updating domtrees dynamically, removing all unreachable blocks

base/compiler/ssair/basicblock.jl

@@ -0,0 +1,32 @@
+# This file is a part of Julia. License is MIT: https://julialang.org/license
+
+"""
+Like UnitRange{Int}, but can handle the `last` field, being temporarily
+< first (this can happen during compacting)
+"""
+struct StmtRange <: AbstractUnitRange{Int}
+    start::Int
+    stop::Int
+end
+
+first(r::StmtRange) = r.start
+last(r::StmtRange) = r.stop
+iterate(r::StmtRange, state=0) = (last(r) - first(r) < state) ? nothing : (first(r) + state, state + 1)
+
+StmtRange(range::UnitRange{Int}) = StmtRange(first(range), last(range))
+
+struct BasicBlock
+    stmts::StmtRange
+    preds::Vector{Int}
+    succs::Vector{Int}
+end
+
+function BasicBlock(stmts::StmtRange)
+    return BasicBlock(stmts, Int[], Int[])
+end
+
+function BasicBlock(old_bb, stmts)
+    return BasicBlock(stmts, old_bb.preds, old_bb.succs)
+end
+
+copy(bb::BasicBlock) = BasicBlock(bb.stmts, copy(bb.preds), copy(bb.succs))