What is varKills in MemSSA used for?

[canliture]

Could someone give me an example to show the importance or useness of varKills? Thanks!

SVF/svf/lib/MSSA/MemSSA.cpp

Lines 126 to 137 in 6620a5f

	// 2. find global names (region name before renaming) of each memory region,
	// collect used mrs in usedRegs, and collect its def basic block in reg2BBMap
	// in the form of mu(r) and r = chi (r)
	// a) mu(r):
	// if(r \not\in varKills) global = global \cup r
	// b) r = chi(r):
	// if(r \not\in varKills) global = global \cup r
	// varKills = varKills \cup r
	// block(r) = block(r) \cup bb_{chi}
	/// get all reachable basic blocks from function entry
	/// ignore dead basic blocks

[yuleisui]

varKills are vars are not live anymore to be put in SSA.