Go 1.27

Generic methods. Size-specialized malloc on. Goroutine-leak profile by default. asynctimerchan and gotypesalias removed. mapsplitgroup experiment. Known-bits and LICM passes. Switch lookup tables. NEON, wasm and portable SIMD. Promoted fields as composite-literal keys.

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)

• Green Tea: span-based marking with vector scan kernels — Done: kernel hardening: symbol names (d8d2b90a46), retpoline-safe assembly (8572b1cfea), requiring POPCNT for GOAMD64=v1 (45929774c3), and requiring AVX512DQ for KMOVB (661aadb7c4). Left open: nothing noted.
• Heap bitmap rewrite and allocation headers — Done: the small all-pointer-array fast path computed scan size as only the first pointer; fixed (40a10063e8). Left open: nothing noted.
• mallocgc decomposition and size-specialized malloc — Done: turned off at cycle start for “regressions in overall icache footprint at scale” (4af8ad24ee); the go1.26.0 tag shipped with it off via a release-branch cherry-pick. Then: tiny functions consolidated (9936a78b78); the fast path split (75560e67c9, 15f44ffcc3); benchmarks (15129eb73b, 24e654197a); classes >128 B and then >class 7 dropped (55089b9e27, 694604e524); dead race/valgrind branches removed (0a151acad8, bfbbe9667e); refactors (722ee60825, 15fd4ff942, c410b4944e, fe4da8e5c5); generator fixes (9301a3eab2, b23aea0c94, 2378242315); acquirem across the fast path (63b51fc270). Routing heap-bits-in-span through the slow path was tried and reverted as slower (dd1da37fa4, 01d183b000). Re-enabled by default (2a93576965). Left open: “We may want to test moving the boundary even lower” (55089b9e27). freegc for pointerful objects is disabled under specialization (TODO in freegc at HEAD).
• Allocation publication, zeroing and preemptibility — Done: a preemptible memclrNoHeapPointersPreemptible for large pointer-free clear() and allocations, chunked at 256 KB, landed (50126a8e44). A stack-pointer fix followed (cd2fa3b48d). Both were reverted because preemptible clears “expose existing unsafe use of notInHeapSlice” (16018b05ae, 5f5f4ccdb3). Left open: #69327 (non-preemptible multi-MB clears blocking STW) remains open pending the notInHeapSlice fix.
• Stack and register root scanning — Done: extended (vector) register state of async-preempted goroutines is scanned conservatively, so vectorized moves may carry pointers (683aa8893a). On arm64 the 16-byte frame holding R30 from pushCall is scanned (a129840779). Left open: nothing noted.
• Address-space layout, tagged pointers and the mem.go layer — Done: sysUnreserve and LSAN coverage (40ec033c33), sysFree docs (4ce2612f21). Left open: “I am not completely confident that we always pass the full region to sysFree” (40ec033c33).
• Linear-memory heaps (Wasm and sbrk platforms) — Done: nil pointer handling in sysFreeOS on sbrk (649897800b). Left open: nothing noted.

Other changes

• Goroutine leak profile user-visible — experiment enabled by default (253aa2a12a) then deleted (afcf04cb64); the main goroutine blocked on select{} is still analysed as leaked for precision but reported as waiting (d81ba6c35d).

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: user-visible asynctimerchan GODEBUG removed, deleting the async code paths (a5bc606a68); stale GODEBUG detection at startup (f5eb66f695). Left open: nothing noted.
• Contended runtime-lock profiling (mutex profile for runtime-internal locks) — Done: m.locks bit-split so lock/unlock count in steps of 16 while acquirem stays +1, so a mutex-count of zero is detectable when acquirem/releasem is interleaved (b99b8feaae; fixes dropped samples in TestRuntimeLockMetricsAndProfile); gscan vs profInsert rank deconflicted (29c1c946aa). Left open: nothing noted.
• testing/synctest bubbles — Done: concurrent race-context use in synctest timers avoided (784ea961a4); crypto/fips uses unbubbled monotonic clock (a81b20a431). Left open: nothing noted.
• Asynchronous preemption: extended register state — Done: conservative scan of extended register state (683aa8893a); loong64 fcsr0 (e76c910108). Left open: nothing noted.
• sync package API evolution — Done: linkname replaced with import (97259c5d6b); Cond.Broadcast lock guidance (1225feb0da). Left open: nothing noted.
• sync/atomic and runtime atomics — Done: PPC64 Add/And/Or SQCST (f4d1304904); linknames simplified (0dcd7ab1b9). Left open: nothing noted.
• Goroutine lifecycle and identity — Done: goroutineleakprofile enabled by default then experiment dropped (253aa2a12a, 16449179ec); secret state inheritance (e26a373785). Left open: nothing noted.
• Fast random numbers for the scheduler — Done: 32-bit cheaprand via 64-bit multiply; cheaprand64 as 64-bit wyrand (27fcec4d8f). Left open: nothing noted.

Other changes

• cgo init wait internal — atomic bool before the init-done channel for C-created threads (4f8aa414f0).
• Misc internal — signal stack clearing when parking Ms (62a1da372a); reflect.typelinks returns types (87fae3622d); panic record cleanup (e93b26688c); AIX GCData (bd1b41eb81); tracebacklabels default (3694f33692); invalid GODEBUG messages (0ed83956d3); Int16 atomic non-goal documented (0af7dbf1e6).

