These PRs were merged into their stack base branches instead of main. This merges perf/alloc-hugepages (with the CI fixes below) into main. Conflicts: order-parity.json (union of entries); scr_alloc.c/scr_alloc.test.ts, where main already has the worker exit trim (#858, adapted to the pre-hugepages allocator): resolved by taking the hugepages allocator and re-applying the original trim commits written on top of it (ea88b87c + 4816696d, clean apply on an identical base).
A stale narrowing read in a call argument whose parameter accepts the declared type read as declared, so the callee's lowering tests the stored value. For standard-library callees that lowering is often specialized to the argument types programs pass: after `combo.p = {...}; combo()` the argument of `JSON.stringify(combo.p)` became `T | undefined` (SC1090), and after `ci(slow)` the handle of `timers.clearInterval(fast)` became `number | null` (SC2020), so 2072-expando-function-members.ts and 1804-timers-module.ts stopped compiling.
Call and construction arguments (directly or inside literal arguments) now read as declared only where the callee lowers any value of the parameter type: user callees, console methods, and standard-library parameters typed by a type parameter (`push(...items: T[])`, `Map.set`). Other standard-library arguments keep the checker's narrowing and the checked extraction.
The `nneg` flag on `uitofp` is LLVM 19 syntax. Sanitized builds hand the textual module to the host clang, and Ubuntu 24.04's clang 18 rejects it ("expected type"), which failed every Linux sanitized Effect shard. These operands are size_t values below 2^63, so `sitofp` converts them identically, is accepted by every supported LLVM, and still lowers to one cvtsi2sd on x86-64 (LLVM 19+ canonicalizes it to `uitofp nneg` where it can prove the sign).
Since #837 a type is traced only if it lies in a cycle-capable component or reaches an intrinsic reference; a type that merely holds a cycle cannot be reached back from it. In both backend-analysis cases `record:outer` only holds `record:cycle`, so the Node oracle and the native compiler agree on ["record:cycle"] and the expectations still listed `record:outer`.
Brings in cc7c6cb7 (inline truncation decided for the host when no triple is given), which this branch predates; without it the native bootstrap's LLVM comparison with the Node seed fails on x86-64 Linux.
The custom Dockerfile.sandbox image builds the LLVM helper against the same LLVM 22 CMake exports as the managed bootstrap, which reference the Polly libraries; without libpolly-22-dev CMake configure fails.
Three workers each hold and drop about 80 MB of small objects and exit;
three more then allocate as much again in the arenas the first ones
returned (on Linux the first ones hand those pages back when they exit).
Records the fixture's preflight/order baseline.
A script thread that exits parks its allocator arena with every freed
block still resident, so the memory of a finished worker stays with the
process until another thread claims the arena. On Linux, a parking thread
that carved at least 16 MiB now hands back every page of its arena that
holds only free blocks (MADV_DONTNEED), relinks the remaining free blocks
in address order, and keeps the returned page runs as zeroed regions that
the next owner carves before the slice frontier. It also trims glibc
malloc. SCR_SA_STATS=1 reports what each park returned; SCR_SA_TRIM=0
turns it off.
Publication (@scriptc/threads publish() and the zero-copy delivery of
deeply frozen plain-data graphs) makes objects immortal: nothing frees
them, and the RC audit already stops counting them. LeakSanitizer did not
know, so a program that drops its last reference to a published graph
reported every such object as a direct leak whenever leak detection was
on (SCRIPTC_SAN=1 runs on Linux without ASAN_OPTIONS=detect_leaks=0, such
as the documented local fallback). Both publication paths now mark each
object they make immortal with the weak __lsan_ignore_object hook in ASan
builds; ignored chunks are leak-scan roots, so the verdict on the rest of
the heap is unchanged. Other builds compile the hook away.
The sanitized lanes run with detect_leaks=0, so a harness test pins the
contract with LeakSanitizer on (Linux, SCRIPTC_SAN=1 lane).
An empty map's tables are already empty, so clear() returns at once
instead of freeing oversized storage that the next fill would regrow.
Only a clear that removes entries frees storage far larger than them.
