Get all variants to eliminate the default branching if we cannot get the layout of type

9 files changed, 60 insertions, 40 deletions

diff --git a/compiler/rustc_mir_transform/src/uninhabited_enum_branching.rs b/compiler/rustc_mir_transform/src/uninhabited_enum_branching.rs
index d3408d4882f..0ab60259732 100644
--- a/compiler/rustc_mir_transform/src/uninhabited_enum_branching.rs
+++ b/compiler/rustc_mir_transform/src/uninhabited_enum_branching.rs
@@ -95,6 +95,12 @@ impl<'tcx> MirPass<'tcx> for UninhabitedEnumBranching {
 
             let mut allowed_variants = if let Ok(layout) = layout {
                 variant_discriminants(&layout, discriminant_ty, tcx)
+            } else if let Some(variant_range) = discriminant_ty.variant_range(tcx) {
+                variant_range
+                    .map(|variant| {
+                        discriminant_ty.discriminant_for_variant(tcx, variant).unwrap().val
+                    })
+                    .collect()
             } else {
                 continue;
             };
diff --git a/tests/mir-opt/issues/issue_59352.num_to_digit.PreCodegen.after.panic-abort.mir b/tests/mir-opt/issues/issue_59352.num_to_digit.PreCodegen.after.panic-abort.mir
index f7be8b75db7..bc12002490a 100644
--- a/tests/mir-opt/issues/issue_59352.num_to_digit.PreCodegen.after.panic-abort.mir
+++ b/tests/mir-opt/issues/issue_59352.num_to_digit.PreCodegen.after.panic-abort.mir
@@ -33,13 +33,13 @@ fn num_to_digit(_1: char) -> u32 {
         _3 = &_2;
         StorageLive(_4);
         _4 = discriminant(_2);
-        StorageDead(_3);
-        StorageDead(_2);
-        switchInt(move _4) -> [1: bb2, otherwise: bb7];
+        switchInt(move _4) -> [1: bb2, 0: bb6, otherwise: bb8];
     }
 
     bb2: {
         StorageDead(_4);
+        StorageDead(_3);
+        StorageDead(_2);
         StorageLive(_5);
         _5 = char::methods::<impl char>::to_digit(move _1, const 8_u32) -> [return: bb3, unwind unreachable];
     }
@@ -47,7 +47,7 @@ fn num_to_digit(_1: char) -> u32 {
     bb3: {
         StorageLive(_6);
         _6 = discriminant(_5);
-        switchInt(move _6) -> [0: bb4, 1: bb5, otherwise: bb6];
+        switchInt(move _6) -> [0: bb4, 1: bb5, otherwise: bb8];
     }
 
     bb4: {
@@ -58,20 +58,22 @@ fn num_to_digit(_1: char) -> u32 {
         _0 = move ((_5 as Some).0: u32);
         StorageDead(_6);
         StorageDead(_5);
-        goto -> bb8;
+        goto -> bb7;
     }
 
     bb6: {
-        unreachable;
+        StorageDead(_4);
+        StorageDead(_3);
+        StorageDead(_2);
+        _0 = const 0_u32;
+        goto -> bb7;
     }
 
     bb7: {
-        StorageDead(_4);
-        _0 = const 0_u32;
-        goto -> bb8;
+        return;
     }
 
     bb8: {
-        return;
+        unreachable;
     }
 }
diff --git a/tests/mir-opt/issues/issue_59352.num_to_digit.PreCodegen.after.panic-unwind.mir b/tests/mir-opt/issues/issue_59352.num_to_digit.PreCodegen.after.panic-unwind.mir
index e76fe992ac7..6c7e10a4525 100644
--- a/tests/mir-opt/issues/issue_59352.num_to_digit.PreCodegen.after.panic-unwind.mir
+++ b/tests/mir-opt/issues/issue_59352.num_to_digit.PreCodegen.after.panic-unwind.mir
@@ -33,13 +33,13 @@ fn num_to_digit(_1: char) -> u32 {
         _3 = &_2;
         StorageLive(_4);
         _4 = discriminant(_2);
-        StorageDead(_3);
-        StorageDead(_2);
-        switchInt(move _4) -> [1: bb2, otherwise: bb7];
+        switchInt(move _4) -> [1: bb2, 0: bb6, otherwise: bb8];
     }
 
     bb2: {
         StorageDead(_4);
+        StorageDead(_3);
+        StorageDead(_2);
         StorageLive(_5);
         _5 = char::methods::<impl char>::to_digit(move _1, const 8_u32) -> [return: bb3, unwind continue];
     }
@@ -47,7 +47,7 @@ fn num_to_digit(_1: char) -> u32 {
     bb3: {
         StorageLive(_6);
         _6 = discriminant(_5);
-        switchInt(move _6) -> [0: bb4, 1: bb5, otherwise: bb6];
+        switchInt(move _6) -> [0: bb4, 1: bb5, otherwise: bb8];
     }
 
