Fix struct field tracking and add tests for it

6 files changed, 145 insertions, 10 deletions

diff --git a/compiler/rustc_mir_dataflow/src/value_analysis.rs b/compiler/rustc_mir_dataflow/src/value_analysis.rs
index f428cd5ee82..17d349fb526 100644
--- a/compiler/rustc_mir_dataflow/src/value_analysis.rs
+++ b/compiler/rustc_mir_dataflow/src/value_analysis.rs
@@ -151,9 +151,7 @@ pub trait ValueAnalysis<'tcx> {
     ) -> ValueOrPlace<Self::Value> {
         match rvalue {
             Rvalue::Use(operand) => self.handle_operand(operand, state),
-            Rvalue::CopyForDeref(place) => {
-                self.handle_operand(&Operand::Copy(*place), state)
-            }
+            Rvalue::CopyForDeref(place) => self.handle_operand(&Operand::Copy(*place), state),
             Rvalue::Ref(..) | Rvalue::AddressOf(..) => {
                 // We don't track such places.
                 ValueOrPlace::top()
@@ -638,9 +636,7 @@ impl Map {
                 return;
             }
             projection.push(PlaceElem::Field(field, ty));
-            self.register_with_filter_rec(
-                tcx, local, projection, ty, filter, exclude,
-            );
+            self.register_with_filter_rec(tcx, local, projection, ty, filter, exclude);
             projection.pop();
         });
     }
@@ -842,13 +838,17 @@ fn iter_fields<'tcx>(
             }
         }
         ty::Adt(def, substs) => {
+            if def.is_union() {
+                return;
+            }
             for (v_index, v_def) in def.variants().iter_enumerated() {
+                let variant = if def.is_struct() { None } else { Some(v_index) };
                 for (f_index, f_def) in v_def.fields.iter().enumerate() {
                     let field_ty = f_def.ty(tcx, substs);
                     let field_ty = tcx
                         .try_normalize_erasing_regions(ty::ParamEnv::reveal_all(), field_ty)
                         .unwrap_or(field_ty);
-                    f(Some(v_index), f_index.into(), field_ty);
+                    f(variant, f_index.into(), field_ty);
                 }
             }
         }
diff --git a/compiler/rustc_mir_transform/src/dataflow_const_prop.rs b/compiler/rustc_mir_transform/src/dataflow_const_prop.rs
index e88125777f1..e1c7b6ab180 100644
--- a/compiler/rustc_mir_transform/src/dataflow_const_prop.rs
+++ b/compiler/rustc_mir_transform/src/dataflow_const_prop.rs
@@ -7,9 +7,7 @@ use rustc_data_structures::fx::FxHashMap;
 use rustc_middle::mir::visit::{MutVisitor, Visitor};
 use rustc_middle::mir::*;
 use rustc_middle::ty::{self, Ty, TyCtxt};
-use rustc_mir_dataflow::value_analysis::{
-    Map, State, TrackElem, ValueAnalysis, ValueOrPlace,
-};
+use rustc_mir_dataflow::value_analysis::{Map, State, TrackElem, ValueAnalysis, ValueOrPlace};
 use rustc_mir_dataflow::{lattice::FlatSet, Analysis, ResultsVisitor, SwitchIntEdgeEffects};
 use rustc_span::DUMMY_SP;
 
diff --git a/src/test/mir-opt/dataflow-const-prop/enum.main.DataflowConstProp.diff b/src/test/mir-opt/dataflow-const-prop/enum.main.DataflowConstProp.diff
new file mode 100644
index 00000000000..2ced794e628
--- /dev/null
+++ b/src/test/mir-opt/dataflow-const-prop/enum.main.DataflowConstProp.diff
@@ -0,0 +1,61 @@
+- // MIR for `main` before DataflowConstProp
++ // MIR for `main` after DataflowConstProp
+  
+  fn main() -> () {
