swift234

[simplify-cfg] Refactor simplifyConditional and teach it how to simplify (cond_br (enum_is_tag)) when there is a dominating enum_is_tag on the same value.

This pattern occurs a lot in the following benchmark:

let     loopcount     = 1000000000
let     arraysize     = 100000
let     range          = 100..<200
let     prtrange     = (range.startIndex-2)..<(range.startIndex+2)
var vector          = [Double]( count: 5000, repeatedValue: 0.0 )
let     alfa          = 1.0
for var i=0;i<loopcount;i++ {
  vector[range] = vector[range].map() { $0 + alfa }
}

Swift SVN r22273