Rollup merge of #73130 - wesleywiser:remove_const_prop_for_indirects, r=oli-obk

Remove const prop for indirects

This was only used by one mir-opt test and since it causes buggy behavior under `-Zmir-opt-level=2`, it seems like we should remove it.

This was split out from #71946.

Closes #72679
Closes #72372
Closes #72285

5 files changed, 82 insertions, 96 deletions

diff --git a/src/librustc_mir/interpret/intern.rs b/src/librustc_mir/interpret/intern.rs
index 3c724c79b40..cab13d379a2 100644
--- a/src/librustc_mir/interpret/intern.rs
+++ b/src/librustc_mir/interpret/intern.rs
@@ -293,7 +293,6 @@ pub enum InternKind {
     Static(hir::Mutability),
     Constant,
     Promoted,
-    ConstProp,
 }
 
 /// Intern `ret` and everything it references.
@@ -314,9 +313,7 @@ pub fn intern_const_alloc_recursive<M: CompileTimeMachine<'mir, 'tcx>>(
     let base_intern_mode = match intern_kind {
         InternKind::Static(mutbl) => InternMode::Static(mutbl),
         // FIXME: what about array lengths, array initializers?
-        InternKind::Constant | InternKind::ConstProp | InternKind::Promoted => {
-            InternMode::ConstBase
-        }
+        InternKind::Constant | InternKind::Promoted => InternMode::ConstBase,
     };
 
     // Type based interning.
@@ -358,7 +355,10 @@ pub fn intern_const_alloc_recursive<M: CompileTimeMachine<'mir, 'tcx>>(
             Err(error) => {
                 ecx.tcx.sess.delay_span_bug(
                     ecx.tcx.span,
-                    "error during interning should later cause validation failure",
+                    &format!(
+                        "error during interning should later cause validation failure: {}",
+                        error
+                    ),
                 );
                 // Some errors shouldn't come up because creating them causes
                 // an allocation, which we should avoid. When that happens,
@@ -399,7 +399,7 @@ pub fn intern_const_alloc_recursive<M: CompileTimeMachine<'mir, 'tcx>>(
                     // immutability is so important.
                     alloc.mutability = Mutability::Not;
                 }
-                InternKind::Constant | InternKind::ConstProp => {
+                InternKind::Constant => {
                     // If it's a constant, we should not have any "leftovers" as everything
                     // is tracked by const-checking.
                     // FIXME: downgrade this to a warning? It rejects some legitimate consts,
diff --git a/src/librustc_mir/transform/const_prop.rs b/src/librustc_mir/transform/const_prop.rs
index 83ed2fc2d43..17ca918d32c 100644
--- a/src/librustc_mir/transform/const_prop.rs
+++ b/src/librustc_mir/transform/const_prop.rs
@@ -27,9 +27,9 @@ use rustc_trait_selection::traits;
 
 use crate::const_eval::error_to_const_error;
 use crate::interpret::{
-    self, compile_time_machine, intern_const_alloc_recursive, AllocId, Allocation, Frame, ImmTy,
-    Immediate, InternKind, InterpCx, LocalState, LocalValue, Memory, MemoryKind, OpTy,
-    Operand as InterpOperand, PlaceTy, Pointer, ScalarMaybeUninit, StackPopCleanup,
+    self, compile_time_machine, AllocId, Allocation, Frame, ImmTy, Immediate, InterpCx, LocalState,
+    LocalValue, Memory, MemoryKind, OpTy, Operand as InterpOperand, PlaceTy, Pointer,
+    ScalarMaybeUninit, StackPopCleanup,
 };
 use crate::transform::{MirPass, MirSource};
 
@@ -702,11 +702,6 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
                 ScalarMaybeUninit::Scalar(l),
                 ScalarMaybeUninit::Scalar(r),
             )) => l.is_bits() && r.is_bits(),
-            interpret::Operand::Indirect(_) if mir_opt_level >= 2 => {
-                let mplace = op.assert_mem_place(&self.ecx);
-                intern_const_alloc_recursive(&mut self.ecx, InternKind::ConstProp, mplace, false);
-                true
-            }
             _ => false,
         }
     }
diff --git a/src/test/mir-opt/const_prop/discriminant.rs b/src/test/mir-opt/const_prop/discriminant.rs
index 04541b94ad7..13e8eb3e44e 100644
--- a/src/test/mir-opt/const_prop/discriminant.rs
+++ b/src/test/mir-opt/const_prop/discriminant.rs
@@ -1,5 +1,10 @@
 // compile-flags: -O
 
