Go 1.6

GC pause work: root jobs in workers, decentralised state machine. Hand-written parser replaces yacc. cgo pointer checks (cgocheck). mips64. PIE and shared libraries on more architectures. MSan. Concurrent-map-misuse detection.

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 Memory management: GC and allocator (Go 1.0–1.17)

Pause work: root jobs in workers, STW loops removed, decentralised state machine, background GC goroutine removed.

• Concurrent sweep and proportional sweep — Done: remove the in-use page loop and the sweep-wait loop from the STW phases (dac220b0a9, 9a31d38f65); sweep termination decentralised (9630c47e8c, a51905fa04); credit fixes (7407d8e582, 6383fb6152, 87d939dee8, c1cbe5b577, ff5c945382); simplified mSpan_Sweep (70462f90ec). Left open: nothing noted.
• Concurrent mark: write barriers and the dev.garbage collector — Done: concurrent scan and mark-2 root rescans performed by GC workers (82d14d77da, fbf273250f); span roots, data/BSS root marking partitioned into 256K chunks (d3df04cd8c); finalizer-bearing objects scanned concurrently (608c1b0d56); STW loops over all spans removed (dac220b0a9, 9a31d38f65); work buffers 256 B → larger (1870572180), two cached workbufs per gcWork to cut flapping (b6c0934a9b), work.partial removed (feb92a8e8c), eager balancing of buffers (9439fa1078); GODEBUG=cgocheck=2 uses the barrier to detect Go pointers written to non-Go memory (be1ef46775) user-visible. Left open: stack re-scan in mark termination still O(# stacks); fixed in 1.7 (2a889b9d93^1.7) and removed in 1.8 (hybrid barrier).
• Decentralized GC state machine and mark termination simplification — Done: decentralised start, sweep termination, mark done (f54bcedce1, 9630c47e8c, a51905fa04, 12e23f05ff, c99d7f7f85, 171204b561, 3842596284), GC coordinator goroutine removed (d5ba582166, bbf2da00fc), gcMode type (fbd2660af3), GCstw phase removed (a42f668654), state lifted into work (1959621584, b0d5e5c500, 3cd56b4dca). Left open: mark 2 and gchelper still present.
• GC pacer: trigger controller, assists and background utilisation — Done: direct per-G assist balance, assists before allocating, preemptible, park/ready (89c341c5e9, 65aa2da617, 456528304d, 15aa6bbd5a), heap distance (9e77c89868), proportional sweep fixes (7407d8e582, 6383fb6152, 87d939dee8). Left open: nothing noted.
• Finalizers and span specials — Done: concurrent scan of finalizer objects (608c1b0d56), tiny-alloc finalization fix (bf606094ee). Left open: nothing noted.
• Mark work distribution: parfor, work buffers, gcWork and root jobs — Done: root jobs and buffers (572f08a064, d3df04cd8c, 1870572180, b6c0934a9b, 9439fa1078, feb92a8e8c, 62ba520b23, dcd9e5bc0f), mark workers attached to P after parking (eb3b1830b0). Left open: nothing noted.
• Allocation-site profiling and GC debugging modes — Done: cgocheck=2 (be1ef46775) user-visible. Left open: nothing noted.

Other changes

• Closed GC races internal — tiny-allocator clear in mark termination (835c83b40d, 4d39bb6a3a), stat underflow (97dc591534), sleep/wakeup of assists (b05f18e3f7).
• Diagnostics and API hygiene internal — pointer diagnostics (b7c55ba496, 97b64d88eb, b307910b6e, 14aacc2fd8, 26397f1383), assist/drain consolidation (39ed682206, 9b3cdaf0a3, c18b163c15, 4cca1cc05e, 28f458ce5b, d986bf2741, 1698018955, 4ac4085f8e), stack span freeing outside STW (56ad88b1ff), nowritebarrierrec annotations (ab9d5f38be, 27df2e3f76), stack barrier races (a4a57bb4f9, d446ba99a4), sweep trace (4ad64cadf8, 1e1ea66991), unsafe clean-ups (4c2465d47d, 4562784bae, c279250946, 7df8ba136c, 29330c118d, 4ff231bca1, c17c42e8a5, ee0305e036, 7d1d642956), Plan 9/Windows (31430bda09, 1cb53ce36b).
• Update gcController.scanWork regularly internal — The GC controller now updates scanWork regularly during scanning. (8e8219deb5)

Scheduler and concurrency

From Scheduler and concurrency runtime (Go 1.0–1.17)

Simplified buffered channels, fewer thread wakeups, GC-work handoff; threads: channels, scheduler.

