Extend SimplifyLocals to remove ZST writes

simonvandel · erikdesjardins · commit 4e901be57d23 · 2021-03-13T17:58:11.000-05:00
diff --git a/compiler/rustc_mir/src/transform/simplify.rs b/compiler/rustc_mir/src/transform/simplify.rs
@@ -333,7 +333,7 @@ pub fn simplify_locals<'tcx>(body: &mut Body<'tcx>, tcx: TyCtxt<'tcx>) {
     // count. For example, if we removed `_2 = discriminant(_1)`, then we'll subtract one from
     // `use_counts[_1]`. That in turn might make `_1` unused, so we loop until we hit a
     // fixedpoint where there are no more unused locals.
-    remove_unused_definitions(&mut used_locals, body);
+    remove_unused_definitions(&mut used_locals, body, tcx);
 
     // Finally, we'll actually do the work of shrinking `body.local_decls` and remapping the `Local`s.
     let map = make_local_map(&mut body.local_decls, &used_locals);
@@ -462,12 +462,22 @@ impl Visitor<'_> for UsedLocals {
 }
 
 /// Removes unused definitions. Updates the used locals to reflect the changes made.
-fn remove_unused_definitions<'a, 'tcx>(used_locals: &'a mut UsedLocals, body: &mut Body<'tcx>) {
+fn remove_unused_definitions<'a, 'tcx>(
+    used_locals: &'a mut UsedLocals,
+    body: &mut Body<'tcx>,
+    tcx: TyCtxt<'tcx>,
+) {
     // The use counts are updated as we remove the statements. A local might become unused
     // during the retain operation, leading to a temporary inconsistency (storage statements or
     // definitions referencing the local might remain). For correctness it is crucial that this
     // computation reaches a fixed point.
 
+    let def_id = body.source.def_id();
+    let is_static = tcx.is_static(def_id);
+    let param_env = tcx.param_env(def_id);
+
+    let local_decls = body.local_decls.clone();
+
     let mut modified = true;
     while modified {
         modified = false;
@@ -479,7 +489,21 @@ fn remove_unused_definitions<'a, 'tcx>(used_locals: &'a mut UsedLocals, body: &m
                     StatementKind::StorageLive(local) | StatementKind::StorageDead(local) => {
                         used_locals.is_used(*local)
                     }
-                    StatementKind::Assign(box (place, _)) => used_locals.is_used(place.local),
+                    StatementKind::Assign(box (place, _)) => {
+                        let used = used_locals.is_used(place.local);
+                        let mut is_zst = false;
+
+                        // ZST locals can be removed
+                        if used && !is_static {
+                            let ty = local_decls[place.local].ty;
+                            let param_env_and = param_env.and(ty);
+                            if let Ok(layout) = tcx.layout_of(param_env_and) {
+                                is_zst = layout.is_zst();
+                            }
+                        }
+
+                        used && !is_zst
+                    }
 
                     StatementKind::SetDiscriminant { ref place, .. } => {
                         used_locals.is_used(place.local)
diff --git a/src/test/codegen/naked-functions.rs b/src/test/codegen/naked-functions.rs
@@ -9,6 +9,7 @@
 #[naked]
 pub fn naked_empty() {
     // CHECK-NEXT: {{.+}}:
+    // CHECK-NEXT: %0 = alloca {}, align 1
     // CHECK-NEXT: ret void
 }
 
@@ -18,6 +19,7 @@ pub fn naked_empty() {
 // CHECK-NEXT: define void @naked_with_args(i{{[0-9]+( %a)?}})
 pub fn naked_with_args(a: isize) {
     // CHECK-NEXT: {{.+}}:
+    // CHECK-NEXT: %0 = alloca {}, align 1
     // CHECK: ret void
 }
 
diff --git a/src/test/mir-opt/const_prop/control_flow_simplification.hello.PreCodegen.before.mir b/src/test/mir-opt/const_prop/control_flow_simplification.hello.PreCodegen.before.mir
@@ -4,7 +4,6 @@ fn hello() -> () {
     let mut _0: ();                      // return place in scope 0 at $DIR/control-flow-simplification.rs:11:14: 11:14
 
