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// Copyright 2014 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package runtime
import (
// Should be a built-in for unsafe.Pointer?
func add(p unsafe.Pointer, x uintptr) unsafe.Pointer {
return unsafe.Pointer(uintptr(p) + x)
// getg returns the pointer to the current g.
// The compiler rewrites calls to this function into instructions
// that fetch the g directly (from TLS or from the dedicated register).
func getg() *g
// mcall switches from the g to the g0 stack and invokes fn(g),
// where g is the goroutine that made the call.
// mcall saves g's current PC/SP in g->sched so that it can be restored later.
// It is up to fn to arrange for that later execution, typically by recording
// g in a data structure, causing something to call ready(g) later.
// mcall returns to the original goroutine g later, when g has been rescheduled.
// fn must not return at all; typically it ends by calling schedule, to let the m
// run other goroutines.
// mcall can only be called from g stacks (not g0, not gsignal).
// This must NOT be go:noescape: if fn is a stack-allocated closure,
// fn puts g on a run queue, and g executes before fn returns, the
// closure will be invalidated while it is still executing.
func mcall(fn func(*g))
// systemstack runs fn on a system stack.
// It is common to use a func literal as the argument, in order
// to share inputs and outputs with the code around the call
// to system stack:
// ... set up y ...
// systemstack(func() {
// x = bigcall(y)
// })
// ... use x ...
// For the gc toolchain this permits running a function that requires
// additional stack space in a context where the stack can not be
// split. We don't really need additional stack space in gccgo, since
// stack splitting is handled separately. But to keep things looking
// the same, we do switch to the g0 stack here if necessary.
func systemstack(fn func()) {
gp := getg()
mp := gp.m
if gp == mp.g0 || gp == mp.gsignal {
} else if gp == mp.curg {
fn1 := func(origg *g) {
} else {
var badsystemstackMsg = "fatal: systemstack called from unexpected goroutine"
func badsystemstack() {
sp := stringStructOf(&badsystemstackMsg)
write(2, sp.str, int32(sp.len))
// memclrNoHeapPointers clears n bytes starting at ptr.
// Usually you should use typedmemclr. memclrNoHeapPointers should be
// used only when the caller knows that *ptr contains no heap pointers
// because either:
// *ptr is initialized memory and its type is pointer-free, or
// *ptr is uninitialized memory (e.g., memory that's being reused
// for a new allocation) and hence contains only "junk".
// The (CPU-specific) implementations of this function are in memclr_*.s.
func memclrNoHeapPointers(ptr unsafe.Pointer, n uintptr)
//go:linkname reflect_memclrNoHeapPointers reflect.memclrNoHeapPointers
func reflect_memclrNoHeapPointers(ptr unsafe.Pointer, n uintptr) {
memclrNoHeapPointers(ptr, n)
// memmove copies n bytes from "from" to "to".
//extern __builtin_memmove
func memmove(to, from unsafe.Pointer, n uintptr)
//go:linkname reflect_memmove reflect.memmove
func reflect_memmove(to, from unsafe.Pointer, n uintptr) {
memmove(to, from, n)
//extern __builtin_memcmp
func memcmp(a, b unsafe.Pointer, size uintptr) int32
// exported value for testing
var hashLoad = float32(loadFactorNum) / float32(loadFactorDen)
func fastrand() uint32 {
mp := getg().m
// Implement xorshift64+: 2 32-bit xorshift sequences added together.
// Shift triplet [17,7,16] was calculated as indicated in Marsaglia's
// Xorshift paper:
// This generator passes the SmallCrush suite, part of TestU01 framework:
s1, s0 := mp.fastrand[0], mp.fastrand[1]
s1 ^= s1 << 17
s1 = s1 ^ s0 ^ s1>>7 ^ s0>>16
mp.fastrand[0], mp.fastrand[1] = s0, s1
return s0 + s1
func fastrandn(n uint32) uint32 {
// This is similar to fastrand() % n, but faster.
// See
return uint32(uint64(fastrand()) * uint64(n) >> 32)
//go:linkname sync_fastrand sync.fastrand
func sync_fastrand() uint32 { return fastrand() }
// in internal/bytealg/equal_*.s
func memequal(a, b unsafe.Pointer, size uintptr) bool
// noescape hides a pointer from escape analysis. noescape is
// the identity function but escape analysis doesn't think the
// output depends on the input. noescape is inlined and currently
// compiles down to zero instructions.
func noescape(p unsafe.Pointer) unsafe.Pointer {
x := uintptr(p)
return unsafe.Pointer(x ^ 0)
func jmpdefer(fv *funcval, argp uintptr)
func exit1(code int32)
func setg(gg *g)
//extern __builtin_trap
func breakpoint()
func asminit() {}
func reflectcall(fntype *functype, fn *funcval, isInterface, isMethod bool, params, results *unsafe.Pointer)
func procyield(cycles uint32)
type neverCallThisFunction struct{}
// goexit is the return stub at the top of every goroutine call stack.
// Each goroutine stack is constructed as if goexit called the
// goroutine's entry point function, so that when the entry point
// function returns, it will return to goexit, which will call goexit1
// to perform the actual exit.
// This function must never be called directly. Call goexit1 instead.
