Rollup merge of #68911 - jonas-schievink:inherent-overlap, r=petrochenkov

[rust.git] / src / librustc_passes / liveness.rs

diff --git a/src/librustc_passes/liveness.rs b/src/librustc_passes/liveness.rs
index 0426f3fbea23600133eac6fa68623a9a4f4cf1b9..b355a47c39470559e5431d220e3349299b9dd280 100644 (file)
--- a/src/librustc_passes/liveness.rs
+++ b/src/librustc_passes/liveness.rs
@@ -822,8 +822,15 @@ fn merge_from_succ(&mut self, ln: LiveNode, succ_ln: LiveNode, first_merge: bool
             return false;
         }
 
-        let mut changed = false;
+        let mut any_changed = false;
         self.indices2(ln, succ_ln, |this, idx, succ_idx| {
+            // This is a special case, pulled out from the code below, where we
+            // don't have to do anything. It occurs about 60-70% of the time.
+            if this.rwu_table.packed_rwus[succ_idx] == INV_INV_FALSE {
+                return;
+            }
+
+            let mut changed = false;
             let mut rwu = this.rwu_table.get(idx);
             let succ_rwu = this.rwu_table.get(succ_idx);
             if succ_rwu.reader.is_valid() && !rwu.reader.is_valid() {
@@ -843,6 +850,7 @@ fn merge_from_succ(&mut self, ln: LiveNode, succ_ln: LiveNode, first_merge: bool
 
             if changed {
                 this.rwu_table.assign_unpacked(idx, rwu);
+                any_changed = true;
             }
         });
 
@@ -851,9 +859,9 @@ fn merge_from_succ(&mut self, ln: LiveNode, succ_ln: LiveNode, first_merge: bool
             ln,
             self.ln_str(succ_ln),
             first_merge,
-            changed
+            any_changed
         );
-        return changed;
+        return any_changed;
     }
 
     // Indicates that a local variable was *defined*; we know that no
@@ -1513,13 +1521,16 @@ fn report_unused(&self, spans: Vec<Span>, hir_id: HirId, ln: LiveNode, var: Vari
                 if ln == self.s.exit_ln { false } else { self.assigned_on_exit(ln, var).is_some() };
 
             if is_assigned {
-                self.ir.tcx.lint_hir_note(
-                    lint::builtin::UNUSED_VARIABLES,
-                    hir_id,
-                    spans,
-                    &format!("variable `{}` is assigned to, but never used", name),
-                    &format!("consider using `_{}` instead", name),
-                );
+                self.ir
+                    .tcx
+                    .struct_span_lint_hir(
+                        lint::builtin::UNUSED_VARIABLES,
+                        hir_id,
+                        spans,
+                        &format!("variable `{}` is assigned to, but never used", name),
+                    )
+                    .note(&format!("consider using `_{}` instead", name))
+                    .emit();
             } else {
                 let mut err = self.ir.tcx.struct_span_lint_hir(
                     lint::builtin::UNUSED_VARIABLES,