(CLRLSLDI [c] (SRDconst [s] x)) && mergePPC64ClrlsldiSrd(int64(c),s) != 0 => (RLWINM [mergePPC64ClrlsldiSrd(int64(c),s)] x)
(SLDconst [l] (SRWconst [r] x)) && mergePPC64SldiSrw(l,r) != 0 => (RLWINM [mergePPC64SldiSrw(l,r)] x)
// The following reduction shows up frequently too. e.g b[(x>>14)&0xFF]
(CLRLSLDI [c] i:(RLWINM [s] x)) && mergePPC64ClrlsldiRlwinm(c,s) != 0 => (RLWINM [mergePPC64ClrlsldiRlwinm(c,s)] x)

	}
	return encodePPC64RotateMask(r_3, int64(mask_3), 32)
}

// Compute the encoded RLWINM constant from combining (SLDconst [sld] (SRWconst [srw] x)),
// or return 0 if they cannot be combined.
func mergePPC64SldiSrw(sld, srw int64) int64 {
	if sld > srw || srw >= 32 {
		return 0
	}
	mask_r := uint32(0xFFFFFFFF) >> uint(srw)
	mask_l := uint32(0xFFFFFFFF) >> uint(sld)
	mask := (mask_r & mask_l) << uint(sld)