[Runtime] Initialize function pointers with the original values, check against those values to call directly.
[Runtime] Initialize function pointers with the original values, check against those values to call directly.

Instruments relies on the old values being there so it can call the original implementation. This has very slightly worse codegen but the impact should be minimal.
nathawes/swift,harlanhaskins/swift,stephentyrone/swift,lorentey/swift,devincoughlin/swift,hooman/swift,harlanhaskins/swift,sschiau/swift,stephentyrone/swift,CodaFi/swift,glessard/swift,airspeedswift/swift,ahoppen/swift,xwu/swift,airspeedswift/swift,tkremenek/swift,parkera/swift,devincoughlin/swift,gribozavr/swift,jckarter/swift,stephentyrone/swift,parkera/swift,sschiau/swift,karwa/swift,tkremenek/swift,nathawes/swift,ahoppen/swift,devincoughlin/swift,nathawes/swift,JGiola/swift,hooman/swift,apple/swift,xwu/swift,devincoughlin/swift,gribozavr/swift,nathawes/swift,roambotics/swift,harlanhaskins/swift,xwu/swift,devincoughlin/swift,rudkx/swift,hooman/swift,hooman/swift,sschiau/swift,lorentey/swift,ahoppen/swift,CodaFi/swift,parkera/swift,aschwaighofer/swift,hooman/swift,benlangmuir/swift,benlangmuir/swift,gribozavr/swift,xwu/swift,ahoppen/swift,jmgc/swift,devincoughlin/swift,rudkx/swift,karwa/swift,atrick/swift,aschwaighofer/swift,glessard/swift,gribozavr/swift,jmgc/swift,aschwaighofer/swift,tkremenek/swift,roambotics/swift,atrick/swift,glessard/swift,tkremenek/swift,atrick/swift,benlangmuir/swift,karwa/swift,gregomni/swift,apple/swift,allevato/swift,allevato/swift,xwu/swift,harlanhaskins/swift,gribozavr/swift,stephentyrone/swift,gregomni/swift,karwa/swift,apple/swift,airspeedswift/swift,CodaFi/swift,aschwaighofer/swift,jmgc/swift,hooman/swift,lorentey/swift,jckarter/swift,karwa/swift,airspeedswift/swift,gregomni/swift,apple/swift,devincoughlin/swift,allevato/swift,parkera/swift,aschwaighofer/swift,CodaFi/swift,jmgc/swift,tkremenek/swift,xwu/swift,roambotics/swift,nathawes/swift,xwu/swift,parkera/swift,atrick/swift,parkera/swift,hooman/swift,atrick/swift,lorentey/swift,CodaFi/swift,lorentey/swift,allevato/swift,ahoppen/swift,karwa/swift,rudkx/swift,airspeedswift/swift,glessard/swift,gribozavr/swift,gregomni/swift,parkera/swift,tkremenek/swift,nathawes/swift,rudkx/swift,jmgc/swift,gregomni/swift,sschiau/swift,nathawes/swift,allevato/swift,allevato/swift,airspeedswift/swift,jckarter/swift,harlanhaskins/swift,glessard/swift,jmgc/swift,tkremenek/swift,rudkx/swift,JGiola/swift,lorentey/swift,airspeedswift/swift,lorentey/swift,roambotics/swift,stephentyrone/swift,karwa/swift,apple/swift,gribozavr/swift,gregomni/swift,sschiau/swift,CodaFi/swift,roambotics/swift,atrick/swift,sschiau/swift,glessard/swift,harlanhaskins/swift,gribozavr/swift,lorentey/swift,jckarter/swift,stephentyrone/swift,roambotics/swift,jckarter/swift,karwa/swift,jckarter/swift,JGiola/swift,jmgc/swift,JGiola/swift,sschiau/swift,parkera/swift,JGiola/swift,CodaFi/swift,benlangmuir/swift,rudkx/swift,benlangmuir/swift,JGiola/swift,sschiau/swift,devincoughlin/swift,benlangmuir/swift,aschwaighofer/swift,stephentyrone/swift,harlanhaskins/swift,aschwaighofer/swift,allevato/swift,jckarter/swift,apple/swift,ahoppen/swift