Auto merge of #71911 - wesleywiser:const_prop_small_cleanups, r=oli-obk

[mir-opt] Small ConstProp cleanup

8 files changed, 88 insertions, 45 deletions

diff --git a/src/librustc_mir/transform/const_prop.rs b/src/librustc_mir/transform/const_prop.rs
index 17ca918d32c..529e63ab967 100644
--- a/src/librustc_mir/transform/const_prop.rs
+++ b/src/librustc_mir/transform/const_prop.rs
@@ -716,8 +716,6 @@ enum ConstPropMode {
     OnlyInsideOwnBlock,
     /// The `Local` can be propagated into but reads cannot be propagated.
     OnlyPropagateInto,
-    /// No propagation is allowed at all.
-    NoPropagation,
 }
 
 struct CanConstProp {
@@ -788,7 +786,7 @@ impl<'tcx> Visitor<'tcx> for CanConstProp {
                                 "local {:?} can't be propagated because of multiple assignments",
                                 local,
                             );
-                            *other = ConstPropMode::NoPropagation;
+                            *other = ConstPropMode::OnlyPropagateInto;
                         }
                     }
                 }
@@ -815,7 +813,7 @@ impl<'tcx> Visitor<'tcx> for CanConstProp {
             | MutatingUse(MutatingUseContext::Borrow)
             | MutatingUse(MutatingUseContext::AddressOf) => {
                 trace!("local {:?} can't be propagaged because it's used: {:?}", local, context);
-                self.can_const_prop[local] = ConstPropMode::NoPropagation;
+                self.can_const_prop[local] = ConstPropMode::OnlyPropagateInto;
             }
         }
     }
@@ -847,31 +845,28 @@ impl<'mir, 'tcx> MutVisitor<'tcx> for ConstPropagator<'mir, 'tcx> {
             if let Ok(place_layout) = self.tcx.layout_of(self.param_env.and(place_ty)) {
                 let can_const_prop = self.can_const_prop[place.local];
                 if let Some(()) = self.const_prop(rval, place_layout, source_info, place) {
-                    if can_const_prop != ConstPropMode::NoPropagation {
-                        // This will return None for variables that are from other blocks,
-                        // so it should be okay to propagate from here on down.
-                        if let Some(value) = self.get_const(place) {
-                            if self.should_const_prop(value) {
-                                trace!("replacing {:?} with {:?}", rval, value);
-                                self.replace_with_const(rval, value, source_info);
-                                if can_const_prop == ConstPropMode::FullConstProp
-                                    || can_const_prop == ConstPropMode::OnlyInsideOwnBlock
-                                {
-                                    trace!("propagated into {:?}", place);
-                                }
-                            }
-                            if can_const_prop == ConstPropMode::OnlyInsideOwnBlock {
-                                trace!(
-                                    "found local restricted to its block. Will remove it from const-prop after block is finished. Local: {:?}",
-                                    place.local
-                                );
-                                self.locals_of_current_block.insert(place.local);
+                    // This will return None for variables that are from other blocks,
+                    // so it should be okay to propagate from here on down.
+                    if let Some(value) = self.get_const(place) {
+                        if self.should_const_prop(value) {
+                            trace!("replacing {:?} with {:?}", rval, value);
+                            self.replace_with_const(rval, value, source_info);
