// if called from a non-go thread.
	XORPS	X15, X15
	XORQ	R14, R14

	get_tls(AX)
	CMPQ	AX, $0
	JE	2(PC)
	// Exception from Go thread, set R14.
	MOVQ	g(AX), R14

	// Reserve space for spill slots.
	ADJSP	$16
	MOVQ	CX, AX
	MOVQ	DX, BX
	// Calling ABIInternal because TLS might be nil.
	CALL	runtime·sigtrampgo<ABIInternal>(SB)
	// Return value is already stored in AX.

	ADJSP	$-16

	// does not own the mutex and competes with new arriving goroutines over
	// the ownership. New arriving goroutines have an advantage -- they are
	// already running on CPU and there can be lots of them, so a woken up
	// waiter has good chances of losing. In such case it is queued at front
	// of the wait queue. If a waiter fails to acquire the mutex for more than 1ms,
	// it switches mutex to the starvation mode.
	//