enhance `ConstGoto` mir-opt by moving up `StorageDead` statements

5 files changed, 167 insertions, 127 deletions

diff --git a/compiler/rustc_mir_transform/src/const_goto.rs b/compiler/rustc_mir_transform/src/const_goto.rs
index 905173b0457..5acf939f06b 100644
--- a/compiler/rustc_mir_transform/src/const_goto.rs
+++ b/compiler/rustc_mir_transform/src/const_goto.rs
@@ -39,7 +39,9 @@ impl<'tcx> MirPass<'tcx> for ConstGoto {
         opt_finder.visit_body(body);
         let should_simplify = !opt_finder.optimizations.is_empty();
         for opt in opt_finder.optimizations {
-            let terminator = body.basic_blocks_mut()[opt.bb_with_goto].terminator_mut();
+            let block = &mut body.basic_blocks_mut()[opt.bb_with_goto];
+            block.statements.extend(opt.stmts_move_up);
+            let terminator = block.terminator_mut();
             let new_goto = TerminatorKind::Goto { target: opt.target_to_use_in_goto };
             debug!("SUCCESS: replacing `{:?}` with `{:?}`", terminator.kind, new_goto);
             terminator.kind = new_goto;
@@ -68,12 +70,15 @@ impl<'tcx> Visitor<'tcx> for ConstGotoOptimizationFinder<'_, 'tcx> {
                 // Now check that the target of this Goto switches on this place.
                 let target_bb = &self.body.basic_blocks()[target];
 
-                // FIXME(simonvandel): We are conservative here when we don't allow
-                // any statements in the target basic block.
-                // This could probably be relaxed to allow `StorageDead`s which could be
-                // copied to the predecessor of this block.
-                if !target_bb.statements.is_empty() {
-                    None?
+                // The `StorageDead(..)` statement does not affect the functionality of mir.
+                // We can move this part of the statement up to the predecessor.
+                let mut stmts_move_up = Vec::new();
+                for stmt in &target_bb.statements {
+                    if let StatementKind::StorageDead(..) = stmt.kind {
+                        stmts_move_up.push(stmt.clone())
+                    } else {
+                        None?;
+                    }
                 }
 
                 let target_bb_terminator = target_bb.terminator();
@@ -87,6 +92,7 @@ impl<'tcx> Visitor<'tcx> for ConstGotoOptimizationFinder<'_, 'tcx> {
                     self.optimizations.push(OptimizationToApply {
                         bb_with_goto: location.block,
                         target_to_use_in_goto,
+                        stmts_move_up,
                     });
                 }
             }
@@ -97,14 +103,15 @@ impl<'tcx> Visitor<'tcx> for ConstGotoOptimizationFinder<'_, 'tcx> {
     }
 }
 
-struct OptimizationToApply {
+struct OptimizationToApply<'tcx> {
     bb_with_goto: BasicBlock,
     target_to_use_in_goto: BasicBlock,
+    stmts_move_up: Vec<Statement<'tcx>>,
 }
 
 pub struct ConstGotoOptimizationFinder<'a, 'tcx> {
     tcx: TyCtxt<'tcx>,
     body: &'a Body<'tcx>,
     param_env: ParamEnv<'tcx>,
-    optimizations: Vec<OptimizationToApply>,
+    optimizations: Vec<OptimizationToApply<'tcx>>,
 }
diff --git a/src/test/mir-opt/const_goto_storage.match_nested_if.ConstGoto.diff b/src/test/mir-opt/const_goto_storage.match_nested_if.ConstGoto.diff
new file mode 100644
index 00000000000..aee7e22a60f
--- /dev/null
+++ b/src/test/mir-opt/const_goto_storage.match_nested_if.ConstGoto.diff
@@ -0,0 +1,102 @@
+- // MIR for `match_nested_if` before ConstGoto
++ // MIR for `match_nested_if` after ConstGoto
+  
+  fn match_nested_if() -> bool {
+      let mut _0: bool;                    // return place in scope 0 at $DIR/const_goto_storage.rs:2:25: 2:29
+      let _1: bool;                        // in scope 0 at $DIR/const_goto_storage.rs:3:9: 3:12
+-     let mut _2: ();                      // in scope 0 at $DIR/const_goto_storage.rs:3:21: 3:23
+-     let mut _3: bool;                    // in scope 0 at $DIR/const_goto_storage.rs:4:15: 8:10