+                            if can_const_prop == ConstPropMode::FullConstProp
+                                || can_const_prop == ConstPropMode::OnlyInsideOwnBlock
+                            {
+                                trace!("propagated into {:?}", place);
                             }
                         }
                     }
-                    if can_const_prop == ConstPropMode::OnlyPropagateInto
-                        || can_const_prop == ConstPropMode::NoPropagation
-                    {
+                    if can_const_prop == ConstPropMode::OnlyInsideOwnBlock {
+                        trace!(
+                            "found local restricted to its block. Will remove it from const-prop after block is finished. Local: {:?}",
+                            place.local
+                        );
+                        self.locals_of_current_block.insert(place.local);
+                    }
+
+                    if can_const_prop == ConstPropMode::OnlyPropagateInto {
                         trace!("can't propagate into {:?}", place);
                         if place.local != RETURN_PLACE {
                             Self::remove_const(&mut self.ecx, place.local);
diff --git a/src/test/mir-opt/const_prop/mutable_variable_aggregate_mut_ref/rustc.main.ConstProp.diff b/src/test/mir-opt/const_prop/mutable_variable_aggregate_mut_ref/rustc.main.ConstProp.diff
index 44203ac327a..0d703068d41 100644
--- a/src/test/mir-opt/const_prop/mutable_variable_aggregate_mut_ref/rustc.main.ConstProp.diff
+++ b/src/test/mir-opt/const_prop/mutable_variable_aggregate_mut_ref/rustc.main.ConstProp.diff
@@ -23,13 +23,15 @@
                                            // + ty: i32
                                            // + val: Value(Scalar(0x0000002a))
                                            // mir::Constant
-                                           // + span: $DIR/mutable_variable_aggregate_mut_ref.rs:5:18: 5:20
+-                                          // + span: $DIR/mutable_variable_aggregate_mut_ref.rs:5:18: 5:20
++                                          // + span: $DIR/mutable_variable_aggregate_mut_ref.rs:5:17: 5:25
                                            // + literal: Const { ty: i32, val: Value(Scalar(0x0000002a)) }
                                            // ty::Const
                                            // + ty: i32
                                            // + val: Value(Scalar(0x0000002b))
                                            // mir::Constant
-                                           // + span: $DIR/mutable_variable_aggregate_mut_ref.rs:5:22: 5:24
+-                                          // + span: $DIR/mutable_variable_aggregate_mut_ref.rs:5:22: 5:24
++                                          // + span: $DIR/mutable_variable_aggregate_mut_ref.rs:5:17: 5:25
                                            // + literal: Const { ty: i32, val: Value(Scalar(0x0000002b)) }
           StorageLive(_2);                 // scope 1 at $DIR/mutable_variable_aggregate_mut_ref.rs:6:9: 6:10
           _2 = &mut _1;                    // scope 1 at $DIR/mutable_variable_aggregate_mut_ref.rs:6:13: 6:19
diff --git a/src/test/mir-opt/simplify-arm-identity/32bit/rustc.main.SimplifyArmIdentity.diff b/src/test/mir-opt/simplify-arm-identity/32bit/rustc.main.SimplifyArmIdentity.diff
index dfd6d6f0f2e..94759dca038 100644
--- a/src/test/mir-opt/simplify-arm-identity/32bit/rustc.main.SimplifyArmIdentity.diff
+++ b/src/test/mir-opt/simplify-arm-identity/32bit/rustc.main.SimplifyArmIdentity.diff
@@ -39,14 +39,13 @@
       }
   
