Don't call reserveCapacity if constructing an empty uninitalized array.
Don't call reserveCapacity if constructing an empty uninitalized array.

This speeds up empty array literals and fixes the performance regression in the Havlak benchmark.
See <rdar://problem/18480488> PerfReg: Havlak - Megaclang - r353047-r353195 - 3x



Swift SVN r22427

jckarter/swift,shahmishal/swift,JGiola/swift,dduan/swift,hooman/swift,mightydeveloper/swift,hooman/swift,karwa/swift,practicalswift/swift,nathawes/swift,gregomni/swift,djwbrown/swift,uasys/swift,gottesmm/swift,gribozavr/swift,Ivacker/swift,therealbnut/swift,ahoppen/swift,swiftix/swift.old,emilstahl/swift,rudkx/swift,harlanhaskins/swift,dduan/swift,apple/swift,CodaFi/swift,SwiftAndroid/swift,sdulal/swift,frootloops/swift,JGiola/swift,hooman/swift,return/swift,OscarSwanros/swift,shajrawi/swift,frootloops/swift,shahmishal/swift,parkera/swift,devincoughlin/swift,swiftix/swift.old,tardieu/swift,allevato/swift,glessard/swift,jopamer/swift,codestergit/swift,SwiftAndroid/swift,jmgc/swift,nathawes/swift,xedin/swift,danielmartin/swift,austinzheng/swift,djwbrown/swift,tinysun212/swift-windows,russbishop/swift,allevato/swift,huonw/swift,lorentey/swift,tjw/swift,jopamer/swift,therealbnut/swift,CodaFi/swift,airspeedswift/swift,IngmarStein/swift,gottesmm/swift,amraboelela/swift,atrick/swift,emilstahl/swift,uasys/swift,bitjammer/swift,ahoppen/swift,huonw/swift,xedin/swift,bitjammer/swift,alblue/swift,shahmishal/swift,atrick/swift,stephentyrone/swift,dduan/swift,sschiau/swift,LeoShimonaka/swift,arvedviehweger/swift,kentya6/swift,hughbe/swift,kentya6/swift,karwa/swift,modocache/swift,cbrentharris/swift,hooman/swift,gmilos/swift,xwu/swift,MukeshKumarS/Swift,allevato/swift,harlanhaskins/swift,kentya6/swift,jckarter/swift,lorentey/swift,kperryua/swift,felix91gr/swift,nathawes/swift,kperryua/swift,brentdax/swift,amraboelela/swift,tkremenek/swift,benlangmuir/swift,allevato/swift,frootloops/swift,parkera/swift,practicalswift/swift,IngmarStein/swift,brentdax/swift,austinzheng/swift,tardieu/swift,kperryua/swift,russbishop/swift,therealbnut/swift,sdulal/swift,CodaFi/swift,amraboelela/swift,aschwaighofer/swift,xedin/swift,emilstahl/swift,tinysun212/swift-windows,jmgc/swift,lorentey/swift,kstaring/swift,nathawes/swift,IngmarStein/swift,zisko/swift,jtbandes/swift,parkera/swift,aschwaighofer/swift,atrick/swift,kperryua/swift,airspeedswift/swift,return/swift,parkera/swift,slavapestov/swift,tjw/swift,MukeshKumarS/Swift,adrfer/swift,Jnosh/swift,jckarter/swift,return/swift,airspeedswift/swift,jopamer/swift,return/swift,felix91gr/swift,dreamsxin/swift,jckarter/swift,rudkx/swift,MukeshKumarS/Swift,gregomni/swift,shajrawi/swift,austinzheng/swift,frootloops/swift,adrfer/swift,Jnosh/swift,danielmartin/swift,jmgc/swift,apple/swift,felix91gr/swift,parkera/swift,arvedviehweger/swift,khizkhiz/swift,uasys/swift,swiftix/swift,harlanhaskins/swift,sschiau/swift,natecook1000/swift,JGiola/swift,gottesmm/swift,ken0nek/swift,OscarSwanros/swift,benlangmuir/swift,Ivacker/swift,swiftix/swift,brentdax/swift,emilstahl/swift,MukeshKumarS/Swift,zisko/swift,mightydeveloper/swift,ben-ng/swift,roambotics/swift,KrishMunot/swift,jmgc/swift,felix91gr/swift,johnno1962d/swift,brentdax/swift,slavapestov/swift,bitjammer/swift,manavgabhawala/swift,modocache/swift,jckarter/swift,shajrawi/swift,dduan/swift,IngmarStein/swift,cbrentharris/swift,rudkx/swift,deyton/swift,sdulal/swift,uasys/swift,tkremenek/swift,SwiftAndroid/swift,stephentyrone/swift,mightydeveloper/swift,slavapestov/swift,slavapestov/swift,karwa/swift,dduan/swift,danielmartin/swift,OscarSwanros/swift,swiftix/swift,sschiau/swift,natecook1000/swift,austinzheng/swift,roambotics/swift,tardieu/swift,ken0nek/swift,lorentey/swift,allevato/swift,shahmishal/swift,glessard/swift,sdulal/swift,roambotics/swift,Jnosh/swift,Ivacker/swift,atrick/swift,jopamer/swift,tinysun212/swift-windows,parkera/swift,aschwaighofer/swift,manavgabhawala/swift,djwbrown/swift,calebd/swift,apple/swift,dduan/swift,uasys/swift,swiftix/swift.old,harlanhaskins/swift,karwa/swift,hughbe/swift,lorentey/swift,tinysun212/swift-windows,tardieu/swift,ben-ng/swift,shajrawi/swift,milseman/swift,gribozavr/swift,Ivacker/swift,kstaring/swift,gmilos/swift,huonw/swift,milseman/swift,mightydeveloper/swift,hooman/swift,KrishMunot/swift,calebd/swift,tinysun212/swift-windows,glessard/swift,adrfer/swift,swiftix/swift.old,LeoShimonaka/swift,KrishMunot/swift,airspeedswift/swift,austinzheng/swift,hughbe/swift,khizkhiz/swift,ben-ng/swift,sschiau/swift,sschiau/swift,JGiola/swift,MukeshKumarS/Swift,therealbnut/swift,shajrawi/swift,shahmishal/swift,cbrentharris/swift,karwa/swift,LeoShimonaka/swift,kstaring/swift,gregomni/swift,adrfer/swift,CodaFi/swift,KrishMunot/swift,benlangmuir/swift,cbrentharris/swift,alblue/swift,aschwaighofer/swift,uasys/swift,ahoppen/swift,harlanhaskins/swift,slavapestov/swift,ahoppen/swift,gribozavr/swift,gregomni/swift,Jnosh/swift,glessard/swift,johnno1962d/swift,tjw/swift,practicalswift/swift,Jnosh/swift,glessard/swift,SwiftAndroid/swift,JaSpa/swift,JaSpa/swift,rudkx/swift,stephentyrone/swift,emilstahl/swift,tkremenek/swift,tardieu/swift,JaSpa/swift,kusl/swift,calebd/swift,codestergit/swift,ken0nek/swift,kusl/swift,JGiola/swift,jopamer/swift,gribozavr/swift,amraboelela/swift,kstaring/swift,kentya6/swift,deyton/swift,hughbe/swift,sdulal/swift,arvedviehweger/swift,jckarter/swift,stephentyrone/swift,natecook1000/swift,practicalswift/swift,tkremenek/swift,adrfer/swift,arvedviehweger/swift,gottesmm/swift,glessard/swift,return/swift,LeoShimonaka/swift,ben-ng/swift,harlanhaskins/swift,airspeedswift/swift,gregomni/swift,deyton/swift,nathawes/swift,atrick/swift,milseman/swift,Jnosh/swift,calebd/swift,zisko/swift,zisko/swift,kusl/swift,jmgc/swift,LeoShimonaka/swift,ken0nek/swift,stephentyrone/swift,amraboelela/swift,shajrawi/swift,roambotics/swift,amraboelela/swift,johnno1962d/swift,zisko/swift,gribozavr/swift,gottesmm/swift,bitjammer/swift,cbrentharris/swift,roambotics/swift,zisko/swift,hooman/swift,codestergit/swift,benlangmuir/swift,karwa/swift,parkera/swift,KrishMunot/swift,jopamer/swift,russbishop/swift,kperryua/swift,kperryua/swift,kentya6/swift,jtbandes/swift,swiftix/swift.old,swiftix/swift.old,jmgc/swift,SwiftAndroid/swift,kperryua/swift,apple/swift,devincoughlin/swift,sdulal/swift,dduan/swift,apple/swift,xedin/swift,alblue/swift,lorentey/swift,sschiau/swift,brentdax/swift,brentdax/swift,gribozavr/swift,kusl/swift,jtbandes/swift,Ivacker/swift,tinysun212/swift-windows,kentya6/swift,felix91gr/swift,adrfer/swift,devincoughlin/swift,kentya6/swift,xedin/swift,xwu/swift,shajrawi/swift,gmilos/swift,jtbandes/swift,djwbrown/swift,LeoShimonaka/swift,calebd/swift,arvedviehweger/swift,IngmarStein/swift,therealbnut/swift,ahoppen/swift,devincoughlin/swift,apple/swift,airspeedswift/swift,nathawes/swift,natecook1000/swift,LeoShimonaka/swift,manavgabhawala/swift,xwu/swift,kusl/swift,khizkhiz/swift,danielmartin/swift,Ivacker/swift,swiftix/swift,IngmarStein/swift,swiftix/swift,karwa/swift,felix91gr/swift,djwbrown/swift,sdulal/swift,shajrawi/swift,natecook1000/swift,KrishMunot/swift,stephentyrone/swift,manavgabhawala/swift,natecook1000/swift,practicalswift/swift,devincoughlin/swift,OscarSwanros/swift,JaSpa/swift,sschiau/swift,aschwaighofer/swift,mightydeveloper/swift,mightydeveloper/swift,aschwaighofer/swift,nathawes/swift,MukeshKumarS/Swift,calebd/swift,calebd/swift,xedin/swift,alblue/swift,allevato/swift,johnno1962d/swift,shahmishal/swift,shahmishal/swift,djwbrown/swift,gmilos/swift,amraboelela/swift,kstaring/swift,huonw/swift,kstaring/swift,xwu/swift,rudkx/swift,practicalswift/swift,roambotics/swift,cbrentharris/swift,JaSpa/swift,practicalswift/swift,emilstahl/swift,manavgabhawala/swift,shahmishal/swift,rudkx/swift,uasys/swift,jmgc/swift,gottesmm/swift,jtbandes/swift,deyton/swift,huonw/swift,devincoughlin/swift,harlanhaskins/swift,manavgabhawala/swift,adrfer/swift,xwu/swift,tinysun212/swift-windows,tkremenek/swift,JGiola/swift,jopamer/swift,natecook1000/swift,djwbrown/swift,emilstahl/swift,swiftix/swift,khizkhiz/swift,kstaring/swift,zisko/swift,tjw/swift,milseman/swift,CodaFi/swift,therealbnut/swift,milseman/swift,hughbe/swift,kentya6/swift,modocache/swift,hughbe/swift,sschiau/swift,parkera/swift,LeoShimonaka/swift,huonw/swift,return/swift,felix91gr/swift,devincoughlin/swift,gribozavr/swift,cbrentharris/swift,practicalswift/swift,ben-ng/swift,xedin/swift,slavapestov/swift,bitjammer/swift,khizkhiz/swift,manavgabhawala/swift,OscarSwanros/swift,tjw/swift,mightydeveloper/swift,alblue/swift,russbishop/swift,sdulal/swift,karwa/swift,SwiftAndroid/swift,frootloops/swift,Ivacker/swift,xwu/swift,brentdax/swift,CodaFi/swift,swiftix/swift,tardieu/swift,cbrentharris/swift,IngmarStein/swift,benlangmuir/swift,modocache/swift,ken0nek/swift,johnno1962d/swift,arvedviehweger/swift,swiftix/swift.old,ahoppen/swift,deyton/swift,therealbnut/swift,tkremenek/swift,danielmartin/swift,codestergit/swift,johnno1962d/swift,ken0nek/swift,benlangmuir/swift,atrick/swift,gregomni/swift,JaSpa/swift,tardieu/swift,ben-ng/swift,lorentey/swift,johnno1962d/swift,bitjammer/swift,gmilos/swift,Ivacker/swift,gribozavr/swift,modocache/swift,OscarSwanros/swift,modocache/swift,JaSpa/swift,codestergit/swift,tkremenek/swift,MukeshKumarS/Swift,alblue/swift,tjw/swift,swiftix/swift.old,Jnosh/swift,devincoughlin/swift,codestergit/swift,arvedviehweger/swift,danielmartin/swift,ben-ng/swift,deyton/swift,gmilos/swift,hooman/swift,frootloops/swift,khizkhiz/swift,tjw/swift,ken0nek/swift,allevato/swift,jtbandes/swift,russbishop/swift,huonw/swift,SwiftAndroid/swift,modocache/swift,CodaFi/swift,kusl/swift,danielmartin/swift,mightydeveloper/swift,jtbandes/swift,milseman/swift,OscarSwanros/swift,slavapestov/swift,austinzheng/swift,gottesmm/swift,russbishop/swift,xedin/swift,airspeedswift/swift,xwu/swift,emilstahl/swift,khizkhiz/swift,kusl/swift,lorentey/swift,kusl/swift,alblue/swift,bitjammer/swift,codestergit/swift,deyton/swift,frootloops/swift,aschwaighofer/swift,dreamsxin/swift,jckarter/swift,stephentyrone/swift,gmilos/swift,return/swift,KrishMunot/swift,hughbe/swift,milseman/swift,russbishop/swift,austinzheng/swift