+-     let mut _4: bool;                    // in scope 0 at $DIR/const_goto_storage.rs:4:18: 4:76
+-     let mut _5: bool;                    // in scope 0 at $DIR/const_goto_storage.rs:4:21: 4:52
+-     let mut _6: bool;                    // in scope 0 at $DIR/const_goto_storage.rs:4:24: 4:28
++     let mut _2: bool;                    // in scope 0 at $DIR/const_goto_storage.rs:4:24: 4:28
+      scope 1 {
+          debug val => _1;                 // in scope 1 at $DIR/const_goto_storage.rs:3:9: 3:12
+      }
+  
+      bb0: {
+          StorageLive(_1);                 // scope 0 at $DIR/const_goto_storage.rs:3:9: 3:12
+-         StorageLive(_2);                 // scope 0 at $DIR/const_goto_storage.rs:3:21: 3:23
+-         StorageLive(_3);                 // scope 0 at $DIR/const_goto_storage.rs:4:15: 8:10
+-         StorageLive(_4);                 // scope 0 at $DIR/const_goto_storage.rs:4:18: 4:76
+-         StorageLive(_5);                 // scope 0 at $DIR/const_goto_storage.rs:4:21: 4:52
+-         StorageLive(_6);                 // scope 0 at $DIR/const_goto_storage.rs:4:24: 4:28
+-         _6 = const true;                 // scope 0 at $DIR/const_goto_storage.rs:4:24: 4:28
+-         switchInt(move _6) -> [false: bb2, otherwise: bb1]; // scope 0 at $DIR/const_goto_storage.rs:4:24: 4:28
++         StorageLive(_2);                 // scope 0 at $DIR/const_goto_storage.rs:4:24: 4:28
++         _2 = const true;                 // scope 0 at $DIR/const_goto_storage.rs:4:24: 4:28
++         switchInt(move _2) -> [false: bb2, otherwise: bb1]; // scope 0 at $DIR/const_goto_storage.rs:4:24: 4:28
+      }
+  
+      bb1: {
+-         _5 = const true;                 // scope 0 at $DIR/const_goto_storage.rs:4:31: 4:35
+-         goto -> bb3;                     // scope 0 at $DIR/const_goto_storage.rs:4:21: 4:52
+-     }
+- 
+-     bb2: {
+-         _5 = const false;                // scope 0 at $DIR/const_goto_storage.rs:4:45: 4:50
+-         goto -> bb3;                     // scope 0 at $DIR/const_goto_storage.rs:4:21: 4:52
+-     }
+- 
+-     bb3: {
+-         StorageDead(_6);                 // scope 0 at $DIR/const_goto_storage.rs:4:51: 4:52
+-         switchInt(move _5) -> [false: bb5, otherwise: bb4]; // scope 0 at $DIR/const_goto_storage.rs:4:21: 4:52
+-     }
+- 
+-     bb4: {
+-         _4 = const true;                 // scope 0 at $DIR/const_goto_storage.rs:4:55: 4:59
+-         goto -> bb6;                     // scope 0 at $DIR/const_goto_storage.rs:4:18: 4:76
+-     }
+- 
+-     bb5: {
+-         _4 = const false;                // scope 0 at $DIR/const_goto_storage.rs:4:69: 4:74
+-         goto -> bb6;                     // scope 0 at $DIR/const_goto_storage.rs:4:18: 4:76
+-     }
+- 
+-     bb6: {
+-         StorageDead(_5);                 // scope 0 at $DIR/const_goto_storage.rs:4:75: 4:76
+-         switchInt(move _4) -> [false: bb8, otherwise: bb7]; // scope 0 at $DIR/const_goto_storage.rs:4:18: 4:76
+-     }
+- 
+-     bb7: {
+-         _3 = const true;                 // scope 0 at $DIR/const_goto_storage.rs:5:13: 5:17
+-         goto -> bb9;                     // scope 0 at $DIR/const_goto_storage.rs:4:15: 8:10
+-     }
+- 
+-     bb8: {
+-         _3 = const false;                // scope 0 at $DIR/const_goto_storage.rs:7:13: 7:18
+-         goto -> bb9;                     // scope 0 at $DIR/const_goto_storage.rs:4:15: 8:10
+-     }
+- 
+-     bb9: {
+-         switchInt(move _3) -> [false: bb11, otherwise: bb10]; // scope 0 at $DIR/const_goto_storage.rs:4:15: 8:10
+-     }
+- 
+-     bb10: {
+-         StorageDead(_4);                 // scope 0 at $DIR/const_goto_storage.rs:8:9: 8:10
+-         StorageDead(_3);                 // scope 0 at $DIR/const_goto_storage.rs:8:9: 8:10
++         StorageDead(_2);                 // scope 0 at $DIR/const_goto_storage.rs:4:51: 4:52
+          _1 = const true;                 // scope 0 at $DIR/const_goto_storage.rs:10:17: 10:21
+-         goto -> bb12;                    // scope 0 at $DIR/const_goto_storage.rs:10:17: 10:21
