[PATCH] D18712: [LoopUnroll] Fix the way we update DT after complete unrolling.

[Sanjoy Das via llvm-commits]

sanjoy added a comment.

Hi Michael,

How about loops like these:

  define void @f() {
  entry:
    br label %loop.header
  
  loop.header:
    %iv = phi i32 [ 0, %entry ], [ %iv.inc, %latch ]
    %iv.inc = add i32 %iv, 1
    br i1 undef, label %diamond, label %latch
  
  diamond:
    br i1 undef, label %left, label %right
  
  left:
    br i1 undef, label %exit, label %merge
  
  right:
    br i1 undef, label %exit, label %merge
  
  merge:
    br label %latch
  
  latch:
    %end.cond = icmp eq i32 %iv, 1
    br i1 %end.cond, label %exit1, label %loop.header
  
  exit:
    ret void
  
  exit1:
    ret void
  }

?

`exit` is dominated by `diamond` (not a loop exit), but after unrolling `exit` becomes dominated by `loop.header`.


http://reviews.llvm.org/D18712