• The G-M-P scheduler: from global-lock M:N to per-P run queues, spinning Ms and work stealing — Done: only spinning Ms wake new spinning Ms (fewer thread wakeups) fb6f8a96f2; p.runq as []guintptr 0ca4488cc1; nmspinning comparison fix 3efe36d4c4; handoff P starts an M when only GC work exists (deadlock with locked Gs) f309bf3eef; unnecessary worker wakeups removed; proc1.go merged into proc.go 386fa03609.
• Network poller: from the netFD select loop to the runtime-integrated epoll/kqueue/IOCP poller — Done: throw on unexpected netpoll error instead of looping b6d115a583.
• Channels and select — Done: simplified buffered channels 8e496f1d69, e410a527b2.
• sync.Map, atomic.Value and sync/atomic — Done: mips64 d58081cf0a.
• Goroutine and M lifecycle: caches, ids, LockOSThread, Goexit, cgo extra Ms, deadlock detection — Done: NumGoroutine/Stack agree on excluding system goroutines c5bafc8281, fac8202c3f.
• Stop-the-world, safe points and GC–scheduler interaction — Done: stack barrier lock for traceback f90b48e0d3, 3f22adecc7, d446ba99a4; mark workers attach to P after parking eb3b1830b0, 09940b92a0; P handoff starts M for GC work f309bf3eef; forced GC only when not running 01baf13ba5; idle mark workers not started when barriers cleared 20f276e237.

Other changes

• Signal handling and cgo internal — a7d2b4d7ce, 70c9a8187a, 934e055f41, 7af0839e11.
• Windows/trace fixes internal — 001a75a74c, f32f2954fb (never allocate new M when jumping time forward), 7b767f4e52 (internal/race).
• Tracing/profiling safety internal — 03227bb55e (traceBufPtr to avoid write barriers in sysmon/scheduler), 50d8d4e834, b50b24837d, 9c04d00214, 86f1944e86, 5a68eb9f25, 0abf443513.

Data structures and type metadata

From Runtime data structures and type metadata (Go 1.0–1.17)

Atomic pointer writes in memmove/memclr, aeshash DoS hardening, removal of type.zero, concurrent-map-misuse detection.

• Hash map core: from the first hashmap.c to the 8-entry bucket design — Done: stop returning t.zero on a miss (38519e69d0, af78482d6b), skip key overwrite on update when not needed (00c638d243), best-effort detection of concurrent map misuse via a flag next to h.count (50c5042047).
• Hash functions and algorithm tables: memhash, AES hash, fallback hash — Done: aeshash DoS hardening (91059de095).
• Runtime type descriptors: layout, shrinking and name encoding — Done: zero field removed (af78482d6b), _Kind constants removed (2961cab965), methods sorted with sort.Interface (bca70a66a7).
• Interface values, itabs and type assertions — Done: type-safe iface/eface (84afa1be76), convT2E/I race read (9172a1b573).
• memmove, memclr, duff routines and pointer-write atomicity — Done: duffzero/duffcopy amd64 (2421c6e3df, 5cf281a9b7), pointer-atomic memmove/memclr (4b7d5f0b94, 2c911143fd, 168a51b3a1, 9f6df6c940), ppc64 NOFRAME (45c06b27a4).
• internal/bytealg and string/byte comparison primitives — Done: ppc64 and identical-slice shortcut (32d3b96e8b, 805e56ef47).
• Strings: concatenation, conversion and printing helpers — Done: string files merged and stringStructOf (881b0e7880, d4a7ea1b71), stack buffer fix (4d02b12417).
• Soft-float, 64-bit division and complex arithmetic helpers — Done: “add r11, pc, r11” (40af15f28e), mips64 support in reflect and runtime asm (559fb85af6, 424738e43e).

Other changes

• Reflect and msan internal — runtime package identified via myimportpath (45c3cf68b0), reflect.mapassign noescape (8d31a86a1e), msan calls (73f329f472), embedded unexported structs RO and access (adf9b30e55, afe9837b23), DeepEqual NaN-key and unsafe.Pointer handling (a77182f47f, 928fe05a4f).

