Test/otherwise is last variant switchs

.github/workflows/ci.yml

@@ -50,18 +50,8 @@ jobs:
     strategy:
       matrix:
         include:
-          - name: mingw-check
-            os: ubuntu-20.04-4core-16gb
-            env: {}
-          - name: mingw-check-tidy
-            os: ubuntu-20.04-4core-16gb
-            env: {}
-          - name: x86_64-gnu-llvm-16
-            env:
-              ENABLE_GCC_CODEGEN: "1"
-            os: ubuntu-20.04-16core-64gb
-          - name: x86_64-gnu-tools
-            os: ubuntu-20.04-16core-64gb
+          - name: dist-loongarch64-linux
+            os: ubuntu-20.04
             env: {}
     timeout-minutes: 600
     runs-on: "${{ matrix.os }}"
@@ -271,22 +261,22 @@ jobs:
             os: ubuntu-20.04-8core-32gb
             env: {}
           - name: mingw-check
-            os: ubuntu-20.04-4core-16gb
+            os: ubuntu-20.04
             env: {}
           - name: test-various
             os: ubuntu-20.04-8core-32gb
             env: {}
           - name: x86_64-gnu
-            os: ubuntu-20.04-4core-16gb
+            os: ubuntu-20.04
             env: {}
           - name: x86_64-gnu-stable
             env:
               IMAGE: x86_64-gnu
               RUST_CI_OVERRIDE_RELEASE_CHANNEL: stable
               CI_ONLY_WHEN_CHANNEL: nightly
-            os: ubuntu-20.04-4core-16gb
+            os: ubuntu-20.04
           - name: x86_64-gnu-aux
-            os: ubuntu-20.04-4core-16gb
+            os: ubuntu-20.04
             env: {}
           - name: x86_64-gnu-integration
             env:
@@ -307,7 +297,7 @@ jobs:
               RUST_BACKTRACE: 1
             os: ubuntu-20.04-8core-32gb
           - name: x86_64-gnu-nopt
-            os: ubuntu-20.04-4core-16gb
+            os: ubuntu-20.04
             env: {}
           - name: x86_64-gnu-tools
             env:

compiler/rustc_middle/src/mir/terminator.rs

@@ -74,6 +74,17 @@ impl SwitchTargets {
     pub fn target_for_value(&self, value: u128) -> BasicBlock {
         self.iter().find_map(|(v, t)| (v == value).then_some(t)).unwrap_or_else(|| self.otherwise())
     }
+
+    /// Adds a new target to the switch. But You cannot add an already present value.
+    #[inline]
+    pub fn add_target(&mut self, value: u128, bb: BasicBlock) {
+        let value = Pu128(value);
+        if self.values.contains(&value) {
+            bug!("target value {:?} already present", value);
+        }
+        self.values.push(value);
+        self.targets.insert(self.targets.len() - 1, bb);
+    }
 }
 
 pub struct SwitchTargetsIter<'a> {

compiler/rustc_mir_transform/src/uninhabited_enum_branching.rs

@@ -78,6 +78,7 @@ impl<'tcx> MirPass<'tcx> for UninhabitedEnumBranching {
         trace!("UninhabitedEnumBranching starting for {:?}", body.source);
 
         let mut removable_switchs = Vec::new();
+        let mut otherwise_is_last_variant_switchs = Vec::new();
 
         for (bb, bb_data) in body.basic_blocks.iter_enumerated() {
             trace!("processing block {:?}", bb);
@@ -92,8 +93,14 @@ impl<'tcx> MirPass<'tcx> for UninhabitedEnumBranching {
                 tcx.param_env_reveal_all_normalized(body.source.def_id()).and(discriminant_ty),
             );
 
-            let allowed_variants = if let Ok(layout) = layout {
+            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;
             };
@@ -103,20 +110,29 @@ impl<'tcx> MirPass<'tcx> for UninhabitedEnumBranching {
             let terminator = bb_data.terminator();
             let TerminatorKind::SwitchInt { targets, .. } = &terminator.kind else { bug!() };
 
-            let mut reachable_count = 0;
             for (index, (val, _)) in targets.iter().enumerate() {
-                if allowed_variants.contains(&val) {
-                    reachable_count += 1;
-                } else {
+                if !allowed_variants.remove(&val) {
                     removable_switchs.push((bb, index));
                 }
             }
 
-            if reachable_count == allowed_variants.len() {
+            if allowed_variants.is_empty() {
                 removable_switchs.push((bb, targets.iter().count()));
+            } else if allowed_variants.len() == 1 {
+                #[allow(rustc::potential_query_instability)]
+                let last_variant = *allowed_variants.iter().next().unwrap();
+                otherwise_is_last_variant_switchs.push((bb, last_variant));
             }
         }
 