     bb4: {
@@ -58,20 +58,22 @@ fn num_to_digit(_1: char) -> u32 {
         _0 = move ((_5 as Some).0: u32);
         StorageDead(_6);
         StorageDead(_5);
-        goto -> bb8;
+        goto -> bb7;
     }
 
     bb6: {
-        unreachable;
+        StorageDead(_4);
+        StorageDead(_3);
+        StorageDead(_2);
+        _0 = const 0_u32;
+        goto -> bb7;
     }
 
     bb7: {
-        StorageDead(_4);
-        _0 = const 0_u32;
-        goto -> bb8;
+        return;
     }
 
     bb8: {
-        return;
+        unreachable;
     }
 }
diff --git a/tests/mir-opt/simplify_locals_fixedpoint.foo.SimplifyLocals-final.panic-abort.diff b/tests/mir-opt/simplify_locals_fixedpoint.foo.SimplifyLocals-final.panic-abort.diff
index 3108b7d3e13..c520a159f47 100644
--- a/tests/mir-opt/simplify_locals_fixedpoint.foo.SimplifyLocals-final.panic-abort.diff
+++ b/tests/mir-opt/simplify_locals_fixedpoint.foo.SimplifyLocals-final.panic-abort.diff
@@ -28,7 +28,7 @@
   
       bb1: {
           _4 = discriminant((_1.1: std::option::Option<T>));
-          switchInt(move _4) -> [0: bb2, otherwise: bb3];
+          switchInt(move _4) -> [0: bb2, 1: bb3, otherwise: bb5];
       }
   
       bb2: {
diff --git a/tests/mir-opt/simplify_locals_fixedpoint.foo.SimplifyLocals-final.panic-unwind.diff b/tests/mir-opt/simplify_locals_fixedpoint.foo.SimplifyLocals-final.panic-unwind.diff
index 3ef3be198ed..686581591fc 100644
--- a/tests/mir-opt/simplify_locals_fixedpoint.foo.SimplifyLocals-final.panic-unwind.diff
+++ b/tests/mir-opt/simplify_locals_fixedpoint.foo.SimplifyLocals-final.panic-unwind.diff
@@ -28,7 +28,7 @@
   
       bb1: {
           _4 = discriminant((_1.1: std::option::Option<T>));
-          switchInt(move _4) -> [0: bb2, otherwise: bb3];
+          switchInt(move _4) -> [0: bb2, 1: bb3, otherwise: bb5];
       }
   
       bb2: {
diff --git a/tests/mir-opt/uninhabited_enum_branching.otherwise_t4_uninhabited_default_2.UninhabitedEnumBranching.panic-abort.diff b/tests/mir-opt/uninhabited_enum_branching.otherwise_t4_uninhabited_default_2.UninhabitedEnumBranching.panic-abort.diff
index de6944ee423..ac39f6be6c6 100644
--- a/tests/mir-opt/uninhabited_enum_branching.otherwise_t4_uninhabited_default_2.UninhabitedEnumBranching.panic-abort.diff
+++ b/tests/mir-opt/uninhabited_enum_branching.otherwise_t4_uninhabited_default_2.UninhabitedEnumBranching.panic-abort.diff
@@ -16,15 +16,11 @@
           StorageLive(_2);
           _2 = Test4::C;
           _3 = discriminant(_2);
--         switchInt(move _3) -> [0: bb1, 1: bb5, 2: bb6, otherwise: bb2];
-+         switchInt(move _3) -> [0: bb1, 1: bb5, 2: bb6, 3: bb2, otherwise: bb8];
+-         switchInt(move _3) -> [0: bb2, 1: bb5, 2: bb6, otherwise: bb1];
++         switchInt(move _3) -> [0: bb2, 1: bb5, 2: bb6, 3: bb1, otherwise: bb8];
       }
   
       bb1: {
-          switchInt(((_2 as A).0: i32)) -> [1: bb3, 2: bb4, otherwise: bb2];
-      }
-  
-      bb2: {
           StorageLive(_7);
           _7 = const "A(other)D";
           _1 = &(*_7);
@@ -32,6 +28,10 @@
           goto -> bb7;
       }
   
