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

dianqk · dianqk · commit d02299c2267c · 2024-01-24T21:23:15.000+08:00
diff --git 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
@@ -3,7 +3,8 @@
 fn num_to_digit(_1: char) -> u32 {
     debug num => _1;
     let mut _0: u32;
-    let mut _5: std::option::Option<u32>;
+    let mut _5: bool;
+    let mut _6: std::option::Option<u32>;
     scope 1 (inlined char::methods::<impl char>::is_digit) {
         debug self => _1;
         debug radix => const 8_u32;
@@ -15,15 +16,16 @@ fn num_to_digit(_1: char) -> u32 {
         }
     }
     scope 3 (inlined #[track_caller] Option::<u32>::unwrap) {
-        debug self => _5;
-        let mut _6: isize;
-        let mut _7: !;
+        debug self => _6;
+        let mut _7: isize;
+        let mut _8: !;
         scope 4 {
             debug val => _0;
         }
     }
 
     bb0: {
+        StorageLive(_5);
         StorageLive(_3);
         StorageLive(_2);
         _2 = char::methods::<impl char>::to_digit(_1, const 8_u32) -> [return: bb1, unwind unreachable];
@@ -33,45 +35,59 @@ 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: bb3, otherwise: bb11];
     }
 
     bb2: {
-        StorageDead(_4);
-        StorageLive(_5);
-        _5 = char::methods::<impl char>::to_digit(move _1, const 8_u32) -> [return: bb3, unwind unreachable];
+        _5 = const true;
+        goto -> bb4;
     }
 
     bb3: {
-        StorageLive(_6);
-        _6 = discriminant(_5);
-        switchInt(move _6) -> [0: bb4, 1: bb5, otherwise: bb6];
+        _5 = const false;
+        goto -> bb4;
     }
 
     bb4: {
-        _7 = option::unwrap_failed() -> unwind unreachable;
+        StorageDead(_4);
+        StorageDead(_3);
+        StorageDead(_2);
+        switchInt(move _5) -> [0: bb5, otherwise: bb6];
     }
 
     bb5: {
-        _0 = move ((_5 as Some).0: u32);
-        StorageDead(_6);
-        StorageDead(_5);
-        goto -> bb8;
+        _0 = const 0_u32;
+        goto -> bb10;
     }
 
     bb6: {
-        unreachable;
+        StorageLive(_6);
+        _6 = char::methods::<impl char>::to_digit(move _1, const 8_u32) -> [return: bb7, unwind unreachable];
     }
 
     bb7: {
-        StorageDead(_4);
-        _0 = const 0_u32;
-        goto -> bb8;
+        StorageLive(_7);
+        _7 = discriminant(_6);
+        switchInt(move _7) -> [0: bb8, 1: bb9, otherwise: bb11];
     }
 
     bb8: {
+        _8 = option::unwrap_failed() -> unwind unreachable;
+    }
+
+    bb9: {
+        _0 = move ((_6 as Some).0: u32);
+        StorageDead(_7);
+        StorageDead(_6);
+        goto -> bb10;
+    }
+
+    bb10: {
+        StorageDead(_5);
         return;
     }
+
+    bb11: {
+        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
@@ -3,7 +3,8 @@
 fn num_to_digit(_1: char) -> u32 {
     debug num => _1;
     let mut _0: u32;
-    let mut _5: std::option::Option<u32>;
+    let mut _5: bool;
+    let mut _6: std::option::Option<u32>;
     scope 1 (inlined char::methods::<impl char>::is_digit) {
         debug self => _1;
         debug radix => const 8_u32;
@@ -15,15 +16,16 @@ fn num_to_digit(_1: char) -> u32 {
         }
     }
     scope 3 (inlined #[track_caller] Option::<u32>::unwrap) {
-        debug self => _5;
-        let mut _6: isize;
-        let mut _7: !;
+        debug self => _6;
+        let mut _7: isize;
+        let mut _8: !;
         scope 4 {
             debug val => _0;
         }
     }
 
     bb0: {
+        StorageLive(_5);
         StorageLive(_3);
         StorageLive(_2);
         _2 = char::methods::<impl char>::to_digit(_1, const 8_u32) -> [return: bb1, unwind continue];
@@ -33,45 +35,59 @@ 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: bb3, otherwise: bb11];
     }
 
     bb2: {
-        StorageDead(_4);
-        StorageLive(_5);
-        _5 = char::methods::<impl char>::to_digit(move _1, const 8_u32) -> [return: bb3, unwind continue];
+        _5 = const true;
+        goto -> bb4;
     }
 
     bb3: {
-        StorageLive(_6);
-        _6 = discriminant(_5);
-        switchInt(move _6) -> [0: bb4, 1: bb5, otherwise: bb6];
+        _5 = const false;
+        goto -> bb4;
     }
 