++         goto -> bb3;                     // scope 0 at $DIR/const_goto_storage.rs:10:17: 10:21
+      }
+  
+-     bb11: {
+-         StorageDead(_4);                 // scope 0 at $DIR/const_goto_storage.rs:8:9: 8:10
+-         StorageDead(_3);                 // scope 0 at $DIR/const_goto_storage.rs:8:9: 8:10
++     bb2: {
++         StorageDead(_2);                 // scope 0 at $DIR/const_goto_storage.rs:4:51: 4:52
+          _1 = const false;                // scope 0 at $DIR/const_goto_storage.rs:12:14: 12:19
+-         goto -> bb12;                    // scope 0 at $DIR/const_goto_storage.rs:12:14: 12:19
++         goto -> bb3;                     // scope 0 at $DIR/const_goto_storage.rs:12:14: 12:19
+      }
+  
+-     bb12: {
+-         StorageDead(_2);                 // scope 0 at $DIR/const_goto_storage.rs:13:6: 13:7
++     bb3: {
+          _0 = _1;                         // scope 1 at $DIR/const_goto_storage.rs:14:5: 14:8
+          StorageDead(_1);                 // scope 0 at $DIR/const_goto_storage.rs:15:1: 15:2
+          return;                          // scope 0 at $DIR/const_goto_storage.rs:15:2: 15:2
+      }
+  }
+  
diff --git a/src/test/mir-opt/const_goto_storage.rs b/src/test/mir-opt/const_goto_storage.rs
new file mode 100644
index 00000000000..4ef68e7e1fa
--- /dev/null
+++ b/src/test/mir-opt/const_goto_storage.rs
@@ -0,0 +1,19 @@
+// EMIT_MIR const_goto_storage.match_nested_if.ConstGoto.diff
+fn match_nested_if() -> bool {
+    let val = match () {
+        () if if if if true { true } else { false } { true } else { false } {
+            true
+        } else {
+            false
+        } =>
+            {
+                true
+            }
+        _ => false,
+    };
+    val
+}
+
+fn main() {
+    let _ = match_nested_if();
+}
diff --git a/src/test/mir-opt/matches_reduce_branches.match_nested_if.MatchBranchSimplification.32bit.diff b/src/test/mir-opt/matches_reduce_branches.match_nested_if.MatchBranchSimplification.32bit.diff
index 0511b59cf01..2dfb2e1af0d 100644
--- a/src/test/mir-opt/matches_reduce_branches.match_nested_if.MatchBranchSimplification.32bit.diff
+++ b/src/test/mir-opt/matches_reduce_branches.match_nested_if.MatchBranchSimplification.32bit.diff
@@ -4,80 +4,36 @@
   fn match_nested_if() -> bool {
       let mut _0: bool;                    // return place in scope 0 at $DIR/matches_reduce_branches.rs:39:25: 39:29
       let _1: bool;                        // in scope 0 at $DIR/matches_reduce_branches.rs:40:9: 40:12
-      let mut _2: bool;                    // in scope 0 at $DIR/matches_reduce_branches.rs:41:18: 41:76
-      let mut _3: bool;                    // in scope 0 at $DIR/matches_reduce_branches.rs:41:21: 41:52
-      let mut _4: bool;                    // in scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
-+     let mut _5: bool;                    // in scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
-+     let mut _6: bool;                    // in scope 0 at $DIR/matches_reduce_branches.rs:41:21: 41:52
-+     let mut _7: bool;                    // in scope 0 at $DIR/matches_reduce_branches.rs:41:18: 41:76
+      let mut _2: bool;                    // in scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
++     let mut _3: bool;                    // in scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
       scope 1 {
           debug val => _1;                 // in scope 1 at $DIR/matches_reduce_branches.rs:40:9: 40:12
       }
   
       bb0: {
           StorageLive(_1);                 // scope 0 at $DIR/matches_reduce_branches.rs:40:9: 40:12
-          StorageLive(_2);                 // scope 0 at $DIR/matches_reduce_branches.rs:41:18: 41:76
-          StorageLive(_3);                 // scope 0 at $DIR/matches_reduce_branches.rs:41:21: 41:52
-          StorageLive(_4);                 // scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
-          _4 = const true;                 // scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