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=mapsplitgroup added, off by default: groups become ctrl; keys [8]K; elems [8]V so map[K]struct{} no longer pays a padded elem per slot (5560073398; trade-off stated: better key cache behaviour, elem no longer at a fixed offset from its key). Lowering mapaccess1* to mapaccess2* at walk time to share one implementation (62d08234b7); undone in the same cycle because OINDEXMAP is used in expression context and late replacement generated invalid code (2a4fbc3f24), leaving mapaccess1 as a wrapper around mapaccess2. Devirtualised hashing in specialised maps (252a8adbc0), pointer-key fast variants were missing pruneTombstones (03dc8c482f, 3cf84263ec), ctrlGroupMatchH2 on arm64 rewritten to avoid cross-byte borrow false positives (f133609b75), small full maps only grow when inserting a new key (8042aaf03c), correct const for indirect elem flag (51a8f213cd). Left open: mapsplitgroup not default; hashing not yet inlined into map functions (252a8adbc0 says “opens opportunity for further improvement by inlining hashing calls in the future”).
• Map hashing and hash functions (memhash, aeshash, fallback hash) — Done: all assembly hash functions (386/amd64/arm64, aes and noaes) moved from runtime to internal/runtime/maps as “ground work” for rewriting with SIMD intrinsics and inlining into map functions (8594bf4621, 34 files); MemHash{32,64} rewritten with simd/archsimd intrinsics under GOEXPERIMENT=simd (2403e594a5, -8.67% on one geomean, others within noise; MapAccessZero/Empty swings attributed to basic-block alignment); keys passed by value to MemHash{32,64}/StrHash to avoid address-taken keys and reloads, and strHashAES folded into memHashAES (05f75fb9e8). Left open: hash inlining into map ops still future work.
• Compiler-generated equality/hash functions and type descriptor emission (reflectdata) — Done: signature-based equality (30dff416e4, 6eec9bcdb2), signature-based hash (0da8979210), type descriptor alignment set to 8 (a430bc1bd7: cmd/go -88K), MaxPtrmaskBytes back to 16 since GC programs are gone (a409055b7c; tailscaled: types needing runtime-computed masks 6→49, ~100 bytes saved), descriptor size constants moved to internal/abi (d440b8b485), zero-size array element crash fix (cf0c42c2ca), linker handling of runtime.types leading offset based on size, not GOOS (20bc194972), AIX user-created GCData adjustments (bd1b41eb81). Left open: “Maybe a TODO for the future”: only generated comparison functions use signatures, not the code generated for == itself (30dff416e4).
• internal/abi type layout unification and type metadata (rtype → abi.Type) — Done: type descriptor sizes in internal/abi (d440b8b485), MaxPtrmaskBytes=16 (a409055b7c), reflect.typelinks returns types, not offsets, via new runtime accessor; old function kept for linknamers (87fae3622d). Left open: nothing noted.
• reflect implementation: performance, allocation and escape behaviour — Done: conversions between slices of named byte/rune and string (a0796d8af6), Select []runtimeSelect kept on stack (094aacdb04: B/op -12.9%), &zeroVal[0] for zero-sized payloads (60dc96479a), Value.Methods/Fields examples and nil-interface panic (31768104cb, 891f4a8711), MapMaxElemBytes correction (f7d886207f), reflectlite cleanups (b04e7f31c8, d8034799e0). Left open: nothing noted.
• memmove / memclr / memequal / internal/bytealg assembly optimisation — Done: android/arm64 fixes to never read outside 16-byte regions (f5479628d3, 1a0e1fb616), Rabin-Karp helpers unexported (f1e016bb3a). Left open: nothing noted.
• Slice growth, string building and allocation-free bytes/strings helpers — Done: moveSliceNoCap rounds size down to a whole multiple of element size (1a15699a43). Left open: nothing noted.

Other changes

• Runtime print helpers hardened internal — printquoted keeps invalid UTF-8 bytes and fixes decoderune use, printfloat/printcomplex buffer sizes, printint/printuint avoid append (Go 1.26/1.27: cdf8951060, e1e73b316c, cc1241f353, e2c6a2024c^1.26).
• Softfloat fixes internal — softfloat64 add/sub with normal operands cancelling to a subnormal (a2fd613c3e); an earlier 1.26 corner-case alignment was reverted (b9f3accdcf^1.26, bb2a14252b^1.26); 1.18 had rewritten softfloat without float use (aa3d54da07^1.18) and fixed uint64->float32 (16a3cefc93^1.18).
• Smaller max alignment on arm32; race instrumentation for moduleToTypelinksLock internal — 10ed9b6ed5, 1bb3f4ed2b.
• reflect corrections user-visible — Seq/Seq2 with named boolean (0ac9d84e3d), nil array pointer panic (d9a6e74180), docs on TypeAssert corner cases and function pointer comparison (4135faca66, 0969751733).

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: no write barriers in traceRegionAlloc (04772f022a); trace strings truncated before map insertion, fixing a fatal “alloc too large” with long region names (1cfd0dc9a3); ProcSyscallAbandoned string (261d489139); preallocated PC array (34a03bed3c). Left open: nothing noted.
• Frame-pointer unwinding in tracing and profiling; profile stack depth — Done: sentinel for logical stacks in runtime-lock profile removed as dead code (6b7206feb2). Left open: nothing noted.
• Mutex and block profiles, including runtime-internal lock contention — Done: leftover mutexevent linkname removed (84c8483e02); sentinel cleanup (6b7206feb2); patience for trailing thread in test (6c8731962d). Left open: nothing noted.
• CPU profiling, goroutine profiling, pprof labels and the protobuf writer — Done: memory profile records drop redundant bytes fields, 64 bytes saved per memRecord (d247ed00e4); gzip close error returned (8b672822b2); buffered writer in pprof (6eb5a41228); dangling-ID rejection (93a285f2bc^1.28 in 1.28 log). Left open: nothing noted.
• Goroutine leak profile (GC-based leak detection) — Done: main goroutine blocked on select{} excluded (d81ba6c35d); user-visible experiment enabled by default (253aa2a12a, 2026-05-05) and flag deleted the same day (16449179ec, afcf04cb64); flake mitigation by allowing 4–6 leaked goroutines, tracked in #79452 (320e0be23d). Left open: root cause of the 5-instead-of-6 case unknown (320e0be23d).
• runtime/metrics and MemStats — Done: panic in Read with empty slice fixed (6aef900af4); test ensuring Read never needs a stop-the-world (24ec7d2120). Left open: nothing noted.
• Coverage redesign: runtime/coverage, internal/coverage, covdata — Done: first write error is now recorded (78314e0140). Left open: nothing noted.
• Race detector, ASan, MSan and Valgrind integration — Done: LLVM zero-initialization fix (325eedb2a9); arm64 syso without outline atomics (bcdf61fef4); test harness tolerates WaitGroup-reuse panic (86935037f4^1.28). Left open: nothing noted.

Other changes

• GODEBUG removals in crypto/tls user-visible — swept into bucket (a7bc19bf37, 14a4bc2051, 0f4862de57, 1634ae8c7c, 2f57f7626e).

