Merge branch 'enable-dcp'

Author: cjgillot

compiler/rustc_mir_dataflow/src/value_analysis.rs

@@ -720,7 +720,7 @@ impl Map {
     /// This is currently the only way to create a [`Map`]. The way in which the tracked places are
     /// chosen is an implementation detail and may not be relied upon (other than that their type
     /// are scalars).
-    pub fn new<'tcx>(tcx: TyCtxt<'tcx>, body: &Body<'tcx>, value_limit: Option<usize>) -> Self {
+    pub fn new<'tcx>(tcx: TyCtxt<'tcx>, body: &Body<'tcx>, place_limit: Option<usize>) -> Self {
         let mut map = Self {
             locals: IndexVec::new(),
             projections: FxHashMap::default(),
@@ -730,7 +730,7 @@ impl Map {
             inner_values_buffer: Vec::new(),
         };
         let exclude = excluded_locals(body);
-        map.register(tcx, body, exclude, value_limit);
+        map.register(tcx, body, exclude, place_limit);
         debug!("registered {} places ({} nodes in total)", map.value_count, map.places.len());
         map
     }
@@ -741,9 +741,9 @@ impl Map {
         tcx: TyCtxt<'tcx>,
         body: &Body<'tcx>,
         exclude: BitSet<Local>,
-        value_limit: Option<usize>,
+        place_limit: Option<usize>,
     ) {
-        let mut worklist = VecDeque::with_capacity(value_limit.unwrap_or(body.local_decls.len()));
+        let mut worklist = VecDeque::with_capacity(place_limit.unwrap_or(body.local_decls.len()));
         let param_env = tcx.param_env_reveal_all_normalized(body.source.def_id());
 
         // Start by constructing the places for each bare local.
@@ -766,8 +766,8 @@ impl Map {
         // `elem1` is either `Some(Variant(i))` or `None`.
         while let Some((mut place, elem1, elem2, ty)) = worklist.pop_front() {
             // The user requires a bound on the number of created values.
-            if let Some(value_limit) = value_limit
-                && self.value_count >= value_limit
+            if let Some(place_limit) = place_limit
+                && self.places.len() >= place_limit
             {
                 break;
             }

compiler/rustc_mir_transform/src/dataflow_const_prop.rs

@@ -25,23 +25,18 @@ use crate::const_prop::throw_machine_stop_str;
 
 // These constants are somewhat random guesses and have not been optimized.
 // If `tcx.sess.mir_opt_level() >= 4`, we ignore the limits (this can become very expensive).
-const BLOCK_LIMIT: usize = 100;
 const PLACE_LIMIT: usize = 100;
 
 pub struct DataflowConstProp;
 
 impl<'tcx> MirPass<'tcx> for DataflowConstProp {
     fn is_enabled(&self, sess: &rustc_session::Session) -> bool {
-        sess.mir_opt_level() >= 3
+        sess.mir_opt_level() >= 2
     }
 
     #[instrument(skip_all level = "debug")]
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         debug!(def_id = ?body.source.def_id());
-        if tcx.sess.mir_opt_level() < 4 && body.basic_blocks.len() > BLOCK_LIMIT {
-            debug!("aborted dataflow const prop due too many basic blocks");
-            return;
-        }
 
         // We want to have a somewhat linear runtime w.r.t. the number of statements/terminators.
         // Let's call this number `n`. Dataflow analysis has `O(h*n)` transfer function