insert storageDead for not equal temp

Author: simonvandel

compiler/rustc_mir/src/transform/early_otherwise_branch.rs

@@ -46,27 +46,32 @@ impl<'tcx> MirPass<'tcx> for EarlyOtherwiseBranch {
 
         for opt_to_apply in opts_to_apply {
             trace!("SUCCESS: found optimization possibility to apply: {:?}", &opt_to_apply);
-            // create the patch using MirPatch
-            let mut patch = MirPatch::new(body);
 
-            // create temp to store second discriminant in
-            let discr_type = opt_to_apply.infos[0].second_switch_info.discr_ty;
-            let discr_span = opt_to_apply.infos[0].second_switch_info.discr_source_info.span;
-            let temp = patch.new_temp(discr_type, discr_span);
             let statements_before =
                 body.basic_blocks()[opt_to_apply.basic_block_first_switch].statements.len();
             let end_of_block_location = Location {
                 block: opt_to_apply.basic_block_first_switch,
                 statement_index: statements_before,
             };
-            patch.add_statement(end_of_block_location, StatementKind::StorageLive(temp));
+
+            let mut patch = MirPatch::new(body);
+
+            // create temp to store second discriminant in
+            let discr_type = opt_to_apply.infos[0].second_switch_info.discr_ty;
+            let discr_span = opt_to_apply.infos[0].second_switch_info.discr_source_info.span;
+            let second_discriminant_temp = patch.new_temp(discr_type, discr_span);
+
+            patch.add_statement(
+                end_of_block_location,
+                StatementKind::StorageLive(second_discriminant_temp),
+            );
 
             // create assignment of discriminant
             let place_of_adt_to_get_discriminant_of =
                 opt_to_apply.infos[0].second_switch_info.place_of_adt_discr_read;
             patch.add_assign(
                 end_of_block_location,
-                Place::from(temp),
+                Place::from(second_discriminant_temp),
                 Rvalue::Discriminant(place_of_adt_to_get_discriminant_of),
             );
 
@@ -81,7 +86,7 @@ impl<'tcx> MirPass<'tcx> for EarlyOtherwiseBranch {
                 opt_to_apply.infos[0].first_switch_info.discr_used_in_switch;
             let not_equal_rvalue = Rvalue::BinaryOp(
                 not_equal,
-                Operand::Copy(Place::from(temp)),
+                Operand::Copy(Place::from(second_discriminant_temp)),
                 Operand::Copy(Place::from(first_descriminant_place)),
             );
             patch.add_statement(
@@ -126,8 +131,19 @@ impl<'tcx> MirPass<'tcx> for EarlyOtherwiseBranch {
                 ),
             );
 
-            // generate StorageDead for the temp not in use anymore. We use the not_equal_temp in the switch, so we can't mark that dead
-            patch.add_statement(end_of_block_location, StatementKind::StorageDead(temp));
+            // generate StorageDead for the second_discriminant_temp not in use anymore
+            patch.add_statement(
+                end_of_block_location,
+                StatementKind::StorageDead(second_discriminant_temp),
+            );
+
+            // Generate a StorageDead for not_equal_temp in each of the targets, since we moved it into the switch
+            for bb in [false_case, true_case].iter() {
+                patch.add_statement(
+                    Location { block: *bb, statement_index: 0 },
+                    StatementKind::StorageDead(not_equal_temp),
+                );
+            }
 
             patch.apply(body);
         }

src/test/mir-opt/early_otherwise_branch.opt1.EarlyOtherwiseBranch.diff

@@ -40,6 +40,7 @@
       }
 
       bb1: {
++         StorageDead(_11);                // scope 0 at $DIR/early_otherwise_branch.rs:6:14: 6:15
           _0 = const 1_u32;                // scope 0 at $DIR/early_otherwise_branch.rs:6:14: 6:15
           goto -> bb4;                     // scope 0 at $DIR/early_otherwise_branch.rs:4:5: 7:6
       }
@@ -70,6 +71,7 @@
 +     }
 + 
 +     bb6: {
++         StorageDead(_11);                // scope 0 at $DIR/early_otherwise_branch.rs:5:19: 5:26
 +         switchInt(_7) -> [1_isize: bb3, otherwise: bb1]; // scope 0 at $DIR/early_otherwise_branch.rs:5:19: 5:26
       }
   }

