diff --git a/src/librustc/mir/mod.rs b/src/librustc/mir/mod.rs
index 34fc81a495e249682fa9ccd9bf63c2ab47b731e5..797836f166173f0366e7838afe7ce65cb3cca6b2 100644
--- a/src/librustc/mir/mod.rs
+++ b/src/librustc/mir/mod.rs
@@ -69,6 +69,17 @@ fn local_decls(&self) -> &LocalDecls<'tcx> {
     }
 }
 
+/// The various "big phases" that MIR goes through.
+///
+/// Warning: ordering of variants is significant
+#[derive(Copy, Clone, RustcEncodable, RustcDecodable, Debug, PartialEq, Eq, PartialOrd, Ord)]
+pub enum MirPhase {
+    Build,
+    Const,
+    Validated,
+    Optimized,
+}
+
 /// Lowered representation of a single function.
 #[derive(Clone, RustcEncodable, RustcDecodable, Debug)]
 pub struct Mir<'tcx> {
@@ -76,6 +87,13 @@ pub struct Mir<'tcx> {
     /// that indexes into this vector.
     basic_blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>,
 
+    /// Records how far through the "desugaring and optimization" process this particular
+    /// MIR has traversed. This is particularly useful when inlining, since in that context
+    /// we instantiate the promoted constants and add them to our promoted vector -- but those
+    /// promoted items have already been optimized, whereas ours have not. This field allows
+    /// us to see the difference and forego optimization on the inlined promoted items.
+    pub phase: MirPhase,
+
     /// List of source scopes; these are referenced by statements
     /// and used for debuginfo. Indexed by a `SourceScope`.
     pub source_scopes: IndexVec<SourceScope, SourceScopeData>,
@@ -151,6 +169,7 @@ pub fn new(
         );
 
         Mir {
+            phase: MirPhase::Build,
             basic_blocks,
             source_scopes,
             source_scope_local_data,
@@ -368,6 +387,7 @@ pub enum Safety {
 }
 
 impl_stable_hash_for!(struct Mir<'tcx> {
+    phase,
     basic_blocks,
     source_scopes,
     source_scope_local_data,
@@ -616,6 +636,13 @@ pub enum ImplicitSelfKind {
     None
 });
 
+impl_stable_hash_for!(enum self::MirPhase {
+    Build,
+    Const,
+    Validated,
+    Optimized,
+});
+
 mod binding_form_impl {
     use ich::StableHashingContext;
     use rustc_data_structures::stable_hasher::{HashStable, StableHasher, StableHasherResult};
@@ -2777,6 +2804,7 @@ pub enum ClosureOutlivesSubject<'tcx> {
 
 CloneTypeFoldableAndLiftImpls! {
     BlockTailInfo,
+    MirPhase,
     Mutability,
     SourceInfo,
     UpvarDecl,
@@ -2789,6 +2817,7 @@ pub enum ClosureOutlivesSubject<'tcx> {
 
 BraceStructTypeFoldableImpl! {
     impl<'tcx> TypeFoldable<'tcx> for Mir<'tcx> {
+        phase,
         basic_blocks,
         source_scopes,
         source_scope_local_data,
diff --git a/src/librustc_mir/transform/mod.rs b/src/librustc_mir/transform/mod.rs
index d18836999dccfe7629c1c8221274c6a161571443..61e150ea12a2261837519190bbc905806bff5b38 100644
--- a/src/librustc_mir/transform/mod.rs
+++ b/src/librustc_mir/transform/mod.rs
@@ -11,7 +11,7 @@
 use borrow_check::nll::type_check;
 use build;
 use rustc::hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
-use rustc::mir::{Mir, Promoted};
+use rustc::mir::{Mir, MirPhase, Promoted};
 use rustc::ty::TyCtxt;
 use rustc::ty::query::Providers;
 use rustc::ty::steal::Steal;
@@ -155,9 +155,22 @@ fn run_pass<'a, 'tcx>(&self,
                           mir: &mut Mir<'tcx>);
 }
 
-pub macro run_passes($tcx:ident, $mir:ident, $def_id:ident, $suite_index:expr; $($pass:expr,)*) {{
+pub macro run_passes(
+    $tcx:ident,
+    $mir:ident,
+    $def_id:ident,
+    $suite_index:expr,
+    $mir_phase:expr;
+    $($pass:expr,)*
+) {{
     let suite_index: usize = $suite_index;
     let run_passes = |mir: &mut _, promoted| {
+        let mir: &mut Mir<'_> = mir;
+
+        if mir.phase >= $mir_phase {
+            return;
+        }
+
         let source = MirSource {
             def_id: $def_id,
             promoted
@@ -175,6 +188,8 @@ fn run_pass<'a, 'tcx>(&self,
             index += 1;
         };
         $(run_pass(&$pass);)*
+
+        mir.phase = $mir_phase;
     };
 
     run_passes(&mut $mir, None);
@@ -192,7 +207,7 @@ fn mir_const<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) -> &'tcx Stea
     let _ = tcx.unsafety_check_result(def_id);
 
     let mut mir = tcx.mir_built(def_id).steal();
-    run_passes![tcx, mir, def_id, 0;
+    run_passes![tcx, mir, def_id, 0, MirPhase::Const;
         // Remove all `EndRegion` statements that are not involved in borrows.
         cleanup_post_borrowck::CleanEndRegions,
 
@@ -214,7 +229,7 @@ fn mir_validated<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) -> &'tcx
     }
 
     let mut mir = tcx.mir_const(def_id).steal();
-    run_passes![tcx, mir, def_id, 1;
+    run_passes![tcx, mir, def_id, 1, MirPhase::Validated;
         // What we need to run borrowck etc.
         qualify_consts::QualifyAndPromoteConstants,
         simplify::SimplifyCfg::new("qualify-consts"),
@@ -232,7 +247,7 @@ fn optimized_mir<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) -> &'tcx
     }
 
     let mut mir = tcx.mir_validated(def_id).steal();
-    run_passes![tcx, mir, def_id, 2;
+    run_passes![tcx, mir, def_id, 2, MirPhase::Optimized;
         // Remove all things not needed by analysis
         no_landing_pads::NoLandingPads,
         simplify_branches::SimplifyBranches::new("initial"),
diff --git a/src/test/ui/issues/issue-50411.rs b/src/test/ui/issues/issue-50411.rs
new file mode 100644
index 0000000000000000000000000000000000000000..1ba47d3b932ef70171f87e442d6d9fbdc506bc57
--- /dev/null
+++ b/src/test/ui/issues/issue-50411.rs
@@ -0,0 +1,11 @@
+// Regression test for #50411: the MIR inliner was causing problems
+// here because it would inline promoted code (which had already had
+// elaborate-drops invoked on it) and then try to elaboate drops a
+// second time. Uncool.
+
+// compile-flags:-Zmir-opt-level=3
+// compile-pass
+
+fn main() {
+    let _ = (0 .. 1).filter(|_| [1].iter().all(|_| true)).count();
+}