     bb0: {
-        _0 = const ();                   // scope 0 at $DIR/control-flow-simplification.rs:14:6: 14:6
         return;                          // scope 0 at $DIR/control-flow-simplification.rs:15:2: 15:2
     }
 }
diff --git a/src/test/mir-opt/const_prop/optimizes_into_variable.main.SimplifyLocals.after.32bit.mir b/src/test/mir-opt/const_prop/optimizes_into_variable.main.SimplifyLocals.after.32bit.mir
@@ -22,7 +22,6 @@ fn main() -> () {
         _2 = const 3_i32;                // scope 1 at $DIR/optimizes_into_variable.rs:13:13: 13:34
         StorageLive(_3);                 // scope 2 at $DIR/optimizes_into_variable.rs:14:9: 14:10
         _3 = const 42_u32;               // scope 2 at $DIR/optimizes_into_variable.rs:14:13: 14:38
-        _0 = const ();                   // scope 0 at $DIR/optimizes_into_variable.rs:11:11: 15:2
         StorageDead(_3);                 // scope 2 at $DIR/optimizes_into_variable.rs:15:1: 15:2
         StorageDead(_2);                 // scope 1 at $DIR/optimizes_into_variable.rs:15:1: 15:2
         StorageDead(_1);                 // scope 0 at $DIR/optimizes_into_variable.rs:15:1: 15:2
diff --git a/src/test/mir-opt/const_prop/optimizes_into_variable.main.SimplifyLocals.after.64bit.mir b/src/test/mir-opt/const_prop/optimizes_into_variable.main.SimplifyLocals.after.64bit.mir
@@ -22,7 +22,6 @@ fn main() -> () {
         _2 = const 3_i32;                // scope 1 at $DIR/optimizes_into_variable.rs:13:13: 13:34
         StorageLive(_3);                 // scope 2 at $DIR/optimizes_into_variable.rs:14:9: 14:10
         _3 = const 42_u32;               // scope 2 at $DIR/optimizes_into_variable.rs:14:13: 14:38
-        _0 = const ();                   // scope 0 at $DIR/optimizes_into_variable.rs:11:11: 15:2
         StorageDead(_3);                 // scope 2 at $DIR/optimizes_into_variable.rs:15:1: 15:2
         StorageDead(_2);                 // scope 1 at $DIR/optimizes_into_variable.rs:15:1: 15:2
         StorageDead(_1);                 // scope 0 at $DIR/optimizes_into_variable.rs:15:1: 15:2
diff --git a/src/test/mir-opt/dest-prop/cycle.main.DestinationPropagation.diff b/src/test/mir-opt/dest-prop/cycle.main.DestinationPropagation.diff
@@ -56,7 +56,6 @@
           StorageLive(_6);                 // scope 3 at $DIR/cycle.rs:14:10: 14:11
 -         _6 = _1;                         // scope 3 at $DIR/cycle.rs:14:10: 14:11
 +         _6 = _4;                         // scope 3 at $DIR/cycle.rs:14:10: 14:11
-          _5 = const ();                   // scope 4 at $DIR/cycle.rs:14:5: 14:12
           StorageDead(_6);                 // scope 3 at $DIR/cycle.rs:14:11: 14:12
           StorageDead(_5);                 // scope 3 at $DIR/cycle.rs:14:12: 14:13
           _0 = const ();                   // scope 0 at $DIR/cycle.rs:8:11: 15:2
diff --git a/src/test/mir-opt/dest-prop/union.main.DestinationPropagation.diff b/src/test/mir-opt/dest-prop/union.main.DestinationPropagation.diff
@@ -31,7 +31,6 @@
           StorageLive(_3);                 // scope 1 at $DIR/union.rs:15:5: 15:27
           StorageLive(_4);                 // scope 1 at $DIR/union.rs:15:10: 15:26
           _4 = (_1.0: u32);                // scope 2 at $DIR/union.rs:15:19: 15:24
-          _3 = const ();                   // scope 3 at $DIR/union.rs:15:5: 15:27
           StorageDead(_4);                 // scope 1 at $DIR/union.rs:15:26: 15:27
           StorageDead(_3);                 // scope 1 at $DIR/union.rs:15:27: 15:28
           _0 = const ();                   // scope 0 at $DIR/union.rs:8:11: 16:2
diff --git a/src/test/mir-opt/inline/inline_compatibility.inlined_no_sanitize.Inline.diff b/src/test/mir-opt/inline/inline_compatibility.inlined_no_sanitize.Inline.diff
@@ -16,7 +16,6 @@
 -     }
 - 
 -     bb1: {
-+         _1 = const ();                   // scope 1 at $DIR/inline-compatibility.rs:24:5: 24:18
           StorageDead(_1);                 // scope 0 at $DIR/inline-compatibility.rs:24:18: 24:19
           _0 = const ();                   // scope 0 at $DIR/inline-compatibility.rs:23:37: 25:2
           return;                          // scope 0 at $DIR/inline-compatibility.rs:25:2: 25:2
diff --git a/src/test/mir-opt/inline/inline_compatibility.inlined_target_feature.Inline.diff b/src/test/mir-opt/inline/inline_compatibility.inlined_target_feature.Inline.diff
@@ -16,7 +16,6 @@
 -     }
 - 
 -     bb1: {
-+         _1 = const ();                   // scope 1 at $DIR/inline-compatibility.rs:13:5: 13:21
           StorageDead(_1);                 // scope 0 at $DIR/inline-compatibility.rs:13:21: 13:22
           _0 = const ();                   // scope 0 at $DIR/inline-compatibility.rs:12:40: 14:2
           return;                          // scope 0 at $DIR/inline-compatibility.rs:14:2: 14:2
diff --git a/src/test/mir-opt/inline/inline_cycle.two.Inline.diff b/src/test/mir-opt/inline/inline_cycle.two.Inline.diff
@@ -37,7 +37,6 @@
 +         StorageDead(_5);                 // scope 1 at $DIR/inline-cycle.rs:49:5: 49:12
 +         StorageDead(_4);                 // scope 1 at $DIR/inline-cycle.rs:49:5: 49:12
 +         StorageDead(_3);                 // scope 1 at $DIR/inline-cycle.rs:49:5: 49:12
-+         _1 = const ();                   // scope 1 at $DIR/inline-cycle.rs:49:5: 49:12
 +         StorageDead(_2);                 // scope 0 at $DIR/inline-cycle.rs:49:5: 49:12
           StorageDead(_1);                 // scope 0 at $DIR/inline-cycle.rs:49:12: 49:13
           _0 = const ();                   // scope 0 at $DIR/inline-cycle.rs:48:10: 50:2
diff --git a/src/test/mir-opt/inline/inline_options.main.Inline.after.mir b/src/test/mir-opt/inline/inline_options.main.Inline.after.mir
@@ -48,7 +48,6 @@ fn main() -> () {
 