--         switchInt(move _4) -> [false: bb2, otherwise: bb1]; // scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
+          StorageLive(_2);                 // scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
+          _2 = const true;                 // scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
+-         switchInt(move _2) -> [false: bb2, otherwise: bb1]; // scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
 -     }
 - 
 -     bb1: {
--         _3 = const true;                 // scope 0 at $DIR/matches_reduce_branches.rs:41:31: 41:35
--         goto -> bb3;                     // scope 0 at $DIR/matches_reduce_branches.rs:41:21: 41:52
--     }
-- 
--     bb2: {
--         _3 = const false;                // scope 0 at $DIR/matches_reduce_branches.rs:41:45: 41:50
--         goto -> bb3;                     // scope 0 at $DIR/matches_reduce_branches.rs:41:21: 41:52
--     }
-- 
--     bb3: {
-+         StorageLive(_5);                 // scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
-+         _5 = move _4;                    // scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
-+         _3 = Ne(_5, const false);        // scope 0 at $DIR/matches_reduce_branches.rs:41:45: 41:50
-+         StorageDead(_5);                 // scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
-          StorageDead(_4);                 // scope 0 at $DIR/matches_reduce_branches.rs:41:51: 41:52
--         switchInt(move _3) -> [false: bb5, otherwise: bb4]; // scope 0 at $DIR/matches_reduce_branches.rs:41:21: 41:52
--     }
-- 
--     bb4: {
--         _2 = const true;                 // scope 0 at $DIR/matches_reduce_branches.rs:41:55: 41:59
--         goto -> bb6;                     // scope 0 at $DIR/matches_reduce_branches.rs:41:18: 41:76
--     }
-- 
--     bb5: {
--         _2 = const false;                // scope 0 at $DIR/matches_reduce_branches.rs:41:69: 41:74
--         goto -> bb6;                     // scope 0 at $DIR/matches_reduce_branches.rs:41:18: 41:76
--     }
-- 
--     bb6: {
-+         StorageLive(_6);                 // scope 0 at $DIR/matches_reduce_branches.rs:41:21: 41:52
-+         _6 = move _3;                    // scope 0 at $DIR/matches_reduce_branches.rs:41:21: 41:52
-+         _2 = Ne(_6, const false);        // scope 0 at $DIR/matches_reduce_branches.rs:41:69: 41:74
-+         StorageDead(_6);                 // scope 0 at $DIR/matches_reduce_branches.rs:41:21: 41:52
-          StorageDead(_3);                 // scope 0 at $DIR/matches_reduce_branches.rs:41:75: 41:76
--         switchInt(move _2) -> [false: bb8, otherwise: bb7]; // scope 0 at $DIR/matches_reduce_branches.rs:41:18: 41:76
--     }
-- 
--     bb7: {
-+         StorageLive(_7);                 // scope 0 at $DIR/matches_reduce_branches.rs:41:18: 41:76
-+         _7 = move _2;                    // scope 0 at $DIR/matches_reduce_branches.rs:41:18: 41:76
-          StorageDead(_2);                 // scope 0 at $DIR/matches_reduce_branches.rs:45:9: 45:10
++         StorageLive(_3);                 // scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
++         _3 = move _2;                    // scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
+          StorageDead(_2);                 // scope 0 at $DIR/matches_reduce_branches.rs:41:51: 41:52
 -         _1 = const true;                 // scope 0 at $DIR/matches_reduce_branches.rs:47:13: 47:17
--         goto -> bb9;                     // scope 0 at $DIR/matches_reduce_branches.rs:47:13: 47:17
+-         goto -> bb3;                     // scope 0 at $DIR/matches_reduce_branches.rs:47:13: 47:17
 -     }
 - 
--     bb8: {
--         StorageDead(_2);                 // scope 0 at $DIR/matches_reduce_branches.rs:45:9: 45:10
+-     bb2: {
+-         StorageDead(_2);                 // scope 0 at $DIR/matches_reduce_branches.rs:41:51: 41:52
 -         _1 = const false;                // scope 0 at $DIR/matches_reduce_branches.rs:49:14: 49:19
--         goto -> bb9;                     // scope 0 at $DIR/matches_reduce_branches.rs:49:14: 49:19
