From b556690c53d87ea7530c631d3c257da3567e5a9a Mon Sep 17 00:00:00 2001
From: cjkenn <cjkenn@users.noreply.github.com>
Date: Wed, 18 Nov 2020 19:16:23 -0500
Subject: [PATCH] move checks later into optimization passes

---
 .../src/transform/multiple_return_terminators.rs     | 11 +++++------
 .../rustc_mir/src/transform/remove_unneeded_drops.rs | 10 ++++++----
 compiler/rustc_mir/src/transform/unreachable_prop.rs | 12 ++++++------
 3 files changed, 17 insertions(+), 16 deletions(-)

diff --git a/compiler/rustc_mir/src/transform/multiple_return_terminators.rs b/compiler/rustc_mir/src/transform/multiple_return_terminators.rs
index 4a66bc45ae3..617086622cc 100644
--- a/compiler/rustc_mir/src/transform/multiple_return_terminators.rs
+++ b/compiler/rustc_mir/src/transform/multiple_return_terminators.rs
@@ -14,14 +14,9 @@ fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
             return;
         }
 
-        if !tcx.consider_optimizing(|| {
-            format!("MultipleReturnTerminators {:?} ", body.source.def_id())
-        }) {
-            return;
-        }
-
         // find basic blocks with no statement and a return terminator
         let mut bbs_simple_returns = BitSet::new_empty(body.basic_blocks().len());
+        let def_id = body.source.def_id();
         let bbs = body.basic_blocks_mut();
         for idx in bbs.indices() {
             if bbs[idx].statements.is_empty()
@@ -32,6 +27,10 @@ fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         }
 
         for bb in bbs {
+            if !tcx.consider_optimizing(|| format!("MultipleReturnTerminators {:?} ", def_id)) {
+                break;
+            }
+
             if let TerminatorKind::Goto { target } = bb.terminator().kind {
                 if bbs_simple_returns.contains(target) {
                     bb.terminator_mut().kind = TerminatorKind::Return;
diff --git a/compiler/rustc_mir/src/transform/remove_unneeded_drops.rs b/compiler/rustc_mir/src/transform/remove_unneeded_drops.rs
index 2a72751071b..221114eebaa 100644
--- a/compiler/rustc_mir/src/transform/remove_unneeded_drops.rs
+++ b/compiler/rustc_mir/src/transform/remove_unneeded_drops.rs
@@ -11,10 +11,6 @@
 
 impl<'tcx> MirPass<'tcx> for RemoveUnneededDrops {
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
-        if !tcx.consider_optimizing(|| format!("RemoveUnneededDrops {:?} ", body.source.def_id())) {
-            return;
-        }
-
         trace!("Running RemoveUnneededDrops on {:?}", body.source);
         let mut opt_finder = RemoveUnneededDropsOptimizationFinder {
             tcx,
@@ -25,6 +21,12 @@ fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         opt_finder.visit_body(body);
         let should_simplify = !opt_finder.optimizations.is_empty();
         for (loc, target) in opt_finder.optimizations {
+            if !tcx
+                .consider_optimizing(|| format!("RemoveUnneededDrops {:?} ", body.source.def_id()))
+            {
+                break;
+            }
+
             let terminator = body.basic_blocks_mut()[loc.block].terminator_mut();
             debug!("SUCCESS: replacing `drop` with goto({:?})", target);
             terminator.kind = TerminatorKind::Goto { target };
diff --git a/compiler/rustc_mir/src/transform/unreachable_prop.rs b/compiler/rustc_mir/src/transform/unreachable_prop.rs
index 4100a50c225..e39c8656021 100644
--- a/compiler/rustc_mir/src/transform/unreachable_prop.rs
+++ b/compiler/rustc_mir/src/transform/unreachable_prop.rs
@@ -18,12 +18,6 @@ fn run_pass<'tcx>(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
             return;
         }
 
-        if !tcx
-            .consider_optimizing(|| format!("UnreachablePropagation {:?} ", body.source.def_id()))
-        {
-            return;
-        }
-
         let mut unreachable_blocks = FxHashSet::default();
         let mut replacements = FxHashMap::default();
 
@@ -56,6 +50,12 @@ fn run_pass<'tcx>(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
 
         let replaced = !replacements.is_empty();
         for (bb, terminator_kind) in replacements {
+            if !tcx.consider_optimizing(|| {
+                format!("UnreachablePropagation {:?} ", body.source.def_id())
+            }) {
+                break;
+            }
+
             body.basic_blocks_mut()[bb].terminator_mut().kind = terminator_kind;
         }