Merge borrowed locals too.

compiler/rustc_mir_transform/src/copy_prop.rs

@@ -111,7 +111,10 @@ impl<'tcx> MutVisitor<'tcx> for Replacer<'_, 'tcx> {
 
     fn visit_local(&mut self, local: &mut Local, ctxt: PlaceContext, _: Location) {
         let new_local = self.copy_classes[*local];
-        if self.borrowed_locals.contains(*local) || self.borrowed_locals.contains(new_local) {
+        // We must not unify two locals that are borrowed. But this is fine if one is borrowed and
+        // the other is not. We chose to check the original local, and not the target. That way, if
+        // the original local is borrowed and the target is not, we do not pessimize the whole class.
+        if self.borrowed_locals.contains(*local) {
             return;
         }
         match ctxt {

tests/mir-opt/copy-prop/borrowed_local.borrowed.CopyProp.panic-abort.diff

@@ -7,13 +7,14 @@
       let mut _3: &u32;
   
       bb0: {
-          _2 = _1;
+-         _2 = _1;
           _3 = &_1;
           _0 = opaque::<&u32>(_3) -> [return: bb1, unwind unreachable];
       }
   
       bb1: {
-          _0 = opaque::<u32>(_2) -> [return: bb2, unwind unreachable];
+-         _0 = opaque::<u32>(_2) -> [return: bb2, unwind unreachable];
++         _0 = opaque::<u32>(_1) -> [return: bb2, unwind unreachable];
       }
   
       bb2: {

tests/mir-opt/copy-prop/borrowed_local.borrowed.CopyProp.panic-unwind.diff

@@ -7,13 +7,14 @@
       let mut _3: &u32;
   
       bb0: {
-          _2 = _1;
+-         _2 = _1;
           _3 = &_1;
           _0 = opaque::<&u32>(_3) -> [return: bb1, unwind continue];
       }
   
       bb1: {
-          _0 = opaque::<u32>(_2) -> [return: bb2, unwind continue];
+-         _0 = opaque::<u32>(_2) -> [return: bb2, unwind continue];
++         _0 = opaque::<u32>(_1) -> [return: bb2, unwind continue];
       }
   
       bb2: {

tests/mir-opt/copy-prop/borrowed_local.rs

@@ -46,11 +46,10 @@ fn compare_address() -> bool {
 fn borrowed(x: u32) -> bool {
     // CHECK-LABEL: fn borrowed(
     // CHECK: bb0: {
-    // CHECK-NEXT: _2 = _1;
     // CHECK-NEXT: _3 = &_1;
     // CHECK-NEXT: _0 = opaque::<&u32>(_3)
     // CHECK: bb1: {
-    // CHECK-NEXT: _0 = opaque::<u32>(_2)
+    // CHECK-NEXT: _0 = opaque::<u32>(_1)
     mir!(
         {
             let a = x;

tests/mir-opt/pre-codegen/slice_filter.variant_a-{closure#0}.PreCodegen.after.mir