+      bb2: {
+          switchInt(((_2 as A).0: i32)) -> [1: bb3, 2: bb4, otherwise: bb1];
+      }
+  
       bb3: {
           _1 = const "A(1)";
           goto -> bb7;
diff --git a/tests/mir-opt/uninhabited_enum_branching.otherwise_t5_uninhabited_default.UninhabitedEnumBranching.panic-abort.diff b/tests/mir-opt/uninhabited_enum_branching.otherwise_t5_uninhabited_default.UninhabitedEnumBranching.panic-abort.diff
index aaede2dd924..8180428a6f4 100644
--- a/tests/mir-opt/uninhabited_enum_branching.otherwise_t5_uninhabited_default.UninhabitedEnumBranching.panic-abort.diff
+++ b/tests/mir-opt/uninhabited_enum_branching.otherwise_t5_uninhabited_default.UninhabitedEnumBranching.panic-abort.diff
@@ -5,7 +5,7 @@
       let mut _0: ();
       let _1: &str;
       let mut _2: Test5<T>;
-      let mut _3: isize;
+      let mut _3: i8;
       let _4: &str;
       let _5: &str;
       let _6: &str;
@@ -15,7 +15,8 @@
           StorageLive(_2);
           _2 = Test5::<T>::C;
           _3 = discriminant(_2);
-          switchInt(move _3) -> [0: bb2, 1: bb3, 2: bb4, otherwise: bb1];
+-         switchInt(move _3) -> [255: bb2, 0: bb3, 5: bb4, otherwise: bb1];
++         switchInt(move _3) -> [255: bb2, 0: bb3, 5: bb4, 3: bb1, otherwise: bb7];
       }
   
       bb1: {
@@ -56,6 +57,10 @@
           StorageDead(_1);
           _0 = const ();
           return;
++     }
++ 
++     bb7: {
++         unreachable;
       }
   }
   
diff --git a/tests/mir-opt/uninhabited_enum_branching.otherwise_t5_uninhabited_default.UninhabitedEnumBranching.panic-unwind.diff b/tests/mir-opt/uninhabited_enum_branching.otherwise_t5_uninhabited_default.UninhabitedEnumBranching.panic-unwind.diff
index edaaa0db588..b13d5816aed 100644
--- a/tests/mir-opt/uninhabited_enum_branching.otherwise_t5_uninhabited_default.UninhabitedEnumBranching.panic-unwind.diff
+++ b/tests/mir-opt/uninhabited_enum_branching.otherwise_t5_uninhabited_default.UninhabitedEnumBranching.panic-unwind.diff
@@ -5,7 +5,7 @@
       let mut _0: ();
       let _1: &str;
       let mut _2: Test5<T>;
-      let mut _3: isize;
+      let mut _3: i8;
       let _4: &str;
       let _5: &str;
       let _6: &str;
@@ -15,7 +15,8 @@
           StorageLive(_2);
           _2 = Test5::<T>::C;
           _3 = discriminant(_2);
-          switchInt(move _3) -> [0: bb2, 1: bb3, 2: bb4, otherwise: bb1];
+-         switchInt(move _3) -> [255: bb2, 0: bb3, 5: bb4, otherwise: bb1];
++         switchInt(move _3) -> [255: bb2, 0: bb3, 5: bb4, 3: bb1, otherwise: bb8];
       }
   
       bb1: {
@@ -60,6 +61,10 @@
   
       bb7 (cleanup): {
           resume;
++     }
++ 
++     bb8: {
++         unreachable;
       }
   }
   
diff --git a/tests/mir-opt/uninhabited_enum_branching.rs b/tests/mir-opt/uninhabited_enum_branching.rs
index a60ca0288e8..e31bf0227d5 100644
--- a/tests/mir-opt/uninhabited_enum_branching.rs
+++ b/tests/mir-opt/uninhabited_enum_branching.rs
@@ -32,11 +32,12 @@ enum Test4 {
     D,
 }
 
+#[repr(i8)]
 enum Test5<T> {
-    A(T),
-    B(T),
-    C,
-    D,
+    A(T) = -1,
+    B(T) = 0,
+    C = 5,
+    D = 3,
 }
 
 struct Plop {
@@ -165,10 +166,9 @@ fn otherwise_t4() {
 fn otherwise_t5_uninhabited_default<T>() {
     // CHECK-LABEL: fn otherwise_t5_uninhabited_default(
     // CHECK: [[discr:_.*]] = discriminant(
-    // CHECK: switchInt(move [[discr]]) -> [0: bb2, 1: bb3, 2: bb4, otherwise: bb1];
-    // CHECK: bb1: {
-    // CHECK-NOT: unreachable;
-    // CHECK: }
+    // CHECK: switchInt(move [[discr]]) -> [255: bb2, 0: bb3, 5: bb4, 3: bb1, otherwise: [[unreachable:bb.*]]];
+    // CHECK: [[unreachable]]: {
+    // CHECK-NEXT: unreachable;
     match Test5::<T>::C {
         Test5::A(_) => "A(T)",
         Test5::B(_) => "B(T)",