Move BasicBlock to separate source file

This is so we can add type declarations to fields in ir.jl that are domtrees,
by breaking the dependency loop between domtree.jl (uses basic blocks but
defines domtrees) and ir.jl (uses domtrees but defined basic 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))

base/compiler/ssair/driver.jl

@@ -10,8 +10,9 @@ else
     end
 end
 
-include("compiler/ssair/ir.jl")
+include("compiler/ssair/basicblock.jl")
 include("compiler/ssair/domtree.jl")
+include("compiler/ssair/ir.jl")
 include("compiler/ssair/slot2ssa.jl")
 include("compiler/ssair/queries.jl")
 include("compiler/ssair/passes.jl")

base/compiler/ssair/ir.jl

@@ -5,38 +5,11 @@ Core.PhiNode() = Core.PhiNode(Any[], Any[])
 
 isterminator(@nospecialize(stmt)) = isa(stmt, GotoNode) || isa(stmt, GotoIfNot) || isa(stmt, ReturnNode)
 
-"""
-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))
-
 struct CFG
     blocks::Vector{BasicBlock}
     index::Vector{Int} # map from instruction => basic-block number
                        # TODO: make this O(1) instead of O(log(n_blocks))?
-    domtree # TODO type
+    domtree::DomTree
 end
 
 function CFG(blocks::Vector{BasicBlock}, index::Vector{Int})
@@ -527,7 +500,7 @@ mutable struct IncrementalCompact
     ir::IRCode
     result::InstructionStream
     result_bbs::Vector{BasicBlock}
-    result_domtree # TODO type
+    result_domtree::DomTree
 
     ssa_rename::Vector{Any}
     # `bb_rename_pred` is for renaming predecessors to the blocks they have