fixup! Add a domtree to every CFG, avoiding constructing them explicitly when needed

Author: vchuravy

base/compiler/ssair/ir.jl

@@ -11,7 +11,6 @@ struct CFG
                        # TODO: make this O(1) instead of O(log(n_blocks))?
     domtree::DomTree
 end
-copy(c::CFG) = CFG(BasicBlock[copy(b) for b in c.blocks], copy(c.index))
 
 function CFG(blocks::Vector{BasicBlock}, index::Vector{Int})
     return CFG(blocks, index, construct_domtree(blocks))