OS layer, stacks and panics

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

• Defer, panic and recover re-implementation — Done: skip ahead to previous panic (50d988e4e0), gopanicFP removed (e93b26688c), PanicNilError.Error gets runtime error: prefix so it fully satisfies runtime.Error (16e8e06751). Left open: nothing noted.
• Symbol tables, runtime.Caller and CallersFrames — Done: generic methods formatted properly in tracebacks (0252b4be03), pprof labels simplified in tracebacks (19c994cc0c). Left open: nothing noted.
• C-to-Go callbacks: extra-M reuse, system-stack bounds, init gating — Done: atomic-bool init gate (4f8aa414f0, f40560ff89 race annotation); cgocallbackg uses ABIInternal on amd64 (631fc4e629), arm64 (d44e4e062b), loong64 (8329d31307) so autogenerated linker frames show; Windows cgo thread init moved to Go (bf1c1b3bde); runtime/cgo pthread helpers and x_cgo_init/crosscall1 deduplicated (65b9017c0e, 8a0bc29bed, a01a4f9802); asmcgocall tolerates missing G (0a56bf8858); clang mmap bug workaround removed (a00f0ed521); X15 cleared before cgocallbackg (52fd498a96). Left open: nothing noted.
• Library entry points and runtime initialization — Done: initialization partly in Go (6bdfdb5f51), libInit without G (78d5260426). Left open: nothing noted.
• runtime/secret and data-independent timing (DIT) — Done: secret state inherited by goroutines (e26a373785); cgo crash fix (1dd2bef375); crash tests under memory-validating modes (841fafcd58). Left open: nothing noted.
• Signals and async-preemption machinery — Done: os/signal ignores bogus signals (c2fabf1a26), dieFromSignal for pid 1 (974764364a), fcsr save loong64 (e76c910108), ios SIGSEGV emulation removed (fdd485c5f1). Left open: nothing noted.
• Syscall layer: AllThreadsSyscall, internal/runtime/syscall, libc and Windows SyscallN — Done: SyscallN limit removed (7c42da1bc5); error code returned as value (4216fa3d04, 9b4244e9ea); 32-bit time handling (ba402cd756, 4e06ed21ac, 04dc12c1a1). Left open: nothing noted.
• Windows runtime port — Done: minimum Windows 10 (341b5e2c02), thread init moved to Go (bf1c1b3bde), ARM64 feature detection (45138d477d). Left open: nothing noted.
• New, ported and removed platforms — Done: linux/ppc64 ELFv2 and cgo/external linking (35c5deb1d4, 364de84f36); riscv64 FENCE refinement (ab7c8279a0). Left open: nothing noted.
• CPU feature detection, GOAMD64 checks and cpu GODEBUG options — Done: RISC-V vector crypto and zbc (ed1646a8ae, 122eb7d035), Windows ARM64 via IsProcessorFeaturePresent (45138d477d). Left open: nothing noted.

Other changes

• Misc internal — runtime/cgo C cleanups (03d9d24404, 2eb890bde3, a3b5ce2234, b2b1e923ed, bdd4c38ce3, ad168c5131, c7d87cda53), Solaris stack bound via pthreads and -lsocket -lxnet (0b39555723, e30e65f7a8), ENOSYS value on mips (c918cbd556), guard on unexpected return pc (d2aad0df60), spectre retpoline asm fix (8572b1cfea), arm64 32-bit hash seed (8fe0c0eb63), Windows error-code zero-extension (3ebdf12d7c), scan small frame from sigctxt.pushCall (a129840779), loong64 time simplification (d61c0c9283).
• Bounds-check/ID tables internal — hash functions moved to internal/runtime/maps (8594bf4621), caa169ee48, 4dde0f6c36, 594517bf2b linkname exports.
• checkclose: small cleanups internal — (b8be5de81e, ef90a565b5 docs).

Compiler frontend · types2

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

• Bringing up generics in types2 (type-parameter operands, core/structural types, tparam-as-interface) — Done: unconstrained type parameters in type-set ranges now yield (nil, nil) and are handled in append, copy and NewSignatureType (a6949e942c). 674ceb7c7b fixes the conversion error for a pointer to a type parameter. Left open: nothing noted.
• Type sets, union terms, interfaces and constraint satisfaction — Done: a6949e942c handles unconstrained type sets; 1ca1b6e866 substitutes receiver type arguments into method type-parameter bounds, so G[int].M with P interface{~*T} is ~*int (generic-methods work; the language side e84da0405b is outside this bucket). Left open: nothing noted.
• Instantiation, Named types, Context deduplication and lazy expansion — Done: bdd2182ec5 does not reuse declared Funcs for expanded methods. 3b00b08c44 stashes the receiver on method selections to restore the Info.Instances invariant that instantiating Uses[id].Type() with Instances[id].TypeArgs gives an equivalent of Instances[id].Type. efddb5ac61 user-friendly panics in Instantiate. 183e201251 sets underlying for imported types.
• Type inference and unification — Done: f757de83f4 fixes inference “irregularity in certain assignment contexts” by briefly permitting generic expressions between genericExpr and assignment (removes exprWithHint); 96bc97f6a3 allows type-argument inference for map keys; 3d4ee07f7f fails interface inference against generic methods (a generic method never satisfies an interface method).
• Generic type aliases and Alias type nodes — Done: 6edb9f9c51 removes the gotypesalias GODEBUG flag (37 files, −619 lines), 7239eead28 traverses aliases in the completeness check, 37bce6617f alias tests.
• Type declaration cycles, valid-type detection and the object path — Done: a977717393, eb845eca72 instantiated-cycle errors include type arguments, 5fb2392a6f.
• Language features as seen by the type checker (by release) — Done: user-visible 9f7e98d263 promoted field names as keys in struct literals (#9859). 710014bcc3 adds a small generic trie (trie.go) to detect overlapping selectors in such literals. 238d7bddeb the yield function in range-over-func cannot be variadic. Generic methods: 79cae3bd1a, 3d4ee07f7f, 1ca1b6e866 (spec change in e84da0405b, which is outside this bucket). ed3ec75df4 limits constant string addition to 10 GiB; d8cab4c45a disables the length check because go/constant avoids constructing string constants and the check would eagerly build them (“may need a new API”).
• Composite-literal type elision via target types (#12854) — Done: 96bc97f6a3 (map-key inference “will be more relevant when implementing #12854”), f757de83f4.
• Method receiver checking — Done: 1ca1b6e866 and 3b00b08c44 (see Named thread).
• Error reporting: codes, messages, and sub-errors — Done: 2d37c20778 field selected on type, 803d53a53c, 28279274c8.
• Robustness: invariants, incomplete types and importers — Done: 183e201251, 8c4c897d0a repeat of an importer change for types2, efddb5ac61.

