From ca1c47e8d4af399f006316d39b4c612c8a73babc Mon Sep 17 00:00:00 2001
From: Tim Besard <tim.besard@gmail.com>
Date: Fri, 30 Sep 2022 10:01:29 +0200
Subject: [PATCH] Show basic block statement ranges in CFG output.

---
 base/compiler/ssair/show.jl | 14 +++++++++++---
 test/show.jl                | 14 ++++++++++++++
 2 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/base/compiler/ssair/show.jl b/base/compiler/ssair/show.jl
index b490713c3190d..5f3df8d83429d 100644
--- a/base/compiler/ssair/show.jl
+++ b/base/compiler/ssair/show.jl
@@ -16,10 +16,18 @@ import Base: show_unquoted
 using Base: printstyled, with_output_color, prec_decl, @invoke
 
 function Base.show(io::IO, cfg::CFG)
+    print(io, "CFG with $(length(cfg.blocks)) blocks:")
     for (idx, block) in enumerate(cfg.blocks)
-        print(io, idx, "\t=>\t")
-        join(io, block.succs, ", ")
-        println(io)
+        print(io, "\n  bb ", idx)
+        if block.stmts.start == block.stmts.stop
+            print(io, " (stmt ", block.stmts.start, ")")
+        else
+            print(io, " (stmts ", block.stmts.start, ":", block.stmts.stop, ")")
+        end
+        if !isempty(block.succs)
+            print(io, " → bb ")
+            join(io, block.succs, ", ")
+        end
     end
 end
 
diff --git a/test/show.jl b/test/show.jl
index bdcfa3895f593..6cf5b35001f61 100644
--- a/test/show.jl
+++ b/test/show.jl
@@ -2516,3 +2516,17 @@ end
     ir = Core.Compiler.complete(compact)
     verify_display(ir)
 end
+
+@testset "IRCode: CFG display" begin
+    # get a cfg
+    function foo(i)
+        j = i+42
+        j == 1 ? 1 : 2
+    end
+    ir = only(Base.code_ircode(foo, (Int,)))[1]
+    cfg = ir.cfg
+
+    str = sprint(io->show(io, cfg))
+    @test contains(str, r"CFG with \d+ blocks")
+    @test contains(str, r"bb 1 \(stmt.+\) → bb.*")
+end