       bb1: {
-          ((_2 as Foo).0: u8) = const 0u8; // scope 1 at $DIR/simplify-arm-identity.rs:21:21: 21:32
+          _2 = const Dst::Foo(0u8);        // scope 1 at $DIR/simplify-arm-identity.rs:21:21: 21:32
                                            // ty::Const
-                                           // + ty: u8
+                                           // + ty: Dst
                                            // + val: Value(Scalar(0x00))
                                            // mir::Constant
-                                           // + span: $DIR/simplify-arm-identity.rs:21:30: 21:31
-                                           // + literal: Const { ty: u8, val: Value(Scalar(0x00)) }
-          discriminant(_2) = 0;            // scope 1 at $DIR/simplify-arm-identity.rs:21:21: 21:32
+                                           // + span: $DIR/simplify-arm-identity.rs:21:21: 21:32
+                                           // + literal: Const { ty: Dst, val: Value(Scalar(0x00)) }
           goto -> bb4;                     // scope 1 at $DIR/simplify-arm-identity.rs:19:18: 22:6
       }
   
diff --git a/src/test/mir-opt/simplify-arm-identity/64bit/rustc.main.SimplifyArmIdentity.diff b/src/test/mir-opt/simplify-arm-identity/64bit/rustc.main.SimplifyArmIdentity.diff
index f2bbd195869..ba21f16b685 100644
--- a/src/test/mir-opt/simplify-arm-identity/64bit/rustc.main.SimplifyArmIdentity.diff
+++ b/src/test/mir-opt/simplify-arm-identity/64bit/rustc.main.SimplifyArmIdentity.diff
@@ -39,14 +39,13 @@
       }
   
       bb1: {
-          ((_2 as Foo).0: u8) = const 0u8; // scope 1 at $DIR/simplify-arm-identity.rs:21:21: 21:32
+          _2 = const Dst::Foo(0u8);        // scope 1 at $DIR/simplify-arm-identity.rs:21:21: 21:32
                                            // ty::Const
-                                           // + ty: u8
+                                           // + ty: Dst
                                            // + val: Value(Scalar(0x00))
                                            // mir::Constant
-                                           // + span: $DIR/simplify-arm-identity.rs:21:30: 21:31
-                                           // + literal: Const { ty: u8, val: Value(Scalar(0x00)) }
-          discriminant(_2) = 0;            // scope 1 at $DIR/simplify-arm-identity.rs:21:21: 21:32
+                                           // + span: $DIR/simplify-arm-identity.rs:21:21: 21:32
+                                           // + literal: Const { ty: Dst, val: Value(Scalar(0x00)) }
           goto -> bb4;                     // scope 1 at $DIR/simplify-arm-identity.rs:19:18: 22:6
       }
   
diff --git a/src/test/mir-opt/simplify-arm-identity/rustc.main.SimplifyArmIdentity.diff b/src/test/mir-opt/simplify-arm-identity/rustc.main.SimplifyArmIdentity.diff
index b2517cb7012..e7373391b79 100644
--- a/src/test/mir-opt/simplify-arm-identity/rustc.main.SimplifyArmIdentity.diff
+++ b/src/test/mir-opt/simplify-arm-identity/rustc.main.SimplifyArmIdentity.diff
@@ -33,15 +33,14 @@
       }
   
       bb1: {
-          ((_2 as Foo).0: u8) = const 0u8; // scope 1 at $DIR/simplify-arm-identity.rs:20:21: 20:32
+          _2 = const Dst::Foo(0u8);        // bb1[0]: scope 1 at $DIR/simplify-arm-identity.rs:20:21: 20:32
                                            // ty::Const
-                                           // + ty: u8
+                                           // + ty: Dst
                                            // + val: Value(Scalar(0x00))
                                            // mir::Constant
-                                           // + span: $DIR/simplify-arm-identity.rs:20:30: 20:31
-                                           // + literal: Const { ty: u8, val: Value(Scalar(0x00)) }
-          discriminant(_2) = 0;            // scope 1 at $DIR/simplify-arm-identity.rs:20:21: 20:32
-          goto -> bb4;                     // scope 1 at $DIR/simplify-arm-identity.rs:18:18: 21:6
+                                           // + span: $DIR/simplify-arm-identity.rs:20:21: 20:32
+                                           // + literal: Const { ty: Dst, val: Value(Scalar(0x00)) }
+          goto -> bb4;                     // bb1[1]: scope 1 at $DIR/simplify-arm-identity.rs:18:18: 21:6
       }
   
       bb2: {
diff --git a/src/test/mir-opt/simplify-locals-removes-unused-discriminant-reads.rs b/src/test/mir-opt/simplify-locals-removes-unused-discriminant-reads.rs
index 067fa879b40..7047b542aa6 100644
--- a/src/test/mir-opt/simplify-locals-removes-unused-discriminant-reads.rs
+++ b/src/test/mir-opt/simplify-locals-removes-unused-discriminant-reads.rs
@@ -9,4 +9,5 @@ fn main() {
     map(None);
 }
 
