(ANDconst [c] (MOVWZreg x)) => (ANDconst [c&0xFFFFFFFF] x)

// Eliminate unnecessary sign/zero extend following right shift
(MOV(B|H|W)Zreg (SRWconst [c] (MOVBZreg x))) => (SRWconst [c] (MOVBZreg x))
(MOV(H|W)Zreg (SRWconst [c] (MOVHZreg x))) => (SRWconst [c] (MOVHZreg x))
(MOVWZreg (SRWconst [c] (MOVWZreg x))) => (SRWconst [c] (MOVWZreg x))
(MOV(B|H|W)reg (SRAWconst [c] (MOVBreg x))) => (SRAWconst [c] (MOVBreg x))

			break
		}
		c := auxIntToInt64(y.AuxInt)
		if !(uint64(c) <= 0xFF) {
			break
		}
		v.copyOf(y)
		return true
	}
	// match: (MOVBZreg (SRWconst [c] (MOVBZreg x)))
	// result: (SRWconst [c] (MOVBZreg x))
	for {
		if v_0.Op != OpPPC64SRWconst {
			break
		}
		c := auxIntToInt64(v_0.AuxInt)
		v_0_0 := v_0.Args[0]
		if v_0_0.Op != OpPPC64MOVBZreg {
			break

// and return mask & m.
func mergePPC64RShiftMask(m, s, nbits int64) int64 {
	smask := uint64((1<<uint(nbits))-1) >> uint(s)
	return m & int64(smask)
}

// Combine (ANDconst [m] (SRWconst [s])) into (RLWINM [y]) or return 0
func mergePPC64AndSrwi(m, s int64) int64 {
	mask := mergePPC64RShiftMask(m, s, 32)
	if !isPPC64WordRotateMask(mask) {
		return 0
	}