diff --git a/compiler/rustc_mir/src/transform/mod.rs b/compiler/rustc_mir/src/transform/mod.rs
index 5c201594ddd..bbe83aa3bd8 100644
--- a/compiler/rustc_mir/src/transform/mod.rs
+++ b/compiler/rustc_mir/src/transform/mod.rs
@@ -48,6 +48,7 @@ pub mod remove_unneeded_drops;
 pub mod remove_zsts;
 pub mod required_consts;
 pub mod rustc_peek;
+pub mod separate_const_switch;
 pub mod simplify;
 pub mod simplify_branches;
 pub mod simplify_comparison_integral;
@@ -501,6 +502,7 @@ fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         // inst combine is after MatchBranchSimplification to clean up Ne(_1, false)
         &multiple_return_terminators::MultipleReturnTerminators,
         &instcombine::InstCombine,
+        &separate_const_switch::SeparateConstSwitch,
         &const_prop::ConstProp,
         &simplify_branches::SimplifyBranches::new("after-const-prop"),
         &early_otherwise_branch::EarlyOtherwiseBranch,
diff --git a/compiler/rustc_mir/src/transform/separate_const_switch.rs b/compiler/rustc_mir/src/transform/separate_const_switch.rs
new file mode 100644
index 00000000000..87cd27984a0
--- /dev/null
+++ b/compiler/rustc_mir/src/transform/separate_const_switch.rs
@@ -0,0 +1,343 @@
+//! A pass that duplicates switch-terminated blocks
+//! into a new copy for each predecessor, provided
+//! the predecessor sets the value being switched
+//! over to a constant.
+//!
+//! The purpose of this pass is to help constant
+//! propagation passes to simplify the switch terminator
+//! of the copied blocks into gotos when some predecessors
+//! statically determine the output of switches.
+//!
+//! ```text
+//!     x = 12 ---              ---> something
+//!               \            / 12
+//!                --> switch x
+//!               /            \ otherwise
+//!     x = y  ---              ---> something else
+//! ```
+//! becomes
+//! ```text
+//!     x = 12 ---> switch x ------> something
+//!                          \ / 12
+//!                           X
+//!                          / \ otherwise
+//!     x = y  ---> switch x ------> something else
+//! ```
+//! so it can hopefully later be turned by another pass into
+//! ```text
+//!     x = 12 --------------------> something
+//!                            / 12
+//!                           /
+//!                          /   otherwise
+//!     x = y  ---- switch x ------> something else
+//! ```
+//!
+//! This optimization is meant to cover simple cases
+//! like `?` desugaring. For now, it thus focuses on
+//! simplicity rather than completeness (it notably
+//! sometimes duplicates abusively).
+
+use crate::transform::MirPass;
+use rustc_middle::mir::*;
+use rustc_middle::ty::TyCtxt;
+use smallvec::SmallVec;
+
+pub struct SeparateConstSwitch;
+
+impl<'tcx> MirPass<'tcx> for SeparateConstSwitch {
+    fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
+        if tcx.sess.mir_opt_level() < 4 {
+            return;
+        }
+
+        // If execution did something, applying a simplification layer
+        // helps later passes optimize the copy away.
+        if separate_const_switch(body) > 0 {
+            super::simplify::simplify_cfg(tcx, body);
+        }
+    }
+}
+
+/// Returns the amount of blocks that were duplicated
+pub fn separate_const_switch<'tcx>(body: &mut Body<'tcx>) -> usize {
+    let mut new_blocks: SmallVec<[(BasicBlock, BasicBlock); 6]> = SmallVec::new();
+    let predecessors = body.predecessors();
+    'block_iter: for (block_id, block) in body.basic_blocks().iter_enumerated() {
+        if let TerminatorKind::SwitchInt {
+            discr: Operand::Copy(switch_place) | Operand::Move(switch_place),
+            ..
+        } = block.terminator().kind
+        {
+            // If the block is on an unwind path, do not
+            // apply the optimization as unwind paths
+            // rely on a unique parent invariant
+            if block.is_cleanup {
+                continue 'block_iter;
+            }
+
+            // If the block has fewer than 2 predecessors, ignore it
+            // we could maybe chain blocks that have exactly one
+            // predecessor, but for now we ignore that
+            if predecessors[block_id].len() < 2 {
+                continue 'block_iter;
+            }
+
+            // First, let's find a non-const place
+            // that determines the result of the switch
+            if let Some(switch_place) = find_determining_place(switch_place, block) {
+                // We now have an input place for which it would
+                // be interesting if predecessors assigned it from a const
+
+                let mut predecessors_left = predecessors[block_id].len();
+                'predec_iter: for predecessor_id in predecessors[block_id].iter().copied() {
+                    let predecessor = &body.basic_blocks()[predecessor_id];
+
+                    // First we make sure the predecessor jumps
+                    // in a reasonable way
+                    match &predecessor.terminator().kind {
+                        // The following terminators are
+                        // unconditionally valid
+                        TerminatorKind::Goto { .. } | TerminatorKind::SwitchInt { .. } => {}
+
+                        TerminatorKind::FalseEdge { real_target, .. } => {
+                            if *real_target != block_id {
+                                continue 'predec_iter;
+                            }
+                        }
+
+                        // The following terminators are not allowed
+                        TerminatorKind::Resume
+                        | TerminatorKind::Drop { .. }
+                        | TerminatorKind::DropAndReplace { .. }
+                        | TerminatorKind::Call { .. }
+                        | TerminatorKind::Assert { .. }
+                        | TerminatorKind::FalseUnwind { .. }
+                        | TerminatorKind::Yield { .. }
+                        | TerminatorKind::Abort
+                        | TerminatorKind::Return
+                        | TerminatorKind::Unreachable
+                        | TerminatorKind::InlineAsm { .. }
+                        | TerminatorKind::GeneratorDrop => {
+                            continue 'predec_iter;
+                        }
+                    }
+
+                    if is_likely_const(switch_place, predecessor) {
+                        new_blocks.push((predecessor_id, block_id));
+                        predecessors_left -= 1;
+                        if predecessors_left < 2 {
+                            // If the original block only has one predecessor left,
+                            // we have nothing left to do
+                            break 'predec_iter;
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    // Once the analysis is done, perform the duplication
+    let body_span = body.span;
+    let copied_blocks = new_blocks.len();
+    let blocks = body.basic_blocks_mut();
+    for (pred_id, target_id) in new_blocks {
+        let new_block = blocks[target_id].clone();
+        let new_block_id = blocks.push(new_block);
+        let terminator = blocks[pred_id].terminator_mut();
+
+        match terminator.kind {
+            TerminatorKind::Goto { ref mut target } => {
+                *target = new_block_id;
+            }
+
+            TerminatorKind::FalseEdge { ref mut real_target, .. } => {
+                if *real_target == target_id {
+                    *real_target = new_block_id;
+                }
+            }
+
+            TerminatorKind::SwitchInt { ref mut targets, .. } => {
+                targets.all_targets_mut().iter_mut().for_each(|x| {
+                    if *x == target_id {
+                        *x = new_block_id;
+                    }
+                });
+            }
+
+            TerminatorKind::Resume
+            | TerminatorKind::Abort
+            | TerminatorKind::Return
+            | TerminatorKind::Unreachable
+            | TerminatorKind::GeneratorDrop
+            | TerminatorKind::Assert { .. }
+            | TerminatorKind::DropAndReplace { .. }
+            | TerminatorKind::FalseUnwind { .. }
+            | TerminatorKind::Drop { .. }
+            | TerminatorKind::Call { .. }
+            | TerminatorKind::InlineAsm { .. }
+            | TerminatorKind::Yield { .. } => {
+                span_bug!(
+                    body_span,
+                    "basic block terminator had unexpected kind {:?}",
+                    &terminator.kind
+                )
+            }
+        }
+    }
+
+    copied_blocks
+}
+
+/// This function describes a rough heuristic guessing
+/// whether a place is last set with a const within the block.
+/// Notably, it will be overly pessimistic in cases that are already
+/// not handled by `separate_const_switch`.