The compaction test in delete is marked unlikely.
new Map(m) and new Set(s) copied the source's direct-index size, which
follows the source's peak. The copy now covers its largest live key, and
keys that are sparse for their count hash instead.
An assignment narrows a binding to the assigned arm, and TypeScript keeps
that narrowing across a closure or method that stores another arm. After
`if (acc !== null) return acc;` the checker still types the read as the
old arm, the return slot rejects the declared `T | null`, and the checked
extraction threw on the value the closure stored, where Node returns it.
The compiler itself has this shape (lowerDynObjectLiteral), so the native
compiler aborted with "a value of another type is not representable in
the target union" and closure-nullable-union-return.ts diverged.
A slot that accepts the declared type minus null/undefined now reads the
stale reference as NonNullable<declared>, like a binding narrowed only by
the absence test. Elements and properties of array and object literals
are such slots when the literal itself sits in a typed slot (annotated
declaration, argument, assignment, return of a function with a declared
return type). Untyped literals keep the checked extraction.
Number-keyed maps index small integer keys through a direct table sized
by the largest key ever stored, and bucket tables are sized by the most
entries ever held; neither shrank. scr_map_clear memset both on every
call, even on an empty map, so a collection that was large once paid its
peak size on every later clear. tsc-ts' Relater.reset clears a
Set<number> on every relation check: on Sentry, 36% of the CPU was that
memset.
- clear() resets only the direct-index slots of the entries it removes
(the table is zero at every absent key), resets the bucket table only
when entries pointed into it and it is proportional to them, and frees
storage far larger than the entries removed, returning the map to its
initial state as V8 does. Clearing an empty map does no work.
- delete compacts once fewer than a quarter of at least 64 entries are
live (V8's shrink point), so iteration after mass deletion is O(live).
- Compaction shrinks oversized bucket tables, and after a delete or an
iteration it shrinks the direct index to the surviving keys or moves
keys that became sparse back to hashing. The append path keeps the
current index: it holds a slot of it.
Insertion order and live iteration are unchanged: nothing compacts while
an iteration is active.
Scriptc-compiled strings stop at 2^31 - 1 UTF-8 bytes and exceeding the
cap traps ("scriptc: out of memory") instead of throwing. In the native
compiler the self-hosted IR was one 515 MB string, and the frontend
cache entry JSON.stringify'd LLVM and IR together into one ~920 MB
string, about 2.3x below the trap.
- NativeExecutableInput.ir is compact IR as ~16M-char parts; every IR
output is written with writeTextPartsSync.
- Frontend cache entries move to scriptc.native-frontend.v3: the input
metadata carries placeholders and the LLVM and IR follow as separate
members, so the entry is written as parts with an incremental digest
(NativeCache.writeParts). Entries a native reader could not decode as
one string are neither published nor read (NativeCache.read maxBytes),
turning the old trap into a cache miss.
- SCRIPTC_BOOTSTRAP_IR_INPUT decodes the seed IR per function with
deserializeModuleBytes.
The native LLVM text remains one string (344 MB for the compiler,
~6x below the native cap).
The self-hosted compiler's compact IR is ~515-528M characters, a few
million below V8's maximum string length (2^29 - 24). serializeModule
joined it into one string, deserializeModule parsed one string, and the
native bootstrap comparison read cli.ir.json and cli.ll as utf8 strings,
so any compiler growth crashed --emit=ir and the bootstrap tests with
"RangeError: Invalid string length".
- serializeModuleParts returns the compact encoding as ordered parts
(header, one part per function, remainder). serializeModule(mod, true)
is their join, so the on-disk format is byte-identical.
- deserializeModuleBytes splits a UTF-8 Buffer at the root object's
"functions" array with a byte-level scanner and parses the header and
each function separately. Malformed input falls back to the
whole-document parse for its exact error.
- The Node API writes --emit=ir, --emit-ir sidecars and --emit=llvm
through writeTextParts (the former writeLlvmSource batching writer).
- The native bootstrap harness decodes IR per function and compares
LLVM as Buffers, removing ABI-check lines at the byte level.
- The self-hosting serialization fixture gains a "bytes" mode so the
scriptc-compiled serializer exercises both new entry points.
