Go 1.24

Swiss-table maps. Spinbit mutex. HashTrieMap-backed sync.Map. weak and AddCleanup. synctest experiment. Generic type aliases. prove’s limit table. mallocgc specialization. vDSO getrandom. Closure-favoring inliner.

Each area lists the stage every thread reached in this release (with what was left open afterwards), then changes that are not part of a thread. Thread names link to the full thread on its topic page.

Memory management

From Runtime: memory allocator and garbage collector (Go 1.18–1.28)

• Heap bitmap rewrite and allocation headers — Done: GC programs removed from types (45869f5931) and stack objects (5a0f2a7a7c). Small-object bitmap writes were sped up: skipping span.heapBits (−8%, 56fb8350c8) and pre-writing the single possible 8-byte pattern (−6%, 721c04ae4e). Left open: nothing noted.
• mallocgc decomposition and size-specialized malloc — Done: micro-optimizations (31437f25f2, 6686edc0e7, d8997c8c1f, 8df6413e11, e750a0cdb3, 60ee99cf5d), path split (8730fcf885; −11.6% geomean), and specialized heapSetType (a1c4fb4361; −20.6% geomean). ASAN poisoning was fixed after the split (fb2a7f8ce1, 4bf98186b5). Left open: “We can probably also do more with the size class lookups” (8730fcf885). The split dropped the fresh-span zeroing skip for large pointerful objects (fixed in 1.25, df9888ea4e^1.25).
• Finalizers, runtime.AddCleanup and the cleanup queue — Done: user-visible AddCleanup (0531768b30) and Stop (6a2fb15475). Fixes: the stop search could loop or corrupt non-cleanup specials (7f049eac1b); the closure was kept alive while the special became visible (d69e6f63c3); the arg == ptr check (9d21ef3bd4). SetFinalizer validates arguments before the GC-mode check (252e9def65). Docs (8c3e391573) and race-detector tips in zombie reports (09f9b5e361). Left open: SetFinalizer is to be deprecated (0531768b30).
• Weak pointers and the unique package — Done: user-visible the public weak package with Strong renamed to Value (a65f1a467f) and docs (c46ba1f9ef, adfd81d8cd, 07398d2e57, 87dbfb9fa7, 772f024c61). Correctness: shading on conversion (79fd633632), blocking during mark termination (80d306da50, test 3bd08b9792), keeping the handle alive while the special is published (88cfad0c89), uintptr special offsets for interior weak pointers >64 KiB (d87878c62b), and a zero Pointer.Value returning nil (d62154db83). unique: stored keys are the clone, not the input (21ac23a96f); zero-size types (2927aa10ab); TypeFor (755c18ecdf); tests and docs (23c9efa244, 1596a6c8ec, b7e4d2067c, a785d11ac4). HashTrieMap moved to internal/sync with a usable zero value (4804d0daca, e8c5e6d635). Left open: the special offset could later be packed with the kind to recover memory (d87878c62b).
• Mark worker scheduling and GC work queues — Done: futile worker acquisition avoided (e50913cefc). Left open: nothing noted.
• Allocation publication, zeroing and preemptibility — Done: a publication barrier for delayed-zeroed noscan large objects, for user code on weak memory (acd072a078). Left open: nothing noted.
• Address-space layout, tagged pointers and the mem.go layer — Done: iOS address-bit docs (cdca671855). Left open: nothing noted.
• Linear-memory heaps (Wasm and sbrk platforms) — Done: Wasm uses unused linear memory at the break, including linker-reserved initial memory (4510586f93); aligned reservations round the break instead of over-reserving, and sbrk systems drop arena hints (22664f33b7). Left open: nothing noted.

Scheduler and concurrency

From Runtime: scheduler, timers, channels, locks and synchronization (Go 1.18–1.28)

