for c := sdom[b.ID].child; c != nil; c = sdom[c.ID].sibling {
		addDFphis(x, h, c, f, defForUses, newphis, sdom) // TODO: convert to explicit stack from recursion.
	}
}

// findLastMems maps block ids to last memory-output op in a block, if any.
func findLastMems(f *Func) []*Value {

	var stores []*Value
	lastMems := f.Cache.allocValueSlice(f.NumBlocks())
	defer f.Cache.freeValueSlice(lastMems)
	storeUse := f.newSparseSet(f.NumValues())