[mir-opt] Allow debuginfo to be generated for a constant or a Place

Prior to this commit, debuginfo was always generated by mapping a name
to a Place. This has the side-effect that `SimplifyLocals` cannot remove
locals that are only used for debuginfo because their other uses have
been const-propagated.

To allow these locals to be removed, we now allow debuginfo to point to
a constant value. The `ConstProp` pass detects when debuginfo points to
a local with a known constant value and replaces it with the value. This
allows the later `SimplifyLocals` pass to remove the local.

9 files changed, 151 insertions, 48 deletions

diff --git a/src/test/incremental/hashes/let_expressions.rs b/src/test/incremental/hashes/let_expressions.rs
index 918e72582d6..2c37b2e78ff 100644
--- a/src/test/incremental/hashes/let_expressions.rs
+++ b/src/test/incremental/hashes/let_expressions.rs
@@ -86,7 +86,7 @@ pub fn change_mutability_of_slot() {
 
 #[cfg(not(cfail1))]
 #[rustc_clean(cfg="cfail2",
-    except="hir_owner_nodes,typeck,optimized_mir")]
+    except="hir_owner_nodes,typeck")]
 #[rustc_clean(cfg="cfail3")]
 pub fn change_mutability_of_slot() {
     let _x: u64 = 0;
@@ -166,7 +166,7 @@ pub fn change_mutability_of_binding_in_pattern() {
 