+fn is_likely_const<'tcx>(mut tracked_place: Place<'tcx>, block: &BasicBlockData<'tcx>) -> bool {
+    for statement in block.statements.iter().rev() {
+        match &statement.kind {
+            StatementKind::Assign(assign) => {
+                if assign.0 == tracked_place {
+                    match assign.1 {
+                        // These rvalues are definitely constant
+                        Rvalue::Use(Operand::Constant(_))
+                        | Rvalue::Ref(_, _, _)
+                        | Rvalue::AddressOf(_, _)
+                        | Rvalue::Cast(_, Operand::Constant(_), _)
+                        | Rvalue::NullaryOp(_, _)
+                        | Rvalue::UnaryOp(_, Operand::Constant(_)) => return true,
+
+                        // These rvalues make things ambiguous
+                        Rvalue::Repeat(_, _)
+                        | Rvalue::ThreadLocalRef(_)
+                        | Rvalue::Len(_)
+                        | Rvalue::BinaryOp(_, _)
+                        | Rvalue::CheckedBinaryOp(_, _)
+                        | Rvalue::Aggregate(_, _) => return false,
+
+                        // These rvalues move the place to track
+                        Rvalue::Cast(_, Operand::Copy(place) | Operand::Move(place), _)
+                        | Rvalue::Use(Operand::Copy(place) | Operand::Move(place))
+                        | Rvalue::UnaryOp(_, Operand::Copy(place) | Operand::Move(place))
+                        | Rvalue::Discriminant(place) => tracked_place = place,
+                    }
+                }
+            }
+
+            // If the discriminant is set, it is always set
+            // as a constant, so the job is done.
+            // As we are **ignoring projections**, if the place
+            // we are tracking sees its discriminant be set,
+            // that means we had to be tracking the discriminant
+            // specifically (as it is impossible to switch over
+            // an enum directly, and if we were switching over
+            // its content, we would have had to at least cast it to
+            // some variant first)
+            StatementKind::SetDiscriminant { place, .. } => {
+                if **place == tracked_place {
+                    return true;
+                }
+            }
+
+            // If inline assembly is found, we probably should
+            // not try to analyze the code
+            StatementKind::LlvmInlineAsm(_) => return false,
+
+            // These statements have no influence on the place
+            // we are interested in
+            StatementKind::FakeRead(_)
+            | StatementKind::StorageLive(_)
+            | StatementKind::Retag(_, _)
+            | StatementKind::AscribeUserType(_, _)
+            | StatementKind::Coverage(_)
+            | StatementKind::StorageDead(_)
+            | StatementKind::CopyNonOverlapping(_)
+            | StatementKind::Nop => {}
+        }
+    }
+
+    // If no good reason for the place to be const is found,
+    // give up. We could maybe go up predecessors, but in
+    // most cases giving up now should be sufficient.
+    false
+}
+
+/// Finds a unique place that entirely determines the value
+/// of `switch_place`, if it exists. This is only a heuristic.
+/// Ideally we would like to track multiple determining places
+/// for some edge cases, but one is enough for a lot of situations.
+fn find_determining_place<'tcx>(
+    mut switch_place: Place<'tcx>,
+    block: &BasicBlockData<'tcx>,
+) -> Option<Place<'tcx>> {
+    for statement in block.statements.iter().rev() {
+        match &statement.kind {
+            StatementKind::Assign(op) => {
+                if op.0 != switch_place {
+                    continue;
+                }
+
+                match op.1 {
+                    // The following rvalues move the place
+                    // that may be const in the predecessor
+                    Rvalue::Use(Operand::Move(new) | Operand::Copy(new))
+                    | Rvalue::UnaryOp(_, Operand::Copy(new) | Operand::Move(new))
+                    | Rvalue::Cast(_, Operand::Move(new) | Operand::Copy(new), _)
+                    | Rvalue::Repeat(Operand::Move(new) | Operand::Copy(new), _)
+                    | Rvalue::Discriminant(new)
+                    => switch_place = new,
+
+                    // The following rvalues might still make the block
+                    // be valid but for now we reject them
+                    Rvalue::Len(_)
+                    | Rvalue::Ref(_, _, _)
+                    | Rvalue::BinaryOp(_, _)
+                    | Rvalue::CheckedBinaryOp(_, _)
+                    | Rvalue::Aggregate(_, _)
+
+                    // The following rvalues definitely mean we cannot
+                    // or should not apply this optimization
+                    | Rvalue::Use(Operand::Constant(_))
+                    | Rvalue::Repeat(Operand::Constant(_), _)
+                    | Rvalue::ThreadLocalRef(_)
+                    | Rvalue::AddressOf(_, _)
+                    | Rvalue::NullaryOp(_, _)
+                    | Rvalue::UnaryOp(_, Operand::Constant(_))
+                    | Rvalue::Cast(_, Operand::Constant(_), _)
+                    => return None,
+                }
+            }
+
+            // These statements have no influence on the place
+            // we are interested in
+            StatementKind::FakeRead(_)
+            | StatementKind::StorageLive(_)
+            | StatementKind::StorageDead(_)
+            | StatementKind::Retag(_, _)
+            | StatementKind::AscribeUserType(_, _)
+            | StatementKind::Coverage(_)
+            | StatementKind::CopyNonOverlapping(_)
+            | StatementKind::Nop => {}
+
+            // If inline assembly is found, we probably should
+            // not try to analyze the code
+            StatementKind::LlvmInlineAsm(_) => return None,
+
+            // If the discriminant is set, it is always set
+            // as a constant, so the job is already done.
+            // As we are **ignoring projections**, if the place
+            // we are tracking sees its discriminant be set,
+            // that means we had to be tracking the discriminant
+            // specifically (as it is impossible to switch over
+            // an enum directly, and if we were switching over
+            // its content, we would have had to at least cast it to
+            // some variant first)
+            StatementKind::SetDiscriminant { place, .. } => {
+                if **place == switch_place {
+                    return None;
+                }
+            }
+        }
+    }
+
+    Some(switch_place)
+}
diff --git a/src/test/mir-opt/separate_const_switch.identity.ConstProp.diff b/src/test/mir-opt/separate_const_switch.identity.ConstProp.diff
new file mode 100644
index 00000000000..57299cee7b7
--- /dev/null
+++ b/src/test/mir-opt/separate_const_switch.identity.ConstProp.diff
@@ -0,0 +1,140 @@
+- // MIR for `identity` before ConstProp
++ // MIR for `identity` after ConstProp
+  
+  fn identity(_1: Result<i32, i32>) -> Result<i32, i32> {
+      debug x => _1;                       // in scope 0 at $DIR/separate_const_switch.rs:28:13: 28:14
+      let mut _0: std::result::Result<i32, i32>; // return place in scope 0 at $DIR/separate_const_switch.rs:28:37: 28:53
+      let mut _2: i32;                     // in scope 0 at $DIR/separate_const_switch.rs:29:8: 29:10
+      let mut _3: std::ops::ControlFlow<std::result::Result<std::convert::Infallible, i32>, i32>; // in scope 0 at $DIR/separate_const_switch.rs:29:8: 29:10
+      let mut _4: std::result::Result<i32, i32>; // in scope 0 at $DIR/separate_const_switch.rs:29:8: 29:9
+      let mut _5: isize;                   // in scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+      let _6: std::result::Result<std::convert::Infallible, i32>; // in scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+      let mut _7: !;                       // in scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+      let mut _8: std::result::Result<std::convert::Infallible, i32>; // in scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+      let _9: i32;                         // in scope 0 at $DIR/separate_const_switch.rs:29:8: 29:10
+      scope 1 {
+          debug residual => _6;            // in scope 1 at $DIR/separate_const_switch.rs:29:9: 29:10
+          scope 2 {
+              scope 8 (inlined <Result<i32, i32> as FromResidual<Result<Infallible, i32>>>::from_residual) { // at $DIR/separate_const_switch.rs:29:8: 29:10
+                  debug residual => _8;    // in scope 8 at $DIR/separate_const_switch.rs:29:8: 29:10
+                  let _16: i32;            // in scope 8 at $DIR/separate_const_switch.rs:29:8: 29:10
+                  let mut _17: i32;        // in scope 8 at $DIR/separate_const_switch.rs:29:8: 29:10
+                  let mut _18: i32;        // in scope 8 at $DIR/separate_const_switch.rs:29:8: 29:10
+                  scope 9 {
+                      debug e => _16;      // in scope 9 at $DIR/separate_const_switch.rs:29:8: 29:10
+                      scope 10 (inlined <i32 as From<i32>>::from) { // at $DIR/separate_const_switch.rs:29:8: 29:10
+                          debug t => _18;  // in scope 10 at $DIR/separate_const_switch.rs:29:8: 29:10
+                      }
+                  }
+              }
+          }
+      }
+      scope 3 {
+          debug val => _9;                 // in scope 3 at $DIR/separate_const_switch.rs:29:8: 29:10
+          scope 4 {
+          }
+      }
+      scope 5 (inlined <Result<i32, i32> as Try>::branch) { // at $DIR/separate_const_switch.rs:29:8: 29:10