• Timer rewrite: per-P timer heap, timer.lock, and GC-able synchronous timer channels — Done: Stop/Reset racing with a running timer now returns true when the run is cancelled (2ebaff4890); isSending bit cleared before locking the channel (ce60f70374), not used for tickers (48849e0866), then turned into an atomic.Int32 counter so more than 8 concurrent firings can be tracked (6a49f81edc; timer struct grows 96→104 bytes within its size class); avoid panic reading an expired synctest timer channel (4ce116a884). Left open: nothing noted.
• Runtime mutex: tri-state futex/sema locks → “spinbit” mutex — Done: groundwork: futex OSes can use the sema-based mutex via new spinbitmutex GOEXPERIMENT value, off by default (18c2461af3); then the spinbit algorithm itself, gated by that experiment and enabled by default where Xchg8 exists (fd050b3c6d); control-flow cleanup (adc9c45587, -2.9% MutexCapture geomean). Left open: platforms needing emulated Xchg8 still on the old tri-state code; two implementations to maintain.
• testing/synctest bubbles — Done: internal synctest.Run/Wait with fake clock hooks in chan, coro, mgc, lockrank (d90ce588ea); user-visible experimental testing/synctest under GOEXPERIMENT=synctest (76e4efdc77); deadlock avoidance when copying stacks (1d28fa8c43); bubble membership propagated through syscall/js callbacks (a8eddaf758); Run return happens-after goroutine exits (3924fe92b6^1.25, 1.25). Left open: experiment only.
• Coroutines (iter.Pull runtime support) — Done: goroutine profile invariants upheld in coroswitch (2a98a1849f). Left open: nothing noted.
• Asynchronous preemption: extended register state — Done: VZEROUPPER dropped from darwin/amd64 asyncPreempt (fe87b586c0). Left open: nothing noted.
• sync package API evolution — Done: sync.Mutex implementation moved to internal/sync so sync can later depend on internal/concurrent (frame skip for mutex profiling adjusted) (6c66005285); explicit noCopy fields (53b2b64b64); HashTrieMap added to Map tests/benchmarks (50f1888814); RWMutex upgrade/downgrade doc (bc0406333f). Left open: Map not yet replaced by HashTrieMap in this log.
• sync/atomic and runtime atomics — Done: intrinsics marked noescape (e30ce3c498); loong64 acquire loads (geomean -74%/-45%) (3214129a83); arm native And8/Or8 (c5d424bfca). Left open: nothing noted.
• Netpoller — Done: kqueue EVFILT_USER one-shot events save about one syscall per wakeup (21b5f2637a). Left open: nothing noted.

Other changes

• cgo callbacks and Goexit on C threads internal — stack bounds saved/restored at cgocallback so repeated C->Go calls on the main thread avoid slow pthread_getattr_np (76a8409eb8); syscallbp as unsafe.Pointer (54fe0fd43f); clearer Goexit-on-C-thread error (3da4281df1, 820329508a).
• Weak-to-strong blocking at mark termination internal — 80d306da50.
• Misc internal — injectglist holds trace acquire across casgstatus (f025d19e7b); synctest idle defer (953a1bec48); js notes without maps (2caf638e2f); wasmimport pointer types (73ac82f990); getcallerpc noescape (a02516a379); linkname for wireguard (846fc6345d); arm And8/Or8 fix (5dbb0a5c6b); fips service indicator (f0b51a2099).

Data structures and type metadata

From Runtime: maps, built-in data structures, hashing, randomness and type metadata (Go 1.18–1.28)

• Swiss-table maps (GOEXPERIMENT=swissmap → only implementation) — Done: user-visible GOEXPERIMENT=swissmap created with forked files (057b703407), ABI/compiler integration split into old and swiss variants (4f7dc282c4), fast variants initially disabled (1985c0ccf9), initial table without incremental growth (0733682e5f), wired into the runtime enough to pass all.bash (c39bc22c14; missing: race/concurrent-write detection, stack-allocated maps, fast variants, indirect key/elem, all added later in the cycle: 2220fd3636, b5fec2cf54, f782e16162). Extendible hashing (d94b7a1876), small-map direct group (77e3d8cf13), mapaccess1/mapassign moved from runtime to internal/runtime/maps (0564fa6820), capacity hints (3b424cfa9d), shift/modulo optimisations (bb46b754be, cd54b9bae9), deleted-slot reuse (efa43c57b1), big-endian support (3352db152b), no re-copy of indirect key/elem on grow (d4b0bd28ee), single hash on delete (4c8ab993cd), int-key small-map lookups (d51f92e737), simpler small-group lookup that stops once no filled slots remain (a867e5e5a6, -11% geomean), constant elem offset for int64/string keys (c14fc500c7, 253a9933d1), one fewer hot-path load (63f762bcde), hash a copy of the key rather than the key (d13e6d0b08). Iteration: Iter stores the group across Next calls (aefb173b0a, 7b3ac0ca5d) and uses a hybrid single-slot-then-group-match strategy (7c40544441: low-load maps had regressed +60% vs old maps; testing a full group match on every call regressed mostly-full maps, hence the hybrid). Small-map lookups with long string keys do a quick equality prefilter over all slots and only hash if more than one passes (04807d3acf); return after fatal keeps the key in a register in the probe loop (43725ba283). reflect got swiss GroupSize support (02df9bbdbd) and dropped mapiterkey/mapiterelem (7ba074fe43). Compatibility: mapiterinit/mapiternext are linknamed by third parties with the old hiter layout, so new mapIterStart/mapIterNext were introduced for the toolchain and the old names became a compat layer (78e6f2a1c8, 8071f2a169). Left open: default on but GOEXPERIMENT still exists; nothing in the 1.24 messages noting concrete unfinished items besides the “single table without directory” idea in 77e3d8cf13 (“left for later”).
• Compiler-generated equality/hash functions and type descriptor emission (reflectdata) — Done: GC programs removed from type descriptors; the runtime builds the pointer bitmap on demand (45869f5931, -110 net lines: reflectdata, linker data.go/decodesym.go, abi.Type, reflect.type); abi.NoEscape treated as cheap call (b6efbd4efc). Left open: MaxPtrmaskBytes stayed at 2048 (revisited in 1.27).
• internal/abi type layout unification and type metadata (rtype → abi.Type) — Done: GC programs removed from abi.Type handling (45869f5931). Left open: nothing noted.
• reflect implementation: performance, allocation and escape behaviour — Done: structType.Field avoids allocation (493517bb5c), swiss GroupSize (02df9bbdbd), MapIter without mapiterkey/elem (7ba074fe43), MapOf flag tests (7dac9898c3). Left open: nothing noted.
• memmove / memclr / memequal / internal/bytealg assembly optimisation — Done: loong64 memmove/memclr/Compare (547baafa37, 501b389efc, 50e536daa1), arm64 Equal (b915399e7e), arm64 memclr block alignment (b4712ab055), riscv64 IndexByte (606a0bd9c8). Left open: nothing noted.
• Concurrent hash-trie map (internal/sync.HashTrieMap) — Done: all above. Left open: reverted optimisation of CompareAndSwap/Swap.
• Classic map maintenance and maps package helpers (pre-swiss) — Done: 1b4cf43e42, 1f8fa4941f, linkname allowlists for map functions (8391579ece). Left open: swiss replacement.