Other changes

• Selector diagnostics internal — 6d89ab44cc, 3d4ee07f7f.
• Mechanical operand refactor internal — operand.typ and operand.mode renamed typ_/mode_ and all access replaced by accessors and invalidate()/isValid() (052e64e938, fd146ff3b3, cfe0f55571, cd92bae42f, 934a79ff2f, e2a34c7e9b); preparation for other work, unrecorded purpose in these messages.
• Misc user-visible — 91a81e5ae1 go/types String methods; b32177443d first argument to copy never nil.
• Small fixes, unifier/assignment refactors, message and tracing tweaks internal — 2 commits: 8ca47fab42, 7fd116f864

Compiler frontend · syntax, IR, generics

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

• Generics via GC-shape stenciling and runtime dictionaries — Done: shape signatures and hasShape for shaped functions (b4a084d328, 2dbd51e3b4), nested-instantiation reshaping fix (b1772bacc7), SIMD types in instantiation (38ed614748); generic methods extend the model (separate thread).
• Unified IR: one serialization for noding, stenciling, inlining and export — Done: UIR V3 -> V4 for generic methods (fd961d3eb3, a25e961a83 reverted b7db5702b0, final f3f3d0859a); promoted struct fields encoded for composite literals (d9a600a73b); common UIR version factored (655aa335c9); README (820c83da80).
• Old typechecker and IR node-model cleanup — Done: leftover constant checking removed (73db2f85aa, bf1b0973db).
• Generic methods (type parameters on methods) — Done: user-visible parsers stop rejecting method type parameters, type checkers do (06dc5db75d), then “allow generic methods starting with Go 1.27” (e84da0405b). Shape helpers (b4a084d328, 2dbd51e3b4), isConcreteMethod/isGenericMethod (3524089944), encoding (affadc7997, 8c61ad873a, 328950b13c), decoding (ae1edbeb2f, f4b87f314d, ad7d6071ac importer, ac5968dac4, 57868d0019), fd961d3eb3 bumps pkgbits version; experiment gating 87fe5fafba fixes use of the compiler’s own build experiment instead of the user-code experiment; 4e4b780652 hoists a version assertion (otherwise generic methods are silently dropped on old UIR versions); f3f3d0859a makes V4 default (V3 on opt-out), e212a16d1e flips the experiment default, fdd592745d tests. Left open: the experiment was explicitly “not included in the Go 1.27 release”; wrappers omitted (perf optimisation missing).
• Static initialization and package init — Done: 1b7e5836ad splits large init functions (compile-time win for #77153) but 3233439691 reverts; OCONVIFACE unwrapped for OAS2 (45c6fb4b9b); embedded-field offsets in static init (e2c188568d).
• Compile-time performance, concurrency and the self-PGO’d compiler — Done: ac2b8fc093 profile refresh (Unicode -6.3%); e296659b12 plumbs the profile through the inliner and body reader; flags marked concurrency-ok (ba057f7950, 9eb830a807); 439a82ad25 unsorted diagnostics flag.
• Compiler debugging infrastructure: bisect/hash debugging, flags, dumps — Done: -d=astdump (835d6d42c4), HTML output with collapse/expand (ae7b257f24, a3688ab13e; commit says AI-assisted), -d=ssa/phase/@keyword=value options (bef396c339^1.28) in 1.28.
• Frontend support for new language features and spec changes — Done: user-visible generic methods (own thread), promoted fields as composite-literal keys (d9a600a73b, 30bfe53dd7, c0cd914383), linknamestd (46755cb4de), 1 GiB string-constant limit (543703d352), consolidated size limits (b8e0cb88c8), new line-directive semantics (a7ea4a7ecd, 1926d1d95d), loopvar workarounds removed (8da2be3cd0), bloop refinements (540ccca0a7, bae9486d07), nointerface method / constraint (8ddf0031cf).
• The syntax package (parser, scanner, tree) — Done: //line filenames resolve relative to source directory (a7ea4a7ecd).
• Method wrappers and promoted-method sharing — Done: skip incomplete types in needWrapper (b77fdc333a).
• SIMD frontend: the “midway” source-to-source translator — Done: HTML “syntax” formatter for IR (fda1299caf), first midway translator (f1aa77c984), cleanups (e07983a299), debugging flag (7624fb3f0a), sizeof non-constant for simd types (ee5e65d491), renaming types with dependent methods (cc1ee09473), method type-checking for inference (14596908b7).
• ir.StaticValue, ReassignOracle and function-variable tracking — Done: singly assigned function variables treated as static callees in escape analysis, e.g. var visit func(*Node); visit = func... (f4bfb1a9c6), generalised to FuncAssignments with teeHole merging of known callees’ escape tags (5af294bac7), merged into the oracle (84e0c4965a), parens unwrapped (2f0459745c). Left open: 2f0459745c calls it “a parity step needed before more callers can switch from ir.StaticValue to ReassignOracle”.

Other changes

• ABI docs internal — loong64 (baa6b1f2bf), s390x/riscv64 (1.26 2e5d12a277^1.26, 927c89bbc5^1.26).
• Compiler error user-visible — oversized map element reports error rather than ICE (3b5954c634), hint for unexported fields in “too few values” (e4bc71dac5).
• Conversions internal — constant-to-type-parameter conversion fix (6278b729c6), 8fd906ad11.
• Unified IR: noder/writer/reader refinements and pkgbits (1.27) 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 (2de90fd48f, dadc8a5cd2, 085187dc17, e7a2019a1b, dd8efe4b96)
• Old typechecker and IR node-model cleanup (1.27) internal — removal of unused typecheck/ir/types code (Ntype, CurFunc uses, vargen, Resolve dependencies), more typed IR node construction, simplified DeclFunc/NewMethodExpr and constant handling (914b632202, 2677fe9bbe)
• Housekeeping (1.27) internal — dead-code removal, ioutil/seek/slices/atomic-type replacements, README edits, debug-flag removal, assorted small bug fixes and doc comments (adb64adfd7, a535896627, b408256be7, 9ce4f3876e, 82c5ec222a, 879b659ae0, ce4fc9417c, 0ac1ebdce6, 679b34ec94)

