// systemstack calls fn directly and returns.
// Otherwise, systemstack is being called from the limited stack
// of an ordinary goroutine. In this case, systemstack switches
// to the per-OS-thread stack, calls fn, and switches back.
// 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 ...

type Extensions struct {
	// x-kubernetes-preserve-unknown-fields stops the API server
	// decoding step from pruning fields which are not specified
	// in the validation schema. This affects fields recursively,
	// but switches back to normal pruning behaviour if nested
	// properties or additionalProperties are specified in the schema.
	// False means that the pruning behaviour is inherited from the parent.
	// False does not mean to activate pruning.

var counterSelectExec = telemetry.NewCounter("go/toolchain/select-exec")

// TestVersionSwitch is set in the test go binary to the value in $TESTGO_VERSION_SWITCH.
// Valid settings are:
//
//	"switch" - simulate version switches by reinvoking the test go binary with a different TESTGO_VERSION.
//	"mismatch" - like "switch" but forget to set TESTGO_VERSION, so it looks like we invoked a mismatched toolchain

// are no arguments.
TEXT	runtime·racecall(SB), NOSPLIT, $0-0
	MOVD	fn+0(FP), R1
	MOVD	arg0+8(FP), R2
	MOVD	arg1+16(FP), R3
	MOVD	arg2+24(FP), R4
	MOVD	arg3+32(FP), R5
	JMP	racecall<>(SB)

// Switches SP to g0 stack and calls R1. Arguments are already set.
TEXT	racecall<>(SB), NOSPLIT, $0-0
	BL	runtime·save_g(SB)		// Save g for callbacks.
	MOVD	R15, R7				// Save SP.
	MOVD	g_m(g), R8			// R8 = thread.

func panicdottypeE(have, want, iface *byte)
func panicdottypeI(have, want, iface *byte)
func panicnildottype(want *byte)
func typeAssert(s *byte, typ *byte) *byte

// interface switches
func interfaceSwitch(s *byte, t *byte) (int, *byte)

// interface equality. Type/itab pointers are already known to be equal, so
// we only need to pass one.
func ifaceeq(tab *uintptr, x, y unsafe.Pointer) (ret bool)

	if err != nil {
		return nil, err
	}
	return &dataCloser{c, c.Text.DotWriter()}, nil
}

var testHookStartTLS func(*tls.Config) // nil, except for tests

// SendMail connects to the server at addr, switches to TLS if
// possible, authenticates with the optional mechanism a if possible,
// and then sends an email from address from, to addresses to, with
// message msg.

TEXT	runtime·racecall(SB), NOSPLIT, $0-0
	MOVQ	fn+0(FP), AX
	MOVQ	arg0+8(FP), RARG0
	MOVQ	arg1+16(FP), RARG1
	MOVQ	arg2+24(FP), RARG2
	MOVQ	arg3+32(FP), RARG3
	JMP	racecall<>(SB)

// Switches SP to g0 stack and calls (AX). Arguments already set.
TEXT	racecall<>(SB), NOSPLIT|NOFRAME, $0-0
	MOVQ	g_m(R14), R13
	// Switch to g0 stack.
	MOVQ	SP, R12		// callee-saved, preserved across the CALL
	MOVQ	m_g0(R13), R10

TEXT	runtime·racecall(SB), NOSPLIT, $0-0
	MOVD	fn+0(FP), R9
	MOVD	arg0+8(FP), R0
	MOVD	arg1+16(FP), R1
	MOVD	arg2+24(FP), R2
	MOVD	arg3+32(FP), R3
	JMP	racecall<>(SB)

// Switches SP to g0 stack and calls (R9). Arguments already set.
// Clobbers R19, R20.
TEXT	racecall<>(SB), NOSPLIT|NOFRAME, $0-0
	MOVD	g_m(g), R10
	// Switch to g0 stack.
	MOVD	RSP, R19	// callee-saved, preserved across the CALL

		} else {
			T = check.varType(e)
			if !isValid(T) {
				continue L
			}
		}
		// look for duplicate types
		// (quadratic algorithm, but type switches tend to be reasonably small)
		for t, other := range seen {
			if T == nil && t == nil || T != nil && t != nil && Identical(T, t) {
				// talk about "case" rather than "type" because of nil case
				Ts := "nil"

		} else {
			T = check.varType(e)
			if !isValid(T) {
				continue L
			}
		}
		// look for duplicate types
		// (quadratic algorithm, but type switches tend to be reasonably small)
		for t, other := range seen {
			if T == nil && t == nil || T != nil && t != nil && Identical(T, t) {
				// talk about "case" rather than "type" because of nil case
				Ts := "nil"