     bb4: {
         StorageDead(_5);                 // scope 1 at $DIR/inline-options.rs:10:5: 10:21
-        _2 = const ();                   // scope 1 at $DIR/inline-options.rs:10:5: 10:21
         StorageDead(_2);                 // scope 0 at $DIR/inline-options.rs:10:21: 10:22
         _0 = const ();                   // scope 0 at $DIR/inline-options.rs:8:11: 11:2
         return;                          // scope 0 at $DIR/inline-options.rs:11:2: 11:2
diff --git a/src/test/mir-opt/inline/issue_76997_inline_scopes_parenting.main.Inline.after.mir b/src/test/mir-opt/inline/issue_76997_inline_scopes_parenting.main.Inline.after.mir
@@ -28,8 +28,6 @@ fn main() -> () {
         StorageLive(_5);                 // scope 1 at $DIR/issue-76997-inline-scopes-parenting.rs:6:5: 6:10
         _5 = move (_3.0: ());            // scope 1 at $DIR/issue-76997-inline-scopes-parenting.rs:6:5: 6:10
         StorageLive(_6);                 // scope 2 at $DIR/issue-76997-inline-scopes-parenting.rs:6:5: 6:10
-        _6 = const ();                   // scope 2 at $DIR/issue-76997-inline-scopes-parenting.rs:6:5: 6:10
-        _0 = const ();                   // scope 3 at $DIR/issue-76997-inline-scopes-parenting.rs:6:5: 6:10
         StorageDead(_6);                 // scope 2 at $DIR/issue-76997-inline-scopes-parenting.rs:6:5: 6:10
         StorageDead(_5);                 // scope 1 at $DIR/issue-76997-inline-scopes-parenting.rs:6:5: 6:10
         StorageDead(_4);                 // scope 1 at $DIR/issue-76997-inline-scopes-parenting.rs:6:9: 6:10
diff --git a/src/test/mir-opt/issue_73223.main.PreCodegen.32bit.diff b/src/test/mir-opt/issue_73223.main.PreCodegen.32bit.diff
@@ -117,7 +117,6 @@
           StorageDead(_10);                // scope 3 at $SRC_DIR/core/src/macros/mod.rs:LL:COL
           StorageDead(_9);                 // scope 3 at $SRC_DIR/core/src/macros/mod.rs:LL:COL
           StorageDead(_6);                 // scope 3 at $SRC_DIR/core/src/macros/mod.rs:LL:COL
-          _0 = const ();                   // scope 0 at $DIR/issue-73223.rs:1:11: 9:2
           StorageDead(_4);                 // scope 1 at $DIR/issue-73223.rs:9:1: 9:2
           StorageDead(_1);                 // scope 0 at $DIR/issue-73223.rs:9:1: 9:2
           return;                          // scope 0 at $DIR/issue-73223.rs:9:2: 9:2
diff --git a/src/test/mir-opt/issue_73223.main.PreCodegen.64bit.diff b/src/test/mir-opt/issue_73223.main.PreCodegen.64bit.diff
@@ -117,7 +117,6 @@
           StorageDead(_10);                // scope 3 at $SRC_DIR/core/src/macros/mod.rs:LL:COL
           StorageDead(_9);                 // scope 3 at $SRC_DIR/core/src/macros/mod.rs:LL:COL
           StorageDead(_6);                 // scope 3 at $SRC_DIR/core/src/macros/mod.rs:LL:COL
-          _0 = const ();                   // scope 0 at $DIR/issue-73223.rs:1:11: 9:2
           StorageDead(_4);                 // scope 1 at $DIR/issue-73223.rs:9:1: 9:2
           StorageDead(_1);                 // scope 0 at $DIR/issue-73223.rs:9:1: 9:2
           return;                          // scope 0 at $DIR/issue-73223.rs:9:2: 9:2
diff --git a/src/test/mir-opt/lower_intrinsics.f_u64.PreCodegen.before.mir b/src/test/mir-opt/lower_intrinsics.f_u64.PreCodegen.before.mir
@@ -27,7 +27,6 @@ fn f_u64() -> () {
         StorageDead(_3);                 // scope 1 at $DIR/lower_intrinsics.rs:35:5: 35:21
         StorageDead(_2);                 // scope 1 at $DIR/lower_intrinsics.rs:35:5: 35:21
         StorageDead(_1);                 // scope 0 at $DIR/lower_intrinsics.rs:35:5: 35:21
-        _0 = const ();                   // scope 0 at $DIR/lower_intrinsics.rs:34:16: 36:2
         return;                          // scope 0 at $DIR/lower_intrinsics.rs:36:2: 36:2
     }
 }
diff --git a/src/test/mir-opt/lower_intrinsics.f_unit.PreCodegen.before.mir b/src/test/mir-opt/lower_intrinsics.f_unit.PreCodegen.before.mir
@@ -22,7 +22,6 @@ fn f_unit() -> () {
     bb1: {
         StorageDead(_2);                 // scope 1 at $DIR/lower_intrinsics.rs:29:5: 29:19
         StorageDead(_1);                 // scope 0 at $DIR/lower_intrinsics.rs:29:18: 29:19
-        _0 = const ();                   // scope 0 at $DIR/lower_intrinsics.rs:28:17: 30:2
         return;                          // scope 0 at $DIR/lower_intrinsics.rs:30:2: 30:2
     }
 }
diff --git a/src/test/mir-opt/multiple_return_terminators.test.MultipleReturnTerminators.diff b/src/test/mir-opt/multiple_return_terminators.test.MultipleReturnTerminators.diff
@@ -13,12 +13,10 @@
       }
   