 #[cfg(not(cfail1))]
 #[rustc_clean(cfg="cfail2",
-    except="hir_owner_nodes,typeck,optimized_mir")]
+    except="hir_owner_nodes,typeck")]
 #[rustc_clean(cfg="cfail3")]
 pub fn change_mutability_of_binding_in_pattern() {
     let (mut _a, _b) = (99u8, 'q');
diff --git a/src/test/mir-opt/const_debuginfo.main.ConstDebugInfo.diff b/src/test/mir-opt/const_debuginfo.main.ConstDebugInfo.diff
new file mode 100644
index 00000000000..47c3239b8bf
--- /dev/null
+++ b/src/test/mir-opt/const_debuginfo.main.ConstDebugInfo.diff
@@ -0,0 +1,115 @@
+- // MIR for `main` before ConstDebugInfo
++ // MIR for `main` after ConstDebugInfo
+  
+  fn main() -> () {
+      let mut _0: ();                      // return place in scope 0 at $DIR/const_debuginfo.rs:8:11: 8:11
+      let _1: u8;                          // in scope 0 at $DIR/const_debuginfo.rs:9:9: 9:10
+      let mut _5: u8;                      // in scope 0 at $DIR/const_debuginfo.rs:12:15: 12:20
+      let mut _6: u8;                      // in scope 0 at $DIR/const_debuginfo.rs:12:15: 12:16
+      let mut _7: u8;                      // in scope 0 at $DIR/const_debuginfo.rs:12:19: 12:20
+      let mut _8: u8;                      // in scope 0 at $DIR/const_debuginfo.rs:12:23: 12:24
+      let mut _14: u32;                    // in scope 0 at $DIR/const_debuginfo.rs:21:13: 21:16
+      let mut _15: u32;                    // in scope 0 at $DIR/const_debuginfo.rs:21:19: 21:22
+      scope 1 {
+-         debug x => _1;                   // in scope 1 at $DIR/const_debuginfo.rs:9:9: 9:10
++         debug x => const 1_u8;           // in scope 1 at $DIR/const_debuginfo.rs:9:9: 9:10
+          let _2: u8;                      // in scope 1 at $DIR/const_debuginfo.rs:10:9: 10:10
+          scope 2 {
+-             debug y => _2;               // in scope 2 at $DIR/const_debuginfo.rs:10:9: 10:10
++             debug y => const 2_u8;       // in scope 2 at $DIR/const_debuginfo.rs:10:9: 10:10
+              let _3: u8;                  // in scope 2 at $DIR/const_debuginfo.rs:11:9: 11:10
+              scope 3 {
+-                 debug z => _3;           // in scope 3 at $DIR/const_debuginfo.rs:11:9: 11:10
++                 debug z => const 3_u8;   // in scope 3 at $DIR/const_debuginfo.rs:11:9: 11:10
+                  let _4: u8;              // in scope 3 at $DIR/const_debuginfo.rs:12:9: 12:12
+                  scope 4 {
+-                     debug sum => _4;     // in scope 4 at $DIR/const_debuginfo.rs:12:9: 12:12
++                     debug sum => const 6_u8; // in scope 4 at $DIR/const_debuginfo.rs:12:9: 12:12
+                      let _9: &str;        // in scope 4 at $DIR/const_debuginfo.rs:14:9: 14:10
+                      scope 5 {
+-                         debug s => _9;   // in scope 5 at $DIR/const_debuginfo.rs:14:9: 14:10
++                         debug s => const "hello, world!"; // in scope 5 at $DIR/const_debuginfo.rs:14:9: 14:10
+                          let _10: (bool, bool, u32); // in scope 5 at $DIR/const_debuginfo.rs:16:9: 16:10
+                          scope 6 {
+                              debug f => _10; // in scope 6 at $DIR/const_debuginfo.rs:16:9: 16:10
+                              let _11: std::option::Option<u16>; // in scope 6 at $DIR/const_debuginfo.rs:18:9: 18:10
+                              scope 7 {
+                                  debug o => _11; // in scope 7 at $DIR/const_debuginfo.rs:18:9: 18:10
+                                  let _12: Point; // in scope 7 at $DIR/const_debuginfo.rs:20:9: 20:10
+                                  scope 8 {
+                                      debug p => _12; // in scope 8 at $DIR/const_debuginfo.rs:20:9: 20:10
+                                      let _13: u32; // in scope 8 at $DIR/const_debuginfo.rs:21:9: 21:10
+                                      scope 9 {
+-                                         debug a => _13; // in scope 9 at $DIR/const_debuginfo.rs:21:9: 21:10
++                                         debug a => const 64_u32; // in scope 9 at $DIR/const_debuginfo.rs:21:9: 21:10
+                                      }
+                                  }
+                              }
+                          }
+                      }
+                  }
+              }
+          }
+      }
+  
+      bb0: {
+          StorageLive(_1);                 // scope 0 at $DIR/const_debuginfo.rs:9:9: 9:10
+          _1 = const 1_u8;                 // scope 0 at $DIR/const_debuginfo.rs:9:13: 9:16
+          StorageLive(_2);                 // scope 1 at $DIR/const_debuginfo.rs:10:9: 10:10
+          _2 = const 2_u8;                 // scope 1 at $DIR/const_debuginfo.rs:10:13: 10:16
+          StorageLive(_3);                 // scope 2 at $DIR/const_debuginfo.rs:11:9: 11:10
+          _3 = const 3_u8;                 // scope 2 at $DIR/const_debuginfo.rs:11:13: 11:16
+          StorageLive(_4);                 // scope 3 at $DIR/const_debuginfo.rs:12:9: 12:12
+          StorageLive(_5);                 // scope 3 at $DIR/const_debuginfo.rs:12:15: 12:20
+          StorageLive(_6);                 // scope 3 at $DIR/const_debuginfo.rs:12:15: 12:16
+          _6 = const 1_u8;                 // scope 3 at $DIR/const_debuginfo.rs:12:15: 12:16
+          StorageLive(_7);                 // scope 3 at $DIR/const_debuginfo.rs:12:19: 12:20
+          _7 = const 2_u8;                 // scope 3 at $DIR/const_debuginfo.rs:12:19: 12:20
+          _5 = const 3_u8;                 // scope 3 at $DIR/const_debuginfo.rs:12:15: 12:20
+          StorageDead(_7);                 // scope 3 at $DIR/const_debuginfo.rs:12:19: 12:20
+          StorageDead(_6);                 // scope 3 at $DIR/const_debuginfo.rs:12:19: 12:20
+          StorageLive(_8);                 // scope 3 at $DIR/const_debuginfo.rs:12:23: 12:24
+          _8 = const 3_u8;                 // scope 3 at $DIR/const_debuginfo.rs:12:23: 12:24
+          _4 = const 6_u8;                 // scope 3 at $DIR/const_debuginfo.rs:12:15: 12:24
+          StorageDead(_8);                 // scope 3 at $DIR/const_debuginfo.rs:12:23: 12:24
+          StorageDead(_5);                 // scope 3 at $DIR/const_debuginfo.rs:12:23: 12:24
+          StorageLive(_9);                 // scope 4 at $DIR/const_debuginfo.rs:14:9: 14:10
+          _9 = const "hello, world!";      // scope 4 at $DIR/const_debuginfo.rs:14:13: 14:28
+                                           // ty::Const
+                                           // + ty: &str
+                                           // + val: Value(Slice { data: Allocation { bytes: [104, 101, 108, 108, 111, 44, 32, 119, 111, 114, 108, 100, 33], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [8191], len: Size { raw: 13 } }, size: Size { raw: 13 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 13 })
+                                           // mir::Constant
+                                           // + span: $DIR/const_debuginfo.rs:14:13: 14:28
+                                           // + literal: Const { ty: &str, val: Value(Slice { data: Allocation { bytes: [104, 101, 108, 108, 111, 44, 32, 119, 111, 114, 108, 100, 33], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [8191], len: Size { raw: 13 } }, size: Size { raw: 13 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 13 }) }
+          StorageLive(_10);                // scope 5 at $DIR/const_debuginfo.rs:16:9: 16:10
+          (_10.0: bool) = const true;      // scope 5 at $DIR/const_debuginfo.rs:16:13: 16:34
+          (_10.1: bool) = const false;     // scope 5 at $DIR/const_debuginfo.rs:16:13: 16:34
+          (_10.2: u32) = const 123_u32;    // scope 5 at $DIR/const_debuginfo.rs:16:13: 16:34
+          StorageLive(_11);                // scope 6 at $DIR/const_debuginfo.rs:18:9: 18:10
+          ((_11 as Some).0: u16) = const 99_u16; // scope 6 at $DIR/const_debuginfo.rs:18:13: 18:24
+          discriminant(_11) = 1;           // scope 6 at $DIR/const_debuginfo.rs:18:13: 18:24
+          StorageLive(_12);                // scope 7 at $DIR/const_debuginfo.rs:20:9: 20:10
+          (_12.0: u32) = const 32_u32;     // scope 7 at $DIR/const_debuginfo.rs:20:13: 20:35
+          (_12.1: u32) = const 32_u32;     // scope 7 at $DIR/const_debuginfo.rs:20:13: 20:35
+          StorageLive(_13);                // scope 8 at $DIR/const_debuginfo.rs:21:9: 21:10
+          StorageLive(_14);                // scope 8 at $DIR/const_debuginfo.rs:21:13: 21:16
+          _14 = const 32_u32;              // scope 8 at $DIR/const_debuginfo.rs:21:13: 21:16
+          StorageLive(_15);                // scope 8 at $DIR/const_debuginfo.rs:21:19: 21:22
+          _15 = const 32_u32;              // scope 8 at $DIR/const_debuginfo.rs:21:19: 21:22
+          _13 = const 64_u32;              // scope 8 at $DIR/const_debuginfo.rs:21:13: 21:22
+          StorageDead(_15);                // scope 8 at $DIR/const_debuginfo.rs:21:21: 21:22
+          StorageDead(_14);                // scope 8 at $DIR/const_debuginfo.rs:21:21: 21:22
+          _0 = const ();                   // scope 0 at $DIR/const_debuginfo.rs:8:11: 22:2
+          StorageDead(_13);                // scope 8 at $DIR/const_debuginfo.rs:22:1: 22:2
+          StorageDead(_12);                // scope 7 at $DIR/const_debuginfo.rs:22:1: 22:2
+          StorageDead(_11);                // scope 6 at $DIR/const_debuginfo.rs:22:1: 22:2
+          StorageDead(_10);                // scope 5 at $DIR/const_debuginfo.rs:22:1: 22:2
+          StorageDead(_9);                 // scope 4 at $DIR/const_debuginfo.rs:22:1: 22:2
+          StorageDead(_4);                 // scope 3 at $DIR/const_debuginfo.rs:22:1: 22:2
+          StorageDead(_3);                 // scope 2 at $DIR/const_debuginfo.rs:22:1: 22:2
+          StorageDead(_2);                 // scope 1 at $DIR/const_debuginfo.rs:22:1: 22:2
+          StorageDead(_1);                 // scope 0 at $DIR/const_debuginfo.rs:22:1: 22:2
+          return;                          // scope 0 at $DIR/const_debuginfo.rs:22:2: 22:2
+      }
+  }
+  
diff --git a/src/test/mir-opt/const_debuginfo.rs b/src/test/mir-opt/const_debuginfo.rs
new file mode 100644
index 00000000000..a66d66c60c7
--- /dev/null
+++ b/src/test/mir-opt/const_debuginfo.rs
@@ -0,0 +1,24 @@
+// compile-flags: -C overflow-checks=no
+
+struct Point {
+    x: u32,
+    y: u32,
+}
+
+fn main() {
+    let x = 1u8;
+    let y = 2u8;
+    let z = 3u8;
+    let sum = x + y + z;
+
+    let s = "hello, world!";
+
+    let f = (true, false, 123u32);
+
+    let o = Some(99u16);
+
+    let p = Point { x: 32, y: 32 };
+    let a = p.x + p.y;
+}
+
+// EMIT_MIR const_debuginfo.main.ConstDebugInfo.diff
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
index a78a6341c29..e4fbba3abfe 100644
--- 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
@@ -2,30 +2,18 @@
 