+          debug self => _4;                // in scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+          let mut _10: isize;              // in scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+          let _11: i32;                    // in scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+          let mut _12: i32;                // in scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+          let _13: i32;                    // in scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+          let mut _14: std::result::Result<std::convert::Infallible, i32>; // in scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+          let mut _15: i32;                // in scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+          scope 6 {
+              debug v => _11;              // in scope 6 at $DIR/separate_const_switch.rs:29:8: 29:10
+          }
+          scope 7 {
+              debug e => _13;              // in scope 7 at $DIR/separate_const_switch.rs:29:8: 29:10
+          }
+      }
+  
+      bb0: {
+          StorageLive(_2);                 // scope 0 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageLive(_3);                 // scope 0 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageLive(_4);                 // scope 0 at $DIR/separate_const_switch.rs:29:8: 29:9
+          _4 = _1;                         // scope 0 at $DIR/separate_const_switch.rs:29:8: 29:9
+          StorageLive(_10);                // scope 0 at $DIR/separate_const_switch.rs:29:8: 29:10
+          _10 = discriminant(_4);          // scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+          switchInt(move _10) -> [0_isize: bb5, 1_isize: bb3, otherwise: bb4]; // scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+      }
+  
+      bb1: {
+          StorageLive(_9);                 // scope 0 at $DIR/separate_const_switch.rs:29:8: 29:10
+          _9 = ((_3 as Continue).0: i32);  // scope 0 at $DIR/separate_const_switch.rs:29:8: 29:10
+          _2 = _9;                         // scope 4 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageDead(_9);                 // scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+          ((_0 as Ok).0: i32) = move _2;   // scope 0 at $DIR/separate_const_switch.rs:29:5: 29:11
+          discriminant(_0) = 0;            // scope 0 at $DIR/separate_const_switch.rs:29:5: 29:11
+          StorageDead(_2);                 // scope 0 at $DIR/separate_const_switch.rs:29:10: 29:11
+          StorageDead(_3);                 // scope 0 at $DIR/separate_const_switch.rs:30:1: 30:2
+          return;                          // scope 0 at $DIR/separate_const_switch.rs:30:2: 30:2
+      }
+  
+      bb2: {
+          StorageLive(_6);                 // scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+          _6 = ((_3 as Break).0: std::result::Result<std::convert::Infallible, i32>); // scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+          StorageLive(_8);                 // scope 2 at $DIR/separate_const_switch.rs:29:9: 29:10
+          _8 = _6;                         // scope 2 at $DIR/separate_const_switch.rs:29:9: 29:10
+          StorageLive(_16);                // scope 8 at $DIR/separate_const_switch.rs:29:8: 29:10
+          _16 = move ((_8 as Err).0: i32); // scope 8 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageLive(_17);                // scope 9 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageLive(_18);                // scope 9 at $DIR/separate_const_switch.rs:29:8: 29:10
+          _18 = move _16;                  // scope 9 at $DIR/separate_const_switch.rs:29:8: 29:10
+          _17 = move _18;                  // scope 10 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageDead(_18);                // scope 9 at $DIR/separate_const_switch.rs:29:8: 29:10
+          ((_0 as Err).0: i32) = move _17; // scope 9 at $DIR/separate_const_switch.rs:29:8: 29:10
+          discriminant(_0) = 1;            // scope 9 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageDead(_17);                // scope 9 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageDead(_16);                // scope 8 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageDead(_8);                 // scope 2 at $DIR/separate_const_switch.rs:29:9: 29:10
+          StorageDead(_6);                 // scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+          StorageDead(_2);                 // scope 0 at $DIR/separate_const_switch.rs:29:10: 29:11
+          StorageDead(_3);                 // scope 0 at $DIR/separate_const_switch.rs:30:1: 30:2
+          return;                          // scope 0 at $DIR/separate_const_switch.rs:30:2: 30:2
+      }
+  
+      bb3: {
+          StorageLive(_13);                // scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+          _13 = move ((_4 as Err).0: i32); // scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageLive(_14);                // scope 7 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageLive(_15);                // scope 7 at $DIR/separate_const_switch.rs:29:8: 29:10
+          _15 = move _13;                  // scope 7 at $DIR/separate_const_switch.rs:29:8: 29:10
+          ((_14 as Err).0: i32) = move _15; // scope 7 at $DIR/separate_const_switch.rs:29:8: 29:10
+          discriminant(_14) = 1;           // scope 7 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageDead(_15);                // scope 7 at $DIR/separate_const_switch.rs:29:8: 29:10
+          ((_3 as Break).0: std::result::Result<std::convert::Infallible, i32>) = move _14; // scope 7 at $DIR/separate_const_switch.rs:29:8: 29:10
+          discriminant(_3) = 1;            // scope 7 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageDead(_14);                // scope 7 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageDead(_13);                // scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageDead(_10);                // scope 0 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageDead(_4);                 // scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+-         _5 = discriminant(_3);           // scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+-         switchInt(move _5) -> [0_isize: bb1, otherwise: bb2]; // scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
++         _5 = const 1_isize;              // scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
++         switchInt(const 1_isize) -> [0_isize: bb1, otherwise: bb2]; // scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+      }
+  
+      bb4: {
+          unreachable;                     // scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+      }
+  
+      bb5: {
+          StorageLive(_11);                // scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+          _11 = move ((_4 as Ok).0: i32);  // scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageLive(_12);                // scope 6 at $DIR/separate_const_switch.rs:29:8: 29:10
+          _12 = move _11;                  // scope 6 at $DIR/separate_const_switch.rs:29:8: 29:10
+          ((_3 as Continue).0: i32) = move _12; // scope 6 at $DIR/separate_const_switch.rs:29:8: 29:10
+          discriminant(_3) = 0;            // scope 6 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageDead(_12);                // scope 6 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageDead(_11);                // scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageDead(_10);                // scope 0 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageDead(_4);                 // scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+-         _5 = discriminant(_3);           // scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+-         switchInt(move _5) -> [0_isize: bb1, otherwise: bb2]; // scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
++         _5 = const 0_isize;              // scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
++         switchInt(const 0_isize) -> [0_isize: bb1, otherwise: bb2]; // scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+      }
+  }
+  
diff --git a/src/test/mir-opt/separate_const_switch.identity.PreCodegen.after.mir b/src/test/mir-opt/separate_const_switch.identity.PreCodegen.after.mir
new file mode 100644
index 00000000000..dee45c58403
--- /dev/null
+++ b/src/test/mir-opt/separate_const_switch.identity.PreCodegen.after.mir
@@ -0,0 +1,122 @@
+// MIR for `identity` after PreCodegen
+
+fn identity(_1: Result<i32, i32>) -> Result<i32, i32> {
+    debug x => _1;                       // in scope 0 at $DIR/separate_const_switch.rs:28:13: 28:14
+    let mut _0: std::result::Result<i32, i32>; // return place in scope 0 at $DIR/separate_const_switch.rs:28:37: 28:53
+    let mut _2: i32;                     // in scope 0 at $DIR/separate_const_switch.rs:29:8: 29:10
+    let mut _3: std::ops::ControlFlow<std::result::Result<std::convert::Infallible, i32>, i32>; // in scope 0 at $DIR/separate_const_switch.rs:29:8: 29:10
+    let mut _4: std::result::Result<i32, i32>; // in scope 0 at $DIR/separate_const_switch.rs:29:8: 29:9
+    let _5: std::result::Result<std::convert::Infallible, i32>; // in scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+    let mut _6: std::result::Result<std::convert::Infallible, i32>; // in scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+    let _7: i32;                         // in scope 0 at $DIR/separate_const_switch.rs:29:8: 29:10
+    scope 1 {
+        debug residual => _5;            // in scope 1 at $DIR/separate_const_switch.rs:29:9: 29:10
+        scope 2 {
+            scope 8 (inlined <Result<i32, i32> as FromResidual<Result<Infallible, i32>>>::from_residual) { // at $DIR/separate_const_switch.rs:29:8: 29:10
+                debug residual => _6;    // in scope 8 at $DIR/separate_const_switch.rs:29:8: 29:10
+                let _14: i32;            // in scope 8 at $DIR/separate_const_switch.rs:29:8: 29:10
+                let mut _15: i32;        // in scope 8 at $DIR/separate_const_switch.rs:29:8: 29:10
+                let mut _16: i32;        // in scope 8 at $DIR/separate_const_switch.rs:29:8: 29:10
+                scope 9 {
+                    debug e => _14;      // in scope 9 at $DIR/separate_const_switch.rs:29:8: 29:10