Diagnostics and knobs

From Diagnostics and knobs (Go 1.0–1.17)

msan runtime support; tracer made free of write barriers; debug.SetTraceback; panic frames restored in tracebacks.

• Execution tracer (trace v1): events, per-goroutine sequencing, annotations — Done: write barriers eliminated from the tracer so it can be called from sysmon and the scheduler: traceBufPtr replaces *traceBuf (03227bb55e), the same for traceStack and traceAllocBlock (2be1ed80c5, e9aef43d87), traceBuf slice replaced by an index (f5c42cf88e); blocking-syscall tracing made identical for entersyscall and entersyscallblock (001a75a74c); hashing of trace stacks fixed (739f133837); stack lock acquired in traceEvent (08594ac7c7). Left open: nothing noted beyond the sequencer cost.
• Race detector integration — Done: race1.go merged into race.go (243757576d); instrumented calls have a type width (9179c9cb5c). Left open: nothing noted.
• CPU profiler and runtime/pprof writers (legacy format to compressed protobuf) — Done: SIGPROF handled inside stack barriers (3a2fc06833); GoroutineProfile fixes (313fd1cb13, d9fdbf4820); documentation of SetCPUProfile with c-archive/c-shared (7688ffe134). Left open: nothing noted.
• Heap profile accounting and MemStats — Done: GC/MemProfile interaction documented (08b80ca880). Left open: nothing noted.
• GODEBUG, runtime/debug, debug log and traceback knobs — Done: user-visible debug.SetTraceback (bb0567b304); panics shown in tracebacks again, gopanic rewritten to panic (0c02bc009a); GODEBUG doc pointers to net and net/http (cd91c3b036); debug.Stack via runtime.Stack (2d697b2401). Left open: nothing noted.
• MSan and sanitizer integration — Done: user-visible msan runtime support, with calls inserted by -msan (5174df9087); msanread skipped on the system stack (880a689124). Left open: msanmalloc/msanfree “will be from other runtime functions in a subsequent CL”.

Other changes

• Stack barriers internal — sigprof in stackBarrier, check and debugging (cb859021d1, a7c09ad4fb); write barriers out of gentraceback (b43b375c6c); scan state in goroutine header (c7c7c7031d); linkname instead of assembly stubs for runtime/debug (42c7929c04); literals janitoring (4f33436004); -race nit (1babba2e4c).

OS layer, stacks and panics

From OS interface, stacks and panics (Go 1.5–1.17)

cgo pointer checks (GODEBUG=cgocheck), GOTRACEBACK=single, runtime/internal/{sys,atomic}, the pcvalue cache, mips64 and android/{386,amd64,arm64} ports, c-archive/c-shared signal handling and addmoduledata for shared builds.

