inliner: Emit storage markers for introduced arg temporaries

When introducing argument temporaries during inlining, emit storage
marker statements just before the assignment and in the beginning of
the return block.

This ensures that such temporaries will not be considered live across
yield points after inlining inside a generator.

compiler/rustc_mir/src/transform/inline.rs

@@ -494,7 +494,7 @@ impl Inliner<'tcx> {
                 let return_block = destination.1;
 
                 // Copy the arguments if needed.
-                let args: Vec<_> = self.make_call_args(args, &callsite, caller_body);
+                let args: Vec<_> = self.make_call_args(args, &callsite, caller_body, return_block);
 
                 let bb_len = caller_body.basic_blocks().len();
                 let mut integrator = Integrator {
@@ -541,6 +541,7 @@ impl Inliner<'tcx> {
         args: Vec<Operand<'tcx>>,
         callsite: &CallSite<'tcx>,
         caller_body: &mut Body<'tcx>,
+        return_block: BasicBlock,
     ) -> Vec<Local> {
         let tcx = self.tcx;
 
@@ -569,8 +570,18 @@ impl Inliner<'tcx> {
         // and the vector is `[closure_ref, tmp0, tmp1, tmp2]`.
         if tcx.is_closure(callsite.callee) {
             let mut args = args.into_iter();
-            let self_ = self.create_temp_if_necessary(args.next().unwrap(), callsite, caller_body);
-            let tuple = self.create_temp_if_necessary(args.next().unwrap(), callsite, caller_body);
+            let self_ = self.create_temp_if_necessary(
+                args.next().unwrap(),
+                callsite,
+                caller_body,
+                return_block,
+            );
+            let tuple = self.create_temp_if_necessary(
+                args.next().unwrap(),
+                callsite,
+                caller_body,
+                return_block,
+            );
             assert!(args.next().is_none());
 
             let tuple = Place::from(tuple);
@@ -590,13 +601,13 @@ impl Inliner<'tcx> {
                     Operand::Move(tcx.mk_place_field(tuple, Field::new(i), ty.expect_ty()));
 
                 // Spill to a local to make e.g., `tmp0`.
-                self.create_temp_if_necessary(tuple_field, callsite, caller_body)
+                self.create_temp_if_necessary(tuple_field, callsite, caller_body, return_block)
             });
 
             closure_ref_arg.chain(tuple_tmp_args).collect()
         } else {
             args.into_iter()
-                .map(|a| self.create_temp_if_necessary(a, callsite, caller_body))
+                .map(|a| self.create_temp_if_necessary(a, callsite, caller_body, return_block))
                 .collect()
         }
     }
@@ -608,6 +619,7 @@ impl Inliner<'tcx> {
         arg: Operand<'tcx>,
         callsite: &CallSite<'tcx>,
         caller_body: &mut Body<'tcx>,
+        return_block: BasicBlock,
     ) -> Local {
         // FIXME: Analysis of the usage of the arguments to avoid
         // unnecessary temporaries.
@@ -630,11 +642,19 @@ impl Inliner<'tcx> {
         let arg_tmp = LocalDecl::new(ty, callsite.location.span);
         let arg_tmp = caller_body.local_decls.push(arg_tmp);
 
-        let stmt = Statement {
+        caller_body[callsite.bb].statements.push(Statement {
+            source_info: callsite.location,
+            kind: StatementKind::StorageLive(arg_tmp),
+        });
+        caller_body[callsite.bb].statements.push(Statement {
             source_info: callsite.location,
             kind: StatementKind::Assign(box (Place::from(arg_tmp), arg)),
-        };
-        caller_body[callsite.bb].statements.push(stmt);
+        });
+        caller_body[return_block].statements.insert(
+            0,
+            Statement { source_info: callsite.location, kind: StatementKind::StorageDead(arg_tmp) },
+        );
+
         arg_tmp
     }
 }

src/test/mir-opt/inline/inline_any_operand.bar.Inline.after.mir

@@ -22,9 +22,13 @@ fn bar() -> bool {
                                          // + literal: Const { ty: fn(i32, i32) -> bool {foo}, val: Value(Scalar(<ZST>)) }
         StorageLive(_2);                 // scope 1 at $DIR/inline-any-operand.rs:12:5: 12:6
         _2 = _1;                         // scope 1 at $DIR/inline-any-operand.rs:12:5: 12:6
+        StorageLive(_3);                 // scope 1 at $DIR/inline-any-operand.rs:12:5: 12:13
         _3 = const 1_i32;                // scope 1 at $DIR/inline-any-operand.rs:12:5: 12:13
+        StorageLive(_4);                 // scope 1 at $DIR/inline-any-operand.rs:12:5: 12:13
         _4 = const -1_i32;               // scope 1 at $DIR/inline-any-operand.rs:12:5: 12:13
         _0 = Eq(move _3, move _4);       // scope 2 at $DIR/inline-any-operand.rs:17:5: 17:11
+        StorageDead(_4);                 // scope 1 at $DIR/inline-any-operand.rs:12:5: 12:13
+        StorageDead(_3);                 // scope 1 at $DIR/inline-any-operand.rs:12:5: 12:13
         StorageDead(_2);                 // scope 1 at $DIR/inline-any-operand.rs:12:12: 12:13
         StorageDead(_1);                 // scope 0 at $DIR/inline-any-operand.rs:13:1: 13:2
         return;                          // scope 0 at $DIR/inline-any-operand.rs:13:2: 13:2

