Move SimplifyLocals before ConstProp.

compiler/rustc_mir_transform/src/dead_store_elimination.rs

@@ -71,7 +71,7 @@ pub fn eliminate<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>, borrowed: &BitS
         bbs[block].statements[statement_index].make_nop();
     }
 
-    crate::simplify::SimplifyLocals.run_pass(tcx, body)
+    crate::simplify::simplify_locals(body, tcx)
 }
 
 pub struct DeadStoreElimination;

compiler/rustc_mir_transform/src/lib.rs

@@ -560,6 +560,7 @@ fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
             &multiple_return_terminators::MultipleReturnTerminators,
             &instcombine::InstCombine,
             &separate_const_switch::SeparateConstSwitch,
+            &simplify::SimplifyLocals::new("before-const-prop"),
             //
             // FIXME(#70073): This pass is responsible for both optimization as well as some lints.
             &const_prop::ConstProp,
@@ -578,7 +579,7 @@ fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
             &o1(remove_noop_landing_pads::RemoveNoopLandingPads),
             &o1(simplify::SimplifyCfg::new("final")),
             &nrvo::RenameReturnPlace,
-            &simplify::SimplifyLocals,
+            &simplify::SimplifyLocals::new("final"),
             &multiple_return_terminators::MultipleReturnTerminators,
             &deduplicate_blocks::DeduplicateBlocks,
             // Some cleanup necessary at least for LLVM and potentially other codegen backends.

compiler/rustc_mir_transform/src/simplify.rs

@@ -379,9 +379,21 @@ fn save_unreachable_coverage(
     ));
 }
 
-pub struct SimplifyLocals;
+pub struct SimplifyLocals {
+    label: String,
+}
+
+impl SimplifyLocals {
+    pub fn new(label: &str) -> SimplifyLocals {
+        SimplifyLocals { label: format!("SimplifyLocals-{}", label) }
+    }
+}
 
 impl<'tcx> MirPass<'tcx> for SimplifyLocals {
+    fn name(&self) -> &str {
+        &self.label
+    }
+
     fn is_enabled(&self, sess: &rustc_session::Session) -> bool {
         sess.mir_opt_level() > 0
     }