• New and ported OS/arch targets, 1.5–1.17 — Done: linux/mips64 and mips64le files (a36dda7880, 980b00f55b, e0053f8b1c, 846a9adf05, b2b8559987), android/amd64 syscalls and TLS (30ee5919bd, dfc8649854), android/arm64 (ce8f49f42f, 4480d6a927, c091d4cd25, d26a0952a8, c-shared 73ff7cb1ed), android/386 (34db31d5f5, 05c4c6e2f4, b2259dcef0, 90e26f52c6), runtime/internal/sys machinery (432cb66f16, c3ba74931f, d3498c5abd), a 64 kB system stack on arm (21f35b33c2), and larger frames/stack limits on ppc64 (c83c806535, c1b6e392f5, b8f8969fbd, a4855812e2). Left open: mips64 cgo and runtime tail landed in 1.7.
• Goroutine stack growth, shrinking, GC stack barriers and stack objects — Done: merged stack1.go/stack2.go (db2e73faeb), barrier sync checks (77e528293b, bb6fb929d6, ecf388f3a4, e2bb03f175), recycling large stack spans (0cbf8d13a7), pcvalue cache for stack scan (beedb1ec33: Issue10898 16.5 s to 9.2 s), 64 kB system stack on arm (21f35b33c2).
• Tracebacks, symbol tables and runtime.Callers/CallersFrames — Done: pcvalue cache (beedb1ec33), GOTRACEBACK=single default (bf1de1b141), cgo pointer-check debugging prints (166cfd2c87).
• Defer, panic, recover and Goexit (runtime side) — Done: panic1.go merged into panic.go (9358f7fa61), Go/cgo exported function may not return Go pointers (0e2c635788).
• Signals: masks, forwarding, sigaltstack and the unified Unix signal layer — Done: c-archive/shared signal handling (fbdfa99246, 21b4f234c7, a7d2b4d7ce, e24b2445b4, a7cad52e04, f7e51c1320), SIGCONT/SIGTSTP/SIGCANCEL policy (81b35117d9, 3fd19fdc51), allow signal.Ignore of user-generated throwing signals (81adfa508a), nowritebarrierrec in signal path (84a95be922, e126f30a66), m.sigmask typed sigset (7db77271e4, a7383fc467), drop signal stack on NetBSD/DragonFly threads and related (4c4476c297, 123510bf83, 801bebefa9, aea4de80f9), Darwin sigaltstack fixes (f40c05eea4, 0408ca7de1, fb30270037), OS X TRAP bug (331a6055ab), sigfwd stack alignment (2d916bec96), pthread_sigmask on darwin arm (e884334b55), SIGRTMAX qemu workaround (d10675089d), SIGEMT on mips64 (68c6aad58b), signal-handler sigpanic via r12 on ppc64 (f000523018), sigsetstack on Solaris (956535f5cb), exit status (2c67c8c303), integer compare fix (b9fde8605e), drop unneeded sigfwd on unsupported platforms (9fb79380f0), sigreturn stub (31322996fd), sigsend compare (a94e906c41), EPIPE behaviour (58c73de7d0).
• cgo runtime support: pointer checks, callbacks, extra Ms, C-to-Go call path — Done: pointer checks (9dcc58c3d1, 0e2c635788, d91ec5bb40, e97096661e, dd6753a6f2, 166cfd2c87, 387d5b8cfb), msan with cgo (0c1f0549b8), asmcgocall without a g (3af29fb858), Solaris syscall without g (35a5bd6431), dropm on arm/arm64/ppc64/mips64 (c02aa463db), ppc64le cgocallback (3dda43c6aa), mmap in cgo avoids write barrier (b3c05f08a9).
• Shared-library and buildmode entry points (c-archive, c-shared, plugin, shared) — Done: arm64 and arm addmoduledata (4e3deae96d, 1b4d28f8cf), ppc64le (1ccefcd1b8), 386 (09d7de8d61), shared-mode tweaks (c5856cfdb6, 35d71d6727), darwin/386 (47ccf96a95), arm64 c-shared (73ff7cb1ed), PIC vsyscall on 386 (bc3f14fd2a, 6056cc5df6, 7af0839e11).
• Windows runtime — Done: WriteConsole for print/panic (d958881271), NumCPU with affinity (6410e67a1e), timeBeginPeriod removal then revert (ab4c9298b8 in 1.7), msvcrt link (0b5bcf53ee), larger assumed stack in handlers (fdf9b3c994), usleep2 params (d7c12042bf).
• Assembly-level runtime entry points: memequal/cmp/IndexByte, hashing, atomics and ABI wrappers — Done: ppc64 cmpstring (32d3b96e8b), DOS-proof aeshash (91059de095, 731bdc5115), atomics package (67faca7d9c, b2b8559987, 80d0b98d80, 040932869e), MMX check on 386 and no prefetch on 386 (35e84546d7, 0adf6dce8a), no CMOV on 386 (8c9ef9dd0a), asm index for short strings (95333aea53).
• Plan 9 and NaCl ports — Done: Plan 9 abort notes (d093bf489b), mOS split (58e3ae2fae).

