Merge branch 'enable-dcp'

Author: cjgillot

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