Self-hosted compiler IR (514.6 MB, macOS arm64, Node 24.12):
read old 5.85 s / 4.26 GB max RSS -> new 5.84 s / 1.36 GB
write old 2.05-2.53 s / 4.48 GB -> new 2.30-2.37 s / 2.10 GB
2x module (1.03 GB): old serialize and read throw; new round-trips.
The remaining per-string bound is the largest function (16.3M chars,
~33x headroom) and the header (2.3M chars).
TypeScript keeps the narrowing of a property reference (and of a binding
that a closure assigns) across calls. After `c.cb = fn` or
`if (c.name !== undefined)`, a callback, method or getter that clears or
replaces the property leaves later reads typed by the old value. Lowering
trusted that type: maybeNarrow extracted the union payload unchecked, and
`?.`, truthiness and `typeof` folded by the narrowed type. A second
`c.cb?.()` after a self-clearing callback threw where Node answers
undefined, and `string | undefined`, `string | number` or record fields
read after such a call crashed or reinterpreted memory.
NarrowingStability decides whether a narrowing is provably current: every
property in the reference is construction-only (no store to its name
outside `this.name = ...` in a constructor body, no accessor, no computed
or reflective store into instances) with a stable root, or nothing between
the earliest occurrence of the reference in the use's function and the use
can run other code or store the property through another reference
(standard library calls without callbacks are inert; a loop around the use
contributes its whole body). Proven reads keep the unchecked extraction.
Otherwise the read observes the stored value. In `?.` receivers, absence,
type and truthiness tests, member reads the declared type supports, and
slots that accept the declared type, the reference reads as declared, so
the consumer tests at runtime exactly as Node does. Everywhere else the
extraction is checked and throws Node's TypeError for the consuming
operation (`Cannot read properties of undefined (reading 'x')`,
`o.f is not a function`). Calls through callback fields use the same
message. A null-only receiver of a restored `?.` short-circuits to
undefined, and `typeof` evaluates an effectful union operand once.
The checked failure path groups arms by message so wide unions stay small:
the self-hosted compiler's IR grows by 0.03%. tsc-ts self-check, Linux,
interleaved in one VM: check time -1.5% (noise), `--checkers 8` -1.2%.
Corpus 4650 pins the shapes; a unit test pins which reads stay unchecked.
The cycle analysis gave a header to every type that could reach a cycle,
and its construction-only facts gave up on a whole hierarchy as soon as a
constructor let `this` escape or a type could cross into checked-dynamic
code. Four refinements, all derived from the final IR:
- A constructor's stores stay construction-only up to the first top-level
statement in which `this` escapes. Statements run in order, so earlier
stores complete while the object is private; stores from the escaping
statement on, and every store of a constructor whose ancestor let `this`
escape, are writes. Compound-assignment receiver temporaries count as
`this`. An all-immutable cycle is still impossible: each immutable edge
a -> b is stored before a escapes while b has escaped already.
- Crossing into checked-dynamic code only makes types mutable when the
program contains a runtime store into a dynamic value (int32-slots'
audit, now shared as dynamicFieldStores): typed-ref capsules write native
fields only through such a commit. Without one, hidden property bags
stay empty and add no edges. FFI operands and intrinsics other than
publish stay conservative.
- A type is traced iff it lies in a cycle-capable component or reaches an
intrinsic reference. A type that merely holds a cycle cannot be reached
back from it: its references are external counts.
- Reachability is per class: a slot of static type C reaches C's subtree,
not the whole hierarchy; header presence stays uniform per hierarchy.
tsc-ts (e469e33): traced classes 603 -> 469 of 700, records 64 -> 10 of
202, unions 344 -> 93 of 482; scr_cyc_alloc sites 659 -> 471. Mutable
hierarchy units 243 -> 4. Collector candidates on the self-check
(single-threaded) 6.02M -> 5.55M.
The Node-hosted CLI emits with an empty target triple (the host), while
the native CLI passes its toolchain's triple. Inline truncation keyed on
the triple text alone, so on x86-64 Linux the Node seed emitted
llvm.trunc and the native compiler emitted the inline sequence, and the
native bootstrap's LLVM comparison with the Node seed failed
(self-hosting-native-driver, rebuild-emit). An empty triple now means
the host architecture, as it already does for executable TLS; WASI keeps
the intrinsic. The DataView emission test accepts either truncation
form, since it runs on hosts of both kinds.