+                    scope 10 (inlined <i32 as From<i32>>::from) { // at $DIR/separate_const_switch.rs:29:8: 29:10
+                        debug t => _16;  // in scope 10 at $DIR/separate_const_switch.rs:29:8: 29:10
+                    }
+                }
+            }
+        }
+    }
+    scope 3 {
+        debug val => _7;                 // in scope 3 at $DIR/separate_const_switch.rs:29:8: 29:10
+        scope 4 {
+        }
+    }
+    scope 5 (inlined <Result<i32, i32> as Try>::branch) { // at $DIR/separate_const_switch.rs:29:8: 29:10
+        debug self => _4;                // in scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+        let mut _8: isize;               // in scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+        let _9: i32;                     // in scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+        let mut _10: i32;                // in scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+        let _11: i32;                    // in scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+        let mut _12: std::result::Result<std::convert::Infallible, i32>; // in scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+        let mut _13: i32;                // in scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+        scope 6 {
+            debug v => _9;               // in scope 6 at $DIR/separate_const_switch.rs:29:8: 29:10
+        }
+        scope 7 {
+            debug e => _11;              // in scope 7 at $DIR/separate_const_switch.rs:29:8: 29:10
+        }
+    }
+
+    bb0: {
+        StorageLive(_2);                 // scope 0 at $DIR/separate_const_switch.rs:29:8: 29:10
+        StorageLive(_3);                 // scope 0 at $DIR/separate_const_switch.rs:29:8: 29:10
+        StorageLive(_4);                 // scope 0 at $DIR/separate_const_switch.rs:29:8: 29:9
+        _4 = _1;                         // scope 0 at $DIR/separate_const_switch.rs:29:8: 29:9
+        StorageLive(_8);                 // scope 0 at $DIR/separate_const_switch.rs:29:8: 29:10
+        _8 = discriminant(_4);           // scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+        switchInt(move _8) -> [0_isize: bb3, 1_isize: bb1, otherwise: bb2]; // scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+    }
+
+    bb1: {
+        StorageLive(_11);                // scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+        _11 = move ((_4 as Err).0: i32); // scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+        StorageLive(_12);                // scope 7 at $DIR/separate_const_switch.rs:29:8: 29:10
+        StorageLive(_13);                // scope 7 at $DIR/separate_const_switch.rs:29:8: 29:10
+        _13 = move _11;                  // scope 7 at $DIR/separate_const_switch.rs:29:8: 29:10
+        ((_12 as Err).0: i32) = move _13; // scope 7 at $DIR/separate_const_switch.rs:29:8: 29:10
+        discriminant(_12) = 1;           // scope 7 at $DIR/separate_const_switch.rs:29:8: 29:10
+        StorageDead(_13);                // scope 7 at $DIR/separate_const_switch.rs:29:8: 29:10
+        ((_3 as Break).0: std::result::Result<std::convert::Infallible, i32>) = move _12; // scope 7 at $DIR/separate_const_switch.rs:29:8: 29:10
+        discriminant(_3) = 1;            // scope 7 at $DIR/separate_const_switch.rs:29:8: 29:10
+        StorageDead(_12);                // scope 7 at $DIR/separate_const_switch.rs:29:8: 29:10
+        StorageDead(_11);                // scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+        StorageDead(_8);                 // scope 0 at $DIR/separate_const_switch.rs:29:8: 29:10
+        StorageDead(_4);                 // scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+        StorageLive(_5);                 // scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+        _5 = ((_3 as Break).0: std::result::Result<std::convert::Infallible, i32>); // scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+        StorageLive(_6);                 // scope 2 at $DIR/separate_const_switch.rs:29:9: 29:10
+        _6 = _5;                         // scope 2 at $DIR/separate_const_switch.rs:29:9: 29:10
+        StorageLive(_14);                // scope 8 at $DIR/separate_const_switch.rs:29:8: 29:10
+        _14 = move ((_6 as Err).0: i32); // scope 8 at $DIR/separate_const_switch.rs:29:8: 29:10
+        StorageLive(_15);                // scope 9 at $DIR/separate_const_switch.rs:29:8: 29:10
+        StorageLive(_16);                // scope 9 at $DIR/separate_const_switch.rs:29:8: 29:10
+        _16 = move _14;                  // scope 9 at $DIR/separate_const_switch.rs:29:8: 29:10
+        _15 = move _16;                  // scope 10 at $DIR/separate_const_switch.rs:29:8: 29:10
+        StorageDead(_16);                // scope 9 at $DIR/separate_const_switch.rs:29:8: 29:10
+        ((_0 as Err).0: i32) = move _15; // scope 9 at $DIR/separate_const_switch.rs:29:8: 29:10
+        discriminant(_0) = 1;            // scope 9 at $DIR/separate_const_switch.rs:29:8: 29:10
+        StorageDead(_15);                // scope 9 at $DIR/separate_const_switch.rs:29:8: 29:10
+        StorageDead(_14);                // scope 8 at $DIR/separate_const_switch.rs:29:8: 29:10
+        StorageDead(_6);                 // scope 2 at $DIR/separate_const_switch.rs:29:9: 29:10
+        StorageDead(_5);                 // scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+        StorageDead(_2);                 // scope 0 at $DIR/separate_const_switch.rs:29:10: 29:11
+        StorageDead(_3);                 // scope 0 at $DIR/separate_const_switch.rs:30:1: 30:2
+        return;                          // scope 0 at $DIR/separate_const_switch.rs:30:2: 30:2
+    }
+
+    bb2: {
+        unreachable;                     // scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+    }
+
+    bb3: {
+        StorageLive(_9);                 // scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+        _9 = move ((_4 as Ok).0: i32);   // scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+        StorageLive(_10);                // scope 6 at $DIR/separate_const_switch.rs:29:8: 29:10
+        _10 = move _9;                   // scope 6 at $DIR/separate_const_switch.rs:29:8: 29:10
+        ((_3 as Continue).0: i32) = move _10; // scope 6 at $DIR/separate_const_switch.rs:29:8: 29:10
+        discriminant(_3) = 0;            // scope 6 at $DIR/separate_const_switch.rs:29:8: 29:10
+        StorageDead(_10);                // scope 6 at $DIR/separate_const_switch.rs:29:8: 29:10
+        StorageDead(_9);                 // scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+        StorageDead(_8);                 // scope 0 at $DIR/separate_const_switch.rs:29:8: 29:10
+        StorageDead(_4);                 // scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+        StorageLive(_7);                 // scope 0 at $DIR/separate_const_switch.rs:29:8: 29:10
+        _7 = ((_3 as Continue).0: i32);  // scope 0 at $DIR/separate_const_switch.rs:29:8: 29:10
+        _2 = _7;                         // scope 4 at $DIR/separate_const_switch.rs:29:8: 29:10
+        StorageDead(_7);                 // scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+        ((_0 as Ok).0: i32) = move _2;   // scope 0 at $DIR/separate_const_switch.rs:29:5: 29:11
+        discriminant(_0) = 0;            // scope 0 at $DIR/separate_const_switch.rs:29:5: 29:11
+        StorageDead(_2);                 // scope 0 at $DIR/separate_const_switch.rs:29:10: 29:11
+        StorageDead(_3);                 // scope 0 at $DIR/separate_const_switch.rs:30:1: 30:2
+        return;                          // scope 0 at $DIR/separate_const_switch.rs:30:2: 30:2
+    }
+}
diff --git a/src/test/mir-opt/separate_const_switch.identity.SeparateConstSwitch.diff b/src/test/mir-opt/separate_const_switch.identity.SeparateConstSwitch.diff
new file mode 100644
index 00000000000..4bfd0842db0
--- /dev/null
+++ b/src/test/mir-opt/separate_const_switch.identity.SeparateConstSwitch.diff
@@ -0,0 +1,150 @@
+- // MIR for `identity` before SeparateConstSwitch
++ // MIR for `identity` after SeparateConstSwitch
+  
+  fn identity(_1: Result<i32, i32>) -> Result<i32, i32> {
+      debug x => _1;                       // in scope 0 at $DIR/separate_const_switch.rs:28:13: 28:14
+      let mut _0: std::result::Result<i32, i32>; // return place in scope 0 at $DIR/separate_const_switch.rs:28:37: 28:53
+      let mut _2: i32;                     // in scope 0 at $DIR/separate_const_switch.rs:29:8: 29:10
+      let mut _3: std::ops::ControlFlow<std::result::Result<std::convert::Infallible, i32>, i32>; // in scope 0 at $DIR/separate_const_switch.rs:29:8: 29:10
+      let mut _4: std::result::Result<i32, i32>; // in scope 0 at $DIR/separate_const_switch.rs:29:8: 29:9
+      let mut _5: isize;                   // in scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+      let _6: std::result::Result<std::convert::Infallible, i32>; // in scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+      let mut _7: !;                       // in scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+      let mut _8: std::result::Result<std::convert::Infallible, i32>; // in scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+      let _9: i32;                         // in scope 0 at $DIR/separate_const_switch.rs:29:8: 29:10
+      scope 1 {
+          debug residual => _6;            // in scope 1 at $DIR/separate_const_switch.rs:29:9: 29:10
+          scope 2 {
+              scope 8 (inlined <Result<i32, i32> as FromResidual<Result<Infallible, i32>>>::from_residual) { // at $DIR/separate_const_switch.rs:29:8: 29:10
+                  debug residual => _8;    // in scope 8 at $DIR/separate_const_switch.rs:29:8: 29:10
+                  let _16: i32;            // in scope 8 at $DIR/separate_const_switch.rs:29:8: 29:10
+                  let mut _17: i32;        // in scope 8 at $DIR/separate_const_switch.rs:29:8: 29:10
+                  let mut _18: i32;        // in scope 8 at $DIR/separate_const_switch.rs:29:8: 29:10
