// CallResult the result of a call operation.
type CallResult struct {
	From      Caller
	Opts      CallOptions
	Responses echo.Responses
}

type Caller interface {
	// Call from this Instance to a target Instance.
	Call(options CallOptions) (CallResult, error)
	CallOrFail(t test.Failer, options CallOptions) CallResult
}

type Callers []Caller

// Instances returns an Instances if all callers are Instance, otherwise returns nil.

import (
	"go/ast"
	"go/types"

	"golang.org/x/tools/go/ast/astutil"
	"golang.org/x/tools/internal/typeparams"
)

// Callee returns the named target of a function call, if any:
// a function, method, builtin, or variable.
//
// Functions and methods may potentially have type parameters.
func Callee(info *types.Info, call *ast.CallExpr) types.Object {
	fun := astutil.Unparen(call.Fun)

	// Look through type instantiation if necessary.

			base.ErrorfAt(fn.WBPos, 0, "write barrier prohibited by caller; %v%s", fn.Nname, err.String())
			continue
		}

		// Enqueue fn's calls.
		for _, callee := range c.extraCalls[fn] {
			enqueue(fn, callee.target, callee.lineno)
		}
		if fn.NWBRCalls == nil {
			continue
		}
		for _, callee := range *fn.NWBRCalls {
			target := symToFunc[callee.Sym]
			if target != nil {
				enqueue(fn, target, callee.Pos)

// 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
	MOVD	R30, R20	// callee-saved, preserved across the CALL
	MOVD	m_g0(R10), R11
	CMP	R11, g
	BEQ	call	// already on g0
	MOVD	(g_sched+gobuf_sp)(R11), R12
	MOVD	R12, RSP
call:

TEXT crosscall2_trampoline<>(SB),NOSPLIT,$0-0
	JMP	crosscall2(SB)

// Called by C code generated by cmd/cgo.
// func crosscall2(fn, a unsafe.Pointer, n int32, ctxt uintptr)
// Saves C callee-saved registers and calls cgocallback with three arguments.
// fn is the PC of a func(a unsafe.Pointer) function.
TEXT crosscall2(SB),NOSPLIT|NOFRAME,$0
	/*
	 * We still need to save all callee save register as before, and then

.file "gcc_s390x.S"

/*
 * void crosscall_s390x(void (*fn)(void), void *g)
 *
 * Calling into the go tool chain, where all registers are caller save.
 * Called from standard s390x C ABI, where r6-r13, r15, and f8-f15 are
 * callee-save, so they must be saved explicitly.
 */
.globl crosscall_s390x
crosscall_s390x:
	/* save r6-r15 in the register save area of the calling function */

.file "gcc_arm.S"

/*
 * void crosscall1(void (*fn)(void), void (*setg_gcc)(void *g), void *g)
 *
 * Calling into the gc tool chain, where all registers are caller save.
 * Called from standard ARM EABI, where r4-r11 are callee-save, so they
 * must be saved explicitly.
 */
.globl crosscall1
crosscall1:
	push {r4, r5, r6, r7, r8, r9, r10, r11, ip, lr}
	mov r4, r0
	mov r5, r1
	mov r0, r2

#else
#define EXT(s) s
#endif

/*
 * void crosscall1(void (*fn)(void), void (*setg_gcc)(void*), void *g)
 *
 * Calling into the gc tool chain, where all registers are caller save.
 * Called from standard x86 ABI, where %ebp, %ebx, %esi,
 * and %edi are callee-save, so they must be saved explicitly.
 */
.globl EXT(crosscall1)
EXT(crosscall1):
	pushl %ebp
	movl %esp, %ebp
	pushl %ebx
	pushl %esi
	pushl %edi

#else
#define EXT(s) s
#endif

/*
 * void crosscall1(void (*fn)(void), void (*setg_gcc)(void*), void *g)
 *
 * Calling into the gc tool chain, where all registers are caller save.
 * Called from standard x86-64 ABI, where %rbx, %rbp, %r12-%r15
 * are callee-save so they must be saved explicitly.
 * The standard x86-64 ABI passes the three arguments m, g, fn
 * in %rdi, %rsi, %rdx.
 */
.globl EXT(crosscall1)
EXT(crosscall1):

	MOVD    0(R10), g
	MOVD    g_racectx(g), R3        // goroutine racectx aka *ThreadState
	MOVD	R8, R4			// caller pc set by caller in R8
	// void __tsan_func_enter(ThreadState *thr, void *pc);
	MOVD	$__tsan_func_enter(SB), R8
	BR	racecall<>(SB)
	RET

// func runtime·racefuncexit()
// Called from Go instrumented code.
TEXT	runtime·racefuncexit(SB), NOSPLIT, $0-0
	MOVD    runtime·tls_g(SB), R10
	MOVD    0(R10), g