Array, string and byte lengths, counts, capacities and range-checked indices are size_t values below 2^63, but they were converted with a plain uitofp. On x86-64 without AVX-512 an unsigned 64-bit conversion expands to a five-instruction sequence with two constant-pool loads (unpcklps/subpd/unpckhpd/addsd), and it showed up in the hottest tsc-ts checker loops (compareTypeLists, getPropertyOfTypeEx) between a length load and the conversion back to an integer. `uitofp nneg` states what is already true, so the backend emits one cvtsi2sd. arm64 converts unsigned values in one instruction either way. Byte-number indices, which admit values up to 2^64, keep the unsigned conversion.
TypeScript types `read ?? "text"` as number when the read is typed number,
and `() => xs[i]` as returning number. Declared functions already widened
their returns for both (the primitive result union and the optional
read), but arrow functions and function expressions kept the checker's
return, so the closure narrowed its result and threw "a 'string' value is
not representable" or "undefined is not representable" (the scanbox
`[string, () => unknown][]` probe table).
Unannotated TypeScript lambdas now get the same widened return as
declared functions. A const or global binding of such a lambda keeps the
checker's parameters and takes the widened result, and calls through the
binding count as optional or primitive-union results for the enclosing
function's return.
After `obj.field = bytes[i]` on a `number | undefined` field, TypeScript
narrows later reads to number, so the read extracted the number arm
unchecked and an out-of-range read printed 0 instead of undefined. Locals
declared `T | undefined` had the same problem inside functions
(`let x: number | undefined; x = xs[i]; x + 1` gave 1, not NaN).
The optional-read analysis now records instance fields declared exactly
`T | undefined` that receive a possibly missing value; their narrowed
reads keep the stored union, as runtime-optional record fields already
do, and the value propagates into parameters and returns like other
optional reads. Locals declared that way join the runtime-optional
storage tracking, so bare reads keep the union until a guard proves
presence. A member read through such a field throws Node's "Cannot read
properties of undefined" TypeError.
String.fromCharCode, String.fromCodePoint, the global isNaN and isFinite,
DataView offsets and values, and typed-array slice/subarray bounds took a
`number | undefined` value (an out-of-range read the checker types as
number) through a checked narrow, which threw "undefined is not
representable" or refused to compile. Node converts undefined with
ToNumber: code unit 0, a RangeError for fromCodePoint, isNaN true, offset
0; an undefined slice end is the length.
The Math argument conversion becomes a shared helper that also handles
field reads and any other value lowered as a number-or-undefined union.
Mature and old passes are scheduled by heap growth. While growth-triggered
passes at a level keep finding nothing, the fraction they wait for widens by
doublings from 1/4, and it used to stop at 1, so a large live heap that keeps
growing was walked in full once per doubling. On tsc-ts those walks are most
of the collector's time: in single-threaded Excalidraw, 12 growth-triggered
full passes cost 2.0 s of 14.7 s, the last two walking 2.6M and 5.2M objects
to free 1.4%.
The cap is now 16. That is a memory trade-off: once passes stop finding
garbage, the cycle-headered heap may grow to 17 times its size after the last
pass at a level before the next (it was 2 times), so a program that
accumulates dead cyclic garbage while passes find nothing can hold up to 16
times more of it. Yield-driven narrowing is unchanged: a pass that finds old
garbage moves the fraction straight back to what its yield asks for.
SCR_CYCLE_GROWTH_CAP lowers the cap for memory-sensitive programs, read like
SCR_CYCLE_THRESHOLD: a power of two from 1 to 16 (other positive values round
down, larger ones read as 16); 1 restores the previous schedule.
test_cycle pins the cap on a heap at the growth floor: a dead cycle through
the old generation must go exactly when the heap has grown the configured cap
past the floor (not one doubling earlier, not later), and a pass that finds
old garbage must narrow the fraction at once. cycle.test.ts runs it at the
default cap and at SCR_CYCLE_GROWTH_CAP=1, 3 and 64. The large-chain widening
check keeps its walk bound but no longer waits out the cap on a 266k-node
structure, and now runs after the tests that assume the base schedule.