       bb1: {
-          _0 = const ();                   // scope 0 at $DIR/multiple_return_terminators.rs:5:10: 7:6
           goto -> bb3;                     // scope 0 at $DIR/multiple_return_terminators.rs:5:5: 9:6
       }
   
       bb2: {
-          _0 = const ();                   // scope 0 at $DIR/multiple_return_terminators.rs:7:12: 9:6
           goto -> bb3;                     // scope 0 at $DIR/multiple_return_terminators.rs:5:5: 9:6
       }
   
diff --git a/src/test/mir-opt/remove_unneeded_drops.cannot_opt_generic.RemoveUnneededDrops.diff b/src/test/mir-opt/remove_unneeded_drops.cannot_opt_generic.RemoveUnneededDrops.diff
@@ -14,7 +14,6 @@
           StorageLive(_2);                 // scope 0 at $DIR/remove_unneeded_drops.rs:21:5: 21:12
           StorageLive(_3);                 // scope 0 at $DIR/remove_unneeded_drops.rs:21:10: 21:11
           _3 = move _1;                    // scope 0 at $DIR/remove_unneeded_drops.rs:21:10: 21:11
-          _2 = const ();                   // scope 1 at $DIR/remove_unneeded_drops.rs:21:5: 21:12
           drop(_3) -> [return: bb2, unwind: bb1]; // scope 1 at $DIR/remove_unneeded_drops.rs:21:5: 21:12
       }
   
diff --git a/src/test/mir-opt/remove_unneeded_drops.dont_opt.RemoveUnneededDrops.diff b/src/test/mir-opt/remove_unneeded_drops.dont_opt.RemoveUnneededDrops.diff
@@ -14,7 +14,6 @@
           StorageLive(_2);                 // scope 0 at $DIR/remove_unneeded_drops.rs:9:5: 9:12
           StorageLive(_3);                 // scope 0 at $DIR/remove_unneeded_drops.rs:9:10: 9:11
           _3 = move _1;                    // scope 0 at $DIR/remove_unneeded_drops.rs:9:10: 9:11
-          _2 = const ();                   // scope 1 at $DIR/remove_unneeded_drops.rs:9:5: 9:12
           drop(_3) -> [return: bb2, unwind: bb1]; // scope 1 at $DIR/remove_unneeded_drops.rs:9:5: 9:12
       }
   
