},
			clobberFlags:   true,
			faultOnNilArg0: true,
			faultOnNilArg1: true,
		},

		// Scheduler ensures LoweredGetClosurePtr occurs only in entry block,
		// and sorts it to the very beginning of the block to prevent other
		// use of R26 (arm64.REGCTXT, the closure pointer)
		{name: "LoweredGetClosurePtr", reg: regInfo{outputs: []regMask{buildReg("R26")}}, zeroWidth: true},

				return !opcodeTable[v.Op].zeroWidth
			} else {
				return v.Op == OpInitMem
			}
		}

		// Examine the prolog portion of the block to process special
		// zero-width ops such as Arg, Phi, LoweredGetClosurePtr (etc)
		// whose lifetimes begin at the block starting point. In an
		// entry block, allow for the possibility that we may see Arg
		// ops that appear _after_ other non-zero-width operations.
		// Example:

// Lowering calls
(StaticCall ...) => (CALLstatic ...)
(ClosureCall ...) => (CALLclosure ...)
(InterCall ...) => (CALLinter ...)
(TailCall ...) => (CALLtail ...)

// Miscellaneous
(GetClosurePtr ...) => (LoweredGetClosurePtr ...)
(GetCallerSP ...) => (LoweredGetCallerSP ...)
(GetCallerPC ...) => (LoweredGetCallerPC ...)
(IsNonNil ptr) => (NotEqual (CMPconst [0] ptr))
(IsInBounds idx len) => (LessThan (CMPU idx len))