Measured with tsc-ts origin/parallel-check e469e33, built with this runtime
vs the parent commit, interleaved in one Linux Vercel Sandbox (8 vCPU; 5
rounds, medians; --checkers 8 repeated with 10 rounds). Diagnostics identical.
"cap 1" is this build with SCR_CYCLE_GROWTH_CAP=1:
single-threaded wall RSS cap 1
Excalidraw -10.1% 1283 -> 1263 +0.5%
Playwright -11.0% 1446 -> 1457 +0.3%
--checkers 8
Excalidraw -8.7% / -4.5% 2110 -> 2132 / 2115 -> 2125 +2.6% (10 rounds)
Playwright -7.8% / -7.7% 2616 -> 2634 / 2589 -> 2678 -1.0% (10 rounds)
RSS in MB (max of two runs). The runtime benchmark suite's allocation-heavy
workloads (alloc-trees, word-graph, ast-interp, json-records, records-sort,
functional-pipeline; --layouts=4 --runs=16) are neutral in time and peak RSS
(-0.3% to +1.7%).
indexReadInBounds proves only `i < xs.length`, not that `i` is a
non-negative integer. For `if (f(xs[i]!))` the forwarded-assertion path
used to pass a missing element as undefined; accepting `if` conditions for
every caller turned such reads into the dense bounds trap, which throws for
a negative index where Node passes undefined (tsc-ts: isMatchableRegion and
compareSymbolChains changed ABI). The `if`-condition position is now an
opt-in fact, used by the present-read proof, which also proves the index a
non-negative integer counter.
Code holding the array could detach its buffer between the guard and the
read, so the present-read proof must refuse it. With a genuine NaN also
reaching the parameter and a consumer that observes undefined, the
parameter stays `number | undefined`.
A typed-array read that may name a missing element lowers to a boxed
`number | undefined`, and the optional-value analysis widens every
parameter it reaches for all callers. Two patterns in tsc-ts's relater
boxed its hottest relation methods this way, failing the build's scalar
ABI check ("Boxed numeric arguments in Checker.isTypeAssignableTo"):
- `const regular = this.regularTypes[id]; const sourceId = regular >= 0
? regular : id;` The read is NaN-coded, but its occurrence in the true
arm was rebuilt as `number | undefined`, so `sourceId` and the
parameters of isSimpleTypeRelatedTo and structuredTypeRelatedTo were
boxed. A comparison with a number that is never NaN is false for
undefined and NaN alike, so an occurrence of a never-reassigned binding
under such a guard is a plain, non-NaN number. The analysis now treats
it as one wherever it flows.
- `for (let i = 0; i < sources.length; i++) isTypeAssignableTo(sources[i],
targets[i])` over two Uint32Arrays allocated with the same length. The
parameters also receive a JSON field that may be NaN, so NaN-coding
cannot carry them (`source === target` must tell NaN from undefined).
The reads are now proven present instead: the index is a non-negative
integer counter that only its own function writes, a dominating guard
bounds it by the array's length or by the length of a parallel typed
array allocated with the same length, and each array is a `const`
fixed-length typed array referenced only through element accesses and
`.length`, so no code can detach its buffer. A proven-present read
lowers to the plain element read and is never optional.
indexReadInBounds also accepts a read inside an `if` condition and takes
an optional same-length fact. Reads the proofs do not cover keep the
established lowering: an inclusive bound, a shorter parallel array, a
decreasing or fractional counter, a counter a closure writes, and an
array that escapes all still read undefined, as the new corpus program
typed-array-present-reads checks against Node.
LLVM 22 CMake exports reference the Polly libraries, so building the LLVM helper in a sandbox started from vercel/sandbox/universal fails without libpolly-22-dev. Custom images that already contain it are unaffected.
Every class slice used to opt out of transparent huge pages, so each
4 KiB the bump pointers crossed cost a page fault. Those faults (fault
entry, memcg charge, LRU insertion and the page clear) were 6-14% of
tsc-ts samples in the kernel. Backing the whole reservation with huge
pages removes most of them, but makes the 2 MiB page around every bump
pointer resident at once. A worker executable has up to 32 class slices
per script thread, so tRPC at 8 checkers grew from 558 to 955 MB.