+        for (bb, last_variant) in otherwise_is_last_variant_switchs {
+            let bb_data = &mut body.basic_blocks.as_mut()[bb];
+            let terminator = bb_data.terminator_mut();
+            let TerminatorKind::SwitchInt { targets, .. } = &mut terminator.kind else { bug!() };
+            targets.add_target(last_variant, targets.otherwise());
+            removable_switchs.push((bb, targets.iter().count()));
+        }
+
         if removable_switchs.is_empty() {
             return;
         }

src/ci/docker/host-x86_64/dist-loongarch64-linux/Dockerfile

@@ -26,4 +26,4 @@ ENV CC_loongarch64_unknown_linux_gnu=loongarch64-unknown-linux-gnu-gcc \
 ENV HOSTS=loongarch64-unknown-linux-gnu
 
 ENV RUST_CONFIGURE_ARGS --enable-extended --disable-docs
-ENV SCRIPT python3 ../x.py dist --host $HOSTS --target $HOSTS
+ENV SCRIPT python3 ../x.py build src/tools/miri/cargo-miri --host $HOSTS --target $HOSTS

src/ci/github-actions/ci.yml

@@ -76,7 +76,7 @@ x--expand-yaml-anchors--remove:
     env: {}
 
   - &job-linux-4c
-    os: ubuntu-20.04-4core-16gb
+    os: ubuntu-20.04
     <<: *base-job
 
   - &job-linux-8c
@@ -328,20 +328,9 @@ jobs:
     strategy:
       matrix:
         include:
-          - name: mingw-check
-            <<: *job-linux-4c
-
-          - name: mingw-check-tidy
+          - name: dist-loongarch64-linux
             <<: *job-linux-4c
 
-          - name: x86_64-gnu-llvm-16
-            env:
-              ENABLE_GCC_CODEGEN: "1"
-            <<: *job-linux-16c
-
-          - name: x86_64-gnu-tools
-            <<: *job-linux-16c
-
   auto:
     <<: *base-ci-job
     name: auto - ${{ matrix.name }}

tests/codegen/enum/uninhabited_enum_default_branch.rs

@@ -0,0 +1,24 @@
+// compile-flags: -O
+
+#![crate_type = "lib"]
+
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
+pub struct Int(u32);
+
+const A: Int = Int(201);
+const B: Int = Int(270);
+const C: Int = Int(153);
+
+// CHECK-LABEL: @foo
+// CHECK-SAME: [[TMP0:%.*]])
+// CHECK-NEXT:  start:
+// CHECK-NEXT:    [[TMP1:%.*]] = add i32 [[TMP0]], -201
+// CHECK-NEXT:    [[OR_COND:%.*]] = icmp ult i32 [[TMP1]], 70
+// CHECK-NEXT:    [[TMP2:%.*]] = icmp eq i32 [[TMP0]], 153
+// CHECK-NEXT:    [[SPEC_SELECT:%.*]] = or i1 [[OR_COND]], [[TMP2]]
+// CHECK-NEXT:    ret i1 [[SPEC_SELECT]]
+#[no_mangle]
+pub fn foo(x: Int) -> bool {
+    (x >= A && x <= B)
+        || x == C
+}

tests/mir-opt/funky_arms.float_to_exponential_common.GVN.panic-abort.diff

@@ -69,7 +69,7 @@
           StorageLive(_6);
           _6 = ((*_1).4: std::option::Option<usize>);
           _7 = discriminant(_6);
-          switchInt(move _7) -> [1: bb4, otherwise: bb6];
+          switchInt(move _7) -> [1: bb4, 0: bb6, otherwise: bb9];
       }
 
       bb4: {
@@ -135,5 +135,9 @@
           StorageDead(_6);
           return;
       }
+
+      bb9: {
+          unreachable;
+      }
   }
 

tests/mir-opt/funky_arms.float_to_exponential_common.GVN.panic-unwind.diff

@@ -69,7 +69,7 @@
           StorageLive(_6);
           _6 = ((*_1).4: std::option::Option<usize>);
           _7 = discriminant(_6);
-          switchInt(move _7) -> [1: bb4, otherwise: bb6];
+          switchInt(move _7) -> [1: bb4, 0: bb6, otherwise: bb9];
       }
 
       bb4: {
@@ -135,5 +135,9 @@
           StorageDead(_6);
           return;
       }
+
+      bb9: {
+          unreachable;
+      }
   }
 

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;
+    }
 }