From 136090813af590970a9091f03c088f81f7223851 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?R=C3=A9my=20Rakic?= <remy.rakic+github@gmail.com>
Date: Tue, 22 Dec 2020 23:57:50 +0100
Subject: [PATCH] liveness: stop materializing facts that placeholders are live
 at all points

---
 polonius-engine/src/output/liveness.rs | 20 ++------------------
 polonius-engine/src/output/mod.rs      | 16 +---------------
 2 files changed, 3 insertions(+), 33 deletions(-)

diff --git a/polonius-engine/src/output/liveness.rs b/polonius-engine/src/output/liveness.rs
index f24f6552976..c3c5183076b 100644
--- a/polonius-engine/src/output/liveness.rs
+++ b/polonius-engine/src/output/liveness.rs
@@ -10,7 +10,6 @@
 
 //! An implementation of the origin liveness calculation logic
 
-use std::collections::BTreeSet;
 use std::time::Instant;
 
 use crate::facts::FactTypes;
@@ -23,7 +22,7 @@ pub(super) fn compute_live_origins<T: FactTypes>(
     cfg_edge: &Relation<(T::Point, T::Point)>,
     var_maybe_partly_initialized_on_exit: Relation<(T::Variable, T::Point)>,
     output: &mut Output<T>,
-) -> Vec<(T::Origin, T::Point)> {
+) -> Relation<(T::Origin, T::Point)> {
     let timer = Instant::now();
     let mut iteration = Iteration::new();
 
@@ -151,20 +150,5 @@ pub(super) fn compute_live_origins<T: FactTypes>(
         }
     }
 
-    origin_live_on_entry.elements
-}
-
-pub(super) fn make_universal_regions_live<T: FactTypes>(
-    origin_live_on_entry: &mut Vec<(T::Origin, T::Point)>,
-    cfg_node: &BTreeSet<T::Point>,
-    universal_regions: &[T::Origin],
-) {
-    debug!("make_universal_regions_live()");
-
-    origin_live_on_entry.reserve(universal_regions.len() * cfg_node.len());
-    for &origin in universal_regions.iter() {
-        for &point in cfg_node.iter() {
-            origin_live_on_entry.push((origin, point));
-        }
-    }
+    origin_live_on_entry
 }
diff --git a/polonius-engine/src/output/mod.rs b/polonius-engine/src/output/mod.rs
index 21b173fc390..3e7b8ad4602 100644
--- a/polonius-engine/src/output/mod.rs
+++ b/polonius-engine/src/output/mod.rs
@@ -191,25 +191,13 @@ impl<T: FactTypes> Output<T> {
             drop_of_var_derefs_origin: all_facts.drop_of_var_derefs_origin.clone(),
         };
 
-        let mut origin_live_on_entry = liveness::compute_live_origins(
+        let origin_live_on_entry = liveness::compute_live_origins(
             liveness_ctx,
             &cfg_edge,
             var_maybe_partly_initialized_on_exit,
             &mut result,
         );
 
-        let cfg_node = cfg_edge
-            .iter()
-            .map(|&(point1, _)| point1)
-            .chain(cfg_edge.iter().map(|&(_, point2)| point2))
-            .collect();
-
-        liveness::make_universal_regions_live::<T>(
-            &mut origin_live_on_entry,
-            &cfg_node,
-            &all_facts.universal_region,
-        );
-
         // 3) Borrow checking
 
         // Prepare data as datafrog relations, ready to join.
@@ -222,8 +210,6 @@ impl<T: FactTypes> Output<T> {
         // analysis. If these facts happened to be recorded in separate MIR walks, we might also
         // avoid generating those facts.
 
-        let origin_live_on_entry = origin_live_on_entry.into();
-
         // TODO: also flip the order of this relation's arguments in rustc
         // from `loan_invalidated_at(point, loan)` to `loan_invalidated_at(loan, point)`.
         // to avoid this allocation.