Other changes

• swissmap code cleanups internal — iterator index merge (7de87ebd59), group-index as uintptr (0b652e3ef6), match helpers (378c48e6c7, 490f6a7933), removed dead code (900578d09c, 01e1e5c204, ed035af7b7, 775837f51f).

Diagnostics and knobs

From Runtime: tracing, profiling, metrics and diagnostics (Go 1.18–1.28)

• The new execution tracer (trace v2): generations, per-M buffers, new parser — Done: tracer made reentrant via nosplit core (e76353d5a9); experimental batches reusable (2a3e2e9b29); deterministic reader output (1c4acea03d); Stack.Frames as iter.Seq (89a5a60da6, 6eb40d158a); trace tools merged into cmd/trace (5f073d361f); event size reduced by packing G statuses (705f9848ef). Left open: none noted.
• Frame-pointer unwinding in tracing and profiling; profile stack depth — Done: fix lost root frames (runtime.goexit, _LostContendedRuntimeLock) and expandFrame out-of-bounds (c64ca8c6ef); null termination of GoroutineProfile stacks (49e542aa85). Left open: nothing noted.
• Mutex and block profiles, including runtime-internal lock contention — Done: all sampled events recorded (1416cebdd5), zero-delay events stored (433c1d3b4a), root frame fix (c64ca8c6ef). Left open: attribution (done in 1.25).
• CPU profiling, goroutine profiling, pprof labels and the protobuf writer — Done: user-visible cheaper pprof labels (ca63101df4, benchmark 411ba0ae86); heap profiles hide internal/runtime/maps frames (d0c9142ce3). Left open: nothing noted.
• Coverage redesign: runtime/coverage, internal/coverage, covdata — Done: 128-bit FNV-1a replaces MD5 for file identity (092d18b318); text-format output with multiple packages fixed (50455385b0, 40b3c0e58a); stringslite added to the hard-coded runtime package list (966688a43a). Left open: nothing noted.
• Race detector, ASan, MSan and Valgrind integration — Done: internal/race contents linknamed into runtime (e25b913127); race enabled for internal/runtime/maps (3a6795554d); concurrent map access fatal error treated as a race hit in tests (fc5e8f2f6b). Left open: nothing noted.
• Crash output, runtime/debug, BuildInfo and debuglog — Done: debuglog type-toggled (548158c4a5, eb6743d9d7), tests always run (3e1bda08fb, 13b3af0391, c7227bc72c forces >=10 shards), ParseBuildInfo/String docs (0c460ad014). Left open: nothing noted.

Other changes

• Test hygiene internal — checkPtraceScope (87a89fa451), gdb 15 fix (ff695ca2e3), pprof label hall-of-shame cleanup (6705ac6885).

OS layer, stacks and panics

From Runtime: OS and platform layer, stacks, panics and tracebacks (Go 1.18–1.28)

