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).

Author: yhls

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

@@ -3,38 +3,14 @@
 @inline isexpr(@nospecialize(stmt), head::Symbol) = isa(stmt, Expr) && stmt.head === head
 Core.PhiNode() = Core.PhiNode(Int32[], Any[])
 
-"""
-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))
+isterminator(@nospecialize(stmt)) = isa(stmt, GotoNode) || isa(stmt, GotoIfNot) || isa(stmt, ReturnNode)
 
 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))?
 end
+
 copy(c::CFG) = CFG(BasicBlock[copy(b) for b in c.blocks], copy(c.index))
 
 function cfg_insert_edge!(cfg::CFG, from::Int, to::Int)