 fn main() -> () {
     let mut _0: ();                      // return place in scope 0 at $DIR/optimizes_into_variable.rs:11:11: 11:11
-    let _1: i32;                         // in scope 0 at $DIR/optimizes_into_variable.rs:12:9: 12:10
     scope 1 {
-        debug x => _1;                   // in scope 1 at $DIR/optimizes_into_variable.rs:12:9: 12:10
-        let _2: i32;                     // in scope 1 at $DIR/optimizes_into_variable.rs:13:9: 13:10
+        debug x => const 4_i32;          // in scope 1 at $DIR/optimizes_into_variable.rs:12:9: 12:10
         scope 2 {
-            debug y => _2;               // in scope 2 at $DIR/optimizes_into_variable.rs:13:9: 13:10
-            let _3: u32;                 // in scope 2 at $DIR/optimizes_into_variable.rs:14:9: 14:10
+            debug y => const 3_i32;      // in scope 2 at $DIR/optimizes_into_variable.rs:13:9: 13:10
             scope 3 {
-                debug z => _3;           // in scope 3 at $DIR/optimizes_into_variable.rs:14:9: 14:10
+                debug z => const 42_u32; // in scope 3 at $DIR/optimizes_into_variable.rs:14:9: 14:10
             }
         }
     }
 