+                  scope 9 {
+                      debug e => _16;      // in scope 9 at $DIR/separate_const_switch.rs:29:8: 29:10
+                      scope 10 (inlined <i32 as From<i32>>::from) { // at $DIR/separate_const_switch.rs:29:8: 29:10
+                          debug t => _18;  // in scope 10 at $DIR/separate_const_switch.rs:29:8: 29:10
+                      }
+                  }
+              }
+          }
+      }
+      scope 3 {
+          debug val => _9;                 // in scope 3 at $DIR/separate_const_switch.rs:29:8: 29:10
+          scope 4 {
+          }
+      }
+      scope 5 (inlined <Result<i32, i32> as Try>::branch) { // at $DIR/separate_const_switch.rs:29:8: 29:10
+          debug self => _4;                // in scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+          let mut _10: isize;              // in scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+          let _11: i32;                    // in scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+          let mut _12: i32;                // in scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+          let _13: i32;                    // in scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+          let mut _14: std::result::Result<std::convert::Infallible, i32>; // in scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+          let mut _15: i32;                // in scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+          scope 6 {
+              debug v => _11;              // in scope 6 at $DIR/separate_const_switch.rs:29:8: 29:10
+          }
+          scope 7 {
+              debug e => _13;              // in scope 7 at $DIR/separate_const_switch.rs:29:8: 29:10
+          }
+      }
+  
+      bb0: {
+          StorageLive(_2);                 // scope 0 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageLive(_3);                 // scope 0 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageLive(_4);                 // scope 0 at $DIR/separate_const_switch.rs:29:8: 29:9
+          _4 = _1;                         // scope 0 at $DIR/separate_const_switch.rs:29:8: 29:9
+          StorageLive(_10);                // scope 0 at $DIR/separate_const_switch.rs:29:8: 29:10
+          _10 = discriminant(_4);          // scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+-         switchInt(move _10) -> [0_isize: bb6, 1_isize: bb4, otherwise: bb5]; // scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
++         switchInt(move _10) -> [0_isize: bb5, 1_isize: bb3, otherwise: bb4]; // scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+      }
+  
+      bb1: {
+-         StorageDead(_10);                // scope 0 at $DIR/separate_const_switch.rs:29:8: 29:10
+-         StorageDead(_4);                 // scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+-         _5 = discriminant(_3);           // scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+-         switchInt(move _5) -> [0_isize: bb2, otherwise: bb3]; // scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+-     }
+- 
+-     bb2: {
+          StorageLive(_9);                 // scope 0 at $DIR/separate_const_switch.rs:29:8: 29:10
+          _9 = ((_3 as Continue).0: i32);  // scope 0 at $DIR/separate_const_switch.rs:29:8: 29:10
+          _2 = _9;                         // scope 4 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageDead(_9);                 // scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+          ((_0 as Ok).0: i32) = move _2;   // scope 0 at $DIR/separate_const_switch.rs:29:5: 29:11
+          discriminant(_0) = 0;            // scope 0 at $DIR/separate_const_switch.rs:29:5: 29:11
+          StorageDead(_2);                 // scope 0 at $DIR/separate_const_switch.rs:29:10: 29:11
+          StorageDead(_3);                 // scope 0 at $DIR/separate_const_switch.rs:30:1: 30:2
+          return;                          // scope 0 at $DIR/separate_const_switch.rs:30:2: 30:2
+      }
+  
+-     bb3: {
++     bb2: {
+          StorageLive(_6);                 // scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+          _6 = ((_3 as Break).0: std::result::Result<std::convert::Infallible, i32>); // scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+          StorageLive(_8);                 // scope 2 at $DIR/separate_const_switch.rs:29:9: 29:10
+          _8 = _6;                         // scope 2 at $DIR/separate_const_switch.rs:29:9: 29:10
+          StorageLive(_16);                // scope 8 at $DIR/separate_const_switch.rs:29:8: 29:10
+          _16 = move ((_8 as Err).0: i32); // scope 8 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageLive(_17);                // scope 9 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageLive(_18);                // scope 9 at $DIR/separate_const_switch.rs:29:8: 29:10
+          _18 = move _16;                  // scope 9 at $DIR/separate_const_switch.rs:29:8: 29:10
+          _17 = move _18;                  // scope 10 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageDead(_18);                // scope 9 at $DIR/separate_const_switch.rs:29:8: 29:10
+          ((_0 as Err).0: i32) = move _17; // scope 9 at $DIR/separate_const_switch.rs:29:8: 29:10
+          discriminant(_0) = 1;            // scope 9 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageDead(_17);                // scope 9 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageDead(_16);                // scope 8 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageDead(_8);                 // scope 2 at $DIR/separate_const_switch.rs:29:9: 29:10
+          StorageDead(_6);                 // scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+          StorageDead(_2);                 // scope 0 at $DIR/separate_const_switch.rs:29:10: 29:11
+          StorageDead(_3);                 // scope 0 at $DIR/separate_const_switch.rs:30:1: 30:2
+          return;                          // scope 0 at $DIR/separate_const_switch.rs:30:2: 30:2
+      }
+  
+-     bb4: {
++     bb3: {
+          StorageLive(_13);                // scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+          _13 = move ((_4 as Err).0: i32); // scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageLive(_14);                // scope 7 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageLive(_15);                // scope 7 at $DIR/separate_const_switch.rs:29:8: 29:10
+          _15 = move _13;                  // scope 7 at $DIR/separate_const_switch.rs:29:8: 29:10
+          ((_14 as Err).0: i32) = move _15; // scope 7 at $DIR/separate_const_switch.rs:29:8: 29:10
+          discriminant(_14) = 1;           // scope 7 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageDead(_15);                // scope 7 at $DIR/separate_const_switch.rs:29:8: 29:10
+          ((_3 as Break).0: std::result::Result<std::convert::Infallible, i32>) = move _14; // scope 7 at $DIR/separate_const_switch.rs:29:8: 29:10
+          discriminant(_3) = 1;            // scope 7 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageDead(_14);                // scope 7 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageDead(_13);                // scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+-         goto -> bb1;                     // scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
++         StorageDead(_10);                // scope 0 at $DIR/separate_const_switch.rs:29:8: 29:10
++         StorageDead(_4);                 // scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
++         _5 = discriminant(_3);           // scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
++         switchInt(move _5) -> [0_isize: bb1, otherwise: bb2]; // scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+      }
+  
+-     bb5: {
++     bb4: {
+          unreachable;                     // scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+      }
+  
+-     bb6: {
++     bb5: {
+          StorageLive(_11);                // scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+          _11 = move ((_4 as Ok).0: i32);  // scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageLive(_12);                // scope 6 at $DIR/separate_const_switch.rs:29:8: 29:10
+          _12 = move _11;                  // scope 6 at $DIR/separate_const_switch.rs:29:8: 29:10
+          ((_3 as Continue).0: i32) = move _12; // scope 6 at $DIR/separate_const_switch.rs:29:8: 29:10
+          discriminant(_3) = 0;            // scope 6 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageDead(_12);                // scope 6 at $DIR/separate_const_switch.rs:29:8: 29:10
+          StorageDead(_11);                // scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
+-         goto -> bb1;                     // scope 5 at $DIR/separate_const_switch.rs:29:8: 29:10
++         StorageDead(_10);                // scope 0 at $DIR/separate_const_switch.rs:29:8: 29:10
++         StorageDead(_4);                 // scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
++         _5 = discriminant(_3);           // scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
++         switchInt(move _5) -> [0_isize: bb1, otherwise: bb2]; // scope 0 at $DIR/separate_const_switch.rs:29:9: 29:10
+      }
+  }
+  
diff --git a/src/test/mir-opt/separate_const_switch.rs b/src/test/mir-opt/separate_const_switch.rs
new file mode 100644
index 00000000000..5d82acf4d60
--- /dev/null
+++ b/src/test/mir-opt/separate_const_switch.rs
@@ -0,0 +1,35 @@
+#![feature(control_flow_enum)]
+#![feature(try_trait_v2)]
+
+use std::ops::ControlFlow;
+
+// EMIT_MIR separate_const_switch.too_complex.SeparateConstSwitch.diff
+// EMIT_MIR separate_const_switch.too_complex.ConstProp.diff
+// EMIT_MIR separate_const_switch.too_complex.PreCodegen.after.mir
+fn too_complex(x: Result<i32, usize>) -> Option<i32> {
+    // The pass should break the outer match into
+    // two blocks that only have one parent each.