• Symbol tables, runtime.Caller and CallersFrames — Done: user-visible documented that Caller/Frame.File always use forward slashes (0addb2a4ea), that Callers never returns an entry PC (312f7c1bd3), and Frames example fixed (eb1e505f3f). Left open: nothing noted.
• Frame pointers: explicit NOFRAME, FP maintenance and FP unwinding — Done: bp stored as unsafe.Pointer on cgocallback (54fe0fd43f). Left open: nothing noted.
• Stack growth, stack bounds and the crash stack — Done: windows/386 system stack reserve (7eeb0a188e); OpenBSD nosplit limit (4da905bcf0). Left open: nothing noted.
• C-to-Go callbacks: extra-M reuse, system-stack bounds, init gating — Done: C pthreads created detached (18fc547b21); Goexit from a C-created thread gets an informative error (820329508a, after revert a9bd84e037); cgo index into pointer-to-array (76f3208367); Android pthread_getattr_np (bccd686f9d); Cygwin error (3f0b293e70). Left open: nothing noted.
• Library entry points and runtime initialization — Done: wasip1 library mode (0b1494f5d2); AIX _cgo_sys_thread_create fix in lib entry (d49d0e0d3a). Left open: nothing noted.
• Security hardening: AT_SECURE, std fds, AT_RANDOM, gated debug features — Done: arc4random_buf on BSDs (311372c53c); AT_RANDOM overwritten (9a44b8e15a); crypto/rand crashes on error (c050d42e1a, 644628536f). Left open: nothing noted.
• runtime/secret and data-independent timing (DIT) — Done: DIT feature detect and crypto/subtle closure (0826b90172, bc1da38c3d). Left open: goroutine locked to OS thread, no inheritance.
• vDSO, vgetrandom and fast clocks — Done: user-visible vDSO getrandom (eb6f2c24cd) and tuning (86781963cc, 8c269479ed, ba10a38ed0, ba42120723). Left open: only amd64 etc. shipped first; riscv64 later.
• Signals and async-preemption machinery — Done: loong64 debug calls and sigcontext padding (3a55b92ccf, 36e5c84ffa); darwin VZEROUPPER removed (fe87b586c0); ignore SIGSYS in checkPidfd (a3a05ed04c). Left open: nothing noted.
• Syscall layer: AllThreadsSyscall, internal/runtime/syscall, libc and Windows SyscallN — Done: reduced stack usage in syscall.SyscallX (fa7343aca3), wasmimport pointer types (73ac82f990). Left open: nothing noted.
• Windows runtime port — Done: windows/arm nanotime1 fix (c7faf7f514), 386 system stack (7eeb0a188e), stack-memory test relax. Left open: nothing noted.
• New, ported and removed platforms — Done: wasip1 library mode (0b1494f5d2), Wasm memory (4510586f93); internal/goos/cmd known-OS table package (9f0491c524). Left open: nothing noted.
• CPU feature detection, GOAMD64 checks and cpu GODEBUG options — Done: DIT on arm64 (0826b90172), loong64 HWCAP/LAMCAS (0f003f9d15, 065c1359e1). Left open: nothing noted.

Other changes

• Misc internal — fatal messages printed without interleaving (6cb107452a), Goexit-on-C-thread message (3da4281df1), adjustSignalStack indirect call to avoid nosplit overflow (944df9a751), riscv64 asm_riscv64.h and regabi cputicks (26aa8d6eb8, 2707d42966), loong64 regabi cputicks (8efb5ebfd0), wasm epipe check disabled (d39b366841).
• ERMS memmove internal — REP MOVSB for >2KB on modern Intel (4096B copy −26%) (601ea46a53).
• Anonymous mapping names user-visible — prctl(PR_SET_VMA_ANON_NAME) labels like [anon: Go: page summary] (Linux 5.17) (52eaed6633^1.25, early settings 300d9d2714^1.26 in 1.26).
• loong64 CALLFN internal — word-wise arg copy (CallArgCopy 4096B −82%) (992f63583a); ARM64 LSE check at init (4e70258601, reverted 475e08349d, relanded 81c66e71d4^1.25 in 1.25).
• internal/runtime/sys internal — getcallersp moved (4f881115d4), package moved (fc5073bc15).

Compiler frontend · types2

From Compiler frontend: the types2 type checker (Go 1.18–1.28)

• Type sets, union terms, interfaces and constraint satisfaction — Done: typeset iterators replace is/underIs (1e5a72e980, 681751a1fe).
• Instantiation, Named types, Context deduplication and lazy expansion — Done: 818515fd3e Named.cleanup handles aliases; 91af7119cd forbids new methods on generic alias and instantiated types; 2ad53d5a19 forbids methods on cgo-generated types.
• Type inference and unification — Done: 726d898c92 always infer over methods when the type argument is fully known (fix for #66751); 0253c0f4ac error message change; 7703db647c tracing.
• Generic type aliases and Alias type nodes — Done: 9b4b4ae585 fixes a named type instantiated with a generic alias (#68580), 5a1de4ed34 checks that alias type arguments satisfy constraints, e3cbda934c prints alias type parameters, 91af7119cd forbids methods on generic aliases.
• Type declaration cycles, valid-type detection and the object path — Done: bdc6dbbc64, bfc8c5b85a cycle error reporting; 87023bb27f deterministic init-cycle output.
• Per-file language versions and version gating — Done: 0b4ab20d2c (only use fileVersion if >= 1.21), reverted by 2693f77b35, replaced by aeac0b6cbf (use max(fileVersion, go1.21) if a file version is present), 9b1f8f32b8 (go/types: compute effective Go version independent of token.Pos).
• Language features as seen by the type checker (by release) — Done: c9afcbade7 requires iterator yield to return bool (work-around); 8a4b439ee6 adds a README.md.
• Method receiver checking — Done: e0ca2e04b8, 1b7285d1ab, ea82219d1c, 86bec1ec19, 385e963e70, b631b8e674 error positions. Left open: the parser can optionally keep parentheses in type expressions (disabled by default, per 86bec1ec19).
• Error reporting: codes, messages, and sub-errors — Done: 7d9802ac5e qualify named types by kind (compositeKind), 3dc146da7f, bfc8c5b85a, 76f3e0ac8d, bcb934ad11.
• Sharing code between go/types and types2 — Done: 0fb35efe5b, a17356cd23, 0fc3b127a0; 7ad9a2c65f; Scope methods 5fe3b31cf8/80316510d3/6ad3933e28 removing dependency on Scope.LookupParent.