     bb4: {
-        _7 = option::unwrap_failed() -> unwind continue;
+        StorageDead(_4);
+        StorageDead(_3);
+        StorageDead(_2);
+        switchInt(move _5) -> [0: bb5, otherwise: bb6];
     }
 
     bb5: {
-        _0 = move ((_5 as Some).0: u32);
-        StorageDead(_6);
-        StorageDead(_5);
-        goto -> bb8;
+        _0 = const 0_u32;
+        goto -> bb10;
     }
 
     bb6: {
-        unreachable;
+        StorageLive(_6);
+        _6 = char::methods::<impl char>::to_digit(move _1, const 8_u32) -> [return: bb7, unwind continue];
     }
 
     bb7: {
-        StorageDead(_4);
-        _0 = const 0_u32;
-        goto -> bb8;
+        StorageLive(_7);
+        _7 = discriminant(_6);
+        switchInt(move _7) -> [0: bb8, 1: bb9, otherwise: bb11];
     }
 
     bb8: {
+        _8 = option::unwrap_failed() -> unwind continue;
+    }
+
+    bb9: {
+        _0 = move ((_6 as Some).0: u32);
+        StorageDead(_7);
+        StorageDead(_6);
+        goto -> bb10;
+    }
+
+    bb10: {
+        StorageDead(_5);
         return;
     }
+
+    bb11: {
+        unreachable;
+    }
 }
diff --git a/tests/mir-opt/pre-codegen/checked_ops.step_forward.PreCodegen.after.mir b/tests/mir-opt/pre-codegen/checked_ops.step_forward.PreCodegen.after.mir
@@ -4,66 +4,12 @@ fn step_forward(_1: u32, _2: usize) -> u32 {
     debug x => _1;
     debug n => _2;
     let mut _0: u32;
-    scope 1 (inlined <u32 as Step>::forward) {
-        debug start => _1;
-        debug n => _2;
-        let _3: std::option::Option<u32>;
-        let mut _4: &std::option::Option<u32>;
-        let mut _7: bool;
-        let mut _8: u32;
-        scope 2 {
-        }
-        scope 3 (inlined Option::<u32>::is_none) {
-            debug self => _4;
-            let mut _6: bool;
-            scope 4 (inlined Option::<u32>::is_some) {
-                debug self => _4;
-                let mut _5: isize;
-            }
-        }
-        scope 5 (inlined core::num::<impl u32>::wrapping_add) {
-            debug self => _1;
-            debug rhs => _8;
-        }
-    }
 
     bb0: {
-        StorageLive(_7);
-        StorageLive(_4);
-        StorageLive(_3);
-        _3 = <u32 as Step>::forward_checked(_1, _2) -> [return: bb1, unwind continue];
+        _0 = <u32 as Step>::forward(move _1, move _2) -> [return: bb1, unwind continue];
     }
 
     bb1: {
-        _4 = &_3;
-        StorageLive(_6);
-        StorageLive(_5);
-        _5 = discriminant(_3);
-        _6 = Eq(_5, const 1_isize);
-        StorageDead(_5);
-        _7 = Not(move _6);
-        StorageDead(_6);
-        switchInt(move _7) -> [0: bb2, otherwise: bb3];
-    }
-
-    bb2: {
-        StorageDead(_3);
-        StorageDead(_4);
-        goto -> bb4;
-    }
-
-    bb3: {
-        StorageDead(_3);
-        StorageDead(_4);
-        assert(!const true, "attempt to compute `{} + {}`, which would overflow", const _, const 1_u32) -> [success: bb4, unwind continue];
-    }
-
-    bb4: {
-        StorageDead(_7);
-        StorageLive(_8);
-        _8 = _2 as u32 (IntToInt);
-        _0 = Add(_1, _8);
-        StorageDead(_8);
         return;
     }
 }
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
@@ -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
@@ -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_t5_uninhabited_default.UninhabitedEnumBranching.diff b/tests/mir-opt/uninhabited_enum_branching.otherwise_t5_uninhabited_default.UninhabitedEnumBranching.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
@@ -30,11 +30,12 @@ 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 {
@@ -163,10 +164,9 @@ 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)",

Original file line number	Diff line number	Diff line change
`@@ -28,7 +28,7 @@`
`28`	`28`
`29`	`29`	`bb1: {`
`30`	`30`	`_4 = discriminant((_1.1: std::option::Option<T>));`
`31`		`- switchInt(move _4) -> [0: bb2, otherwise: bb3];`
	`31`	`+ switchInt(move _4) -> [0: bb2, 1: bb3, otherwise: bb5];`
`32`	`32`	`}`
`33`	`33`
`34`	`34`	`bb2: {`