+    // Parents are one of the two branches of the first
+    // match, so a later pass can propagate constants.
+    match {
+        match x {
+            Ok(v) => ControlFlow::Continue(v),
+            Err(r) => ControlFlow::Break(r),
+        }
+    } {
+        ControlFlow::Continue(v) => Some(v),
+        ControlFlow::Break(r) => None,
+    }
+}
+
+// EMIT_MIR separate_const_switch.identity.SeparateConstSwitch.diff
+// EMIT_MIR separate_const_switch.identity.ConstProp.diff
+// EMIT_MIR separate_const_switch.identity.PreCodegen.after.mir
+fn identity(x: Result<i32, i32>) -> Result<i32, i32> {
+    Ok(x?)
+}
+
+fn main() {
+    too_complex(Ok(0));
+    identity(Ok(0));
+}
diff --git a/src/test/mir-opt/separate_const_switch.too_complex.ConstProp.diff b/src/test/mir-opt/separate_const_switch.too_complex.ConstProp.diff
new file mode 100644
index 00000000000..973b7838eca
--- /dev/null
+++ b/src/test/mir-opt/separate_const_switch.too_complex.ConstProp.diff
@@ -0,0 +1,91 @@
+- // MIR for `too_complex` before ConstProp
++ // MIR for `too_complex` after ConstProp
+  
+  fn too_complex(_1: Result<i32, usize>) -> Option<i32> {
+      debug x => _1;                       // in scope 0 at $DIR/separate_const_switch.rs:9:16: 9:17
+      let mut _0: std::option::Option<i32>; // return place in scope 0 at $DIR/separate_const_switch.rs:9:42: 9:53
+      let mut _2: std::ops::ControlFlow<usize, i32>; // in scope 0 at $DIR/separate_const_switch.rs:14:11: 19:6
+      let mut _3: isize;                   // in scope 0 at $DIR/separate_const_switch.rs:16:13: 16:18
+      let _4: i32;                         // in scope 0 at $DIR/separate_const_switch.rs:16:16: 16:17
+      let mut _5: i32;                     // in scope 0 at $DIR/separate_const_switch.rs:16:44: 16:45
+      let _6: usize;                       // in scope 0 at $DIR/separate_const_switch.rs:17:17: 17:18
+      let mut _7: usize;                   // in scope 0 at $DIR/separate_const_switch.rs:17:42: 17:43
+      let mut _8: isize;                   // in scope 0 at $DIR/separate_const_switch.rs:20:9: 20:33
+      let _9: i32;                         // in scope 0 at $DIR/separate_const_switch.rs:20:31: 20:32
+      let mut _10: i32;                    // in scope 0 at $DIR/separate_const_switch.rs:20:42: 20:43
+      let _11: usize;                      // in scope 0 at $DIR/separate_const_switch.rs:21:28: 21:29
+      scope 1 {
+          debug v => _4;                   // in scope 1 at $DIR/separate_const_switch.rs:16:16: 16:17
+      }
+      scope 2 {
+          debug r => _6;                   // in scope 2 at $DIR/separate_const_switch.rs:17:17: 17:18
+      }
+      scope 3 {
+          debug v => _9;                   // in scope 3 at $DIR/separate_const_switch.rs:20:31: 20:32
+      }
+      scope 4 {
+          debug r => _11;                  // in scope 4 at $DIR/separate_const_switch.rs:21:28: 21:29
+      }
+  
+      bb0: {
+          StorageLive(_2);                 // scope 0 at $DIR/separate_const_switch.rs:14:11: 19:6
+          _3 = discriminant(_1);           // scope 0 at $DIR/separate_const_switch.rs:16:13: 16:18
+          switchInt(move _3) -> [0_isize: bb2, otherwise: bb1]; // scope 0 at $DIR/separate_const_switch.rs:16:13: 16:18
+      }
+  
+      bb1: {
+          StorageLive(_6);                 // scope 0 at $DIR/separate_const_switch.rs:17:17: 17:18
+          _6 = ((_1 as Err).0: usize);     // scope 0 at $DIR/separate_const_switch.rs:17:17: 17:18
+          StorageLive(_7);                 // scope 2 at $DIR/separate_const_switch.rs:17:42: 17:43
+          _7 = _6;                         // scope 2 at $DIR/separate_const_switch.rs:17:42: 17:43
+          ((_2 as Break).0: usize) = move _7; // scope 2 at $DIR/separate_const_switch.rs:17:23: 17:44
+          discriminant(_2) = 1;            // scope 2 at $DIR/separate_const_switch.rs:17:23: 17:44
+          StorageDead(_7);                 // scope 2 at $DIR/separate_const_switch.rs:17:43: 17:44
+          StorageDead(_6);                 // scope 0 at $DIR/separate_const_switch.rs:17:43: 17:44
+-         _8 = discriminant(_2);           // scope 0 at $DIR/separate_const_switch.rs:20:9: 20:33
+-         switchInt(move _8) -> [0_isize: bb4, otherwise: bb3]; // scope 0 at $DIR/separate_const_switch.rs:20:9: 20:33
++         _8 = const 1_isize;              // scope 0 at $DIR/separate_const_switch.rs:20:9: 20:33
++         switchInt(const 1_isize) -> [0_isize: bb4, otherwise: bb3]; // scope 0 at $DIR/separate_const_switch.rs:20:9: 20:33
+      }
+  
+      bb2: {
+          StorageLive(_4);                 // scope 0 at $DIR/separate_const_switch.rs:16:16: 16:17
+          _4 = ((_1 as Ok).0: i32);        // scope 0 at $DIR/separate_const_switch.rs:16:16: 16:17
+          StorageLive(_5);                 // scope 1 at $DIR/separate_const_switch.rs:16:44: 16:45
+          _5 = _4;                         // scope 1 at $DIR/separate_const_switch.rs:16:44: 16:45
+          ((_2 as Continue).0: i32) = move _5; // scope 1 at $DIR/separate_const_switch.rs:16:22: 16:46
+          discriminant(_2) = 0;            // scope 1 at $DIR/separate_const_switch.rs:16:22: 16:46
+          StorageDead(_5);                 // scope 1 at $DIR/separate_const_switch.rs:16:45: 16:46
+          StorageDead(_4);                 // scope 0 at $DIR/separate_const_switch.rs:16:45: 16:46
+-         _8 = discriminant(_2);           // scope 0 at $DIR/separate_const_switch.rs:20:9: 20:33
+-         switchInt(move _8) -> [0_isize: bb4, otherwise: bb3]; // scope 0 at $DIR/separate_const_switch.rs:20:9: 20:33
++         _8 = const 0_isize;              // scope 0 at $DIR/separate_const_switch.rs:20:9: 20:33
++         switchInt(const 0_isize) -> [0_isize: bb4, otherwise: bb3]; // scope 0 at $DIR/separate_const_switch.rs:20:9: 20:33
+      }
+  
+      bb3: {
+          StorageLive(_11);                // scope 0 at $DIR/separate_const_switch.rs:21:28: 21:29
+          _11 = ((_2 as Break).0: usize);  // scope 0 at $DIR/separate_const_switch.rs:21:28: 21:29
+          discriminant(_0) = 0;            // scope 4 at $DIR/separate_const_switch.rs:21:34: 21:38
+          StorageDead(_11);                // scope 0 at $DIR/separate_const_switch.rs:21:37: 21:38
+          goto -> bb5;                     // scope 0 at $DIR/separate_const_switch.rs:14:5: 22:6
+      }
+  
+      bb4: {
+          StorageLive(_9);                 // scope 0 at $DIR/separate_const_switch.rs:20:31: 20:32
+          _9 = ((_2 as Continue).0: i32);  // scope 0 at $DIR/separate_const_switch.rs:20:31: 20:32
+          StorageLive(_10);                // scope 3 at $DIR/separate_const_switch.rs:20:42: 20:43