@@ -10,18 +10,18 @@ fn variant_a::{closure#0}(_1: &mut {closure@$DIR/slice_filter.rs:7:25: 7:39}, _2
     let mut _8: &&usize;
     let _9: &usize;
     let mut _10: &&usize;
-    let mut _15: bool;
+    let mut _13: bool;
+    let mut _14: &&usize;
+    let _15: &usize;
     let mut _16: &&usize;
-    let _17: &usize;
+    let mut _19: bool;
-    let mut _18: &&usize;
+    let mut _20: &&usize;
+    let _21: &usize;
+    let mut _22: &&usize;
     let mut _23: bool;
     let mut _24: &&usize;
     let _25: &usize;
     let mut _26: &&usize;
-    let mut _29: bool;
-    let mut _30: &&usize;
-    let _31: &usize;
-    let mut _32: &&usize;
     scope 1 {
         debug a => _4;
         debug b => _5;
@@ -30,47 +30,39 @@ fn variant_a::{closure#0}(_1: &mut {closure@$DIR/slice_filter.rs:7:25: 7:39}, _2
         scope 2 (inlined std::cmp::impls::<impl PartialOrd for &usize>::le) {
             debug self => _8;
             debug other => _10;
-            let mut _11: &usize;
-            let mut _12: &usize;
             scope 3 (inlined std::cmp::impls::<impl PartialOrd for usize>::le) {
-                debug self => _11;
+                debug self => _4;
-                debug other => _12;
+                debug other => _9;
-                let mut _13: usize;
+                let mut _11: usize;
-                let mut _14: usize;
+                let mut _12: usize;
             }
         }
         scope 4 (inlined std::cmp::impls::<impl PartialOrd for &usize>::le) {
-            debug self => _16;
+            debug self => _14;
-            debug other => _18;
+            debug other => _16;
-            let mut _19: &usize;
-            let mut _20: &usize;
             scope 5 (inlined std::cmp::impls::<impl PartialOrd for usize>::le) {
-                debug self => _19;
+                debug self => _7;
-                debug other => _20;
+                debug other => _15;
-                let mut _21: usize;
+                let mut _17: usize;
-                let mut _22: usize;
+                let mut _18: usize;
             }
         }
         scope 6 (inlined std::cmp::impls::<impl PartialOrd for &usize>::le) {
-            debug self => _24;
+            debug self => _20;
-            debug other => _26;
+            debug other => _22;
-            let mut _27: &usize;
-            let mut _28: &usize;
             scope 7 (inlined std::cmp::impls::<impl PartialOrd for usize>::le) {
-                debug self => _27;
+                debug self => _6;
-                debug other => _28;
+                debug other => _21;
             }
         }
         scope 8 (inlined std::cmp::impls::<impl PartialOrd for &usize>::le) {
-            debug self => _30;
+            debug self => _24;
-            debug other => _32;
+            debug other => _26;
-            let mut _33: &usize;
-            let mut _34: &usize;
             scope 9 (inlined std::cmp::impls::<impl PartialOrd for usize>::le) {
-                debug self => _33;
+                debug self => _5;
-                debug other => _34;
+                debug other => _25;
-                let mut _35: usize;
+                let mut _27: usize;
-                let mut _36: usize;
+                let mut _28: usize;
             }
         }
     }
@@ -81,22 +73,16 @@ fn variant_a::{closure#0}(_1: &mut {closure@$DIR/slice_filter.rs:7:25: 7:39}, _2
         _5 = &((*_3).1: usize);
         _6 = &((*_3).2: usize);
         _7 = &((*_3).3: usize);
-        StorageLive(_15);
+        StorageLive(_13);
         StorageLive(_8);
         _8 = &_4;
         StorageLive(_10);
         _9 = &((*_3).2: usize);
         _10 = &_9;
-        StorageLive(_11);
+        _11 = ((*_3).0: usize);
-        StorageLive(_12);
+        _12 = ((*_3).2: usize);
-        _11 = _4;
+        _13 = Le(_11, _12);
-        _12 = _9;
+        switchInt(move _13) -> [0: bb1, otherwise: bb2];
-        _13 = ((*_3).0: usize);
-        _14 = ((*_3).2: usize);
-        _15 = Le(_13, _14);
-        StorageDead(_12);
-        StorageDead(_11);
-        switchInt(move _15) -> [0: bb1, otherwise: bb2];
     }
 