Other changes

• assembly, atomics and architecture internal — user-visible bytes: improve Compare function on amd64 for large byte arrays (32add8d7c8)
• cgo and C interop internal — runtime/cgo: remove __stack_chk_fail_local (db5eb2a2c3); user-visible runtime: fixes for arm64 shared libraries (9f0baca505); runtime/cgo: export _cgo_reginit on ppc64x (8537ff8a39); user-visible runtime: mark cgo callback results as written for msan (8f3f2ccac0); runtime/cgo: assume Solaris thread stack is at least 1 MB (cd58f44b20); runtime/cgo: more +build cgo tags (3a21f0a9c1)
• Linux, vDSO, time and auxv internal — user-visible runtime: add a missing hex conversion (24be0997a2); user-visible runtime: check that masks and shifts are correct aligned (3583a44ed2); user-visible runtime: move arch1_$GOARCH.go into arch_$GOARCH.go (1cf05ee612); user-visible runtime: remove redundant type cast (3be4d59820); user-visible runtime: remove a redundant nil pointer check (5d88323fa6); user-visible runtime: change odd ‘print1_write’ file names (ef986fa3fc); user-visible runtime: move m’s OS-specific semaphore fields into mOS (ec9aae772c); user-visible runtime: copy sqrt normalization bugfix from math (fb7178e7cc); user-visible runtime: delete runtime/internal/atomic/textflag.h (7c38ae084e); user-visible runtime: replace tls0 with m0.tls (7bb38f6e47); user-visible runtime: remove zgoarch_*.go files (06eb504ca4); user-visible runtime: fix conflict resolution in golang.org/cl/14207 (fd2bc8681d); user-visible runtime: remove erroneous go:noescape declaration (28f9d96c75); user-visible runtime: remove redundant empty function call from Breakpoint on arm (d326a96419)
• BSD, Solaris, AIX, Plan 9, NaCl internal — all: use one ‘l’ when cancelling everywhere except Solaris (67ddae87b9); user-visible runtime: return errno value from Solaris mmap as expected (c93193aec0)
• other runtime/OS plumbing internal — pprof: improve sampling for heap profiling (27ee719fb3)
• signals and crashes internal — user-visible runtime, os/signal: use //go:linkname instead of assembly stubs to get access to runtime functions (0b8d583320); user-visible runtime: fix errno sign for some mmap and mincore cases (cc0a04d351)
• Darwin/iOS internal — user-visible runtime: fix darwin/arm64 build (c5a2f364d3)
• Generated zgoarch update and newosproc internal — Regenerated zgoarch_*.go and made newosproc asm access m.id directly. (15b51d6ae6, dbdd8c2c94)

Compiler frontend

From Compiler frontend (Go 1.1–1.9)

Hand-written recursive-descent parser replaces yacc, compact binary export data under -newexport, captureless-closure constants, go:noinline, -msan, mass NodeList→slice cleanup.

• The C-to-Go translation of the compiler (cmd/gc → cmd/internal/gc → cmd/compile/internal/gc) — Done: leftovers cleaned: cb0e98b833 “fix some C to Go translation leftovers”, dd42eff8fe/703bd83623/22452ac592/dab0dac01a/391cc54da8/bab01a0b4b/d5fe165ca0/a2119aca7d/b9dbb030d5 convert ad-hoc NodeList uses to []*Node, 8712e1867b/8937780c8a/e03c7896a7/9ac0fff70a/a20fbe8e18 bool conversions, cd7d7382bb and 53d43cb556 introduce types for decl contexts and untyped constant kinds; b569b87ca1 replaces yacc (see parser thread). Left open: NodeList itself.
• Parser: from yacc to a hand-written recursive-descent parser — Done: b569b87ca1 recursive-descent parser (default), b5fe07710f yacc removed, 247959d9b8 rejects identifiers beginning with a non-ASCII digit, e18cd34c76 correct line for :=, fe762b6466 parenthesized go/defer message. Left open: gc’s parser still builds Nodes directly, not a separate AST.
• Binary export data and the object-file split — Done: user-visible ae2f54a771 binary format behind -newexport, 3d3bc88bb5 export list as slice, e6ccfc1ad1, 92ba69d216, 91c8e5f80b, d37d76af43, ab5d2bf92f (don’t export Note field in bodies), feb2a5d610. Left open: no inline bodies in binary form; not default.
• Closures, method values and variable capture — Done: 4f97ec0866.
• Language changes and rules as implemented in the compiler — Done: user-visible 336c998291, be20948e27, 27691fa467, c488548967, d6a203ecab, 67722fea50, 8a34cf7ee0 (no blank methods on builtins), b60c8203ea.
• Constant arithmetic, Mpint/Mpflt and floating-point constants — Done: 85de30e72f, c396c047c6 (remove restriction on float exponent parsing), 76285213b8, 79a3b561b5, ddbc802b07, 2c11164db5, 715f63778d, 732e2cd746, 50fa646776.
• Static initialization, composite literals and init — Done: 4f97ec0866, aaabe3d849, 1ca7a64a0d.
• Walk-level lowering and runtime-call optimisations — Done: eddd7ff3cd, bca70a66a7.
• Write barriers, precise stacks and liveness (compiler side) — Done: 3a765430c1, 402e37d4a9, dac87e9ed3 (systemstack only in runtime).
• Compiler data structures: Node, Nodes, Type, and the types package — Done: []*Node migrations (703bd83623, 22452ac592, dab0dac01a, 391cc54da8, bab01a0b4b, d5fe165ca0, a2119aca7d, b9dbb030d5, dd42eff8fe), bool conversions.
• Pragmas, directives and compiler flags — Done: user-visible a92543e1a1, 3a765430c1, 0c69f1303f, dac87e9ed3, 876b7cc227, 3ae4dc8a75, 78c05b8657.
• Race detector and sanitizer instrumentation in the frontend — Done: user-visible 9e902f0f3a, 0c69f1303f.

