1 //! The `CFGPrinter` utility.
2 
3 use alloc::vec::Vec;
4 use core::fmt::{Display, Formatter, Result, Write};
5 
6 use crate::entity::SecondaryMap;
7 use crate::flowgraph::{BlockPredecessor, ControlFlowGraph};
8 use crate::ir::Function;
9 use crate::write::{FuncWriter, PlainWriter};
10 
11 /// A utility for pretty-printing the CFG of a `Function`.
12 pub struct CFGPrinter<'a> {
13     func: &'a Function,
14     cfg: ControlFlowGraph,
15 }
16 
17 /// A utility for pretty-printing the CFG of a `Function`.
18 impl<'a> CFGPrinter<'a> {
19     /// Create a new CFGPrinter.
20     pub fn new(func: &'a Function) -> Self {
21         Self {
22             func,
23             cfg: ControlFlowGraph::with_function(func),
24         }
25     }
26 
27     /// Write the CFG for this function to `w`.
28     pub fn write(&self, w: &mut dyn Write) -> Result {
29         self.header(w)?;
30         self.block_nodes(w)?;
31         self.cfg_connections(w)?;
32         writeln!(w, "}}")
33     }
34 
35     fn header(&self, w: &mut dyn Write) -> Result {
36         writeln!(w, "digraph \"{}\" {{", self.func.name)?;
37         if let Some(entry) = self.func.layout.entry_block() {
38             writeln!(w, "    {{rank=min; {entry}}}")?;
39         }
40         Ok(())
41     }
42 
43     fn block_nodes(&self, w: &mut dyn Write) -> Result {
44         let mut aliases = SecondaryMap::<_, Vec<_>>::new();
45         for v in self.func.dfg.values() {
46             // VADFS returns the immediate target of an alias
47             if let Some(k) = self.func.dfg.value_alias_dest_for_serialization(v) {
48                 aliases[k].push(v);
49             }
50         }
51 
52         for block in &self.func.layout {
53             write!(w, "    {block} [shape=record, label=\"{{")?;
54             crate::write::write_block_header(w, self.func, block, 4)?;
55             // Add all outgoing branch instructions to the label.
56             if let Some(inst) = self.func.layout.last_inst(block) {
57                 write!(w, " | <{inst}>")?;
58                 PlainWriter.write_instruction(w, self.func, &aliases, inst, 0)?;
59             }
60             writeln!(w, "}}\"]")?
61         }
62         Ok(())
63     }
64 
65     fn cfg_connections(&self, w: &mut dyn Write) -> Result {
66         for block in &self.func.layout {
67             for BlockPredecessor {
68                 block: parent,
69                 inst,
70             } in self.cfg.pred_iter(block)
71             {
72                 writeln!(w, "    {parent}:{inst} -> {block}")?;
73             }
74         }
75         Ok(())
76     }
77 }
78 
79 impl<'a> Display for CFGPrinter<'a> {
80     fn fmt(&self, f: &mut Formatter) -> Result {
81         self.write(f)
82     }
83 }
84