Middle end and SSA optimizer

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

• Profile-guided optimization (PGO): hot-call inlining, devirtualization, profile preprocessing — Done:
  • A profile whose graph is empty after scaling now produces a parse error (a1150b5017).
  • The PGO profile is threaded through the inliner and the body reader, so imported generic instantiations see it. Without it, newinliner could clear fn.Inl and crash (e296659b12).
  Left open: nothing noted.
• Inliner: budget, closures, and the interleaved inline/devirtualize driver — Done: walk replaced mapaccess1* calls with mapaccess2* (62d08234b7). Left open: this was reverted outside this bucket and redone in 1.28.
• Escape analysis: call modelling, closures, func-variable callees, and solver speed — Done: user-visible fewer heap allocations.
  • Singly-assigned func variables are treated as static callees, which helps recursive closures (f4bfb1a9c6).
  • Callees are represented as a slice (9be7615aa2), and multiply-assigned func variables merge their callees via teeHole (5af294bac7).
  • Call analysis uses ReassignOracle.StaticValue (1bcfdf2df2).
  Left open: nothing noted.
• Allocation avoidance: stack-allocated slice backing stores and allocation-free literals — Done:
  • A range-over-slice transition is marked in the backing-store analysis (6e04f9f830, #79909).
  • Prove handles Phi(SliceMake, SliceMake) so bounds checks still go away after the stack/heap split (2a1d605e7f, #77375).
  Left open: nothing noted.
• New inliner heuristics (GOEXPERIMENT=newinliner, inline/inlheur) — Done: PGO plumbing fixed a crash where revisitInlinability cleared fn.Inl for PGO-hot functions under newinliner (e296659b12). 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:
  • Multiple induction variables per block (8afbae3e51), including induction-variable pairs such as i, j = i+1, j-1 (faeffecf86, #45078).
  • Ctz and PopCount modelling (a4fda8d32a, f35fb95503, 417d5e6627). noLimit cleanup (8f739162e6, 82ef9f5b21).
  • A stronger subtraction bound using non-equality (14a4cb13e3).
  • No-op And/Or are removed via prove (33504a8696, e7b0a53f31), with the last #68857 workaround dropped (2df8c060e8).
  • Phi of two SliceMakes (2a1d605e7f).
  • Loopbce: overflow logic fixed (f5b77a7e2f, CVE-2026-27143, #78333). Loops that would overflow are not inverted (5edb5d729d). Minimum-integer step handled (e7c75c3ae8). Count-down code cleaned up (831c489f9c).
  Left open: nothing noted.
• Known-bits pass (bitwise constant folding) — Done:
  • The pass itself (7a8dcab743).
  • Support for booleans and Eq (b9e1876c11), Zext (1ad012aa6b), CvtBoolToUint8 (d75902b195), Sext (8963c303b4), Neq (9c0a8a2b46), Lsh/RshU/Rsh (977041b065, 767140eff2, e133fb1569, c72ba16e07), Trunc (2bb808bfc2).
  • Call stack use is limited (be9da6ce60). Shift iteration is faster (880ef11ecf). Debug printing improved (e73e73470e).
  Left open: 7a8dcab743 leaves merging with prove’s limits for “someone … in the future”.
• Memory-op optimization: memcombine, dead stores, store-to-load forwarding, alias analysis, mem2reg — Done:
  • CSE of loads across disjoint stores (c34b99a5e2), recognizing OpVarDef/OpZero as memory definitions (13cab13f78). Memory-access overlap detection fixed (3985ca0b62).
  • DSE learned about Moves (da6a4cd70a, ~<0.1% code) and uses AuxInt for the Move size (6559f48782).
  • memcombine uses HasPointers to match the write-barrier check (deaf3e6789).
  • Small Loads are forwarded through Move (38ac6577cb).
  Left open: the 0 offset case did not match the forwarding rule, fixed in 1.28.
• Lowering of builtins to memory ops: memmove/memclr/memequal inlining and generated equality — Done:
  • Small constant-size MemEq (c7258178cd).
  • Per-signature equality functions (30dff416e4).
  • More OpMove instead of memmove on loong64 (93b78326c3).
  • A preemptible memclrNoHeapPointersPreemptible for large pointer-free clears (50126a8e44, and adf9c27874 for nosplit callers) was reverted (5f5f4ccdb3, 0a750df0b2) because it exposed unsafe uses of notInHeapSlice.
  Left open: 30dff416e4 says == code generation outside equality functions is unchanged (“Maybe a TODO”). Preemptible memclr awaits the notInHeapSlice fix.
• Switch lowering: jump tables, type-switch caches, and switch lookup tables — Done: user-visible faster switches.
  • Lookup tables for constant-returning integer switches (2a902c8a8a), extended to all constant return types (6797caf71a) and fallthroughs (1f5c165a81).
  • A missed case in binary-search-for-switch was fixed (3f3387fab8).
  • Under retpoline, binary search is used for SIMD non-constant immediates (d5ebe8100d).
  Left open: nothing noted.
• Static devirtualization and shape-aware type-assertion pruning — Done: types are compared by pointer identity (09031d907c), with better debug logs (4d1f503396). Impossible type assertions are pruned in generic functions (343fbe2971). Left open: nothing noted.
• Loop variable per-iteration semantics (loopvar) — Done: version detection with line directives was fixed (b408256be7). The compiler’s own x := x capture workarounds were removed (8da2be3cd0). Left open: nothing noted.
• testing.B.Loop support in the compiler (bloop) — Done: extraneous heap allocations from autotmp scope are avoided (bae9486d07). Blank nodes are kept alive (9ce4f3876e). Left open: nothing noted.
• Range-loop and range-over-func lowering in walk — Done: slice/array range loops simplified on loong64 (134035855c). Variadic signature preserved (670038a5a5), label shadowing fixed (f665ff8bc1), and the ranged-over length is not re-evaluated (7395fa1fd8). Left open: nothing noted.
• Sparse conditional constant propagation (sccp) — Done: faster convergence (033b11f257): no duplicate uses on the revisit worklist, no queueing of uses of values already at Bottom, early exit for Bottom values; ~9% less sccp time over make.bash with identical results. Left open: nothing noted.
• Loop-invariant code motion (licm) — Done: pass added (f9f351b130, 346 lines + tests). Hoisting was made opt-in: only ops on an explicit allow-list may be lifted, instead of a deny-list (f93424692d, fixing #78997). In the same cycle zcse was taught not to lift arch-feature-gated instructions (7f7ce373ed^1.28, 1.28 cycle). A separate new “merge conditional branches” pass was disabled as “late in the cycle, try again for 1.28” (31525e9db0, #80102). Left open: the merge-branches pass is off.
• Branch-free lowering: CondSelect-into-math and ARM64 CCMP — Done: CCMP pass for ARM64 AND conditions (fbe55325dd, 5.8k lines mostly generated rules); CondSelect math extended to OR/XOR and contrary forms and non-1 constants (de7f006df2, d9fbe4c90d, 0a36b58888, 68ee544e87), arm64 inline register shifts (a93560b70a), enabled on all arches with PPC64 keeping ISEL when the constant is not 1 (455d4f41fb). Left open: PPC64 other constants unoptimized.
• Constant-folding loads from type metadata and dictionaries — Done: fix to sign-extend AuxInt in rewriteFixedLoad (a78df5aa0a).
• SSA values for zero-sized and multi-field direct-interface types — Done: pointer-shaped types SSA-able despite many 0-sized fields (6435bf46c1); unwrapping of direct interfaces in StructMake/ArrayMake1 (1aa534dbb8); general zero-sized handling and all zero-sized SSA-able (b48b2002fe, 0886e65b11); ICE/bounds-check fixes (b16360470c, 6f19c3b459). Left open: nothing noted.
• ARM64 load/store pairing (LDP/STP) — Done: pair a load with a load in a subsequent block (c8df1410d5); more stp merging (996b985008).