Other changes

• Misc internal — acc90c53e8, 7ebb96a489, 68f4f96c1e, 2dc63d1544, 211cdf1e00, 67ddae87b9, ffe743945f, d08f34e744, 89a68e9f1a, 70da2d0a2a (ICE on invalid declaration), 684218e135, f2eb3de636, 12126752cc, 23791ee11d, 52f111fb34 (BOM corner-case), de2bc5722d, 7218b79f23, af8cd3f6bd, 8ae423ef84, c7a3403140, 918a2644f2, 34cbccd341, 87a65f6ce7, 0bad50f2a4, fe762b6466, a20556bf56, 662ab8be31, de531fc255, 5395846890, d9b32f0c7d, 7ce2402bae, a8fc547f78, 92ba69d216, ab5d2bf92f, dace9397b1, c1ad904bdb; , 888aadfa60 (android/386 pie).
• Dead code and string-compare removal internal — dc3540d982, 7c61d24f97 (deadcode-tool findings: hunk allocator, applywritebarrier_bv, etc.), 6d0178359f, c73df92be6 (stringsCompare removed), 8f931e49f5.
• Vendored math/big updates internal — Updated the compiler’s vendored copy of math/big. (548041ed08, a4599efcfb)
• Comment updates in gc internal — Updated old C-style comments, go.y references and added comments on how declarations and scopes work. (6327e8dc69)

Middle end and SSA optimizer

From Middle end and SSA optimizer (Go 1.0–1.9)

Escape precision for variadic args and loop levels; string compare cleanup (threads: escape analysis, copies/strings).

• Escape analysis (esc.c → esc.go) — Done: f7a39a54e9, 745cdc3ad7, e779bfa5d2. Left open: nothing noted.
• Write-barrier insertion: from gc to the SSA writebarrier pass — Done: 85dd62d5dd. Left open: nothing noted.
• Lowering of copies, strings and slices; intrinsics — Done: eddd7ff3cd, c73df92be6, 7eb94db44c, 423b0cc25a. Left open: nothing noted.

Other changes

• Fixes and diagnostics internal — 05a3b1fce5, 9238cbd57a, 8b1b81f463, 336c998291, 22a204dd0f, 63a6f305ef.

Backends and assemblers

From Backends and assemblers (Go 1.0–1.6)

mips64 port; position-independent code on ppc64le, arm, arm64, 386; AVX/VEX assembler support and AVX2 runtime assembly; code layout split from object writing. Threads: mips64, PIC/TLS, assemblers, zeroing/copying.

