Enable instcombine for mutable reborrows

4 files changed, 9 insertions, 31 deletions

diff --git a/compiler/rustc_mir_transform/src/instcombine.rs b/compiler/rustc_mir_transform/src/instcombine.rs
index 1079377fbac..0534e688703 100644
--- a/compiler/rustc_mir_transform/src/instcombine.rs
+++ b/compiler/rustc_mir_transform/src/instcombine.rs
@@ -110,11 +110,7 @@ impl<'tcx> InstCombineContext<'tcx, '_> {
     fn combine_ref_deref(&self, source_info: &SourceInfo, rvalue: &mut Rvalue<'tcx>) {
         if let Rvalue::Ref(_, _, place) = rvalue {
             if let Some((base, ProjectionElem::Deref)) = place.as_ref().last_projection() {
-                if let ty::Ref(_, _, Mutability::Not) =
-                    base.ty(self.local_decls, self.tcx).ty.kind()
-                {
-                    // The dereferenced place must have type `&_`, so that we don't copy `&mut _`.
-                } else {
+                if rvalue.ty(self.local_decls, self.tcx) != base.ty(self.local_decls, self.tcx).ty {
                     return;
                 }
 
diff --git a/tests/mir-opt/funky_arms.float_to_exponential_common.ConstProp.diff b/tests/mir-opt/funky_arms.float_to_exponential_common.ConstProp.diff
index 5ebaacd4ba9..1f5c533815d 100644
--- a/tests/mir-opt/funky_arms.float_to_exponential_common.ConstProp.diff
+++ b/tests/mir-opt/funky_arms.float_to_exponential_common.ConstProp.diff
@@ -86,8 +86,6 @@
   
       bb6: {
           _10 = ((_7 as Some).0: usize);   // scope 3 at $DIR/funky_arms.rs:+13:17: +13:26
-          StorageLive(_11);                // scope 3 at $DIR/funky_arms.rs:+15:43: +15:46
-          _11 = &mut (*_1);                // scope 3 at $DIR/funky_arms.rs:+15:43: +15:46
           StorageLive(_13);                // scope 3 at $DIR/funky_arms.rs:+15:53: +15:57
           _13 = _6;                        // scope 3 at $DIR/funky_arms.rs:+15:53: +15:57
           StorageLive(_14);                // scope 3 at $DIR/funky_arms.rs:+15:59: +15:79
@@ -95,7 +93,7 @@
           _15 = _10 as u32 (IntToInt);     // scope 3 at $DIR/funky_arms.rs:+15:59: +15:75
           _14 = Add(move _15, const 1_u32); // scope 3 at $DIR/funky_arms.rs:+15:59: +15:79
           StorageDead(_15);                // scope 3 at $DIR/funky_arms.rs:+15:78: +15:79
-          _0 = float_to_exponential_common_exact::<T>(move _11, _2, move _13, move _14, _3) -> bb7; // scope 3 at $DIR/funky_arms.rs:+15:9: +15:87
+          _0 = float_to_exponential_common_exact::<T>(_1, _2, move _13, move _14, _3) -> bb7; // scope 3 at $DIR/funky_arms.rs:+15:9: +15:87
                                            // mir::Constant
                                            // + span: $DIR/funky_arms.rs:26:9: 26:42
                                            // + literal: Const { ty: for<'a, 'b, 'c> fn(&'a mut Formatter<'b>, &'c T, Sign, u32, bool) -> Result<(), std::fmt::Error> {float_to_exponential_common_exact::<T>}, val: Value(<ZST>) }
@@ -104,16 +102,13 @@
       bb7: {
           StorageDead(_14);                // scope 3 at $DIR/funky_arms.rs:+15:86: +15:87
           StorageDead(_13);                // scope 3 at $DIR/funky_arms.rs:+15:86: +15:87
-          StorageDead(_11);                // scope 3 at $DIR/funky_arms.rs:+15:86: +15:87
           goto -> bb10;                    // scope 2 at $DIR/funky_arms.rs:+13:5: +18:6
       }
   
       bb8: {
-          StorageLive(_18);                // scope 2 at $DIR/funky_arms.rs:+17:46: +17:49
-          _18 = &mut (*_1);                // scope 2 at $DIR/funky_arms.rs:+17:46: +17:49
           StorageLive(_20);                // scope 2 at $DIR/funky_arms.rs:+17:56: +17:60
           _20 = _6;                        // scope 2 at $DIR/funky_arms.rs:+17:56: +17:60
-          _0 = float_to_exponential_common_shortest::<T>(move _18, _2, move _20, _3) -> bb9; // scope 2 at $DIR/funky_arms.rs:+17:9: +17:68
+          _0 = float_to_exponential_common_shortest::<T>(_1, _2, move _20, _3) -> bb9; // scope 2 at $DIR/funky_arms.rs:+17:9: +17:68
                                            // mir::Constant
                                            // + span: $DIR/funky_arms.rs:28:9: 28:45
                                            // + literal: Const { ty: for<'a, 'b, 'c> fn(&'a mut Formatter<'b>, &'c T, Sign, bool) -> Result<(), std::fmt::Error> {float_to_exponential_common_shortest::<T>}, val: Value(<ZST>) }
@@ -121,7 +116,6 @@
   
       bb9: {
           StorageDead(_20);                // scope 2 at $DIR/funky_arms.rs:+17:67: +17:68
-          StorageDead(_18);                // scope 2 at $DIR/funky_arms.rs:+17:67: +17:68
           goto -> bb10;                    // scope 2 at $DIR/funky_arms.rs:+13:5: +18:6
       }
   
