swift234

SILGen: Don't box 'let' bindings inside 'switch' patterns.

If all of the bindings in a pattern column are 'let' bindings, don't box the binding. If there is any 'var' in the column, conservatively fall back to binding a box. Factor out the logic for producing an initialization for a variable into an new emitInitializationForVarDecl method that SILGenPattern can use. Add a 'copyInto' method to RValue that can bind a copy of an rvalue to an Initialization.

This doesn't use Chris's new +0 ManagedValue optimization yet, so we end up with an extra copy_value when the value is bound that might still be avoidable.

Swift SVN r12903