Other changes

• Recording/scopes internal — e7b7f44ff8 implicit type-switch case scopes start at “:” , 5bd442aba3, c6531fae58 data race through dot imports, 9593684438 always record a type for inner composite literals, 1d20bce981 doc for Info.Types, 8a4b439ee6 README.
• Small fixes, unifier/assignment refactors, message and tracing tweaks internal — 18 commits: 88bd985239, 0509936823, 1d542efe23, 38c766ee0f, 1a90dcdaaf, 73fa90e290, aca0e2bb27, 829d1b346f, ec67622d04, f6c89abf89, c208b91395, b17a55d095, de46eaadb5, 676d427f77, f328f3ff06, 6f59c11155, 66b6b174b6, 17ed215958

Compiler frontend · syntax, IR, generics

From Compiler frontend: syntax, IR, unified IR and the generics implementation (Go 1.18–1.28)

• Unified IR: one serialization for noding, stenciling, inlining and export — Done: 830621bc09 adds pkgbits.Version; 9e8ea567c8 writes V2 bitstream with aliastypeparams; has-init / derived-func-instance / derived-info-needed fields deprecated (24fd1a043d, c586dbb8b7, 5de9811f37); old indexed-format import dropped (b0bbfb1e0f); export data handling merged into new internal/exportdata (cd35323be9, 0edea47f26).
• Old typechecker and IR node-model cleanup — Done: IsHiddenClosure/IsDeadcodeClosure retired (2e8b3425a2), typecheck getcallerpc/sp builtin sigs and OGETCALLERPC dropped (5b2f71a2c3, 72739bbfa6), types.Type.rparams removed (5d06d165ff), tcSlice/IndexConst/checkmake simplified (d7521704ce, 2d9255b0ea, e6138185db).
• Static initialization and package init — Done: no static init of strings in FIPS mode (5ec1457941, dea12628e6 removes debugging).
• Compile-time performance, concurrency and the self-PGO’d compiler — Done: PGO profile refresh (3ae00f5d29); function wrappers cheaper to compile.
• Compiler debugging infrastructure: bisect/hash debugging, flags, dumps — Done: script-test facility for the compiler (aa97a012b4, b60f88d810 toolchain script conditions, 8246171bae README generation).
• Frontend support for new language features and spec changes — Done: user-visible //go:wasmexport (1cf6e31f0d, docs 32e19fc439), aliases enabled in importer (209ed1a9c7), alias type parameters written (3b36d92c96), tail-call wrapper emission (af0c40311e), dead locals pass (cc258e6785).
• The syntax package (parser, scanner, tree) — Done: parentheses around constraints stripped consistently (1e2114349d), keyword hints in errors (2eac154b1c), missing parameter type message (bae2e968e2).
• Types package internals: size, algorithm kind, TFlag, SIMD flags — Done: GC programs removed from stack frame objects (5a0f2a7a7c), map bucket special cases removed from types.Compare (cf5ec0720f), stack-allocated swiss maps (63ba2b9d84, small maps and makemap_small, #54766).
• Method wrappers and promoted-method sharing — Done: tail-call wrappers (af0c40311e) in the frontend; 7e2487cf65 avoids dynamic type when possible.

Other changes

• Avo ports of amd64 crypto assembly internal — sha256/sha1/sha512/md5/aes/p256 (7 commits, e.g. dbd50a16dc, f9eb06c302, 3b78ca0626, 1e0cba8ee1, 6ee8c07c3c, d61b73c1d1, 004686b6e5); touch compile tests only.
• Optimizations internal — fe69121bc5 []byte(s1+s2), 7e2487cf65 avoid dynamic type, b2aa18b96c stop md5/sha1 for hashes, 5ca785d48d 16-byte hashes.
• Unified IR: noder/writer/reader refinements and pkgbits (1.24) internal — RType/implicit-conversion wiring, *At helpers, optional expression handling, UIR documentation and grammar, pkgbits.Index/SectionKind renames, synthetic closure positions, unsafe.Sizeof handling and related reader/writer fixes (7fcd4a7007, 7dc1ee81f9, e67c0f0c8f)
• Generics: dictionary/shape fixes in the stenciler (1.24) internal — fixes in dictionary passes for type assertions, comparisons, switches, nested instantiation packages, and recursive generic interface instantiation (660e7d60f2)
• Housekeeping (1.24) internal — dead-code removal, ioutil/seek/slices/atomic-type replacements, README edits, debug-flag removal, assorted small bug fixes and doc comments (3f9360345c, 88833c9045, ac51262592, d32133af77, 9cfe3a86d3, d6d5d8c8fb, f15095f543, cc912bd8eb, d288776d91, ab5c22e7ed, 324f41b748, ea38fa5345, 1e740c7669, 0ff1d42507, bb2a5f0556)