diff --git a/tests/mir-opt/inline/issue_58867_inline_as_ref_as_mut.a.Inline.after.mir b/tests/mir-opt/inline/issue_58867_inline_as_ref_as_mut.a.Inline.after.mir
index dc0c3235043..6441a9668de 100644
--- a/tests/mir-opt/inline/issue_58867_inline_as_ref_as_mut.a.Inline.after.mir
+++ b/tests/mir-opt/inline/issue_58867_inline_as_ref_as_mut.a.Inline.after.mir
@@ -8,7 +8,6 @@ fn a(_1: &mut [T]) -> &mut [T] {
     let mut _4: &mut [T];                // in scope 0 at $DIR/issue_58867_inline_as_ref_as_mut.rs:+1:5: +1:15
     scope 1 (inlined <[T] as AsMut<[T]>>::as_mut) { // at $DIR/issue_58867_inline_as_ref_as_mut.rs:3:7: 3:15
         debug self => _4;                // in scope 1 at $SRC_DIR/core/src/convert/mod.rs:LL:COL
-        let mut _5: &mut [T];            // in scope 1 at $SRC_DIR/core/src/convert/mod.rs:LL:COL
     }
 
     bb0: {
@@ -16,10 +15,7 @@ fn a(_1: &mut [T]) -> &mut [T] {
         StorageLive(_3);                 // scope 0 at $DIR/issue_58867_inline_as_ref_as_mut.rs:+1:5: +1:15
         StorageLive(_4);                 // scope 0 at $DIR/issue_58867_inline_as_ref_as_mut.rs:+1:5: +1:15
         _4 = &mut (*_1);                 // scope 0 at $DIR/issue_58867_inline_as_ref_as_mut.rs:+1:5: +1:15
-        StorageLive(_5);                 // scope 1 at $SRC_DIR/core/src/convert/mod.rs:LL:COL
-        _5 = &mut (*_4);                 // scope 1 at $SRC_DIR/core/src/convert/mod.rs:LL:COL
-        _3 = &mut (*_5);                 // scope 1 at $SRC_DIR/core/src/convert/mod.rs:LL:COL
-        StorageDead(_5);                 // scope 1 at $SRC_DIR/core/src/convert/mod.rs:LL:COL
+        _3 = _4;                         // scope 1 at $SRC_DIR/core/src/convert/mod.rs:LL:COL
         _2 = &mut (*_3);                 // scope 0 at $DIR/issue_58867_inline_as_ref_as_mut.rs:+1:5: +1:15
         StorageDead(_4);                 // scope 0 at $DIR/issue_58867_inline_as_ref_as_mut.rs:+1:14: +1:15
         _0 = &mut (*_2);                 // scope 0 at $DIR/issue_58867_inline_as_ref_as_mut.rs:+1:5: +1:15
diff --git a/tests/mir-opt/inline/issue_58867_inline_as_ref_as_mut.b.Inline.after.mir b/tests/mir-opt/inline/issue_58867_inline_as_ref_as_mut.b.Inline.after.mir
index b6aff30149f..21570a88a6b 100644
--- a/tests/mir-opt/inline/issue_58867_inline_as_ref_as_mut.b.Inline.after.mir
+++ b/tests/mir-opt/inline/issue_58867_inline_as_ref_as_mut.b.Inline.after.mir
@@ -8,10 +8,8 @@ fn b(_1: &mut Box<T>) -> &mut T {
     let mut _4: &mut std::boxed::Box<T>; // in scope 0 at $DIR/issue_58867_inline_as_ref_as_mut.rs:+1:5: +1:15
     scope 1 (inlined <Box<T> as AsMut<T>>::as_mut) { // at $DIR/issue_58867_inline_as_ref_as_mut.rs:8:7: 8:15
         debug self => _4;                // in scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
-        let mut _5: &mut T;              // in scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
-        let mut _6: &mut T;              // in scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
-        let mut _7: std::boxed::Box<T>;  // in scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
-        let mut _8: *const T;            // in scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
+        let mut _5: std::boxed::Box<T>;  // in scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
+        let mut _6: *const T;            // in scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
     }
 
     bb0: {
@@ -19,15 +17,9 @@ fn b(_1: &mut Box<T>) -> &mut T {
         StorageLive(_3);                 // scope 0 at $DIR/issue_58867_inline_as_ref_as_mut.rs:+1:5: +1:15
         StorageLive(_4);                 // scope 0 at $DIR/issue_58867_inline_as_ref_as_mut.rs:+1:5: +1:15
         _4 = &mut (*_1);                 // scope 0 at $DIR/issue_58867_inline_as_ref_as_mut.rs:+1:5: +1:15
-        StorageLive(_5);                 // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
-        StorageLive(_6);                 // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
-        _7 = deref_copy (*_4);           // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
-        _8 = (((_7.0: std::ptr::Unique<T>).0: std::ptr::NonNull<T>).0: *const T); // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
-        _6 = &mut (*_8);                 // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
-        _5 = &mut (*_6);                 // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
-        _3 = &mut (*_5);                 // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
-        StorageDead(_6);                 // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
-        StorageDead(_5);                 // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
+        _5 = deref_copy (*_4);           // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
+        _6 = (((_5.0: std::ptr::Unique<T>).0: std::ptr::NonNull<T>).0: *const T); // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
+        _3 = &mut (*_6);                 // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
         _2 = &mut (*_3);                 // scope 0 at $DIR/issue_58867_inline_as_ref_as_mut.rs:+1:5: +1:15
         StorageDead(_4);                 // scope 0 at $DIR/issue_58867_inline_as_ref_as_mut.rs:+1:14: +1:15
         _0 = &mut (*_2);                 // scope 0 at $DIR/issue_58867_inline_as_ref_as_mut.rs:+1:5: +1:15