Perform reference propagation earlier.

compiler/rustc_mir_transform/src/lib.rs

@@ -553,6 +553,7 @@ fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
             &normalize_array_len::NormalizeArrayLen, // has to run after `slice::len` lowering
             &const_goto::ConstGoto,
             &remove_unneeded_drops::RemoveUnneededDrops,
+            &ref_prop::ReferencePropagation,
             &sroa::ScalarReplacementOfAggregates,
             &match_branches::MatchBranchSimplification,
             // inst combine is after MatchBranchSimplification to clean up Ne(_1, false)
@@ -560,7 +561,6 @@ fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
             &instsimplify::InstSimplify,
             &simplify::SimplifyLocals::BeforeConstProp,
             &copy_prop::CopyProp,
-            &ref_prop::ReferencePropagation,
             // Perform `SeparateConstSwitch` after SSA-based analyses, as cloning blocks may
             // destroy the SSA property. It should still happen before const-propagation, so the
             // latter pass will leverage the created opportunities.