     bb0: {
-        StorageLive(_1);                 // scope 0 at $DIR/optimizes_into_variable.rs:12:9: 12:10
-        _1 = const 4_i32;                // scope 0 at $DIR/optimizes_into_variable.rs:12:13: 12:18
-        StorageLive(_2);                 // scope 1 at $DIR/optimizes_into_variable.rs:13:9: 13:10
-        _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
         return;                          // scope 0 at $DIR/optimizes_into_variable.rs:15:2: 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
index a78a6341c29..e4fbba3abfe 100644
--- 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
@@ -2,30 +2,18 @@
 
 fn main() -> () {
     let mut _0: ();                      // return place in scope 0 at $DIR/optimizes_into_variable.rs:11:11: 11:11
-    let _1: i32;                         // in scope 0 at $DIR/optimizes_into_variable.rs:12:9: 12:10
     scope 1 {
-        debug x => _1;                   // in scope 1 at $DIR/optimizes_into_variable.rs:12:9: 12:10
-        let _2: i32;                     // in scope 1 at $DIR/optimizes_into_variable.rs:13:9: 13:10
+        debug x => const 4_i32;          // in scope 1 at $DIR/optimizes_into_variable.rs:12:9: 12:10
         scope 2 {
-            debug y => _2;               // in scope 2 at $DIR/optimizes_into_variable.rs:13:9: 13:10
-            let _3: u32;                 // in scope 2 at $DIR/optimizes_into_variable.rs:14:9: 14:10
+            debug y => const 3_i32;      // in scope 2 at $DIR/optimizes_into_variable.rs:13:9: 13:10
             scope 3 {
-                debug z => _3;           // in scope 3 at $DIR/optimizes_into_variable.rs:14:9: 14:10
+                debug z => const 42_u32; // in scope 3 at $DIR/optimizes_into_variable.rs:14:9: 14:10
             }
         }
     }
 
