{name: "MOVSSloadidx4", argLength: 3, reg: fploadidx, asm: "MOVSS", scale: 4, aux: "SymOff", symEffect: "Read"},
		{name: "MOVSDloadidx1", argLength: 3, reg: fploadidx, asm: "MOVSD", scale: 1, aux: "SymOff", symEffect: "Read"},
		{name: "MOVSDloadidx8", argLength: 3, reg: fploadidx, asm: "MOVSD", scale: 8, aux: "SymOff", symEffect: "Read"},

		// MOVSxstore: floating-point stores

		{name: "MOVBload", argLength: 2, reg: gpload, aux: "SymOff", asm: "MOVB", typ: "Int8", faultOnNilArg0: true, symEffect: "Read"},     // load from arg0 + auxInt + aux.  arg1=mem.
		{name: "MOVBUload", argLength: 2, reg: gpload, aux: "SymOff", asm: "MOVBU", typ: "UInt8", faultOnNilArg0: true, symEffect: "Read"},  // load from arg0 + auxInt + aux.  arg1=mem.

		{name: "MOVHload", argLength: 2, reg: gpload, asm: "MOVH", aux: "SymOff", typ: "Int16", faultOnNilArg0: true, symEffect: "Read"},    // 16 bits, sign extend
		{name: "MOVWload", argLength: 2, reg: gpload, asm: "MOVW", aux: "SymOff", typ: "Int32", faultOnNilArg0: true, symEffect: "Read"},    // 32 bits, sign extend

		symEffect:      SymWrite,
		asm:            x86.AMOVSS,
		reg: regInfo{
			inputs: []inputInfo{
				{1, 65280}, // X0 X1 X2 X3 X4 X5 X6 X7
				{0, 65791}, // AX CX DX BX SP BP SI DI SB
			},
		},
	},
	{
		name:           "MOVSDstore",
		auxType:        auxSymOff,
		argLen:         3,
		faultOnNilArg0: true,
		symEffect:      SymWrite,
		asm:            x86.AMOVSD,

		{name: "MOVBload", argLength: 2, reg: gpload, aux: "SymOff", asm: "MOVB", typ: "Int8", faultOnNilArg0: true, symEffect: "Read"},       // load from arg0 + auxInt + aux.  arg1=mem.

		{name: "MOVHload", argLength: 2, reg: gpload, asm: "MOVH", aux: "SymOff", typ: "Int16", faultOnNilArg0: true, symEffect: "Read"},    // load 2 bytes sign extend
		{name: "MOVHZload", argLength: 2, reg: gpload, asm: "MOVHZ", aux: "SymOff", typ: "UInt16", faultOnNilArg0: true, symEffect: "Read"}, // load 2 bytes zero extend

)

// A SymEffect describes the effect that an SSA Value has on the variable
// identified by the symbol in its Aux field.
type SymEffect int8

const (
	SymRead SymEffect = 1 << iota
	SymWrite
	SymAddr

	SymRdWr = SymRead | SymWrite

	SymNone SymEffect = 0
)

// A Sym represents a symbolic offset from a base register.

	// If the variable is a local, the base pointer will be SP and
	// the Aux field will be a *gc.Node.
	{name: "Addr", argLength: 1, aux: "Sym", symEffect: "Addr"},      // Address of a variable.  Arg0=SB.  Aux identifies the variable.
	{name: "LocalAddr", argLength: 2, aux: "Sym", symEffect: "Addr"}, // Address of a variable.  Arg0=SP. Arg1=mem. Aux identifies the variable.

			args = args[1:]
		}

		// The code below assumes that we have handled all the ops
		// with sym effects already. Sanity check that here.
		// Ignore Args since they can't be autos.
		if v.Op.SymEffect() != SymNone && v.Op != OpArg {
			panic("unhandled op with sym effect")
		}

		if v.Uses == 0 && v.Op != OpNilCheck && !v.Op.IsCall() && !v.Op.HasSideEffects() || len(args) == 0 {

		return -1, 0
	}

	if pos, ok := lv.idx[n]; ok {
		return pos, effect
	}
	return -1, 0
}

// affectedVar returns the *ir.Name node affected by v.
func affectedVar(v *ssa.Value) (*ir.Name, ssa.SymEffect) {
	// Special cases.
	switch v.Op {
	case ssa.OpLoadReg:
		n, _ := ssa.AutoVar(v.Args[0])
		return n, ssa.SymRead
	case ssa.OpStoreReg:
		n, _ := ssa.AutoVar(v)
		return n, ssa.SymWrite