swift234

enhance the optimizer to delete release(allocate()) pairs.  This is enough to zap 2 of
them from the stdlib: ine from Format.printString.String, and one from Char.printFormatted.

This is also enough to resolve rdar://11542743, allowing us to optimize:

func maxtest(x : Int) -> Int {
  return max(x, 0)
}

into:

define i64 @_T1t7maxtestFT1xNSs5Int64_S0_(i64 %x) nounwind {
entry:
  %0 = icmp sgt i64 %x, 0
  %x.y.i = select i1 %0, i64 %x, i64 0
  ret i64 %x.y.i
}

Instead of the mess of retains and releases shown in 11542743.



Swift SVN r2037