diff --git a/src/test/mir-opt/remove_unneeded_drops.opt.RemoveUnneededDrops.diff b/src/test/mir-opt/remove_unneeded_drops.opt.RemoveUnneededDrops.diff
@@ -14,7 +14,6 @@
           StorageLive(_2);                 // scope 0 at $DIR/remove_unneeded_drops.rs:4:5: 4:12
           StorageLive(_3);                 // scope 0 at $DIR/remove_unneeded_drops.rs:4:10: 4:11
           _3 = _1;                         // scope 0 at $DIR/remove_unneeded_drops.rs:4:10: 4:11
-          _2 = const ();                   // scope 1 at $DIR/remove_unneeded_drops.rs:4:5: 4:12
 -         drop(_3) -> bb1;                 // scope 1 at $DIR/remove_unneeded_drops.rs:4:5: 4:12
 -     }
 - 
diff --git a/src/test/mir-opt/remove_unneeded_drops.opt_generic_copy.RemoveUnneededDrops.diff b/src/test/mir-opt/remove_unneeded_drops.opt_generic_copy.RemoveUnneededDrops.diff
@@ -14,7 +14,6 @@
           StorageLive(_2);                 // scope 0 at $DIR/remove_unneeded_drops.rs:14:5: 14:12
           StorageLive(_3);                 // scope 0 at $DIR/remove_unneeded_drops.rs:14:10: 14:11
           _3 = _1;                         // scope 0 at $DIR/remove_unneeded_drops.rs:14:10: 14:11
-          _2 = const ();                   // scope 1 at $DIR/remove_unneeded_drops.rs:14:5: 14:12
 -         drop(_3) -> bb1;                 // scope 1 at $DIR/remove_unneeded_drops.rs:14:5: 14:12
 -     }
 - 
diff --git a/src/test/mir-opt/simplify_locals.c.SimplifyLocals.diff b/src/test/mir-opt/simplify_locals.c.SimplifyLocals.diff
@@ -25,7 +25,7 @@
 -         StorageDead(_3);                 // scope 1 at $DIR/simplify-locals.rs:16:25: 16:26
 -         StorageDead(_4);                 // scope 1 at $DIR/simplify-locals.rs:16:26: 16:27
 -         StorageDead(_2);                 // scope 1 at $DIR/simplify-locals.rs:16:26: 16:27
-          _0 = const ();                   // scope 0 at $DIR/simplify-locals.rs:13:8: 17:2
+-         _0 = const ();                   // scope 0 at $DIR/simplify-locals.rs:13:8: 17:2
           StorageDead(_1);                 // scope 0 at $DIR/simplify-locals.rs:17:1: 17:2
           return;                          // scope 0 at $DIR/simplify-locals.rs:17:2: 17:2
       }
diff --git a/src/test/mir-opt/simplify_locals.d1.SimplifyLocals.diff b/src/test/mir-opt/simplify_locals.d1.SimplifyLocals.diff
@@ -11,7 +11,7 @@
 -         StorageLive(_1);                 // scope 0 at $DIR/simplify-locals.rs:22:13: 22:17
 -         discriminant(_1) = 0;            // scope 0 at $DIR/simplify-locals.rs:22:13: 22:17
 -         StorageDead(_1);                 // scope 0 at $DIR/simplify-locals.rs:22:17: 22:18
-          _0 = const ();                   // scope 0 at $DIR/simplify-locals.rs:20:9: 23:2
+-         _0 = const ();                   // scope 0 at $DIR/simplify-locals.rs:20:9: 23:2
           return;                          // scope 0 at $DIR/simplify-locals.rs:23:2: 23:2
       }
   }
diff --git a/src/test/mir-opt/simplify_locals.d2.SimplifyLocals.diff b/src/test/mir-opt/simplify_locals.d2.SimplifyLocals.diff
@@ -31,7 +31,7 @@
 -                                          // + literal: Const { ty: E, val: Value(Scalar(0x01)) }
 -         StorageDead(_1);                 // scope 0 at $DIR/simplify-locals.rs:28:25: 28:26
 -         StorageDead(_2);                 // scope 0 at $DIR/simplify-locals.rs:28:26: 28:27
-          _0 = const ();                   // scope 0 at $DIR/simplify-locals.rs:26:9: 29:2