+// EMIT_MIR_FOR_EACH_BIT_WIDTH
 // EMIT_MIR rustc.map.SimplifyLocals.diff
diff --git a/src/test/mir-opt/simplify-locals-removes-unused-discriminant-reads/rustc.map.SimplifyLocals.diff b/src/test/mir-opt/simplify-locals-removes-unused-discriminant-reads/32bit/rustc.map.SimplifyLocals.diff
index 0ca54af85e3..2f78671763d 100644
--- a/src/test/mir-opt/simplify-locals-removes-unused-discriminant-reads/rustc.map.SimplifyLocals.diff
+++ b/src/test/mir-opt/simplify-locals-removes-unused-discriminant-reads/32bit/rustc.map.SimplifyLocals.diff
@@ -24,7 +24,13 @@
       }
   
       bb2: {
-          discriminant(_0) = 0;            // scope 0 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:3:17: 3:21
+          _0 = const std::option::Option::<std::boxed::Box<()>>::None; // scope 0 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:3:17: 3:21
+                                           // ty::Const
+                                           // + ty: std::option::Option<std::boxed::Box<()>>
+                                           // + val: Value(Scalar(0x00000000))
+                                           // mir::Constant
+                                           // + span: $DIR/simplify-locals-removes-unused-discriminant-reads.rs:3:17: 3:21
+                                           // + literal: Const { ty: std::option::Option<std::boxed::Box<()>>, val: Value(Scalar(0x00000000)) }
           goto -> bb3;                     // scope 0 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:2:5: 5:6
       }
   
diff --git a/src/test/mir-opt/simplify-locals-removes-unused-discriminant-reads/64bit/rustc.map.SimplifyLocals.diff b/src/test/mir-opt/simplify-locals-removes-unused-discriminant-reads/64bit/rustc.map.SimplifyLocals.diff
new file mode 100644
index 00000000000..a97fa98a7b0
--- /dev/null
+++ b/src/test/mir-opt/simplify-locals-removes-unused-discriminant-reads/64bit/rustc.map.SimplifyLocals.diff
@@ -0,0 +1,42 @@
+- // MIR for `map` before SimplifyLocals
++ // MIR for `map` after SimplifyLocals
+  
+  fn map(_1: std::option::Option<std::boxed::Box<()>>) -> std::option::Option<std::boxed::Box<()>> {
+      debug x => _1;                       // in scope 0 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:1:8: 1:9
+      let mut _0: std::option::Option<std::boxed::Box<()>>; // return place in scope 0 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:1:31: 1:46
+      let mut _2: isize;                   // in scope 0 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:3:9: 3:13
+      let _3: std::boxed::Box<()>;         // in scope 0 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:4:14: 4:15
+-     let mut _4: std::boxed::Box<()>;     // in scope 0 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:4:25: 4:26
+-     let mut _5: isize;                   // in scope 0 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:6:1: 6:2
+-     let mut _6: isize;                   // in scope 0 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:6:1: 6:2
+      scope 1 {
+          debug x => _3;                   // in scope 1 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:4:14: 4:15
+      }
+  
+      bb0: {
+          _2 = discriminant(_1);           // scope 0 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:3:9: 3:13
+          switchInt(move _2) -> [0isize: bb2, otherwise: bb1]; // scope 0 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:3:9: 3:13
+      }
+  
+      bb1: {
+          _0 = move _1;                    // scope 1 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:4:20: 4:27
+          goto -> bb3;                     // scope 0 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:2:5: 5:6
+      }
+  
+      bb2: {
+          _0 = const std::option::Option::<std::boxed::Box<()>>::None; // scope 0 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:3:17: 3:21
+                                           // ty::Const
+                                           // + ty: std::option::Option<std::boxed::Box<()>>
+                                           // + val: Value(Scalar(0x0000000000000000))
+                                           // mir::Constant
+                                           // + span: $DIR/simplify-locals-removes-unused-discriminant-reads.rs:3:17: 3:21
+                                           // + literal: Const { ty: std::option::Option<std::boxed::Box<()>>, val: Value(Scalar(0x0000000000000000)) }
+          goto -> bb3;                     // scope 0 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:2:5: 5:6
+      }
+  
+      bb3: {
+-         _5 = discriminant(_1);           // scope 0 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:6:1: 6:2
+          return;                          // scope 0 at $DIR/simplify-locals-removes-unused-discriminant-reads.rs:6:2: 6:2
+      }
+  }
+