Add comments to `destroy_addr` in SIL.rst.
Add comments to `destroy_addr` in SIL.rst.

`destroy_addr` is never semantically a "no-op". Just because an
instruction can be safely eliminated does not mean the instruction has
no semantics! That would be like saying we could move an unknown
memory read below an otherwise dead store!

parkera/swift,benlangmuir/swift,atrick/swift,nathawes/swift,stephentyrone/swift,devincoughlin/swift,benlangmuir/swift,gribozavr/swift,airspeedswift/swift,nathawes/swift,parkera/swift,glessard/swift,apple/swift,CodaFi/swift,aschwaighofer/swift,stephentyrone/swift,benlangmuir/swift,stephentyrone/swift,allevato/swift,tkremenek/swift,ahoppen/swift,harlanhaskins/swift,nathawes/swift,tkremenek/swift,lorentey/swift,allevato/swift,jmgc/swift,allevato/swift,gregomni/swift,karwa/swift,harlanhaskins/swift,stephentyrone/swift,xwu/swift,CodaFi/swift,lorentey/swift,nathawes/swift,CodaFi/swift,aschwaighofer/swift,benlangmuir/swift,roambotics/swift,JGiola/swift,airspeedswift/swift,harlanhaskins/swift,parkera/swift,jmgc/swift,karwa/swift,airspeedswift/swift,atrick/swift,atrick/swift,atrick/swift,karwa/swift,jckarter/swift,devincoughlin/swift,hooman/swift,hooman/swift,JGiola/swift,airspeedswift/swift,tkremenek/swift,glessard/swift,CodaFi/swift,ahoppen/swift,jmgc/swift,sschiau/swift,parkera/swift,lorentey/swift,tkremenek/swift,tkremenek/swift,xwu/swift,karwa/swift,jckarter/swift,aschwaighofer/swift,nathawes/swift,karwa/swift,sschiau/swift,airspeedswift/swift,allevato/swift,JGiola/swift,xwu/swift,rudkx/swift,rudkx/swift,tkremenek/swift,karwa/swift,gregomni/swift,hooman/swift,CodaFi/swift,sschiau/swift,devincoughlin/swift,rudkx/swift,sschiau/swift,harlanhaskins/swift,jmgc/swift,parkera/swift,roambotics/swift,CodaFi/swift,allevato/swift,stephentyrone/swift,aschwaighofer/swift,xwu/swift,devincoughlin/swift,jckarter/swift,ahoppen/swift,harlanhaskins/swift,stephentyrone/swift,hooman/swift,rudkx/swift,nathawes/swift,rudkx/swift,jmgc/swift,sschiau/swift,ahoppen/swift,parkera/swift,sschiau/swift,apple/swift,gribozavr/swift,hooman/swift,apple/swift,jckarter/swift,hooman/swift,devincoughlin/swift,devincoughlin/swift,roambotics/swift,gribozavr/swift,jmgc/swift,ahoppen/swift,karwa/swift,atrick/swift,benlangmuir/swift,allevato/swift,JGiola/swift,nathawes/swift,atrick/swift,harlanhaskins/swift,stephentyrone/swift,roambotics/swift,parkera/swift,lorentey/swift,gribozavr/swift,JGiola/swift,jmgc/swift,glessard/swift,CodaFi/swift,jckarter/swift,benlangmuir/swift,gribozavr/swift,gregomni/swift,apple/swift,lorentey/swift,hooman/swift,lorentey/swift,aschwaighofer/swift,devincoughlin/swift,xwu/swift,xwu/swift,airspeedswift/swift,gribozavr/swift,JGiola/swift,xwu/swift,karwa/swift,lorentey/swift,apple/swift,sschiau/swift,jckarter/swift,airspeedswift/swift,parkera/swift,roambotics/swift,allevato/swift,glessard/swift,gribozavr/swift,aschwaighofer/swift,harlanhaskins/swift,gribozavr/swift,glessard/swift,ahoppen/swift,gregomni/swift,sschiau/swift,rudkx/swift,glessard/swift,gregomni/swift,roambotics/swift,aschwaighofer/swift,lorentey/swift,tkremenek/swift,devincoughlin/swift,apple/swift,jckarter/swift,gregomni/swift