Other changes

• Misc internal — result selects stay in call block (a415314c0b), bad write-barrier type ICE (244b156e67), array-index/slice-cap ICEs (28b1d8886b, e28acf5506), generic-rules miscompile (8dcb3171f6), race-instrumentation gating (76222756d9).
• Boolean/arith canonicalization internal — x==x folds, bijective-op const comparisons, absorption laws, x+x→x<<1, Mul→shift improvements (74e9214b53, fabaedcbe8, f42f2a3bb3, 74c35fca7a, 666e8c59c9, e0c8676edd, cb41169895); dominator sdom reverse-PO fix (a6c48f2ca9); width checks for ops (819c53c25f).
• Correctness fixes internal — walk of clear arguments and OAS2RECV (b8bccb9798, 9002bd9fa1, 286a79658e), static array init miscompile (dae71067ce), OINDEXMAP (2a4fbc3f24), oversized shifts boundedness (0c3b9f837d), FIPS-mode string literals (ab1a2c8874, e20a1b6035), nil check position merging (7c074f14e6).

Backends and assemblers · architectures, ABI

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

• Register-based calling convention (ABIInternal) ports beyond amd64 — Done: wrappers for embedded interfaces use tail calls e7a09d1ffb, with arch fixes for indirect tail calls 383000da24, arm32 59b188cee2/97d6430458, mips64 a95f60871f.
• Register allocator, scheduler and block-level backend passes — Done: regMask refactored into a struct to allow >64 registers 1901161d96 (later resync 2868672202); riscv64 prefers x8–x15/f8–f15 (compressed-friendly) 4212586726; desired registers propagated through phis (back-edges of innermost loops are dead ends) 5b106947d1; schedule increments after flags 628674a0c1; likely-used values moved into registers before entering a loop 97d6430458; no lift of divides out of loops 9c688e3f4d and lifting ops out of loops made opt-in f93424692d; earlyOk for ops c3a43395bc; double-drop fixes f65692ea56,54ebdf6151; cached sdom reverse PO a6c48f2ca9; reduce lock/scheduler contention in the compiler cc6923e839.
• amd64 code generation and GOAMD64 microarchitecture levels — Done: x86 MOVQ r64,imm32 shortened for positive immediates 0db36238c6; 32-bit copies for 64-bit copies of 32-bit values 478d86446e; float32(round64(float64(x))) optimization (amd64/arm64/wasm) 7336381cd1,425a88193c,d51d4d75a6; flags→bool→flags round-trips removed 9e0467b174; ADC/SBB can eat InvertFlags 9f9476d09b; removal of the multi-register shift (SHRD/SHLD) rewrites because when count≡0 mod 64 they leave lo rather than lo|hi a531ad45f7; miscompile fixes: SETcc/Jcc mapping 38e988efb4, x+x<<63 c3bfc824a5/truncated const shift f2f369db0e; ssa Config branchelim arches 2d33a456c6^1.26 (1.26).
• arm64 code generation and assembler — Done: 128-bit vector ops for Move expansion (FMOVQ/FLDPQ/FSTPQ for 16–64 bytes) ec3373e379,e0ebb4c646; TBZ/TBNZ merge shifts/ROR/SRA 3d4fed3179,1f11689588,5e17860e1b; shift lowering cleanup 0d54be530b; data-driven SVE assembling path 79f3d38562, GP/SIMD reg support 926a1bef08, register with index ce4459cf0e, register lists 1aa9d9a69b, memory forms (14685c05aa,65203e06e6,356b87fa7b), special operands 4398c11b51, immediates 42083b1ea0, ASIMD shifts/arithmetic/misc/reduction/widening/narrowing instructions (9111d85e2f,b1c8857f95,c1352b7df1,f2e70034cc,e73621e34a,9a0be0742b), refactors that move encoding helpers into obj (f827b85425,845b7b0e49,85f838f46c,f91403c2a0); SVE put behind GOEXPERIMENT=simd d7a37379a9; fixes: missing condition in SBFX→SBFIZ 943343f7fe, Rsh with 32-bit rhs miscompile f2f369db0e; RPRFM range prefetch e49b53439d.
• riscv64 compiler and assembler (RVA profiles, vector, compressed) — Done: Zicond codegen for CondSelect, enabled only for the ConstantTimeSelect intrinsic because on predictable branches zicond is 4 instructions vs 2 ca94cf1247,3a29ebeef9; Zbc 91d1a88376, Zvbb/Zvbc 58efaf3859, Zihintpause 081aa64e61, FENCE operands/FENCE.TSO b5b9e3cdfe; CSR pseudo ops ca10097f29; avoid improper control-transfer hints 2d1f571c6b; constant materialization refactor and 32-bit unsigned dfd2e8027c,0a0c9c88fd,7f7e4942f1; float32(abs|sqrt64) f3966c1ada.
• loong64 backend and assembler — Done: math.{Ceil,Trunc,Floor,RoundToEven} intrinsics 3fdac6780b; float32(abs|sqrt64) f65fe3216e; Bswap c61a48619f; unaligned equal functions 045ceb7240; assembler refactored into a single opcode map and instruction file (de0d77c6f8,99d4927f69,b261436c52, merges 003c0bbf16,73f72d8c99,c5f1695f79,9b07a7668c,72f89282ac); ll.acq/sc.rel/sc.q 47f26133bd; FRINT f93504bfd6.
• Duff’s device replaced by generated loops; Zero/Move lowering — Done: vector-based Move expansion on arm64 e0ebb4c646; LoweredMoveLoop/LoweredZeroLoop simplified on loong64 c1c0af1e16,a92edd97bf.
• Stack slot merging, liveness and stack maps — Done: bitvec 2 GB limit removed f745645e58, less reserved memory bfb851c31e.
• Atomics and memory-ordering code generation — Done: ppc64 sync/atomic Add/And/Or sequentially consistent f4d1304904.
• WebAssembly backend — Done: constant folding/identity/mask/sign-extension elimination rules (b764d47e4d,def4e491be,bd5dc3a2fb,65f76a20a3,55de3efde3); vector ops in WASM asm (dev.simd) 3b2c371844.
• s390x, MIPS, 386 and 32-bit ARM backends — Done: arm single BIC for AND with negative-rotated immediates (no REGTMP clobber) 358cf41413; s390x VSTRL 4aa6dad54e; mips NORconst removed 514790c2b9.
• Backend hooks for GOEXPERIMENT=simd (amd64 AVX-512, arm64 SVE, wasm) — Done: X/Y/Z16–31 allocatable e7ec26cf8f, callerSave of AVX-512/mask edc3b161cb/wasm vectors b15400c775; mask optimizations acc4bad854; arm64 helpers 9076ed8750.