+      let mut _0: ();                      // return place in scope 0 at $DIR/enum.rs:+0:11: +0:11
+      let _1: E;                           // in scope 0 at $DIR/enum.rs:+1:9: +1:10
+      let mut _3: isize;                   // in scope 0 at $DIR/enum.rs:+2:23: +2:31
+      scope 1 {
+          debug e => _1;                   // in scope 1 at $DIR/enum.rs:+1:9: +1:10
+          let _2: i32;                     // in scope 1 at $DIR/enum.rs:+2:9: +2:10
+          let _4: i32;                     // in scope 1 at $DIR/enum.rs:+2:29: +2:30
+          let _5: i32;                     // in scope 1 at $DIR/enum.rs:+2:44: +2:45
+          scope 2 {
+              debug x => _2;               // in scope 2 at $DIR/enum.rs:+2:9: +2:10
+          }
+          scope 3 {
+              debug x => _4;               // in scope 3 at $DIR/enum.rs:+2:29: +2:30
+          }
+          scope 4 {
+              debug x => _5;               // in scope 4 at $DIR/enum.rs:+2:44: +2:45
+          }
+      }
+  
+      bb0: {
+          StorageLive(_1);                 // scope 0 at $DIR/enum.rs:+1:9: +1:10
+          Deinit(_1);                      // scope 0 at $DIR/enum.rs:+1:13: +1:21
+          ((_1 as V1).0: i32) = const 0_i32; // scope 0 at $DIR/enum.rs:+1:13: +1:21
+          discriminant(_1) = 0;            // scope 0 at $DIR/enum.rs:+1:13: +1:21
+          StorageLive(_2);                 // scope 1 at $DIR/enum.rs:+2:9: +2:10
+          _3 = discriminant(_1);           // scope 1 at $DIR/enum.rs:+2:19: +2:20
+          switchInt(move _3) -> [0_isize: bb3, 1_isize: bb1, otherwise: bb2]; // scope 1 at $DIR/enum.rs:+2:13: +2:20
+      }
+  
+      bb1: {
+          StorageLive(_5);                 // scope 1 at $DIR/enum.rs:+2:44: +2:45
+          _5 = ((_1 as V2).0: i32);        // scope 1 at $DIR/enum.rs:+2:44: +2:45
+          _2 = _5;                         // scope 4 at $DIR/enum.rs:+2:50: +2:51
+          StorageDead(_5);                 // scope 1 at $DIR/enum.rs:+2:50: +2:51
+          goto -> bb4;                     // scope 1 at $DIR/enum.rs:+2:50: +2:51
+      }
+  
+      bb2: {
+          unreachable;                     // scope 1 at $DIR/enum.rs:+2:19: +2:20
+      }
+  
+      bb3: {
+          StorageLive(_4);                 // scope 1 at $DIR/enum.rs:+2:29: +2:30
+          _4 = ((_1 as V1).0: i32);        // scope 1 at $DIR/enum.rs:+2:29: +2:30
+          _2 = _4;                         // scope 3 at $DIR/enum.rs:+2:35: +2:36
+          StorageDead(_4);                 // scope 1 at $DIR/enum.rs:+2:35: +2:36
+          goto -> bb4;                     // scope 1 at $DIR/enum.rs:+2:35: +2:36
+      }
+  
+      bb4: {
+          _0 = const ();                   // scope 0 at $DIR/enum.rs:+0:11: +3:2
+          StorageDead(_2);                 // scope 1 at $DIR/enum.rs:+3:1: +3:2
+          StorageDead(_1);                 // scope 0 at $DIR/enum.rs:+3:1: +3:2
+          return;                          // scope 0 at $DIR/enum.rs:+3:2: +3:2
+      }
+  }
+  
diff --git a/src/test/mir-opt/dataflow-const-prop/enum.rs b/src/test/mir-opt/dataflow-const-prop/enum.rs
new file mode 100644
index 00000000000..13288577dea
--- /dev/null
+++ b/src/test/mir-opt/dataflow-const-prop/enum.rs
@@ -0,0 +1,13 @@
+// unit-test: DataflowConstProp
+
+// Not trackable, because variants could be aliased.
