260096 transformer: Correct span for lowered namespace symbol (#24222) (camc314) - 42d00d3 semantic: Mark declared class heritage as type references (#24237) (camc314) - 588d997 semantic: Mark TS `PropertyDefinition`s computed fields as type references (#24233) (camc314) - 9b95632 semantic: Mark computed method keys in `TSMethodSignature`s as type references (#24232) (camc314) ### ⚡ Performance - 5b26643 transformer_plugins: Dispatch global defines by trailing name (#23666) (Boshen) - dce0f29 react_compiler: Replace all compiled functions in a single AST walk (#24403) (Boshen) - f85f0d8 ast: Delegate inherited enum variants in clone_in and estree derives (#23555) (Boshen) - 3ff0234 allocator: Remove `unwrap` from `ReplaceWith` (#24365) (overlookmotel) - ab22e80 transformer: Fix Rust 1.97 performance regression (#24354) (camc314) - b47585c parser: Use `ReplaceWith` instead of `TakeIn` (#24018) (overlookmotel) - b227a06 minifier: Use `ReplaceWith` instead of `TakeIn` (#24017) (overlookmotel) Co-authored-by: Boshen <[email protected]>
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What
Terser rewrites
!(a==b||c==d)intoa!=b&&c!=d. oxc only removed the!when a later pass could consume it for free, such as swapping if-else branches. In guards that end in a jump (throw,return,break) and in loop tests there is nothing to swap, so the negation stayed in the output.How
minimize_unarygets aLogicalExpressionarm that distributes the!over&&/||chains. It only fires when every comparison in the chain can invert its operator in place (==,!=,===,!==; relational operators are excluded because!(a<b)is nota>=bunder NaN) and when flipping&&/||does not add parentheses. Under those rules the fold always saves bytes and is its own inverse, so shapes that re-negate the test later (branch swaps,!!collapses) still reach their old output.DCE mode is untouched;
minimize_unaryonly runs in full minify.Example
Before:
After:
Size
jquery, d3, three, victory, echarts, typescript, react and bundle.min each shrink by 0.01–0.02 kB minified; no fixture grows. jquery's gzip column ticks up 0.01 kB even though its raw output shrank — a compression artifact of an equal-or-smaller input. Arena allocation counts rise slightly (+1 to +11 per fixture) from a transient
!wrapper that re-negation builds and immediately unwraps.