[llvm-commits] [patch] Add dominance computation for edges

[Rafael Espíndola]

In LLVM the only value that is defined in an edge is the return value
of an invoke. There are cases however where a fact is true only   in
areas dominated by and edge. For example, in

define i32 @f(i32 %x) {
bb0:
  %cmp = icmp eq i32 %x, 0
  br i1 %cmp, label %bb2, label %bb1
bb1:
  br label %bb2
bb2:
  %cond = phi i32 [ %x, %bb0 ], [ 0, %bb1 ]
  %foo = add i32 %cond, %x
  ret i32 %foo
}

We can replace x with 0 in cond, but not in foo.

The attached patch refactors the code we have to handle invoke so that
it is available to clients that want to know if a use is dominated by
an edge.

Cheers,
Rafael
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