Middle end and SSA optimizer

From Compiler: middle end and SSA optimization (Go 1.18–1.28)

• Inliner: budget, closures, and the interleaved inline/devirtualize driver — Done:
  • Calls to PPARAM functions are favored (a464ffda3e), and calls to closure variables are discounted (ad7f736d8f).
  • user-visible Closure inlining is strongly favored: double budget (170436c045), and a very high budget for closures called once (d524c954b1).
  • Interleaving was refactored into a fixpoint loop (4aa1c02dae).
  • abi.NoEscape counts as a cheap call (b6efbd4efc). “Cheap” runtime calls are detected by go.runtime (c2b580a474).
  • A robust “contains closure” test was added (889abb17e1).
  Left open: the new budgets caused recursion and out-of-memory bugs, fixed in 1.25.
• Escape analysis: call modelling, closures, func-variable callees, and solver speed — Done: fixed escape analysis for rangefunc bodies, which the “-range” closure naming had broken (db40d1a4c4). hash/maphash.Comparable[string] no longer escapes its argument (50a8b3a30e). Left open: nothing noted.
• Prove pass and bounds-check elimination: from poset relations to a dense limit table, topo-sorted walk, and division-aware proofs — Done: the limit-table rewrite.
  • Dense limit table (553443d41f) and the constant rewrite (3b96eebcbd), fixing #66826, #66692 and #48213. Its TODO said “remove constant logic from poset code”; that was done in b97971ea2e.
  • Constant ranges propagate through multiplies and shifts (a4a130f6d0). Boolean and pointer relations (5925cd3d15).
  • The domain relation table was reorganized and the jump-table case simplified (f32ec41df5, aba16d17c5).
  • Simplification: HelloSize −0.83%, CmdGoSize −1.53% text (9b4268c3df).
  • checkbce runs after fuseLate (864aa86448).
  • Jorropo’s limit derivations:
    • bits.Len* (0c7523ff59) and its constant folding (090f03fd2f); bits.TrailingZeros* (f49fe2955d).
    • XOR (49621cc311), OR (57df33814a).
    • Modu, Divu, and Div/Mod with positive arguments (194fa2eb6c, e23ebec90d, 68c431e89f).
    • Trunc, Complement, Negation (4f2c0e5d08, 2f3165973f, 820f58a27f).
  • Fixes: off-by-one (f259e4c916), unsat checked before local facts (3de175f383), cleanups (b538e953ee, 9a4fe7e14a).
  • min/max phis (4dcbb00be2). Limits for newly created values (cb163ff60b, 5123f38e05).
  Left open: the flowLimit workarounds for #68857 (min/max, ModU, And) remained until the 1.26 topo-sort.
• Memory-op optimization: memcombine, dead stores, store-to-load forwarding, alias analysis, mem2reg — Done:
  • An InlMark is not a read for DSE, which avoids double zeroing (b0f7be3cfa).
  • Zeroing right after newobject is removed even when builtin decomposition runs late (b2cdaf7346).
  • CSE removes redundant OpLocalAddrs so DSE and memcombine see more (c4e6ab9750, #70300).
  Left open: nothing noted.
• Lowering of builtins to memory ops: memmove/memclr/memequal inlining and generated equality — Done: constant-size memclr is inlined on loong64 (91d07ac71c). Race instrumentation is added when walkCompare emits memequal (09eefb3a4d). Left open: nothing noted.
• Switch lowering: jump tables, type-switch caches, and switch lookup tables — Done: a type switch with a single runtime-known type and a case variable is optimized (711552e98a). Left open: nothing noted.
• testing.B.Loop support in the compiler (bloop) — Done: user-visible variables are kept alive in b.Loop loops by disabling inlining and devirtualization there (fe2da30cb5). A one-time ramp-up was added, and b.Loop itself is inlined (558f5372fc). Left open: the approach was revisited under #73137, and the 1.26 pass replaced it.
• Range-loop and range-over-func lowering in walk — Done: the “bad iterator” panic status was changed (d311cc95dc). The saved .closureptr is omitted in optimized code (a9ad0ff6ba). Left open: nothing noted.

Other changes

• Misc internal — wasmexport result checking and unwinding (eb975601a0, 2ebe15c67e), OGETCALLERPC removed (72739bbfa6), assertI2I LSyms removed (ab5c22e7ed), atomic logical op typing (dbfa3cacc7), map length type (500675a7c8).
• Intrinsics code split internal — factored out of ssagen with intrinsicBuilders, arch handling and duplicate check (c6c9634515, b6f05cc333, dff15aa610, 7c54e024e8); atomic.Xchg8 on amd64 (dc8902f4eb).
• Misc optimizations internal — shift arithmetic (32f4864216), redundant nil checks (7d2e3da243), pull adds out of unsafe.Pointer<->uintptr (f0b0109242), generalized struct load/store (6d856a804c), tail-call expansion in call block (5428570af7), write-barrier coalescing fix (44a6f817ea), no static string init in FIPS mode (5ec1457941), IsHiddenClosure/IsDeadcodeClosure retired (2e8b3425a2).
• Modernization of compiler code internal — min/max, slices, maps use (~8 commits, e.g. f90f7e90b3, 0a2cc74f5a).