     bb0: {
-        StorageLive(_1);                 // scope 0 at $DIR/optimizes_into_variable.rs:12:9: 12:10
-        _1 = const 4_i32;                // scope 0 at $DIR/optimizes_into_variable.rs:12:13: 12:18
-        StorageLive(_2);                 // scope 1 at $DIR/optimizes_into_variable.rs:13:9: 13:10
-        _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
         return;                          // scope 0 at $DIR/optimizes_into_variable.rs:15:2: 15:2
     }
 }
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
index 3d386e3b175..4abbad2c1ef 100644
--- 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
@@ -11,9 +11,8 @@ fn main() -> () {
         debug f => _1;                   // in scope 1 at $DIR/issue-76997-inline-scopes-parenting.rs:5:9: 5:10
         scope 2 (inlined main::{closure#0}) { // at $DIR/issue-76997-inline-scopes-parenting.rs:6:5: 6:10
             debug x => _5;               // in scope 2 at $DIR/issue-76997-inline-scopes-parenting.rs:6:5: 6:10
-            let _6: ();                  // in scope 2 at $DIR/issue-76997-inline-scopes-parenting.rs:6:5: 6:10
             scope 3 {
-                debug y => _6;           // in scope 3 at $DIR/issue-76997-inline-scopes-parenting.rs:6:5: 6:10
+                debug y => const ();     // in scope 3 at $DIR/issue-76997-inline-scopes-parenting.rs:6:5: 6:10
             }
         }
     }
@@ -27,10 +26,7 @@ fn main() -> () {
         (_3.0: ()) = move _4;            // scope 1 at $DIR/issue-76997-inline-scopes-parenting.rs:6:5: 6:10
         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
         StorageDead(_3);                 // scope 1 at $DIR/issue-76997-inline-scopes-parenting.rs:6:9: 6:10
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
index 654dd8275c9..bd4f148285b 100644
--- a/src/test/mir-opt/lower_intrinsics.f_u64.PreCodegen.before.mir
+++ b/src/test/mir-opt/lower_intrinsics.f_u64.PreCodegen.before.mir
@@ -3,7 +3,7 @@
 fn f_u64() -> () {
     let mut _0: ();                      // return place in scope 0 at $DIR/lower_intrinsics.rs:34:16: 34:16
     scope 1 (inlined f_dispatch::<u64>) { // at $DIR/lower_intrinsics.rs:35:5: 35:21
-        debug t => _2;                   // in scope 1 at $DIR/lower_intrinsics.rs:35:5: 35:21
+        debug t => const 0_u64;          // in scope 1 at $DIR/lower_intrinsics.rs:35:5: 35:21
         let _1: ();                      // in scope 1 at $DIR/lower_intrinsics.rs:35:5: 35:21
         let mut _2: u64;                 // in scope 1 at $DIR/lower_intrinsics.rs:35:5: 35:21
         scope 2 (inlined std::mem::size_of::<u64>) { // at $DIR/lower_intrinsics.rs:35:5: 35:21
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
index dae0cbb65a4..cb3632e0fb1 100644
--- 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
@@ -2,16 +2,12 @@
 
 fn change_loop_body() -> () {
     let mut _0: ();                      // return place in scope 0 at $DIR/while_let_loops.rs:5:27: 5:27
-    let mut _1: i32;                     // in scope 0 at $DIR/while_let_loops.rs:6:9: 6:15
     scope 1 {
-        debug _x => _1;                  // in scope 1 at $DIR/while_let_loops.rs:6:9: 6:15
+        debug _x => const 0_i32;         // in scope 1 at $DIR/while_let_loops.rs:6:9: 6:15
     }
 
     bb0: {
-        StorageLive(_1);                 // scope 0 at $DIR/while_let_loops.rs:6:9: 6:15
-        _1 = const 0_i32;                // scope 0 at $DIR/while_let_loops.rs:6:18: 6:19
         _0 = const ();                   // scope 1 at $DIR/while_let_loops.rs:7:5: 10:6
-        StorageDead(_1);                 // scope 0 at $DIR/while_let_loops.rs:11:1: 11:2
         return;                          // scope 0 at $DIR/while_let_loops.rs:11:2: 11:2
     }
 }
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
index dae0cbb65a4..cb3632e0fb1 100644
--- 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
@@ -2,16 +2,12 @@
 
 fn change_loop_body() -> () {
     let mut _0: ();                      // return place in scope 0 at $DIR/while_let_loops.rs:5:27: 5:27
-    let mut _1: i32;                     // in scope 0 at $DIR/while_let_loops.rs:6:9: 6:15
     scope 1 {
-        debug _x => _1;                  // in scope 1 at $DIR/while_let_loops.rs:6:9: 6:15
+        debug _x => const 0_i32;         // in scope 1 at $DIR/while_let_loops.rs:6:9: 6:15
     }
 
     bb0: {
-        StorageLive(_1);                 // scope 0 at $DIR/while_let_loops.rs:6:9: 6:15
-        _1 = const 0_i32;                // scope 0 at $DIR/while_let_loops.rs:6:18: 6:19
         _0 = const ();                   // scope 1 at $DIR/while_let_loops.rs:7:5: 10:6
-        StorageDead(_1);                 // scope 0 at $DIR/while_let_loops.rs:11:1: 11:2
         return;                          // scope 0 at $DIR/while_let_loops.rs:11:2: 11:2
     }
 }