+-         _0 = const ();                   // scope 0 at $DIR/simplify-locals.rs:26:9: 29:2
           return;                          // scope 0 at $DIR/simplify-locals.rs:29:2: 29:2
       }
   }
diff --git a/src/test/mir-opt/simplify_locals.r.SimplifyLocals.diff b/src/test/mir-opt/simplify_locals.r.SimplifyLocals.diff
@@ -23,7 +23,7 @@
 -         StorageLive(_3);                 // scope 2 at $DIR/simplify-locals.rs:36:13: 36:19
 -         _3 = &mut _1;                    // scope 2 at $DIR/simplify-locals.rs:36:13: 36:19
 -         StorageDead(_3);                 // scope 2 at $DIR/simplify-locals.rs:36:19: 36:20
-          _0 = const ();                   // scope 0 at $DIR/simplify-locals.rs:32:8: 37:2
+-         _0 = const ();                   // scope 0 at $DIR/simplify-locals.rs:32:8: 37:2
           StorageDead(_1);                 // scope 0 at $DIR/simplify-locals.rs:37:1: 37:2
           return;                          // scope 0 at $DIR/simplify-locals.rs:37:2: 37:2
       }
diff --git a/src/test/mir-opt/simplify_locals.t1.SimplifyLocals.diff b/src/test/mir-opt/simplify_locals.t1.SimplifyLocals.diff
@@ -15,7 +15,7 @@
 -         _1 = (*_2);                      // scope 1 at $DIR/simplify-locals.rs:44:14: 44:15
 -         StorageDead(_2);                 // scope 0 at $DIR/simplify-locals.rs:44:17: 44:18
 -         StorageDead(_1);                 // scope 0 at $DIR/simplify-locals.rs:44:17: 44:18
-          _0 = const ();                   // scope 0 at $DIR/simplify-locals.rs:42:9: 45:2
+-         _0 = const ();                   // scope 0 at $DIR/simplify-locals.rs:42:9: 45:2
           return;                          // scope 0 at $DIR/simplify-locals.rs:45:2: 45:2
       }
   }
diff --git a/src/test/mir-opt/simplify_locals.t2.SimplifyLocals.diff b/src/test/mir-opt/simplify_locals.t2.SimplifyLocals.diff
@@ -15,7 +15,7 @@
 -         _1 = &mut (*_2);                 // scope 1 at $DIR/simplify-locals.rs:50:14: 50:20
 -         StorageDead(_2);                 // scope 0 at $DIR/simplify-locals.rs:50:22: 50:23
 -         StorageDead(_1);                 // scope 0 at $DIR/simplify-locals.rs:50:22: 50:23
-          _0 = const ();                   // scope 0 at $DIR/simplify-locals.rs:48:9: 51:2
+-         _0 = const ();                   // scope 0 at $DIR/simplify-locals.rs:48:9: 51:2
           return;                          // scope 0 at $DIR/simplify-locals.rs:51:2: 51:2
       }
   }
diff --git a/src/test/mir-opt/simplify_locals.t3.SimplifyLocals.diff b/src/test/mir-opt/simplify_locals.t3.SimplifyLocals.diff
@@ -19,7 +19,7 @@
 -         StorageDead(_3);                 // scope 0 at $DIR/simplify-locals.rs:56:23: 56:24
 -         StorageDead(_2);                 // scope 0 at $DIR/simplify-locals.rs:56:23: 56:24
 -         StorageDead(_1);                 // scope 0 at $DIR/simplify-locals.rs:56:23: 56:24
-          _0 = const ();                   // scope 0 at $DIR/simplify-locals.rs:54:9: 57:2
+-         _0 = const ();                   // scope 0 at $DIR/simplify-locals.rs:54:9: 57:2
           return;                          // scope 0 at $DIR/simplify-locals.rs:57:2: 57:2
       }
   }
diff --git a/src/test/mir-opt/simplify_locals_fixedpoint.foo.SimplifyLocals.diff b/src/test/mir-opt/simplify_locals_fixedpoint.foo.SimplifyLocals.diff
@@ -30,7 +30,7 @@
       }
   