• Per-architecture compilers 6g/8g/5g/9g and the shared gc code generator — Done: mips64 back end copied from ppc64 (14f919578d, d5cd4ab46a); Etype/Op named types and bool fields (8e7a3ea11e, 8712e1867b, 259466452d, 05c35ac5d1); 387 builds stop using fucomi* (3d01f28e47). Left open: the SSA backend (dev.ssa) was the planned replacement for amd64 in 1.7.
• Register allocation and the peephole optimizer (reg.c, peep.c) — Done: register fix for == (6ec1809b83), regopt must not use REGTMP on ppc64 or CX in PIC (0357c38adf, 61da0e92d0, 9514285da9); AVARLIVE in peep for arm/arm64/mips64/ppc64 (5f23bc8903); duffcopy clobbering X0 (ffb20631fc, 0bef88aa5f).
• Expression and statement code quality in 6g/8g/5g (division, bounds checks, loops, slices, interfaces) — Done: test-first-field-of-struct special case for amd64 and 386 (9aed0b7e3d, f3b064ae01), magic-multiply no longer smashes AX (03c8164849), write barrier on type switch (e3033fc535), Syscall-like functions for liveness (1ac637c766), args_stackmap not for func _ (292ad59291).
• Stack frames, pointer maps and liveness analysis in the compiler — Done: Syscall-like assembly functions recognised for liveness so arguments stay live for the whole call (1ac637c766); no args_stackmap for func _ (292ad59291); AVARLIVE in peephole passes (5f23bc8903).
• Stack frame layout, prologues, stack split and frame pointers — Done: x86 functions aligned and padded with INT $3 (0xCC) rather than 0x00 which can decode as valid instructions (7d2c6eb3f5); PCSP table fixed at morestack calls (66f1f89dc0); fixed stack part centralised (97055dc1f1); ppc64x stack limit raised (c1b6e392f5); stack barriers in ppc64le shared libs (3a1bed82a6).
• Zeroing and copying: Duff’s device, REP, unaligned moves and AVX2 runtime assembly — Done: MOVUPS-based duffzero (2421c6e3df), AVX2 versions of Compare, string compare, IndexByte and memclr (0e23ca41d9, 967564be7e, 321a40721b up to -49% at 4K, b597e1ed54), SSE4.1 Floor/Ceil (37cfb2e07e, ~-30%), duffcopy clobbers X0 (ffb20631fc, 0bef88aa5f).
• Normalising Prog/Addr in cmd/internal/obj (the portable instruction representation) — Done: code layout (span) separated from object writing so the compiler could lay out each function as it is compiled, “should reduce the working set of the compiler. But not until Go 1.7” (ed03dab853); Tlsoffset removal (7bf959c67a); ProgInfo layout (b795ce9ab0).
• Assemblers: 5a/6a/8a/9a and the Go cmd/asm — Done: robustness against fuzzing (7437e3f02e, df37c4b987, 63e2bed0ab, 5e89acb580, 980cb0caf2, 173bf3487f, 49580db149, 49065cbfe4), nested #if (eaea5ade2b), more than one encoding error reported (36edf48a10), -e flag (02717bdc20), mips64 (43ea305435), ARM CMPF/CMPD (36af087aef), arm64 condition-code aliases (61a3ebed55); x86: YMM registers (d2b0c387b2), VEX encodings VZEROUPPER, VMOVDQU, VMOVDQA, VMOVNTDQ (9dd81d6227), then “correct, complete” AVX (8d881b811d), BMI-style PDEP/PEXT (0bae38e094), POPCNT (d3ff40fb1f, 7f620a57d0), HADDPD/HADDPS (e634765941), requested amd64 instructions (863d9b66f8), TSX (e9081b3c76), PSRLW fix (d96b4c494f), reject foo(SB)(AX) (9d6427d899).
• C→Go translation of the toolchain (liblink, assemblers, compilers; dev.cc) — Done: janitoring of map/slice literals and gc (3c37a61455, 7d48573d46, 90f69259ec, 932c1e3dd3, dd42eff8fe, 3e476827a6, 6d0178359f, ea4e321d4d).
• The ppc64 / ppc64le port (dev.power64, 9g/9a/9l) — Done: the PIC/TOC work listed above, SRADCC immediate assembly (10c0753761), epilogue for non-leaf generated methods (710b9ad617), archreloc simplification (d821ae2a9e).
• The arm64 (ARMv8) port (7g/7a/7l) — Done: 3a9bc571b0, 72180c3b82, 3534e2bef4, 80d9106487, 2a031e6a2a, 73d590b4bd, 3578bdf3c3, 61a3ebed55, 5f23bc8903.
• The mips64 port and the mips/mips64 register space — Done: the above. Left open: nothing noted besides that the port starts with the ppc64 structure.
• Position-independent code, dynamic linking and TLS in the assemblers — Done: the list above. Left open: “the make TLS make sense project has quite a few more steps to go” (9e6ba37b86).