src/test/mir-opt/early_otherwise_branch.opt2.EarlyOtherwiseBranch.diff

@@ -46,6 +46,7 @@
       }
 
       bb2: {
++         StorageDead(_12);                // scope 0 at $DIR/early_otherwise_branch.rs:15:14: 15:15
           _0 = const 1_u32;                // scope 0 at $DIR/early_otherwise_branch.rs:15:14: 15:15
           goto -> bb6;                     // scope 0 at $DIR/early_otherwise_branch.rs:12:5: 16:6
       }
@@ -81,6 +82,7 @@
 +     }
 + 
 +     bb8: {
++         StorageDead(_12);                // scope 0 at $DIR/early_otherwise_branch.rs:14:16: 14:20
 +         switchInt(_8) -> [0_isize: bb5, 1_isize: bb4, otherwise: bb2]; // scope 0 at $DIR/early_otherwise_branch.rs:14:16: 14:20
       }
   }

src/test/mir-opt/early_otherwise_branch_3_element_tuple.opt1.EarlyOtherwiseBranch.diff

@@ -51,6 +51,8 @@
       }
 
       bb1: {
++         StorageDead(_17);                // scope 0 at $DIR/early_otherwise_branch_3_element_tuple.rs:7:14: 7:15
++         StorageDead(_15);                // scope 0 at $DIR/early_otherwise_branch_3_element_tuple.rs:7:14: 7:15
           _0 = const 1_u32;                // scope 0 at $DIR/early_otherwise_branch_3_element_tuple.rs:7:14: 7:15
           goto -> bb5;                     // scope 0 at $DIR/early_otherwise_branch_3_element_tuple.rs:5:5: 8:6
       }
@@ -95,10 +97,12 @@
 +     }
 + 
 +     bb7: {
++         StorageDead(_15);                // scope 0 at $DIR/early_otherwise_branch_3_element_tuple.rs:6:19: 6:26
 +         switchInt(_10) -> [1_isize: bb3, otherwise: bb1]; // scope 0 at $DIR/early_otherwise_branch_3_element_tuple.rs:6:19: 6:26
 +     }
 + 
 +     bb8: {
++         StorageDead(_17);                // scope 0 at $DIR/early_otherwise_branch_3_element_tuple.rs:6:28: 6:35
 +         switchInt(_9) -> [1_isize: bb4, otherwise: bb1]; // scope 0 at $DIR/early_otherwise_branch_3_element_tuple.rs:6:28: 6:35
       }
   }

src/test/mir-opt/early_otherwise_branch_68867.try_sum.EarlyOtherwiseBranch.diff

@@ -82,6 +82,7 @@
       }
 
       bb2: {
++         StorageDead(_35);                // scope 0 at $DIR/early_otherwise_branch_68867.rs:24:25: 24:27
           StorageLive(_33);                // scope 0 at $DIR/early_otherwise_branch_68867.rs:24:25: 24:27
           ((_0 as Err).0: ()) = const ();  // scope 0 at $DIR/early_otherwise_branch_68867.rs:24:21: 24:28
           discriminant(_0) = 1;            // scope 0 at $DIR/early_otherwise_branch_68867.rs:24:21: 24:28
@@ -207,6 +208,7 @@
 +     }
 + 
 +     bb13: {
++         StorageDead(_35);                // scope 0 at $DIR/early_otherwise_branch_68867.rs:20:21: 20:30
 +         switchInt(_11) -> [0_isize: bb6, 1_isize: bb7, 2_isize: bb8, 3_isize: bb9, otherwise: bb2]; // scope 0 at $DIR/early_otherwise_branch_68867.rs:20:21: 20:30
       }
   }