[SILMem2Reg] Added explanation to assert.
[SILMem2Reg] Added explanation to assert.

xwu/swift,JGiola/swift,gregomni/swift,ahoppen/swift,apple/swift,roambotics/swift,JGiola/swift,glessard/swift,benlangmuir/swift,roambotics/swift,JGiola/swift,roambotics/swift,rudkx/swift,atrick/swift,xwu/swift,xwu/swift,gregomni/swift,rudkx/swift,apple/swift,apple/swift,rudkx/swift,apple/swift,roambotics/swift,benlangmuir/swift,ahoppen/swift,ahoppen/swift,rudkx/swift,atrick/swift,gregomni/swift,xwu/swift,roambotics/swift,gregomni/swift,apple/swift,benlangmuir/swift,xwu/swift,gregomni/swift,ahoppen/swift,ahoppen/swift,atrick/swift,benlangmuir/swift,glessard/swift,xwu/swift,atrick/swift,glessard/swift,atrick/swift,JGiola/swift,glessard/swift,glessard/swift,atrick/swift,glessard/swift,roambotics/swift,benlangmuir/swift,benlangmuir/swift,gregomni/swift,JGiola/swift,ahoppen/swift,apple/swift,xwu/swift,rudkx/swift,JGiola/swift,rudkx/swift