// atomic ops

		// load from arg0. arg1=mem.
		// returns <value,memory> so they can be properly ordered with other loads.
		// SYNC
		// MOV(B|W)	(Rarg0), Rout
		// SYNC
		{name: "LoweredAtomicLoad8", argLength: 2, reg: gpload, faultOnNilArg0: true},
		{name: "LoweredAtomicLoad32", argLength: 2, reg: gpload, faultOnNilArg0: true},

		// store arg1 to arg0. arg2=mem. returns memory.
		// SYNC

			faultOnNilArg0: true,
			faultOnNilArg1: true,
		},

		// atomic loads.
		// load from arg0. arg1=mem.
		// returns <value,memory> so they can be properly ordered with other loads.
		{name: "LoweredAtomicLoad8", argLength: 2, reg: gpload, faultOnNilArg0: true},
		{name: "LoweredAtomicLoad32", argLength: 2, reg: gpload, faultOnNilArg0: true},
		{name: "LoweredAtomicLoad64", argLength: 2, reg: gpload, faultOnNilArg0: true},

		// atomic loads.
		// load from arg0. arg1=mem.
		// returns <value,memory> so they can be properly ordered with other loads.
		{name: "LoweredAtomicLoad8", argLength: 2, reg: gpload, faultOnNilArg0: true},
		{name: "LoweredAtomicLoad32", argLength: 2, reg: gpload, faultOnNilArg0: true},
		{name: "LoweredAtomicLoad64", argLength: 2, reg: gpload, faultOnNilArg0: true},

			faultOnNilArg0: true,
			faultOnNilArg1: true,
		},

		// Atomic loads.
		// load from arg0. arg1=mem.
		// returns <value,memory> so they can be properly ordered with other loads.
		{name: "LoweredAtomicLoad8", argLength: 2, reg: gpload, faultOnNilArg0: true},
		{name: "LoweredAtomicLoad32", argLength: 2, reg: gpload, faultOnNilArg0: true},
		{name: "LoweredAtomicLoad64", argLength: 2, reg: gpload, faultOnNilArg0: true},

(MOVWUreg x:(MOVBUload _ _)) => (MOVDreg x)
(MOVWUreg x:(MOVHUload _ _)) => (MOVDreg x)
(MOVWUreg x:(MOVWUload _ _)) => (MOVDreg x)

// Avoid zero extension after properly typed atomic operation.
(MOVBUreg x:(Select0 (LoweredAtomicLoad8 _ _))) => (MOVDreg x)
(MOVBUreg x:(Select0 (LoweredAtomicCas32 _ _ _ _))) => (MOVDreg x)
(MOVBUreg x:(Select0 (LoweredAtomicCas64 _ _ _ _))) => (MOVDreg x)

// Avoid sign extension after word arithmetic.

		{name: "LoweredAtomicStore64", argLength: 3, reg: gpstore, typ: "Mem", aux: "Int64", faultOnNilArg0: true, hasSideEffects: true},

		{name: "LoweredAtomicLoad8", argLength: 2, reg: gpload, typ: "UInt8", aux: "Int64", clobberFlags: true, faultOnNilArg0: true},
		{name: "LoweredAtomicLoad32", argLength: 2, reg: gpload, typ: "UInt32", aux: "Int64", clobberFlags: true, faultOnNilArg0: true},