A slice now starts on small pages. Once it has carved 8 MiB, the rest
of its range switches to huge pages (MADV_HUGEPAGE). Only slices that
already hold 8 MiB pay for a partial last huge page. The reservation is
huge-page aligned, so the switch point and every slice start on a 2 MiB
boundary. The slow path raises a slice's bump limit in two steps (to the
switch point, then to the slice end), so the inline fast paths are
unchanged. The policy is Linux-only; other targets keep one limit per
slice, as before. The allocator checks now build with _GNU_SOURCE on
Linux like the runtime packs, so the madvise advice is compiled in and
checked (alignment, contiguous carving across the switch, VmFlags nh/hg).
Measured with tsc-ts best-v1 (parallel-check + 6247795 e24057a 64d9af6
1c42c55), built with this runtime vs origin/main, on two Linux Vercel
Sandboxes (8 vCPU; 5-7 interleaved runs, medians). Columns: wall, max
RSS, minor faults; "all" is MADV_HUGEPAGE on the whole reservation:
single-threaded wall RSS faults all: wall / RSS
Excalidraw -6.1% +0.8% 331k -> 112k -10.0% / +3.5%
Playwright -1.8% +1.0% 371k -> 111k -8.4% / +3.2%
TypeORM -7.2% +0.9% 259k -> 75k -11.8% / +4.1%
tRPC -5.0% +2.0% 101k -> 47k -9.0% / +11.3%
tsc-ts self-check -2.9% +2.6% 158k -> 64k -3.1% / +8.4%
--checkers 8
Excalidraw -2.9% +2.6% 1075k -> 508k -6.3% / +10.6%
Playwright -10.0% +2.6% 739k -> 381k -10.3% / +12.2%
TypeORM -5.9% +2.2% 372k -> 232k -10.1% / +27.7%
tRPC -2.5% +2.5% 159k -> 125k -4.3% / +71.2%
tsc-ts self-check -4.0% +3.9% 213k -> 172k -12.1% / +46.3%
Switching at 2 or 4 MiB was up to about 1.5 points faster single-threaded
but cost up to +11% RSS at 8 checkers. 16 MiB gave back most of the gain.
Prefaulting small pages with MADV_POPULATE_WRITE did not reduce sys time.
Collapsing the small-page prefix with MADV_COLLAPSE at the switch did not
help either. The runtime benchmark suite (--layouts=4 --runs=16) shows a
geomean change of -1.2%: inventory-report -9.9%, validate-errors -5.3%,
log-summary -2.9%, and regex-logs +2.1%. regex-logs peaks at 6.8 MB and
never reaches the switch point; with one binary the policy measures -0.9%
there, so its delta comes from code layout.
The NaN-coded read analysis memoized lookups whose answer can be null
(symbols, eligible functions, call sites, plain-number returns) and read
them back with `map.get(key)!`. Under Node that returns the cached null,
but in the natively compiled compiler `!` is a checked extraction, which
threw "null is not representable" while lowering programs
(self-hosting-native-frontend, the native CLI bootstrap contracts). Read
the cache through an undefined check instead.
Every two-argument Math.min/Math.max was an out-of-line call to
scr_math_min/scr_math_max (94 sites in tsc-ts, including
compareCodePoints and IdentifierTable.intern). LLVM's minimum/maximum
intrinsics have exactly their semantics: NaN propagates and -0 orders
below +0. On x86-64 they lower to minsd/maxsd with inline NaN and
signed-zero handling, on arm64 to fmin/fmax.
A typed-array element read answers undefined for an index outside
[0, length), so the default lowering returns a heap-boxed
`number | undefined` and widens every binding, parameter and return the
read reaches. In the tsc-ts scanner that boxed every character read and
turned every character predicate (isLineBreak, isIdentifierPart, ...)
into a function taking a boxed union.
Most consumers cannot tell undefined from NaN: relational, arithmetic
and bitwise operators, truthiness, Math functions, String.fromCharCode,
typed-array indexing, switch over number cases, and equality with a
number that is never undefined. The new analysis (nan-coded-reads.ts)
follows reads through local bindings, parameters of directly called
functions and methods (no overrides, no value uses), and their returns.