       bb1: {
-          _0 = const ();                   // scope 0 at $DIR/simplify-locals-fixedpoint.rs:8:6: 8:6
+-         _0 = const ();                   // scope 0 at $DIR/simplify-locals-fixedpoint.rs:8:6: 8:6
           goto -> bb7;                     // scope 0 at $DIR/simplify-locals-fixedpoint.rs:4:5: 8:6
       }
   
@@ -51,12 +51,12 @@
       }
   
       bb4: {
-          _0 = const ();                   // scope 1 at $DIR/simplify-locals-fixedpoint.rs:5:21: 7:10
+-         _0 = const ();                   // scope 1 at $DIR/simplify-locals-fixedpoint.rs:5:21: 7:10
           goto -> bb6;                     // scope 1 at $DIR/simplify-locals-fixedpoint.rs:5:9: 7:10
       }
   
       bb5: {
-          _0 = const ();                   // scope 1 at $DIR/simplify-locals-fixedpoint.rs:7:10: 7:10
+-         _0 = const ();                   // scope 1 at $DIR/simplify-locals-fixedpoint.rs:7:10: 7:10
           goto -> bb6;                     // scope 1 at $DIR/simplify-locals-fixedpoint.rs:5:9: 7:10
       }
   
diff --git a/src/test/mir-opt/simplify_locals_removes_unused_consts.main.SimplifyLocals.diff b/src/test/mir-opt/simplify_locals_removes_unused_consts.main.SimplifyLocals.diff
@@ -71,8 +71,8 @@
 -         StorageDead(_9);                 // scope 1 at $DIR/simplify-locals-removes-unused-consts.rs:16:34: 16:35
 -         StorageDead(_11);                // scope 1 at $DIR/simplify-locals-removes-unused-consts.rs:16:35: 16:36
 -         StorageDead(_8);                 // scope 1 at $DIR/simplify-locals-removes-unused-consts.rs:16:35: 16:36
+-         _0 = const ();                   // scope 0 at $DIR/simplify-locals-removes-unused-consts.rs:12:11: 17:2
 +         StorageDead(_2);                 // scope 1 at $DIR/simplify-locals-removes-unused-consts.rs:16:35: 16:36
-          _0 = const ();                   // scope 0 at $DIR/simplify-locals-removes-unused-consts.rs:12:11: 17:2
           return;                          // scope 0 at $DIR/simplify-locals-removes-unused-consts.rs:17:2: 17:2
       }
   }
diff --git a/src/test/mir-opt/uninhabited_enum.process_void.SimplifyLocals.after.mir b/src/test/mir-opt/uninhabited_enum.process_void.SimplifyLocals.after.mir
diff --git a/src/test/mir-opt/while_let_loops.change_loop_body.PreCodegen.after.32bit.mir b/src/test/mir-opt/while_let_loops.change_loop_body.PreCodegen.after.32bit.mir
diff --git a/src/test/mir-opt/while_let_loops.change_loop_body.PreCodegen.after.64bit.mir b/src/test/mir-opt/while_let_loops.change_loop_body.PreCodegen.after.64bit.mir
diff --git a/src/test/mir-opt/while_storage.while_loop.PreCodegen.after.mir b/src/test/mir-opt/while_storage.while_loop.PreCodegen.after.mir

