MOVQ	DX, X2 // X2 = sign bit mask
	CVTTSD2SQ	X0, AX
	ANDNPD	X0, X2 // X2 = sign
	CVTSQ2SD	AX, X1	// X1 = float(int(x))
	CMPSD	X1, X0, 2 // compare LE; X0 = 0xffffffffffffffff or 0
	ORPD	X2, X1 // if X1 = 0.0, incorporate sign
	MOVSD	$1.0, X3
	ANDNPD	X3, X0
	ORPD	X2, X0 // if float(int(x)) <= x {X0 = 1} else {X0 = -0}
	ADDSD	X1, X0
	MOVSD	X0, ret+8(FP)
	RET
isBig_ceil:
	MOVQ	AX, ret+8(FP)
	RET

// func archTrunc(x float64) float64

	CMPQ    AX, BX
	JLE     isInfOrNaN
	// f1, ki := math.Frexp(x); k := float64(ki)
	MOVQ    BX, X0
	MOVQ    $0x000FFFFFFFFFFFFF, AX
	MOVQ    AX, X2
	ANDPD   X0, X2
	MOVSD   $0.5, X0 // 0x3FE0000000000000
	ORPD    X0, X2 // X2= f1
	SHRQ    $52, BX
	ANDL    $0x7FF, BX
	SUBL    $0x3FE, BX
	XORPS   X1, X1 // break dependency for CVTSL2SD
	CVTSL2SD BX, X1 // x1= k, x2= f1
	// if f1 < math.Sqrt2/2 { k -= 1; f1 *= 2 }