// of the mantissa. It will panic if the truncation results in lost information.
func truncate64Fto32F(f float64) float32 {
	if !isExactFloat32(f) {
		panic("truncate64Fto32F: truncation is not exact")
	}
	if !math.IsNaN(f) {
		return float32(f)
	}
	// NaN bit patterns aren't necessarily preserved across conversion
	// instructions so we need to do the conversion manually.
	b := math.Float64bits(f)

(FMOVDstore [off] {sym} ptr (MTVSRD x) mem) => (MOVDstore [off] {sym} ptr x mem)
(MOVDstore [off] {sym} ptr (MFVSRD x) mem) => (FMOVDstore [off] {sym} ptr x mem)

(MTVSRD (MOVDconst [c])) && !math.IsNaN(math.Float64frombits(uint64(c))) => (FMOVDconst [math.Float64frombits(uint64(c))])
(MFVSRD (FMOVDconst [c])) => (MOVDconst [int64(math.Float64bits(c))])