+-         goto -> bb3;                     // scope 0 at $DIR/matches_reduce_branches.rs:49:14: 49:19
 -     }
 - 
--     bb9: {
-+         _1 = Ne(_7, const false);        // scope 0 at $DIR/matches_reduce_branches.rs:49:14: 49:19
-+         StorageDead(_7);                 // scope 0 at $DIR/matches_reduce_branches.rs:41:18: 41:76
+-     bb3: {
++         _1 = Ne(_3, const false);        // scope 0 at $DIR/matches_reduce_branches.rs:49:14: 49:19
++         StorageDead(_3);                 // scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
           _0 = _1;                         // scope 1 at $DIR/matches_reduce_branches.rs:51:5: 51:8
           StorageDead(_1);                 // scope 0 at $DIR/matches_reduce_branches.rs:52:1: 52:2
           return;                          // scope 0 at $DIR/matches_reduce_branches.rs:52:2: 52:2
diff --git a/src/test/mir-opt/matches_reduce_branches.match_nested_if.MatchBranchSimplification.64bit.diff b/src/test/mir-opt/matches_reduce_branches.match_nested_if.MatchBranchSimplification.64bit.diff
index 0511b59cf01..2dfb2e1af0d 100644
--- a/src/test/mir-opt/matches_reduce_branches.match_nested_if.MatchBranchSimplification.64bit.diff
+++ b/src/test/mir-opt/matches_reduce_branches.match_nested_if.MatchBranchSimplification.64bit.diff
@@ -4,80 +4,36 @@
   fn match_nested_if() -> bool {
       let mut _0: bool;                    // return place in scope 0 at $DIR/matches_reduce_branches.rs:39:25: 39:29
       let _1: bool;                        // in scope 0 at $DIR/matches_reduce_branches.rs:40:9: 40:12
-      let mut _2: bool;                    // in scope 0 at $DIR/matches_reduce_branches.rs:41:18: 41:76
-      let mut _3: bool;                    // in scope 0 at $DIR/matches_reduce_branches.rs:41:21: 41:52
-      let mut _4: bool;                    // in scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
-+     let mut _5: bool;                    // in scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
-+     let mut _6: bool;                    // in scope 0 at $DIR/matches_reduce_branches.rs:41:21: 41:52
-+     let mut _7: bool;                    // in scope 0 at $DIR/matches_reduce_branches.rs:41:18: 41:76
+      let mut _2: bool;                    // in scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
++     let mut _3: bool;                    // in scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
       scope 1 {
           debug val => _1;                 // in scope 1 at $DIR/matches_reduce_branches.rs:40:9: 40:12
       }
   
       bb0: {
           StorageLive(_1);                 // scope 0 at $DIR/matches_reduce_branches.rs:40:9: 40:12
-          StorageLive(_2);                 // scope 0 at $DIR/matches_reduce_branches.rs:41:18: 41:76
-          StorageLive(_3);                 // scope 0 at $DIR/matches_reduce_branches.rs:41:21: 41:52
-          StorageLive(_4);                 // scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
-          _4 = const true;                 // scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
--         switchInt(move _4) -> [false: bb2, otherwise: bb1]; // scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
+          StorageLive(_2);                 // scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
+          _2 = const true;                 // scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
+-         switchInt(move _2) -> [false: bb2, otherwise: bb1]; // scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
 -     }
 - 
 -     bb1: {
--         _3 = const true;                 // scope 0 at $DIR/matches_reduce_branches.rs:41:31: 41:35
--         goto -> bb3;                     // scope 0 at $DIR/matches_reduce_branches.rs:41:21: 41:52
--     }
-- 
--     bb2: {
--         _3 = const false;                // scope 0 at $DIR/matches_reduce_branches.rs:41:45: 41:50
--         goto -> bb3;                     // scope 0 at $DIR/matches_reduce_branches.rs:41:21: 41:52
--     }
