IRShow: print invalid SSAValue in red (#46472)

base/compiler/ssair/show.jl

@@ -810,15 +810,19 @@ function show_ir(io::IO, ir::IRCode, config::IRShowConfig=default_config(ir);
                  pop_new_node! = new_nodes_iter(ir))
     used = stmts_used(io, ir)
     cfg = ir.cfg
-    show_ir_stmts(io, ir, 1:length(ir.stmts), config, used, cfg, 1; pop_new_node!)
+    let io = IOContext(io, :maxssaid=>length(ir.stmts))
+        show_ir_stmts(io, ir, 1:length(ir.stmts), config, used, cfg, 1; pop_new_node!)
+    end
     finish_show_ir(io, cfg, config)
 end
 
 function show_ir(io::IO, ci::CodeInfo, config::IRShowConfig=default_config(ci);
                  pop_new_node! = Returns(nothing))
     used = stmts_used(io, ci)
     cfg = compute_basic_blocks(ci.code)
-    show_ir_stmts(io, ci, 1:length(ci.code), config, used, cfg, 1; pop_new_node!)
+    let io = IOContext(io, :maxssaid=>length(ci.code))
+        show_ir_stmts(io, ci, 1:length(ci.code), config, used, cfg, 1; pop_new_node!)
+    end
     finish_show_ir(io, cfg, config)
 end
 
@@ -837,7 +841,9 @@ function show_ir(io::IO, compact::IncrementalCompact, config::IRShowConfig=defau
         end
     end
     pop_new_node! = new_nodes_iter(compact)
-    bb_idx = show_ir_stmts(io, compact, 1:compact.result_idx-1, config, used_compacted, cfg, 1; pop_new_node!)
+    bb_idx = let io = IOContext(io, :maxssaid=>length(compact.result))
+        show_ir_stmts(io, compact, 1:compact.result_idx-1, config, used_compacted, cfg, 1; pop_new_node!)
+    end
 
     # Print uncompacted nodes from the original IR
     stmts = compact.ir.stmts
@@ -847,8 +853,9 @@ function show_ir(io::IO, compact::IncrementalCompact, config::IRShowConfig=defau
         # config.line_info_preprinter(io, "", compact.idx)
         printstyled(io, "─"^(width-indent-1), '\n', color=:red)
     end
-
-    show_ir_stmts(io, compact.ir, compact.idx:length(stmts), config, used_uncompacted, cfg, bb_idx; pop_new_node!)
+    let io = IOContext(io, :maxssaid=>length(compact.ir.stmts))
+        show_ir_stmts(io, compact.ir, compact.idx:length(stmts), config, used_uncompacted, cfg, bb_idx; pop_new_node!)
+    end
 
     finish_show_ir(io, cfg, config)
 end

base/show.jl

@@ -1686,7 +1686,14 @@ end
 
 ## AST printing ##
 
-show_unquoted(io::IO, val::SSAValue, ::Int, ::Int)      = print(io, "%", val.id)
+function show_unquoted(io::IO, val::SSAValue, ::Int, ::Int)
+    if get(io, :maxssaid, typemax(Int))::Int < val.id
+        # invalid SSAValue, print this in red for better recognition
+        printstyled(io, "%", val.id; color=:red)
+    else
+        print(io, "%", val.id)
+    end
+end
 show_unquoted(io::IO, sym::Symbol, ::Int, ::Int)        = show_sym(io, sym, allow_macroname=false)
 show_unquoted(io::IO, ex::LineNumberNode, ::Int, ::Int) = show_linenumber(io, ex.line, ex.file)
 show_unquoted(io::IO, ex::GotoNode, ::Int, ::Int)       = print(io, "goto %", ex.label)