+          _10 = _9;                        // scope 3 at $DIR/separate_const_switch.rs:20:42: 20:43
+          ((_0 as Some).0: i32) = move _10; // scope 3 at $DIR/separate_const_switch.rs:20:37: 20:44
+          discriminant(_0) = 1;            // scope 3 at $DIR/separate_const_switch.rs:20:37: 20:44
+          StorageDead(_10);                // scope 3 at $DIR/separate_const_switch.rs:20:43: 20:44
+          StorageDead(_9);                 // scope 0 at $DIR/separate_const_switch.rs:20:43: 20:44
+          goto -> bb5;                     // scope 0 at $DIR/separate_const_switch.rs:14:5: 22:6
+      }
+  
+      bb5: {
+          StorageDead(_2);                 // scope 0 at $DIR/separate_const_switch.rs:23:1: 23:2
+          return;                          // scope 0 at $DIR/separate_const_switch.rs:23:2: 23:2
+      }
+  }
+  
diff --git a/src/test/mir-opt/separate_const_switch.too_complex.PreCodegen.after.mir b/src/test/mir-opt/separate_const_switch.too_complex.PreCodegen.after.mir
new file mode 100644
index 00000000000..cc941f251ce
--- /dev/null
+++ b/src/test/mir-opt/separate_const_switch.too_complex.PreCodegen.after.mir
@@ -0,0 +1,74 @@
+// MIR for `too_complex` after PreCodegen
+
+fn too_complex(_1: Result<i32, usize>) -> Option<i32> {
+    debug x => _1;                       // in scope 0 at $DIR/separate_const_switch.rs:9:16: 9:17
+    let mut _0: std::option::Option<i32>; // return place in scope 0 at $DIR/separate_const_switch.rs:9:42: 9:53
+    let mut _2: std::ops::ControlFlow<usize, i32>; // in scope 0 at $DIR/separate_const_switch.rs:14:11: 19:6
+    let mut _3: isize;                   // in scope 0 at $DIR/separate_const_switch.rs:16:13: 16:18
+    let _4: i32;                         // in scope 0 at $DIR/separate_const_switch.rs:16:16: 16:17
+    let mut _5: i32;                     // in scope 0 at $DIR/separate_const_switch.rs:16:44: 16:45
+    let _6: usize;                       // in scope 0 at $DIR/separate_const_switch.rs:17:17: 17:18
+    let mut _7: usize;                   // in scope 0 at $DIR/separate_const_switch.rs:17:42: 17:43
+    let _8: i32;                         // in scope 0 at $DIR/separate_const_switch.rs:20:31: 20:32
+    let mut _9: i32;                     // in scope 0 at $DIR/separate_const_switch.rs:20:42: 20:43
+    let _10: usize;                      // in scope 0 at $DIR/separate_const_switch.rs:21:28: 21:29
+    scope 1 {
+        debug v => _4;                   // in scope 1 at $DIR/separate_const_switch.rs:16:16: 16:17
+    }
+    scope 2 {
+        debug r => _6;                   // in scope 2 at $DIR/separate_const_switch.rs:17:17: 17:18
+    }
+    scope 3 {
+        debug v => _8;                   // in scope 3 at $DIR/separate_const_switch.rs:20:31: 20:32
+    }
+    scope 4 {
+        debug r => _10;                  // in scope 4 at $DIR/separate_const_switch.rs:21:28: 21:29
+    }
+
+    bb0: {
+        StorageLive(_2);                 // scope 0 at $DIR/separate_const_switch.rs:14:11: 19:6
+        _3 = discriminant(_1);           // scope 0 at $DIR/separate_const_switch.rs:16:13: 16:18
+        switchInt(move _3) -> [0_isize: bb2, otherwise: bb1]; // scope 0 at $DIR/separate_const_switch.rs:16:13: 16:18
+    }
+
+    bb1: {
+        StorageLive(_6);                 // scope 0 at $DIR/separate_const_switch.rs:17:17: 17:18
+        _6 = ((_1 as Err).0: usize);     // scope 0 at $DIR/separate_const_switch.rs:17:17: 17:18
+        StorageLive(_7);                 // scope 2 at $DIR/separate_const_switch.rs:17:42: 17:43
+        _7 = _6;                         // scope 2 at $DIR/separate_const_switch.rs:17:42: 17:43
+        ((_2 as Break).0: usize) = move _7; // scope 2 at $DIR/separate_const_switch.rs:17:23: 17:44
+        discriminant(_2) = 1;            // scope 2 at $DIR/separate_const_switch.rs:17:23: 17:44
+        StorageDead(_7);                 // scope 2 at $DIR/separate_const_switch.rs:17:43: 17:44
+        StorageDead(_6);                 // scope 0 at $DIR/separate_const_switch.rs:17:43: 17:44
+        StorageLive(_10);                // scope 0 at $DIR/separate_const_switch.rs:21:28: 21:29
+        _10 = ((_2 as Break).0: usize);  // scope 0 at $DIR/separate_const_switch.rs:21:28: 21:29
+        discriminant(_0) = 0;            // scope 4 at $DIR/separate_const_switch.rs:21:34: 21:38
+        StorageDead(_10);                // scope 0 at $DIR/separate_const_switch.rs:21:37: 21:38
+        goto -> bb3;                     // scope 0 at $DIR/separate_const_switch.rs:14:5: 22:6
+    }
+
+    bb2: {
+        StorageLive(_4);                 // scope 0 at $DIR/separate_const_switch.rs:16:16: 16:17
+        _4 = ((_1 as Ok).0: i32);        // scope 0 at $DIR/separate_const_switch.rs:16:16: 16:17
+        StorageLive(_5);                 // scope 1 at $DIR/separate_const_switch.rs:16:44: 16:45
+        _5 = _4;                         // scope 1 at $DIR/separate_const_switch.rs:16:44: 16:45
+        ((_2 as Continue).0: i32) = move _5; // scope 1 at $DIR/separate_const_switch.rs:16:22: 16:46
+        discriminant(_2) = 0;            // scope 1 at $DIR/separate_const_switch.rs:16:22: 16:46
+        StorageDead(_5);                 // scope 1 at $DIR/separate_const_switch.rs:16:45: 16:46
+        StorageDead(_4);                 // scope 0 at $DIR/separate_const_switch.rs:16:45: 16:46
+        StorageLive(_8);                 // scope 0 at $DIR/separate_const_switch.rs:20:31: 20:32
+        _8 = ((_2 as Continue).0: i32);  // scope 0 at $DIR/separate_const_switch.rs:20:31: 20:32
+        StorageLive(_9);                 // scope 3 at $DIR/separate_const_switch.rs:20:42: 20:43
+        _9 = _8;                         // scope 3 at $DIR/separate_const_switch.rs:20:42: 20:43
+        ((_0 as Some).0: i32) = move _9; // scope 3 at $DIR/separate_const_switch.rs:20:37: 20:44
+        discriminant(_0) = 1;            // scope 3 at $DIR/separate_const_switch.rs:20:37: 20:44
+        StorageDead(_9);                 // scope 3 at $DIR/separate_const_switch.rs:20:43: 20:44
+        StorageDead(_8);                 // scope 0 at $DIR/separate_const_switch.rs:20:43: 20:44
+        goto -> bb3;                     // scope 0 at $DIR/separate_const_switch.rs:14:5: 22:6
+    }
+
+    bb3: {
+        StorageDead(_2);                 // scope 0 at $DIR/separate_const_switch.rs:23:1: 23:2
+        return;                          // scope 0 at $DIR/separate_const_switch.rs:23:2: 23:2
+    }
+}
diff --git a/src/test/mir-opt/separate_const_switch.too_complex.SeparateConstSwitch.diff b/src/test/mir-opt/separate_const_switch.too_complex.SeparateConstSwitch.diff
new file mode 100644
index 00000000000..ce32227ed65
--- /dev/null
+++ b/src/test/mir-opt/separate_const_switch.too_complex.SeparateConstSwitch.diff