Original file line number	Diff line number	Diff line change
`@@ -9,6 +9,7 @@`
`9`	`9`	`#[naked]`
`10`	`10`	`pub fn naked_empty() {`
`11`	`11`	`// CHECK-NEXT: {{.+}}:`
	`12`	`+ // CHECK-NEXT: %0 = alloca {}, align 1`
`12`	`13`	`// CHECK-NEXT: ret void`
`13`	`14`	`}`
`14`	`15`
`@@ -18,6 +19,7 @@ pub fn naked_empty() {`
`18`	`19`	`// CHECK-NEXT: define void @naked_with_args(i{{[0-9]+( %a)?}})`
`19`	`20`	`pub fn naked_with_args(a: isize) {`
`20`	`21`	`// CHECK-NEXT: {{.+}}:`
	`22`	`+ // CHECK-NEXT: %0 = alloca {}, align 1`
`21`	`23`	`// CHECK: ret void`
`22`	`24`	`}`
`23`	`25`
Original file line number	Diff line number	Diff line change
`@@ -4,7 +4,6 @@ fn hello() -> () {`
`4`	`4`	`let mut _0: (); // return place in scope 0 at $DIR/control-flow-simplification.rs:11:14: 11:14`
`5`	`5`
`6`	`6`	`bb0: {`
`7`		`- _0 = const (); // scope 0 at $DIR/control-flow-simplification.rs:14:6: 14:6`
`8`	`7`	`return; // scope 0 at $DIR/control-flow-simplification.rs:15:2: 15:2`
`9`	`8`	`}`
`10`	`9`	`}`
Original file line number	Diff line number	Diff line change
`@@ -16,7 +16,6 @@`
`16`	`16`	`- }`
`17`	`17`	`-`
`18`	`18`	`- bb1: {`
`19`		`-+ _1 = const (); // scope 1 at $DIR/inline-compatibility.rs:24:5: 24:18`
`20`	`19`	`StorageDead(_1); // scope 0 at $DIR/inline-compatibility.rs:24:18: 24:19`
`21`	`20`	`_0 = const (); // scope 0 at $DIR/inline-compatibility.rs:23:37: 25:2`
`22`	`21`	`return; // scope 0 at $DIR/inline-compatibility.rs:25:2: 25:2`
Original file line number	Diff line number	Diff line change
`@@ -27,7 +27,6 @@ fn f_u64() -> () {`
`27`	`27`	`StorageDead(_3); // scope 1 at $DIR/lower_intrinsics.rs:35:5: 35:21`
`28`	`28`	`StorageDead(_2); // scope 1 at $DIR/lower_intrinsics.rs:35:5: 35:21`
`29`	`29`	`StorageDead(_1); // scope 0 at $DIR/lower_intrinsics.rs:35:5: 35:21`
`30`		`- _0 = const (); // scope 0 at $DIR/lower_intrinsics.rs:34:16: 36:2`
`31`	`30`	`return; // scope 0 at $DIR/lower_intrinsics.rs:36:2: 36:2`
`32`	`31`	`}`
`33`	`32`	`}`
Original file line number	Diff line number	Diff line change
`@@ -22,7 +22,6 @@ fn f_unit() -> () {`
`22`	`22`	`bb1: {`
`23`	`23`	`StorageDead(_2); // scope 1 at $DIR/lower_intrinsics.rs:29:5: 29:19`
`24`	`24`	`StorageDead(_1); // scope 0 at $DIR/lower_intrinsics.rs:29:18: 29:19`
`25`		`- _0 = const (); // scope 0 at $DIR/lower_intrinsics.rs:28:17: 30:2`
`26`	`25`	`return; // scope 0 at $DIR/lower_intrinsics.rs:30:2: 30:2`
`27`	`26`	`}`
`28`	`27`	`}`
Original file line number	Diff line number	Diff line change
`@@ -13,12 +13,10 @@`
`13`	`13`	`}`
`14`	`14`
`15`	`15`	`bb1: {`
`16`		`- _0 = const (); // scope 0 at $DIR/multiple_return_terminators.rs:5:10: 7:6`
`17`	`16`	`goto -> bb3; // scope 0 at $DIR/multiple_return_terminators.rs:5:5: 9:6`
`18`	`17`	`}`
`19`	`18`
`20`	`19`	`bb2: {`
`21`		`- _0 = const (); // scope 0 at $DIR/multiple_return_terminators.rs:7:12: 9:6`
`22`	`20`	`goto -> bb3; // scope 0 at $DIR/multiple_return_terminators.rs:5:5: 9:6`
`23`	`21`	`}`
`24`	`22`
Original file line number	Diff line number	Diff line change
`@@ -14,7 +14,6 @@`
`14`	`14`	`StorageLive(_2); // scope 0 at $DIR/remove_unneeded_drops.rs:21:5: 21:12`
`15`	`15`	`StorageLive(_3); // scope 0 at $DIR/remove_unneeded_drops.rs:21:10: 21:11`
`16`	`16`	`_3 = move _1; // scope 0 at $DIR/remove_unneeded_drops.rs:21:10: 21:11`
`17`		`- _2 = const (); // scope 1 at $DIR/remove_unneeded_drops.rs:21:5: 21:12`
`18`	`17`	`drop(_3) -> [return: bb2, unwind: bb1]; // scope 1 at $DIR/remove_unneeded_drops.rs:21:5: 21:12`
`19`	`18`	`}`
`20`	`19`
Original file line number	Diff line number	Diff line change
`@@ -25,7 +25,7 @@`
`25`	`25`	`- StorageDead(_3); // scope 1 at $DIR/simplify-locals.rs:16:25: 16:26`
`26`	`26`	`- StorageDead(_4); // scope 1 at $DIR/simplify-locals.rs:16:26: 16:27`
`27`	`27`	`- StorageDead(_2); // scope 1 at $DIR/simplify-locals.rs:16:26: 16:27`
`28`		`- _0 = const (); // scope 0 at $DIR/simplify-locals.rs:13:8: 17:2`
	`28`	`+- _0 = const (); // scope 0 at $DIR/simplify-locals.rs:13:8: 17:2`
`29`	`29`	`StorageDead(_1); // scope 0 at $DIR/simplify-locals.rs:17:1: 17:2`
`30`	`30`	`return; // scope 0 at $DIR/simplify-locals.rs:17:2: 17:2`
`31`	`31`	`}`
Original file line number	Diff line number	Diff line change
`@@ -11,7 +11,7 @@`
`11`	`11`	`- StorageLive(_1); // scope 0 at $DIR/simplify-locals.rs:22:13: 22:17`
`12`	`12`	`- discriminant(_1) = 0; // scope 0 at $DIR/simplify-locals.rs:22:13: 22:17`
`13`	`13`	`- StorageDead(_1); // scope 0 at $DIR/simplify-locals.rs:22:17: 22:18`
`14`		`- _0 = const (); // scope 0 at $DIR/simplify-locals.rs:20:9: 23:2`
	`14`	`+- _0 = const (); // scope 0 at $DIR/simplify-locals.rs:20:9: 23:2`
`15`	`15`	`return; // scope 0 at $DIR/simplify-locals.rs:23:2: 23:2`
`16`	`16`	`}`
`17`	`17`	`}`
Original file line number	Diff line number	Diff line change
`@@ -31,7 +31,7 @@`
`31`	`31`	`- // + literal: Const { ty: E, val: Value(Scalar(0x01)) }`
`32`	`32`	`- StorageDead(_1); // scope 0 at $DIR/simplify-locals.rs:28:25: 28:26`
`33`	`33`	`- StorageDead(_2); // scope 0 at $DIR/simplify-locals.rs:28:26: 28:27`
`34`		`- _0 = const (); // scope 0 at $DIR/simplify-locals.rs:26:9: 29:2`
	`34`	`+- _0 = const (); // scope 0 at $DIR/simplify-locals.rs:26:9: 29:2`
`35`	`35`	`return; // scope 0 at $DIR/simplify-locals.rs:29:2: 29:2`
`36`	`36`	`}`
`37`	`37`	`}`