From 8ca47cd1fe50eb4d160d1ab801f159312a35c54a Mon Sep 17 00:00:00 2001
From: Nicholas Nethercote <n.nethercote@gmail.com>
Date: Fri, 2 Jan 2026 09:29:26 +1100
Subject: [PATCH] Clarify `MoveData::init_loc_map`.

Change the `SmallVec` size from 4 to 1, because that's sufficient in the
vast majority of cases. (This doesn't affect performance in practice, so
it's more of a code clarity change than a performance change.)
---
 compiler/rustc_mir_dataflow/src/move_paths/mod.rs | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/compiler/rustc_mir_dataflow/src/move_paths/mod.rs b/compiler/rustc_mir_dataflow/src/move_paths/mod.rs
index 800d4e406cf09..8be7d210f8dfd 100644
--- a/compiler/rustc_mir_dataflow/src/move_paths/mod.rs
+++ b/compiler/rustc_mir_dataflow/src/move_paths/mod.rs
@@ -177,8 +177,9 @@ pub struct MoveData<'tcx> {
     pub rev_lookup: MovePathLookup<'tcx>,
     pub inits: IndexVec<InitIndex, Init>,
     /// Each Location `l` is mapped to the Inits that are effects
-    /// of executing the code at `l`.
-    pub init_loc_map: LocationMap<SmallVec<[InitIndex; 4]>>,
+    /// of executing the code at `l`. Only very rarely (e.g. inline asm)
+    /// is there more than one Init at any `l`.
+    pub init_loc_map: LocationMap<SmallVec<[InitIndex; 1]>>,
     pub init_path_map: IndexVec<MovePathIndex, SmallVec<[InitIndex; 4]>>,
 }