     bb1: {
@@ -108,99 +94,81 @@ fn variant_a::{closure#0}(_1: &mut {closure@$DIR/slice_filter.rs:7:25: 7:39}, _2
     bb2: {
         StorageDead(_10);
         StorageDead(_8);
-        StorageLive(_23);
-        StorageLive(_16);
-        _16 = &_7;
-        StorageLive(_18);
-        _17 = &((*_3).1: usize);
-        _18 = &_17;
         StorageLive(_19);
-        StorageLive(_20);
+        StorageLive(_14);
-        _19 = _7;
+        _14 = &_7;
-        _20 = _17;
+        StorageLive(_16);
-        StorageLive(_21);
+        _15 = &((*_3).1: usize);
-        _21 = ((*_3).3: usize);
+        _16 = &_15;
-        StorageLive(_22);
+        StorageLive(_17);
-        _22 = ((*_3).1: usize);
+        _17 = ((*_3).3: usize);
-        _23 = Le(move _21, move _22);
+        StorageLive(_18);
-        StorageDead(_22);
+        _18 = ((*_3).1: usize);
-        StorageDead(_21);
+        _19 = Le(move _17, move _18);
-        StorageDead(_20);
+        StorageDead(_18);
-        StorageDead(_19);
+        StorageDead(_17);
-        switchInt(move _23) -> [0: bb3, otherwise: bb8];
+        switchInt(move _19) -> [0: bb3, otherwise: bb8];
     }
 
     bb3: {
-        StorageDead(_18);
         StorageDead(_16);
+        StorageDead(_14);
         goto -> bb4;
     }
 
     bb4: {
-        StorageLive(_29);
+        StorageLive(_23);
-        StorageLive(_24);
+        StorageLive(_20);
-        _24 = &_6;
+        _20 = &_6;
-        StorageLive(_26);
+        StorageLive(_22);
-        _25 = &((*_3).0: usize);
+        _21 = &((*_3).0: usize);
-        _26 = &_25;
+        _22 = &_21;
-        StorageLive(_27);
+        _23 = Le(_12, _11);
-        StorageLive(_28);
+        switchInt(move _23) -> [0: bb5, otherwise: bb6];
-        _27 = _6;
-        _28 = _25;
-        _29 = Le(_14, _13);
-        StorageDead(_28);
-        StorageDead(_27);
-        switchInt(move _29) -> [0: bb5, otherwise: bb6];
     }
 
     bb5: {
-        StorageDead(_26);
+        StorageDead(_22);
-        StorageDead(_24);
+        StorageDead(_20);
         _0 = const false;
         goto -> bb7;
     }
 
     bb6: {
+        StorageDead(_22);
+        StorageDead(_20);
+        StorageLive(_24);
+        _24 = &_5;
+        StorageLive(_26);
+        _25 = &((*_3).3: usize);
+        _26 = &_25;
+        StorageLive(_27);
+        _27 = ((*_3).1: usize);
+        StorageLive(_28);
+        _28 = ((*_3).3: usize);
+        _0 = Le(move _27, move _28);
+        StorageDead(_28);
+        StorageDead(_27);
         StorageDead(_26);
         StorageDead(_24);
-        StorageLive(_30);
-        _30 = &_5;
-        StorageLive(_32);
-        _31 = &((*_3).3: usize);
-        _32 = &_31;
-        StorageLive(_33);
-        StorageLive(_34);
-        _33 = _5;
-        _34 = _31;
-        StorageLive(_35);
-        _35 = ((*_3).1: usize);
-        StorageLive(_36);
-        _36 = ((*_3).3: usize);
-        _0 = Le(move _35, move _36);
-        StorageDead(_36);
-        StorageDead(_35);
-        StorageDead(_34);
-        StorageDead(_33);
-        StorageDead(_32);
-        StorageDead(_30);
         goto -> bb7;
     }
 
     bb7: {
-        StorageDead(_29);
+        StorageDead(_23);
         goto -> bb9;
     }
 
     bb8: {
-        StorageDead(_18);
         StorageDead(_16);
+        StorageDead(_14);
         _0 = const true;
         goto -> bb9;
     }
 
     bb9: {
-        StorageDead(_23);
+        StorageDead(_19);
-        StorageDead(_15);
+        StorageDead(_13);
         return;
     }
 }