From fb79b47b38325a9bf1a94b1bcd5f175731a42e60 Mon Sep 17 00:00:00 2001
From: pca006132 <jl@m-labs.hk>
Date: Fri, 8 Apr 2022 09:18:34 +0800
Subject: [PATCH] escape analysis: fixed infinite loop detection

---
 nac3core/src/toplevel/composer.rs             |  2 +-
 .../src/typecheck/escape_analysis/lifetime.rs | 22 ++++++++++---------
 nac3core/src/typecheck/escape_analysis/mod.rs |  5 ++++-
 nac3standalone/src/main.rs                    |  6 ++++-
 4 files changed, 22 insertions(+), 13 deletions(-)

diff --git a/nac3core/src/toplevel/composer.rs b/nac3core/src/toplevel/composer.rs
index 46b8a7be..61448c68 100644
--- a/nac3core/src/toplevel/composer.rs
+++ b/nac3core/src/toplevel/composer.rs
@@ -1928,7 +1928,7 @@ impl TopLevelComposer {
                                 &args,
                                 &fun_body,
                                 ast.as_ref().unwrap().location,
-                            ).map_err(|e| format!("Escape analysis error: {}\n  in function {}", e, name))?;
+                            ).map_err(|e| format!("Escape analysis error: {}\n  ... in function {}", e, name))?;
                         }
 
                         instance_to_stmt.insert(
diff --git a/nac3core/src/typecheck/escape_analysis/lifetime.rs b/nac3core/src/typecheck/escape_analysis/lifetime.rs
index ff4ee047..942527e6 100644
--- a/nac3core/src/typecheck/escape_analysis/lifetime.rs
+++ b/nac3core/src/typecheck/escape_analysis/lifetime.rs
@@ -123,7 +123,7 @@ impl LifetimeIRBuilder {
                     LifetimeIR::Branch { targets } => {
                         destination_mapping.insert(i, targets);
                     }
-                    _ => unreachable!(),
+                    _ => ()
                 }
             }
         }
@@ -155,28 +155,30 @@ impl LifetimeIRBuilder {
 
     pub fn analyze(&self) -> Result<(), String> {
         let mut analyzers = HashMap::new();
-        analyzers.insert(0, LifetimeAnalyzer::new());
+        analyzers.insert(0, (0, true, LifetimeAnalyzer::new()));
         let mut worklist = vec![0];
-        let mut counter = 0;
         while let Some(bb) = worklist.pop() {
-            counter += 1;
-            if counter > 100 {
-                return Err(format!("escape analyzer stuck in infinite loop?"));
+            let (counter, updated, analyzer) = analyzers.get_mut(&bb).unwrap();
+            *counter += 1;
+            if *counter > 100 {
+                return Err(format!("infinite loop detected at basic block {}", bb));
             }
-            let mut analyzer = analyzers.get(&bb).unwrap().clone();
+            *updated = false;
+            let mut analyzer = analyzer.clone();
             let block = &self.basic_blocks[bb];
             let ir_iter = block.iter().filter_map(|&id| {
                 self.irs[id].as_ref().map(|(ir, loc)| (LifetimeId(id), ir, *loc))
             });
             if let Some(branch) = analyzer.analyze_basic_block(ir_iter)? {
                 for &target in branch.iter() {
-                    if let Some(successor) = analyzers.get_mut(&target.0) {
-                        if successor.merge(&analyzer) {
+                    if let Some((_, updated, successor)) = analyzers.get_mut(&target.0) {
+                        if successor.merge(&analyzer) && !*updated {
                             // changed
                             worklist.push(target.0);
+                            *updated = true;
                         }
                     } else {
-                        analyzers.insert(target.0, analyzer.clone());
+                        analyzers.insert(target.0, (0, true, analyzer.clone()));
                         worklist.push(target.0);
                     }
                 }
diff --git a/nac3core/src/typecheck/escape_analysis/mod.rs b/nac3core/src/typecheck/escape_analysis/mod.rs
index 971cd119..9bd255f6 100644
--- a/nac3core/src/typecheck/escape_analysis/mod.rs
+++ b/nac3core/src/typecheck/escape_analysis/mod.rs
@@ -67,7 +67,10 @@ impl<'a> EscapeAnalyzer<'a> {
             }
         }
         zelf.handle_statements(body)?;
-        zelf.builder.analyze()
+        zelf.builder.remove_empty_bb();
+        zelf.builder.analyze().map_err(|e| {
+            format!("{}\nIR: {}", e, zelf.builder.print_ir())
+        })
     }
 
     fn need_alloca(&mut self, ty: Type) -> bool {
diff --git a/nac3standalone/src/main.rs b/nac3standalone/src/main.rs
index 37925157..a87b9494 100644
--- a/nac3standalone/src/main.rs
+++ b/nac3standalone/src/main.rs
@@ -220,7 +220,11 @@ fn main() {
     let signature = store.from_signature(&mut composer.unifier, &primitive, &signature, &mut cache);
     let signature = store.add_cty(signature);
 
-    composer.start_analysis(true).unwrap();
+    if let Err(e) = composer.start_analysis(true) {
+        eprintln!("{}", e);
+        std::process::exit(1);
+    }
+
 
     let top_level = Arc::new(composer.make_top_level_context());