src/test/mir-opt/inline/inline_closure.foo.Inline.after.mir

@@ -30,9 +30,13 @@ fn foo(_1: T, _2: i32) -> i32 {
         _7 = _2;                         // scope 1 at $DIR/inline-closure.rs:12:10: 12:11
         (_5.0: i32) = move _6;           // scope 1 at $DIR/inline-closure.rs:12:5: 12:12
         (_5.1: i32) = move _7;           // scope 1 at $DIR/inline-closure.rs:12:5: 12:12
+        StorageLive(_8);                 // scope 1 at $DIR/inline-closure.rs:12:5: 12:12
         _8 = move (_5.0: i32);           // scope 1 at $DIR/inline-closure.rs:12:5: 12:12
+        StorageLive(_9);                 // scope 1 at $DIR/inline-closure.rs:12:5: 12:12
         _9 = move (_5.1: i32);           // scope 1 at $DIR/inline-closure.rs:12:5: 12:12
         _0 = _8;                         // scope 2 at $DIR/inline-closure.rs:11:22: 11:24
+        StorageDead(_9);                 // scope 1 at $DIR/inline-closure.rs:12:5: 12:12
+        StorageDead(_8);                 // scope 1 at $DIR/inline-closure.rs:12:5: 12:12
         StorageDead(_7);                 // scope 1 at $DIR/inline-closure.rs:12:11: 12:12
         StorageDead(_6);                 // scope 1 at $DIR/inline-closure.rs:12:11: 12:12
         StorageDead(_5);                 // scope 1 at $DIR/inline-closure.rs:12:11: 12:12

src/test/mir-opt/inline/inline_closure_borrows_arg.foo.Inline.after.mir

@@ -33,9 +33,13 @@ fn foo(_1: T, _2: &i32) -> i32 {
         _7 = &(*_2);                     // scope 1 at $DIR/inline-closure-borrows-arg.rs:16:10: 16:11
         (_5.0: &i32) = move _6;          // scope 1 at $DIR/inline-closure-borrows-arg.rs:16:5: 16:12
         (_5.1: &i32) = move _7;          // scope 1 at $DIR/inline-closure-borrows-arg.rs:16:5: 16:12
+        StorageLive(_8);                 // scope 1 at $DIR/inline-closure-borrows-arg.rs:16:5: 16:12
         _8 = move (_5.0: &i32);          // scope 1 at $DIR/inline-closure-borrows-arg.rs:16:5: 16:12
+        StorageLive(_9);                 // scope 1 at $DIR/inline-closure-borrows-arg.rs:16:5: 16:12
         _9 = move (_5.1: &i32);          // scope 1 at $DIR/inline-closure-borrows-arg.rs:16:5: 16:12
         _0 = (*_8);                      // scope 3 at $DIR/inline-closure-borrows-arg.rs:14:9: 14:18
+        StorageDead(_9);                 // scope 1 at $DIR/inline-closure-borrows-arg.rs:16:5: 16:12
+        StorageDead(_8);                 // scope 1 at $DIR/inline-closure-borrows-arg.rs:16:5: 16:12
         StorageDead(_7);                 // scope 1 at $DIR/inline-closure-borrows-arg.rs:16:11: 16:12
         StorageDead(_6);                 // scope 1 at $DIR/inline-closure-borrows-arg.rs:16:11: 16:12
         StorageDead(_5);                 // scope 1 at $DIR/inline-closure-borrows-arg.rs:16:11: 16:12

src/test/mir-opt/inline/inline_closure_captures.foo.Inline.after.mir

@@ -38,6 +38,7 @@ fn foo(_1: T, _2: i32) -> (i32, T) {
         StorageLive(_8);                 // scope 1 at $DIR/inline-closure-captures.rs:12:7: 12:8
         _8 = _2;                         // scope 1 at $DIR/inline-closure-captures.rs:12:7: 12:8
         (_7.0: i32) = move _8;           // scope 1 at $DIR/inline-closure-captures.rs:12:5: 12:9
+        StorageLive(_11);                // scope 1 at $DIR/inline-closure-captures.rs:12:5: 12:9
         _11 = move (_7.0: i32);          // scope 1 at $DIR/inline-closure-captures.rs:12:5: 12:9
         StorageLive(_9);                 // scope 2 at $DIR/inline-closure-captures.rs:11:19: 11:20
         _9 = (*((*_6).0: &i32));         // scope 2 at $DIR/inline-closure-captures.rs:11:19: 11:20
@@ -47,6 +48,7 @@ fn foo(_1: T, _2: i32) -> (i32, T) {
         (_0.1: T) = move _10;            // scope 2 at $DIR/inline-closure-captures.rs:11:18: 11:24
         StorageDead(_10);                // scope 2 at $DIR/inline-closure-captures.rs:11:23: 11:24
         StorageDead(_9);                 // scope 2 at $DIR/inline-closure-captures.rs:11:23: 11:24
+        StorageDead(_11);                // scope 1 at $DIR/inline-closure-captures.rs:12:5: 12:9
         StorageDead(_8);                 // scope 1 at $DIR/inline-closure-captures.rs:12:8: 12:9
         StorageDead(_7);                 // scope 1 at $DIR/inline-closure-captures.rs:12:8: 12:9
         StorageDead(_6);                 // scope 1 at $DIR/inline-closure-captures.rs:12:8: 12:9

src/test/ui/mir/issue-71793-inline-args-storage.rs

@@ -0,0 +1,16 @@
+// Verifies that inliner emits StorageLive & StorageDead when introducing
+// temporaries for arguments, so that they don't become part of the generator.
+// Regression test for #71793.
+//
+// check-pass
+// edition:2018
+// compile-args: -Zmir-opt-level=2
+
+#![crate_type = "lib"]
+
+pub async fn connect() {}
+
+pub async fn connect_many() {
+    Vec::<String>::new().first().ok_or("").unwrap();
+    connect().await;
+}