+enum E {
+    V1(i32),
+    V2(i32)
+}
+
+// EMIT_MIR enum.main.DataflowConstProp.diff
+fn main() {
+    let e = E::V1(0);
+    let x = match e { E::V1(x) => x, E::V2(x) => x };
+}
diff --git a/src/test/mir-opt/dataflow-const-prop/struct.main.DataflowConstProp.diff b/src/test/mir-opt/dataflow-const-prop/struct.main.DataflowConstProp.diff
new file mode 100644
index 00000000000..cfb2706c167
--- /dev/null
+++ b/src/test/mir-opt/dataflow-const-prop/struct.main.DataflowConstProp.diff
@@ -0,0 +1,52 @@
+- // MIR for `main` before DataflowConstProp
++ // MIR for `main` after DataflowConstProp
+  
+  fn main() -> () {
+      let mut _0: ();                      // return place in scope 0 at $DIR/struct.rs:+0:11: +0:11
+      let mut _1: S;                       // in scope 0 at $DIR/struct.rs:+1:9: +1:14
+      let mut _3: i32;                     // in scope 0 at $DIR/struct.rs:+2:13: +2:16
+      let mut _5: i32;                     // in scope 0 at $DIR/struct.rs:+4:13: +4:14
+      let mut _6: i32;                     // in scope 0 at $DIR/struct.rs:+4:17: +4:20
+      scope 1 {
+          debug s => _1;                   // in scope 1 at $DIR/struct.rs:+1:9: +1:14
+          let _2: i32;                     // in scope 1 at $DIR/struct.rs:+2:9: +2:10
+          scope 2 {
+              debug a => _2;               // in scope 2 at $DIR/struct.rs:+2:9: +2:10
+              let _4: i32;                 // in scope 2 at $DIR/struct.rs:+4:9: +4:10
+              scope 3 {
+                  debug b => _4;           // in scope 3 at $DIR/struct.rs:+4:9: +4:10
+              }
+          }
+      }
+  
+      bb0: {
+          StorageLive(_1);                 // scope 0 at $DIR/struct.rs:+1:9: +1:14
+          Deinit(_1);                      // scope 0 at $DIR/struct.rs:+1:17: +1:21
+          (_1.0: i32) = const 1_i32;       // scope 0 at $DIR/struct.rs:+1:17: +1:21
+          StorageLive(_2);                 // scope 1 at $DIR/struct.rs:+2:9: +2:10
+          StorageLive(_3);                 // scope 1 at $DIR/struct.rs:+2:13: +2:16
+-         _3 = (_1.0: i32);                // scope 1 at $DIR/struct.rs:+2:13: +2:16
+-         _2 = Add(move _3, const 2_i32);  // scope 1 at $DIR/struct.rs:+2:13: +2:20
++         _3 = const 1_i32;                // scope 1 at $DIR/struct.rs:+2:13: +2:16
++         _2 = const 3_i32;                // scope 1 at $DIR/struct.rs:+2:13: +2:20
+          StorageDead(_3);                 // scope 1 at $DIR/struct.rs:+2:19: +2:20
+          (_1.0: i32) = const 3_i32;       // scope 2 at $DIR/struct.rs:+3:5: +3:12
+          StorageLive(_4);                 // scope 2 at $DIR/struct.rs:+4:9: +4:10
+          StorageLive(_5);                 // scope 2 at $DIR/struct.rs:+4:13: +4:14
+-         _5 = _2;                         // scope 2 at $DIR/struct.rs:+4:13: +4:14
++         _5 = const 3_i32;                // scope 2 at $DIR/struct.rs:+4:13: +4:14
+          StorageLive(_6);                 // scope 2 at $DIR/struct.rs:+4:17: +4:20
+-         _6 = (_1.0: i32);                // scope 2 at $DIR/struct.rs:+4:17: +4:20
+-         _4 = Add(move _5, move _6);      // scope 2 at $DIR/struct.rs:+4:13: +4:20
++         _6 = const 3_i32;                // scope 2 at $DIR/struct.rs:+4:17: +4:20
++         _4 = const 6_i32;                // scope 2 at $DIR/struct.rs:+4:13: +4:20
+          StorageDead(_6);                 // scope 2 at $DIR/struct.rs:+4:19: +4:20
+          StorageDead(_5);                 // scope 2 at $DIR/struct.rs:+4:19: +4:20
+          _0 = const ();                   // scope 0 at $DIR/struct.rs:+0:11: +5:2
+          StorageDead(_4);                 // scope 2 at $DIR/struct.rs:+5:1: +5:2
+          StorageDead(_2);                 // scope 1 at $DIR/struct.rs:+5:1: +5:2
+          StorageDead(_1);                 // scope 0 at $DIR/struct.rs:+5:1: +5:2
+          return;                          // scope 0 at $DIR/struct.rs:+5:2: +5:2
+      }
+  }
+  
diff --git a/src/test/mir-opt/dataflow-const-prop/struct.rs b/src/test/mir-opt/dataflow-const-prop/struct.rs
new file mode 100644
index 00000000000..841b279e03e
--- /dev/null
+++ b/src/test/mir-opt/dataflow-const-prop/struct.rs
@@ -0,0 +1,11 @@
+// unit-test: DataflowConstProp
+
+struct S(i32);
+
+// EMIT_MIR struct.main.DataflowConstProp.diff
+fn main() {
+    let mut s = S(1);
+    let a = s.0 + 2;
+    s.0 = 3;
+    let b = a + s.0;
+}