// gentraceback assumes that goexit terminates the stack. A direct
// call on the stack will cause gentraceback to stop walking the stack
// prematurely and if there is leftover state it may panic.
func goexit(neverCallThisFunction)
// publicationBarrier performs a store/store barrier (a "publication"
// or "export" barrier). Some form of synchronization is required
// between initializing an object and making that object accessible to
// another processor. Without synchronization, the initialization
// writes and the "publication" write may be reordered, allowing the
// other processor to follow the pointer and observe an uninitialized
// object. In general, higher-level synchronization should be used,
// such as locking or an atomic pointer write. publicationBarrier is
// for when those aren't an option, such as in the implementation of
// the memory manager.
// There's no corresponding barrier for the read side because the read
// side naturally has a data dependency order. All architectures that
// Go supports or seems likely to ever support automatically enforce
// data dependency ordering.
func publicationBarrier()
// getcallerpc returns the program counter (PC) of its caller's caller.
// getcallersp returns the stack pointer (SP) of its caller's caller.
// The implementation may be a compiler intrinsic; there is not
// necessarily code implementing this on every platform.
// For example:
// func f(arg1, arg2, arg3 int) {
// pc := getcallerpc()
// sp := getcallersp()
// }
// These two lines find the PC and SP immediately following
// the call to f (where f will return).
// The call to getcallerpc and getcallersp must be done in the
// frame being asked about.
// The result of getcallersp is correct at the time of the return,
// but it may be invalidated by any subsequent call to a function
// that might relocate the stack in order to grow or shrink it.
// A general rule is that the result of getcallersp should be used
// immediately and can only be passed to nosplit functions.
func getcallerpc() uintptr
func getcallersp() uintptr // implemented as an intrinsic on all platforms
// getsp returns the stack pointer (SP) of the caller of getsp.
func getsp() uintptr { return getcallersp() }
func asmcgocall(fn, arg unsafe.Pointer) int32 {
return 0
// alignUp rounds n up to a multiple of a. a must be a power of 2.
func alignUp(n, a uintptr) uintptr {
return (n + a - 1) &^ (a - 1)
// alignDown rounds n down to a multiple of a. a must be a power of 2.
func alignDown(n, a uintptr) uintptr {
return n &^ (a - 1)
// divRoundUp returns ceil(n / a).
func divRoundUp(n, a uintptr) uintptr {
// a is generally a power of two. This will get inlined and
// the compiler will optimize the division.
return (n + a - 1) / a
// checkASM returns whether assembly runtime checks have passed.
func checkASM() bool {
return true
// For gccgo this is in the C code.
func osyield()
//extern __go_syscall6
func syscall(trap uintptr, a1, a2, a3, a4, a5, a6 uintptr) uintptr
// For gccgo, to communicate from the C code to the Go code.
//go:linkname setIsCgo
func setIsCgo() {
iscgo = true
// For gccgo, to communicate from the C code to the Go code.
//go:linkname setSupportAES
func setSupportAES(v bool) {
support_aes = v
// Here for gccgo.
func errno() int
// For gccgo these are written in C.
func entersyscall()
func entersyscallblock()
// Get signal trampoline, written in C.
func getSigtramp() uintptr
// The sa_handler field is generally hidden in a union, so use C accessors.
func getSigactionHandler(*_sigaction) uintptr
func setSigactionHandler(*_sigaction, uintptr)
// Get signal code, written in C.
func getSiginfoCode(*_siginfo_t) uintptr
// Retrieve fields from the siginfo_t and ucontext_t pointers passed
// to a signal handler using C, as they are often hidden in a union.
// Returns and, if available, PC where signal occurred.
func getSiginfo(*_siginfo_t, unsafe.Pointer) (sigaddr uintptr, sigpc uintptr)
// Implemented in C for gccgo.
func dumpregs(*_siginfo_t, unsafe.Pointer)
// Implemented in C for gccgo.
func setRandomNumber(uint32)
// Called by gccgo's proc.c.
//go:linkname allocg
func allocg() *g {
return new(g)
// Throw and rethrow an exception.
func throwException()
func rethrowException()
// Fetch the size and required alignment of the _Unwind_Exception type
// used by the stack unwinder.
func unwindExceptionSize() uintptr
const uintptrMask = 1<<(8*sys.PtrSize) - 1
type bitvector struct {
n int32 // # of bits
bytedata *uint8
// ptrbit returns the i'th bit in bv.
// ptrbit is less efficient than iterating directly over bitvector bits,
// and should only be used in non-performance-critical code.
// See adjustpointers for an example of a high-efficiency walk of a bitvector.
func (bv *bitvector) ptrbit(i uintptr) uint8 {
b := *(addb(bv.bytedata, i/8))
return (b >> (i % 8)) & 1
// bool2int returns 0 if x is false or 1 if x is true.
func bool2int(x bool) int {
if x {
return 1
return 0
// abort crashes the runtime in situations where even throw might not
// work. In general it should do something a debugger will recognize
// (e.g., an INT3 on x86). A crash in abort is recognized by the
// signal handler, which will attempt to tear down the runtime
// immediately.
func abort()
// usestackmaps is true if stack map (precise stack scan) is enabled.
var usestackmaps bool
// probestackmaps detects whether there are stack maps.
func probestackmaps() bool
// For the math/bits packages for gccgo.
//go:linkname getDivideError
func getDivideError() error {
return divideError
// For the math/bits packages for gccgo.
//go:linkname getOverflowError
func getOverflowError() error {
return overflowError