Fix possible iterator invalidation in SILMem2Reg
Fix possible iterator invalidation in SILMem2Reg

JGiola/swift,roambotics/swift,glessard/swift,benlangmuir/swift,glessard/swift,roambotics/swift,apple/swift,benlangmuir/swift,benlangmuir/swift,JGiola/swift,apple/swift,roambotics/swift,glessard/swift,apple/swift,benlangmuir/swift,apple/swift,JGiola/swift,JGiola/swift,benlangmuir/swift,JGiola/swift,benlangmuir/swift,roambotics/swift,glessard/swift,glessard/swift,apple/swift,JGiola/swift,roambotics/swift,roambotics/swift,glessard/swift,apple/swift