Other changes

• ssa.Func names storage e7d8668a6a^1.28 (1.28); unify DWARF variable generation 70dc75b79b; alignment field on LSym 67d449c0a6,174c92bd74,28b69f9bb0; FIPS string literals ab1a2c8874; -std flag to assembler 3a0f18376f; linkname check for assembly symbols aee6009ba5.
• 3 small obj/x86 and amd64/386 rules commits internal — e.g. cc: combine some generic AMD64 simplifications; cc: crash if we try to generate a truncated AMD64 const shif; cc: shuffle bits.Sub intrinsic generation on amd64. (5c595a811e,f2b1b38293,212065c922)
• 14 small ssa/regalloc/liveness/obj generic commits internal — e.g. cc: add loclist for removed DCL nodes; cmd/link: modify the register used in trampoline; cc: ensure ops have the expected argument widths. (874c3ceb3f,1e994e0a48,819c53c25f,97c48fd93d,1aa534dbb8,8438ace207,3c8b5e6738,0886e65b11,20897e5e2c,55ff407d4f,4a1c0efa83,80123ef4bf,6565f5517e,9463584647)
• 9 small obj/arm64 and arm64 rules commits internal — e.g. obj: support arm64 FMOVQ from/to global address; obj/arm64: add remaining ASIMD compare instructions; obj: arm64 assembler support unshifted hi for large offsets. (c373c59d68,4dffc57944,f2633386e0,9653f5abd3,684a434e4a,bb2ad49581,6faf5a6df5,7912a25a4e,581c1b1081)
• 8 small obj/loong64 and loong64 asm commits internal — e.g. cc: avoid extending when already sufficiently shifted on loo; obj/loong64: rearrange optab entries; obj/loong64: improve ARNG type register name conversion. (021d5ca042,9697bd96bc,6837583eec,5e6a6840ae,7b5ba1f8ae,ff7dfb5c3b,a1e7a41560,3c770e3233)
• 4 small mips/s390x/arm/wasm commits internal — e.g. cc: (mips64x) optimize float32(abs|sqrt64(float64(x))); obj/wasm: use p.To instead of p.From; [dev.simd] simd: fix wasm bug; size was already 32. (89ba6eec5c,4c6ba57ea7,5db690032c,9c6b9b2ece)
• 1 small obj/riscv and riscv64 rules commits internal — e.g. cmd/asm,obj/riscv: update references to RISC-V specification. (783a68b572)

Backends and assemblers · SIMD

From SIMD: the simd packages and their compiler support (Go 1.18–1.28)

• Compiler SIMD type system, ABI and register-allocation support — Done: isSIMD plumbing reused unchanged for WASM (obj.WasmV128 in ssagen/abi.go) and arm64 NEON (8a1b0c8ecb); unsigned-constant fix for load folding (3f6eabdf09^1.26 was 1.26) ; cgocallback X15 clearing fixes by runtime team (52fd498a96, cross-area). Left open: nothing noted.
• simdgen: the instruction-table-driven generator — Done: multi-architecture parametrisation and ARM64 definitions (8a1b0c8ecb, 8437d1b188, 951257bd14); asmRule for patterns on asm instructions (9922fb1d24); argsMatchRule for broadcast-to-VMOVI folding (098d688071); ImmMax to limit immediate jump-table sizes (b84139dfad); SetElem general-register width detection (f4d50e5ebf); auto-merge of simdgenericOps.go (d3a3061d75); zero-valued fields omitted from simdAMD64ops.go (6fb7a1cddd); decode non-broadcast memory operands (4136ffed69); insert_ordered_map for deterministic output (82489f7402). Left open: sort-order glitch only “attempted to pin down” (e3afca43e2).
• AMD64 archsimd API: AVX, AVX2 and AVX-512 operations — Done: user-visible op additions/fixes: VPSHUF[HL]W and VPEXTR[BW] choices (43a85e04d3, 989942d20a), VPSRL immediate peepholes (aa80d7a7e6), signed Neg() and Mask String() (923c23ea10), VAES capture (83b232b0af), CopySign->MulSign (59740699ed), SumAbsDiff result type (f6c3137899), shift semantics fixes (39b20d32a9), Load/Store renames and GetElem/SetElem bounds panics (b70242b3b9, ff05f35fb6, 13a70de131). Left open: nothing noted.
• Mask representation, masked operations and merge peepholes — Done: user-visible IfElse supersedes Merge (e115b2f987, 6f010acf75), ARM64 IfElse semantics corrected (a2b3c73f75), Mask.ToIntNs repairs (54719fce02), arm64 uint->mask conversions removed because “everyone has signed” (07664b7a53). Left open: nothing noted.
• Memory operands, constant-immediate forms and jump tables — Done: 4136ffed69, 098d688071, aa80d7a7e6, b84139dfad. Left open: nothing noted.
• dev.simd branch, GOEXPERIMENT=simd lifecycle and merges to master — Done: reverse merges a004b4b1b0 (2026-05-26), 0d75fdfd4f (2026-05-29), 33001a6225 (2026-06-01) bring WASM, NEON, midway, GODEBUG=simd emulation switch to master; “for 1.27” API pruning (see API shaping thread). Left open: nothing noted.
• Portable simd package and the “midway” source translator — Done: user-visible first midway translator (f1aa77c984), arm64 support in midway (b7b03d9e3d), emulations (40eb69725e, 10231ce696, d7b3da6e25 rotates, edbc93f594 FP negation, cedf3d5870 unsigned OnesCount), CLMUL (cea3788e05), broadcast (b7327ecacf), GODEBUG switch (a92cf0ee94), shared type file (b2b5aa4d80), endianness test (c910146a98), docs and examples (c086c0e53b, c83d55f695), StorePart returns length (d2b991c840), HiToLo routed through Float64x2 (2458ba018e). Left open: BUG notes in doc.go: reflection calls, SIMD-dependent global var initializers, and modified names in stack traces do not work properly.
• ARM64 NEON archsimd — Done: user-visible initial Add/Sub/Mul (8a1b0c8ecb), then the families above, test generator (61a10105e6), widening renamed LoLong->WidenLo (80ab7bc1fa). Release-trimming for 1.27: const-shift methods postponed (7de45e82f2), SetHi removed and GetHi renamed HiToLo (20e9fe5d36), LookupOrKeep removed (67c2e8b1fb), uint->mask conversions removed (07664b7a53), deprecated As... removed (9a23a318c9), Deinterleave/Transpose renamed (e50343d863), Reduce returns scalar (8d29cf23b1). Left open: multi-register TBL, const shifts needing rename.
• WebAssembly SIMD — Done: user-visible 8742584113 through the above. Left open: nothing noted.
• API shaping and renames before stabilisation — Done: renames above incl. b70242b3b9, fed139a1b3, 35ea327859, 8583ef15c8, 3e04a409d1, 3d6c5301df. Left open: nothing noted.
• Emulation of missing instructions and test infrastructure — Done: 10231ce696, 40eb69725e, edbc93f594, cedf3d5870, test deduplication. Left open: nothing noted.