A slot is NaN-coded when every value it receives is a NaN-coded read or
slot, or any other number (converted with ToNumber on entry), and either:
- it never holds a genuine NaN (integer elements, integer constants,
guarded integer arithmetic), so NaN stands for undefined exactly; any
consumer that takes the value whole (an argument, a stored or returned
value, a literal element, concatenation) gets the exact
`number | undefined` rebuilt, and the optional-read analysis treats
that occurrence as optional, so it lowers as before; or
- every consumer is NaN-insensitive.
Equality of two NaN-coded values that never hold a genuine NaN also
answers true for two NaNs, as undefined === undefined does. Any other
slot keeps the established union lowering; asserted reads (`t[i]!`) are
unchanged.
tsc-ts best-v1 (scriptc main + this commit vs main, Linux sandbox,
Xeon 2.5 GHz, interleaved, medians of 5, diagnostics identical):
| app | parse | total (single-threaded) | wall --checkers 8 |
| --- | --- | --- | --- |
| tRPC | 1.263 -> 0.866 s (-31.4%) | 3.035 -> 2.527 s (-16.7%) | -13.0% |
| Excalidraw | 2.637 -> 1.865 s (-29.3%) | 14.99 -> 14.04 s (-6.3%) | -16.2% |
| Playwright | 3.150 -> 2.202 s (-30.1%) | 12.93 -> 12.14 s (-6.1%) | -12.4% |
| TypeORM | 2.562 -> 2.036 s (-20.5%) | 10.93 -> 10.46 s (-4.3%) | -8.6% |
| self-check | 2.080 -> 1.529 s (-26.5%) | 7.06 -> 6.68 s (-5.4%) | -15.1% |
The tsc-ts IR has 646 instead of 697 scr_union_new_f64 sites (the rest
are cold), 22 instead of 168 typed-read helper calls, and 217 instead of
572 scr_union_get_f64 calls; the scanner's hot functions allocate no
union boxes. Binary size -0.2%.
Baseline x86-64 has no rounding instruction, so every llvm.trunc became
a call to libm's trunc. The typed-array read helper paid that call on
every read: it decided presence with `i >= 0 && i < length &&
Math.trunc(i) === i` before the inline element load.
- Math.trunc (and the DataView offset truncation) now take an integer
round trip on x86-64 targets: values of magnitude below 2^52 go through
fptosi/sitofp with the sign restored by copysign (so -0.5 and -0 give
-0); larger values, NaN and the infinities are already integral and
keep their value. Other targets keep llvm.trunc, which is one
instruction there.
- The ToUint32 slow path is only reached for magnitudes above 2^53 (and
non-finite values), which are integers, so its truncation was a no-op
and is gone.
- For integer element kinds, the read helper performs the element read
that yields NaN for an invalid index (one inline index check) and
answers undefined exactly when that read is NaN: an integer element is
never NaN. Float element kinds keep the range and integrality test.
A closure created above the `let`/`const` it captures holds the binding
in a TDZ box whose NULL payload slot marks "not yet initialized". A
union of one reference arm with `null` and/or `undefined` (`Set<T> |
null`, `string | undefined`, `C | null`) is represented as the bare arm
pointer with NULL standing for the unit arm, so storing that unit value
made the box indistinguishable from the temporal dead zone: every later
read or write threw "Cannot access 'x' before initialization" although
the declaration had run.
The self-hosted compiler trips on exactly this shape in
lowerer.ts (`let dynamicViews: Set<string> | null = null`, read by a
callback created earlier), which made scriptc 0.2.8 fail to build
tsc-ts's relater with SC3004. Node evaluates the source correctly; the
native code was wrong.
TDZ boxes of nullable-union bindings now start at the module's immortal
NULLABLE_ABSENT sentinel and the TDZ test compares against it. No value
of the binding can hold that sentinel, and every RC entry point and the
cycle collector already skip it, so box release, trace and the
initializing store need no other change.
Corpus: 4596-tdz-nullable-forward-capture.
Malte Ubl