Backends and assemblers · architectures, ABI

From Compiler backend: architectures, register allocation, ABI and assemblers (Go 1.18–1.28)

• Register allocator, scheduler and block-level backend passes — Done: regalloc drops values that are not used until after a call 36b45bca66; premature deallocation in loopreschedchecks fixed a8be834912.
• amd64 code generation and GOAMD64 microarchitecture levels — Done: sync/atomic And/Or intrinsics on amd64 c18ff29295, Xchg8 dc8902f4eb; swissmap matchH2/matchEmpty intrinsified with SSE ops (0–3% faster map ops; moved to free functions because methods cannot be intrinsified) dce30a1920; floats stored as integer constants f66db49976.
• arm64 code generation and assembler — Done: bitfield rule additions 7273509466,b92f3f29c1; MADD/MSUB combination more often 98e719f677/fix 0a0a7a5642; STP/LDP around morestack 74163c895a; prologue/epilogue pattern-matched again for small frames (MOVD.W/LDP mismatch noted in the commit) 6d39245514; MSR DIT b5c2b1ec13; UDF for undefined Progs 3e3ce20df8; Xchg8 3aa71c12ea; span7 helpers 557211c150.
• riscv64 compiler and assembler (RVA profiles, vector, compressed) — Done: integer min/max instructions 3d9a89b057; vector instruction encodings and registers 77c53c16e9,4646556ba4; encoding information reworked dc8ceb63a8; shift+add combine for rva22u64 e126129d76; ANDN/ORN/XNOR always provided 0ee5d20b1f; prologue_end DWARF stmt b45c7f1661.
• loong64 backend and assembler — Done: atomics intrinsics based on AM* instructions (xchg 72a92ab5b7, xadd 4f7af5d192, load/store barriers 3214129a83,ac345fb7e7, Cas 5432cd96fd, And/Or 4b0da6b13f, Xchg8 fe7d97d032) — Xchg8 via LAM_BH because LL/SC needs too many temps for an intrinsic; publicationBarrier e534989d18; intrinsics: Abs/Copysign e705a2d16e, Max/Min ff14e08cd3, OnesCount via VPCNT fb9b946adc, TrailingZeros/Len/Bswap/Reverse (ab55465098,d98c51809d,d6fb0ab2c7,583d750fa1), FMA e6cc9d228a, prefetch (1.25) da9c5b142c^1.25; stacksplit branch inverted for static prediction (SP <= stackguard → morestack) 5923a97f43; assembler cleanup series (~12 obj/loong64 commits e.g. bd85a3b153, ee3da50617, 0214749fef); LSX/LASX loads/stores/compares/PCNT 751a817ccc,4ce8c0604e,2751443e92; register-indexed load/store rules ef3e1dae2f; loong64-specific memmove inlining 5f88755f43; NOSPLIT small stacks 0a8dea10ce; many FP/CRC32/FMA/bit-field instructions.
• PPC64 / Power10 backend (GOPPC64, prefixed instructions, PC-relative code) — Done: decimal floating point b03b1acfb0,7403a6a122; MulUintptr intrinsic 2b0a157d68; Xchg8 15618840f6; carry addition rules 745ec75719; shift regression fix 1846dd5a31.
• Prologue, frame pointer, stack split and function alignment (cmd/internal/obj) — Done: arm64 small-frame consistency 6d39245514; drop NOFRAME TODO a4eba85fad.
• Multi-word arithmetic, intrinsics and carry-chain support — Done: PPC64 MulUintptr 2b0a157d68; 386 Ctz64 (relevant to swissmap) 0140aae6d0.
• Atomics and memory-ordering code generation — Done: amd64 And/Or c18ff29295 and Xchg8 dc8902f4eb; PPC64 15618840f6, arm64 3aa71c12ea, loong64 (above).
• WebAssembly backend — Done: wasmexport frameless return PC fix 4ffa2aecc1, parameter types 5a9aeef9d5, detection before runtime init 0b632d26b9.