@@ -0,0 +1,98 @@
+- // MIR for `too_complex` before SeparateConstSwitch
++ // MIR for `too_complex` after SeparateConstSwitch
+  
+  fn too_complex(_1: Result<i32, usize>) -> Option<i32> {
+      debug x => _1;                       // in scope 0 at $DIR/separate_const_switch.rs:9:16: 9:17
+      let mut _0: std::option::Option<i32>; // return place in scope 0 at $DIR/separate_const_switch.rs:9:42: 9:53
+      let mut _2: std::ops::ControlFlow<usize, i32>; // in scope 0 at $DIR/separate_const_switch.rs:14:11: 19:6
+      let mut _3: isize;                   // in scope 0 at $DIR/separate_const_switch.rs:16:13: 16:18
+      let _4: i32;                         // in scope 0 at $DIR/separate_const_switch.rs:16:16: 16:17
+      let mut _5: i32;                     // in scope 0 at $DIR/separate_const_switch.rs:16:44: 16:45
+      let _6: usize;                       // in scope 0 at $DIR/separate_const_switch.rs:17:17: 17:18
+      let mut _7: usize;                   // in scope 0 at $DIR/separate_const_switch.rs:17:42: 17:43
+      let mut _8: isize;                   // in scope 0 at $DIR/separate_const_switch.rs:20:9: 20:33
+      let _9: i32;                         // in scope 0 at $DIR/separate_const_switch.rs:20:31: 20:32
+      let mut _10: i32;                    // in scope 0 at $DIR/separate_const_switch.rs:20:42: 20:43
+      let _11: usize;                      // in scope 0 at $DIR/separate_const_switch.rs:21:28: 21:29
+      scope 1 {
+          debug v => _4;                   // in scope 1 at $DIR/separate_const_switch.rs:16:16: 16:17
+      }
+      scope 2 {
+          debug r => _6;                   // in scope 2 at $DIR/separate_const_switch.rs:17:17: 17:18
+      }
+      scope 3 {
+          debug v => _9;                   // in scope 3 at $DIR/separate_const_switch.rs:20:31: 20:32
+      }
+      scope 4 {
+          debug r => _11;                  // in scope 4 at $DIR/separate_const_switch.rs:21:28: 21:29
+      }
+  
+      bb0: {
+          StorageLive(_2);                 // scope 0 at $DIR/separate_const_switch.rs:14:11: 19:6
+          _3 = discriminant(_1);           // scope 0 at $DIR/separate_const_switch.rs:16:13: 16:18
+          switchInt(move _3) -> [0_isize: bb2, otherwise: bb1]; // scope 0 at $DIR/separate_const_switch.rs:16:13: 16:18
+      }
+  
+      bb1: {
+          StorageLive(_6);                 // scope 0 at $DIR/separate_const_switch.rs:17:17: 17:18
+          _6 = ((_1 as Err).0: usize);     // scope 0 at $DIR/separate_const_switch.rs:17:17: 17:18
+          StorageLive(_7);                 // scope 2 at $DIR/separate_const_switch.rs:17:42: 17:43
+          _7 = _6;                         // scope 2 at $DIR/separate_const_switch.rs:17:42: 17:43
+          ((_2 as Break).0: usize) = move _7; // scope 2 at $DIR/separate_const_switch.rs:17:23: 17:44
+          discriminant(_2) = 1;            // scope 2 at $DIR/separate_const_switch.rs:17:23: 17:44
+          StorageDead(_7);                 // scope 2 at $DIR/separate_const_switch.rs:17:43: 17:44
+          StorageDead(_6);                 // scope 0 at $DIR/separate_const_switch.rs:17:43: 17:44
+-         goto -> bb3;                     // scope 0 at $DIR/separate_const_switch.rs:15:9: 18:10
++         _8 = discriminant(_2);           // scope 0 at $DIR/separate_const_switch.rs:20:9: 20:33
++         switchInt(move _8) -> [0_isize: bb4, otherwise: bb3]; // scope 0 at $DIR/separate_const_switch.rs:20:9: 20:33
+      }
+  
+      bb2: {
+          StorageLive(_4);                 // scope 0 at $DIR/separate_const_switch.rs:16:16: 16:17
+          _4 = ((_1 as Ok).0: i32);        // scope 0 at $DIR/separate_const_switch.rs:16:16: 16:17
+          StorageLive(_5);                 // scope 1 at $DIR/separate_const_switch.rs:16:44: 16:45
+          _5 = _4;                         // scope 1 at $DIR/separate_const_switch.rs:16:44: 16:45
+          ((_2 as Continue).0: i32) = move _5; // scope 1 at $DIR/separate_const_switch.rs:16:22: 16:46
+          discriminant(_2) = 0;            // scope 1 at $DIR/separate_const_switch.rs:16:22: 16:46
+          StorageDead(_5);                 // scope 1 at $DIR/separate_const_switch.rs:16:45: 16:46
+          StorageDead(_4);                 // scope 0 at $DIR/separate_const_switch.rs:16:45: 16:46
+-         goto -> bb3;                     // scope 0 at $DIR/separate_const_switch.rs:15:9: 18:10
+-     }
+- 
+-     bb3: {
+          _8 = discriminant(_2);           // scope 0 at $DIR/separate_const_switch.rs:20:9: 20:33
+-         switchInt(move _8) -> [0_isize: bb5, otherwise: bb4]; // scope 0 at $DIR/separate_const_switch.rs:20:9: 20:33
++         switchInt(move _8) -> [0_isize: bb4, otherwise: bb3]; // scope 0 at $DIR/separate_const_switch.rs:20:9: 20:33
+      }
+  
+-     bb4: {
++     bb3: {
+          StorageLive(_11);                // scope 0 at $DIR/separate_const_switch.rs:21:28: 21:29
+          _11 = ((_2 as Break).0: usize);  // scope 0 at $DIR/separate_const_switch.rs:21:28: 21:29
+          discriminant(_0) = 0;            // scope 4 at $DIR/separate_const_switch.rs:21:34: 21:38
+          StorageDead(_11);                // scope 0 at $DIR/separate_const_switch.rs:21:37: 21:38
+-         goto -> bb6;                     // scope 0 at $DIR/separate_const_switch.rs:14:5: 22:6
++         goto -> bb5;                     // scope 0 at $DIR/separate_const_switch.rs:14:5: 22:6
+      }
+  
+-     bb5: {
++     bb4: {
+          StorageLive(_9);                 // scope 0 at $DIR/separate_const_switch.rs:20:31: 20:32
+          _9 = ((_2 as Continue).0: i32);  // scope 0 at $DIR/separate_const_switch.rs:20:31: 20:32
+          StorageLive(_10);                // scope 3 at $DIR/separate_const_switch.rs:20:42: 20:43
+          _10 = _9;                        // scope 3 at $DIR/separate_const_switch.rs:20:42: 20:43
+          ((_0 as Some).0: i32) = move _10; // scope 3 at $DIR/separate_const_switch.rs:20:37: 20:44
+          discriminant(_0) = 1;            // scope 3 at $DIR/separate_const_switch.rs:20:37: 20:44
+          StorageDead(_10);                // scope 3 at $DIR/separate_const_switch.rs:20:43: 20:44
+          StorageDead(_9);                 // scope 0 at $DIR/separate_const_switch.rs:20:43: 20:44
+-         goto -> bb6;                     // scope 0 at $DIR/separate_const_switch.rs:14:5: 22:6
++         goto -> bb5;                     // scope 0 at $DIR/separate_const_switch.rs:14:5: 22:6
+      }
+  
+-     bb6: {
++     bb5: {
+          StorageDead(_2);                 // scope 0 at $DIR/separate_const_switch.rs:23:1: 23:2
+          return;                          // scope 0 at $DIR/separate_const_switch.rs:23:2: 23:2
+      }
+  }
+