fix bug in 'simplify_branches.rs'

Author: x17jiri

compiler/rustc_mir_transform/src/simplify_branches.rs

@@ -19,23 +19,9 @@ impl<'tcx> MirPass<'tcx> for SimplifyConstCondition {
         let param_env = tcx.param_env_reveal_all_normalized(body.source.def_id());
         'blocks: for block in body.basic_blocks_mut() {
             for stmt in block.statements.iter_mut() {
-                if let StatementKind::Intrinsic(box ref intrinsic) = stmt.kind
-                    && let NonDivergingIntrinsic::Assume(discr) = intrinsic
-                    && let Operand::Constant(ref c) = discr
-                    && let Some(constant) = c.const_.try_eval_bool(tcx, param_env)
-                {
-                    if constant {
-                        stmt.make_nop();
-                    } else {
-                        block.statements.clear();
-                        block.terminator_mut().kind = TerminatorKind::Unreachable;
-                        continue 'blocks;
-                    }
-                }
                 if let StatementKind::Intrinsic(box ref intrinsic) = stmt.kind {
                     match intrinsic {
-                        NonDivergingIntrinsic::Assume(discr)
-                        | NonDivergingIntrinsic::Expect(discr, ..) => {
+                        NonDivergingIntrinsic::Assume(discr) => {
                             if let Operand::Constant(ref c) = discr
                                 && let Some(constant) = c.const_.try_eval_bool(tcx, param_env)
                             {
@@ -48,6 +34,14 @@ impl<'tcx> MirPass<'tcx> for SimplifyConstCondition {
                                 }
                             }
                         }
+                        NonDivergingIntrinsic::Expect(discr, ..) => {
+                            if let Operand::Constant(ref c) = discr
+                                && let Some(constant) = c.const_.try_eval_bool(tcx, param_env)
+                                && constant
+                            {
+                                stmt.make_nop();
+                            }
+                        }
                         _ => {}
                     }
                 }

tests/mir-opt/pre-codegen/checked_ops.checked_shl.PreCodegen.after.mir

@@ -7,7 +7,6 @@ fn checked_shl(_1: u32, _2: u32) -> Option<u32> {
     scope 1 (inlined core::num::<impl u32>::checked_shl) {
         debug self => _1;
         debug rhs => _2;
-        let mut _6: bool;
         scope 2 {
             debug a => _4;
             debug b => _5;
@@ -41,26 +40,21 @@ fn checked_shl(_1: u32, _2: u32) -> Option<u32> {
         _4 = ShlUnchecked(_1, _3);
         StorageDead(_3);
         _5 = Ge(_2, const _);
-        StorageLive(_6);
-        _6 = unlikely(move _5) -> [return: bb1, unwind unreachable];
+        unlikely(_5);
+        switchInt(_5) -> [0: bb1, otherwise: bb2];
     }
 
     bb1: {
-        switchInt(move _6) -> [0: bb2, otherwise: bb3];
-    }
-
-    bb2: {
         _0 = Option::<u32>::Some(_4);
-        goto -> bb4;
+        goto -> bb3;
     }
 
-    bb3: {
+    bb2: {
         _0 = const Option::<u32>::None;
-        goto -> bb4;
+        goto -> bb3;
     }
 
-    bb4: {
-        StorageDead(_6);
+    bb3: {
         StorageDead(_5);
         StorageDead(_4);
         return;