Other changes

• FIPS 140 plumbing in obj internal — verification enabled 6c841e4640; static assembly symbols, static temps, external tests (91d7ab2cef,fd0294b99c,61790207f5, f99f5da18f); builtin linkname disallowed 14e5093ee5.
• Use of slices/min/clear in cmd internal — (d91a2e5b11, f90f7e90b3, 0c16278124, b2a856e82c); cmd/internal/hash 16/20-byte hashes replacing notsha256 (4fd73e5d4c,f033bc1819,5ca785d48d).
• prove learns min/max phis internal 4dcbb00be2.
• Obj tool for Cnames 84e58c84fd; AddRel method 5b20eec8a0.
• 38 small obj/loong64 and loong64 asm commits internal — e.g. obj/loong64: add CPUCFG instructions support; obj/loong64: switch Lookup function call to ABIInternal mode; obj/loong64: fixed operand assignment error for BFPT/BFPF in. (0a9321ad7f,4b89120b12,ff0c2d9634,5881c41e7f,8b51146c69,5ca7d4645f,33b247437f,44663f333b,b53809d75d,a9ad410801,864513dda9,01ab9a016a,950fcf129e,11dbbaffe1,f95ae3d689,e761921688,f428c7b729,b874005a84,4087624473,3ae819ad1c,9b88f58099,38f8596787,4bfc81a727,9177e12ccc,ea08952aa2,2c5b707b3b,f243cf6016,e45c125a3c,db07c8607a,b895dd5630,aef81a7551,0753396628,252fbaf30f,3f694f73d0,7240c6cb97,3ae5ff2a27,65ba6f94b3,2b33434287)
• 9 small ssa/regalloc/liveness/obj generic commits internal — e.g. cc: give function position on function-too-big error; cc: fix typing of atomic logical operations; cc/internal: optimize condition branch implementation. (afe0e60054,dbfa3cacc7,0f58a7be8a,cd9a300afc,e7047bd14d,32bd777a37,8c52cd3da5,81c92352a7,be86f09e01)
• 3 small obj/riscv and riscv64 rules commits internal — e.g. cc: drop TODO in NilCheck for riscv64; obj/riscv: update references to RISC-V specification; obj/riscv: update RISC-V instruction table. (0fe775e9f3,e5e552b816,89d7f03172)
• 3 small cmd/asm commits internal — e.g. cmd/asm/internal: use slices.Contains; cmd/asm: add position to PCALIGN directives; cmd/asm: add support for LDREXB/STREXB. (e6ae2d83ac,4d35dcfa21,3cb0c039e9)
• 1 small mips/s390x/arm/wasm commits internal — e.g. obj/s390x: fix m6 field encoding for VSTRC instruction on s3. (889178d5b6)
• 1 small obj/arm64 and arm64 rules commits internal — e.g. crypto/internal/fips/check: enable windows/arm64. (f61c2603e9)

Linker and object files

From Linker, object files and debug info (Go 1.18–1.28)

• Type, itab and typelink layout (.go.type section, relro rework) — Done: data/bss pointer masks built from the types the linker knows rather than constituent GC programs; when linking against shared libraries it loads the extra relocations needed to break arrays/structs apart 7588cc9b00. Left open: the message says it is part of removing GC programs from the runtime.
• //go:linkname restrictions and the blocklist — Done: user-visible new std linknames blocked fb764cdad0; runtime mapiter compatibility layer for legacy linknames 8071f2a169; FIPS frozen-tree linkname fix 4f48ad5c6b. Left open: nothing noted.
• DWARF quality for debuggers (types, variables, trampolines) — Done: variable_parameter on functype outparams ae33b66c19; DWARF/gdb support for Swiss maps 067c091564; name slice index made self-describing 08770a5b94. Left open: nothing noted.
• Reproducible build IDs, buildinfo and symbol tables — Done: user-visible Mach-O UUID with -B 20ed603118, by default 6a4feb5644, applied to external linking c15e589733; ELF GNU build ID by default 427d1a23ef; not passed if C linker lacks support 15c5580160; cmd/internal/macho package f2d9f5ffca. Left open: nothing noted.
• FIPS 140 support in the linker — Done: symbol kinds 43f889b9e5, 4582f239c3; verification support (disabled) 239dbd7dba; enabled 6c841e4640; large-program fixes 00709919d0; delta applied to RODATA to DATA relocations b9955f0ad9. Left open: nothing noted.
• Per-platform object formats and internal linking (Mach-O, PE, XCOFF, wasm, ppc64, riscv64, loong64) — Done: loong64 trampolines 1d925fcc7e; wasmexport on js/wasm f38d42f2c4; Wasm memory 16 MB to 1 MB extra 24bc473173; PE export cap 65535 78c0ea5df7; riscv64 R_GOT_PCREL_ITYPE_RELOC 371ee1469c^1.25. Left open: nothing noted.

Other changes

• Misc linker internal — new internal-linking relocations (abc3d2c119), isPLTCall arch (c6117e8f05), 20-byte hashes (f033bc1819), asan covctrs alignment (6dc99aa7eb), OpenBSD nosplit limit (4da905bcf0), runtime dependency list (1218566fe5), -s implies -w documented (ba1deb1cee), flag probe ordering (87c03bdf62), assorted cleanups (aec5cc52ad, a1c3e24b54, 4aa5aa63c9, cc912bd8eb, f3c89e21a5, 72801623cb, daa6c9310e, c37d9a0f93).
• Linker script tests internal (f021221a58, 8246171bae).
• cgo noescape/nocallback user-visible (ff271cd391).