Other changes

• Source paths in standard library objects user-visible — $GOROOT/src/... substituted by the linker with the actual $GOROOT/GOROOT_FINAL so binary distributions in other locations show valid paths (83746fd55a).
• -h spam, AUSEFIELD internal — 1d901f55bd, 0b37a6f47b (ignore AUSEFIELD under GOEXPERIMENT=fieldtrack).
• CASE/BCASE removed internal — 3578bdf3c3, 8d478e845c.
• Stack/ARM/x86 miscellany internal — a1e422071c^1.5 arm line numbers after constant pool, d96b4c494f, 50ad337238.
• Remaining small code-generation, optimizer and tooling fixes (3 commits) internal — per-operator and per-back-end bug fixes and cleanups that do not carry design of their own: nil Sym guards, Bool2int removals, REGTMP removal on x86, lex error formatting (448f84a43a, 44ab8bab1c, 00f42437fd)
• Build, portability and warning fixes (1 commits) internal — Plan 9/gcc/clang warnings, yacc/bison, format verbs, buffer sizes, output-file handling and Windows paths in the compilers/assemblers/liblink (53d42fbead)
• TLS and obj cleanups internal — Cleaned up TLS handling, removed dead code and added new x86 instructions. (a5cb76243a, 69a143e388, 1d1f2fb4c6)

Linker and object files

From Linker and object files (Go 1.0–1.9)

PIE and many shared/c-shared architecture additions, -msan, -libgcc/-extar, mips64, ppc64 external linking.

• Go symbol table, pc/line table and function metadata (gosymtab, pclntab, findfunc) — Done: duplicate symtab entries for global functions removed (ebafc80eba); fixed filetab slice size (cf125a36d5).
• DWARF generation in the linker — Done: aranges padding on 32-bit (68aa7fb636), no warnings on unnamed .debug_str symbols (26263354a3).
• External (host) linking and cgo — Done: concurrent object copy for external linking (cf73357e37), -z relro (9a6a8a0586), -z nodelete for shared libs (bd7de94d7f), use a copy of libgcc.a for internal linking and -libgcc (754f707f5f, 8d2f60f8a8), -extar (1aab7b9626), symbols from .a override .so (cd9fc3ebfb).
• Build modes: -shared, c-archive, c-shared, shared, PIE, plugin — Done: user-visible PIE (b7e4de4b1e, 2ffdbd7ce4, 26205cb3c0) and the architecture expansion listed above; -msan option (7b4b96f248); sections .data.rel.ro (2c2cbb69c8).
• From C to Go: cmd/link — Done: dead code cleanup (e92d0d82e0), stringsCompare removal (550b7ccf77), “link go.o first” (6bf794a36d), -W removed (a0c7f57903), -libgcc and -extar flags.
• Linker speed and memory (Go 1.7 focus) — Done: cf73357e37.
• Container writers: Windows PE, Mach-O and Plan 9 — Done: PE .text 32-byte aligned under external link (821e124c24).
• Architecture and OS ports in the linker (arm, power64, arm64, mips, s390x, nacl, BSDs, Solaris) and trampolines — Done: mips64 (053c75411f), ppc64 external and shared (c155e59062, 1ccefcd1b8, 9a476028c0), arm64 addmoduledata (4e3a1e409a^1.9), ARM addmoduledata (1b4d28f8cf), IE TLS on 386 (3bf61fb2e5), R_PPC_REL32 (f1b919574c), new 386/amd64 relocs (914db9f060), ARM cgo ELF headers (3e6334e2e0).
• Build IDs, ABI hashes, flags and determinism — Done: user-visible -msan, -libgcc, -extar flags; $GOROOT substitution (83746fd55a); -W removed.

Other changes

• Misc internal — af799d94f9 pass value being relocated to archreloc (d821ae2a9e simplifies ppc64), bf99d8f843, 06da8fd84a embed runtime.goarm only in the runtime’s module, 4f74de1e4d Solaris buildid, 47ccf96a95 darwin/386 c-archive entry, 712ffc0861 R_AARCH64_RELATIVE for gcdata, 70119accdf, 5e7110b92b ELF phdrs usable by upx, bd7e084d7d plan9_arm header, c7b1ef9918 reject non-main toplevel, f7b66fffc5 force external linking for shared libs on arm, 6bf794a36d link go.o first.
• arm64 addmoduledata internal — 4e3deae96d implements addmoduledata for arm64, enabling shared libraries there.