Other changes

• Generator housekeeping and API polish (grouped, ~22 commits) internal — feature implication/cpufeature docs for mask/merge methods (d8720e1c29, 985b0b3fe2, 096a80ff51), ToMask integer-only on branch copy (63d1eec2bb), per-arch file disambiguation (cb884c6552), Permute rule simplification (cb4f10f62f), generator guidance/annotations/template refactors (6f75386281, abdc5da461, 60b0cc23d6, 62a53580b1, bc1da486f8, c73b7f56e8, 8b42aab894, f844b5eb8b faster env pruning), go.mod/import repair (edf37149c3), broadcast1ToN unexported (a9ed6afb90), shift order/doc changes (3c60677325, acbbcf61df), Select(128)?FromPair renames (6639f3b4d8), BUG note removal (a72a4295ed), emulation String/format repairs (11c4fcb72c, 9e5cf808f6, 642abeced6), NEON SetHi/GetHi first added (3ea9804aef, later changed).
• inline cost multiplier for rotate emulation internal (d7b3da6e25).
• nocheckptr on unsafe helpers internal (1f8aff4386).
• SetElem/GetElem bounds checks user-visible (ff05f35fb6, 13a70de131).

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: .go.type section and relro rewrite 13096a62e6; typelinks removed 481ab86aaf; itabs into .go.type bcc369284d; itablinks removed 6ef7fe9a48; gcmask grouped in noptrbss 291ee5d7de; type descriptor length stored instead of end 1172294145; type:* forced to the start of type data c08f6a5b26; AIX special cases removed ee7a2119ac, 9fd5a5fa7d; runtime.type offset reservation by size rather than GOOS 20bc194972; type descriptor size calculation centralized in internal/abi 3390ec59af; itab sizes recorded 9387929d09; SITABLINK and SFUNCTAB kinds removed 5a928e5a37, 5ec5fdc093; STYPE sort precomputes isItab/typeStr, recovering a dodata regression (714 ms to 325 ms on a large cgo binary versus 207 ms in 1.26.2) 1215bd5ff6. Left open: reflect was to switch to type pointers rather than offsets (message of 481ab86aaf); the dodata regression was only partly recovered (325 ms vs 207 ms).
• DWARF 5 migration — Done: location list representation unified: structured LocListEntry, PutLocationListDwarf4/5 encode directly, single createDwarfVars loop 70dc75b79b. Left open: nothing noted.
• DWARF quality for debuggers (types, variables, trampolines) — Done: dot vars needed by debuggers preserved d7b6fb44b5; preInliningDcls filtering improved b77ae50ad1; heap vars in dead code 9c9e880fe1; simplified closure names (always pre-inlining pkg.outer.funcN) 409f784bea. Left open: nothing noted.
• ELF/relro/hardening and external-link policy — Done: bfd ld 2.36+ replaces gold on linux/arm64 a8032d4c78; PIE on linux/s390x without cgo 58bc91a967. Left open: nothing noted.
• Per-platform object formats and internal linking (Mach-O, PE, XCOFF, wasm, ppc64, riscv64, loong64) — Done: -macos/-macsdk flags and 13.0 minimum 23fde5c48c, 6614616b75; Windows 10 minimum 341b5e2c02; .pdata sorted bbed50aaa3; loong64 immediate range checks b48b6fa2fa; openbsd/mips64 removed 31a8396219. Left open: nothing noted.

Other changes

• Platform fixes internal — Mach-O UNSIGNED relocations and section alignment (f4afab14d0, fdd38337f0), race syso weak import (e22437d192), host .pdata ordering (a6500456f3), loong64 GOT relocs (9def4acb06), dynamic-linker paths (456d0fe409, 81973b4038), .wm4/.wm8 symbols (5f51b09284), MSVC clang+LLD and Windows min-version fallback (b4e37273ce, b3c54d2e59), XCOFF type/gcmask handling (03a6a20740, 5593ea4634, fd7fc1b171), covctrs alignment (4fe1203111), -f ignores version mismatch (cbaecb2830), content-hashed bit for cloned symbols (003833a138), dupok path clarified (8d1c4631fa), flag probes (99d7121934, 8933fb98f3), Mach-O CodeSign avoids a copy (70e521bdff), PE .def name quoting (104f868a02).
• Linker bookkeeping removals internal — SFILEPATH removed and SFirstUnallocated added in 1.26 (61de3a9dae^1.26, 6914dd11c0^1.26), obsolete duffzero/duffcopy code (f766b8da6c), loong64 R_JMPLOONG64 and R_CONST/R_GOTOFF handling (6a71295466, cfb67d0871, 87013ffec0).
• Response file parsing internal GCC-compatible (4b7b1be731).