-- 
--     bb3: {
-+         StorageLive(_5);                 // scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
-+         _5 = move _4;                    // scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
-+         _3 = Ne(_5, const false);        // scope 0 at $DIR/matches_reduce_branches.rs:41:45: 41:50
-+         StorageDead(_5);                 // scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
-          StorageDead(_4);                 // scope 0 at $DIR/matches_reduce_branches.rs:41:51: 41:52
--         switchInt(move _3) -> [false: bb5, otherwise: bb4]; // scope 0 at $DIR/matches_reduce_branches.rs:41:21: 41:52
--     }
-- 
--     bb4: {
--         _2 = const true;                 // scope 0 at $DIR/matches_reduce_branches.rs:41:55: 41:59
--         goto -> bb6;                     // scope 0 at $DIR/matches_reduce_branches.rs:41:18: 41:76
--     }
-- 
--     bb5: {
--         _2 = const false;                // scope 0 at $DIR/matches_reduce_branches.rs:41:69: 41:74
--         goto -> bb6;                     // scope 0 at $DIR/matches_reduce_branches.rs:41:18: 41:76
--     }
-- 
--     bb6: {
-+         StorageLive(_6);                 // scope 0 at $DIR/matches_reduce_branches.rs:41:21: 41:52
-+         _6 = move _3;                    // scope 0 at $DIR/matches_reduce_branches.rs:41:21: 41:52
-+         _2 = Ne(_6, const false);        // scope 0 at $DIR/matches_reduce_branches.rs:41:69: 41:74
-+         StorageDead(_6);                 // scope 0 at $DIR/matches_reduce_branches.rs:41:21: 41:52
-          StorageDead(_3);                 // scope 0 at $DIR/matches_reduce_branches.rs:41:75: 41:76
--         switchInt(move _2) -> [false: bb8, otherwise: bb7]; // scope 0 at $DIR/matches_reduce_branches.rs:41:18: 41:76
--     }
-- 
--     bb7: {
-+         StorageLive(_7);                 // scope 0 at $DIR/matches_reduce_branches.rs:41:18: 41:76
-+         _7 = move _2;                    // scope 0 at $DIR/matches_reduce_branches.rs:41:18: 41:76
-          StorageDead(_2);                 // scope 0 at $DIR/matches_reduce_branches.rs:45:9: 45:10
++         StorageLive(_3);                 // scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
++         _3 = move _2;                    // scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
+          StorageDead(_2);                 // scope 0 at $DIR/matches_reduce_branches.rs:41:51: 41:52
 -         _1 = const true;                 // scope 0 at $DIR/matches_reduce_branches.rs:47:13: 47:17
--         goto -> bb9;                     // scope 0 at $DIR/matches_reduce_branches.rs:47:13: 47:17
+-         goto -> bb3;                     // scope 0 at $DIR/matches_reduce_branches.rs:47:13: 47:17
 -     }
 - 
--     bb8: {
--         StorageDead(_2);                 // scope 0 at $DIR/matches_reduce_branches.rs:45:9: 45:10
+-     bb2: {
+-         StorageDead(_2);                 // scope 0 at $DIR/matches_reduce_branches.rs:41:51: 41:52
 -         _1 = const false;                // scope 0 at $DIR/matches_reduce_branches.rs:49:14: 49:19
--         goto -> bb9;                     // scope 0 at $DIR/matches_reduce_branches.rs:49:14: 49:19
+-         goto -> bb3;                     // scope 0 at $DIR/matches_reduce_branches.rs:49:14: 49:19
 -     }
 - 
--     bb9: {
-+         _1 = Ne(_7, const false);        // scope 0 at $DIR/matches_reduce_branches.rs:49:14: 49:19
-+         StorageDead(_7);                 // scope 0 at $DIR/matches_reduce_branches.rs:41:18: 41:76
+-     bb3: {
++         _1 = Ne(_3, const false);        // scope 0 at $DIR/matches_reduce_branches.rs:49:14: 49:19
++         StorageDead(_3);                 // scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
           _0 = _1;                         // scope 1 at $DIR/matches_reduce_branches.rs:51:5: 51:8
           StorageDead(_1);                 // scope 0 at $DIR/matches_reduce_branches.rs:52:1: 52:2
           return;                          // scope 0 at $DIR/matches_reduce_branches.rs:52:2: 52:2