+// FIXME(wesleywiser): Ideally, we could const-prop away all of this and just be left with
+// `let x = 42` but that doesn't work because const-prop doesn't support `Operand::Indirect`
+// and `InterpCx::eval_place()` always forces an allocation which creates the `Indirect`.
+// Fixing either of those will allow us to const-prop this away.
+
 // EMIT_MIR_FOR_EACH_BIT_WIDTH
 // EMIT_MIR rustc.main.ConstProp.diff
 fn main() {
diff --git a/src/test/mir-opt/const_prop/discriminant/32bit/rustc.main.ConstProp.diff b/src/test/mir-opt/const_prop/discriminant/32bit/rustc.main.ConstProp.diff
index 9979ea95498..1c873f53f37 100644
--- a/src/test/mir-opt/const_prop/discriminant/32bit/rustc.main.ConstProp.diff
+++ b/src/test/mir-opt/const_prop/discriminant/32bit/rustc.main.ConstProp.diff
@@ -2,100 +2,93 @@
 + // MIR for `main` after ConstProp
   
   fn main() -> () {
-      let mut _0: ();                      // return place in scope 0 at $DIR/discriminant.rs:5:11: 5:11
-      let _1: i32;                         // in scope 0 at $DIR/discriminant.rs:6:9: 6:10
-      let mut _2: i32;                     // in scope 0 at $DIR/discriminant.rs:6:13: 6:64
-      let mut _3: std::option::Option<bool>; // in scope 0 at $DIR/discriminant.rs:6:34: 6:44
-      let mut _4: isize;                   // in scope 0 at $DIR/discriminant.rs:6:21: 6:31
+      let mut _0: ();                      // return place in scope 0 at $DIR/discriminant.rs:10:11: 10:11
+      let _1: i32;                         // in scope 0 at $DIR/discriminant.rs:11:9: 11:10
+      let mut _2: i32;                     // in scope 0 at $DIR/discriminant.rs:11:13: 11:64
+      let mut _3: std::option::Option<bool>; // in scope 0 at $DIR/discriminant.rs:11:34: 11:44
+      let mut _4: isize;                   // in scope 0 at $DIR/discriminant.rs:11:21: 11:31
       scope 1 {
-          debug x => _1;                   // in scope 1 at $DIR/discriminant.rs:6:9: 6:10
+          debug x => _1;                   // in scope 1 at $DIR/discriminant.rs:11:9: 11:10
       }
   
       bb0: {
-          StorageLive(_1);                 // scope 0 at $DIR/discriminant.rs:6:9: 6:10
-          StorageLive(_2);                 // scope 0 at $DIR/discriminant.rs:6:13: 6:64
-          StorageLive(_3);                 // scope 0 at $DIR/discriminant.rs:6:34: 6:44
--         _3 = std::option::Option::<bool>::Some(const true); // scope 0 at $DIR/discriminant.rs:6:34: 6:44
-+         _3 = const std::option::Option::<bool>::Some(true); // scope 0 at $DIR/discriminant.rs:6:34: 6:44
+          StorageLive(_1);                 // scope 0 at $DIR/discriminant.rs:11:9: 11:10
+          StorageLive(_2);                 // scope 0 at $DIR/discriminant.rs:11:13: 11:64
+          StorageLive(_3);                 // scope 0 at $DIR/discriminant.rs:11:34: 11:44
+-         _3 = std::option::Option::<bool>::Some(const true); // scope 0 at $DIR/discriminant.rs:11:34: 11:44
++         _3 = const std::option::Option::<bool>::Some(true); // scope 0 at $DIR/discriminant.rs:11:34: 11:44
                                            // ty::Const
 -                                          // + ty: bool
 +                                          // + ty: std::option::Option<bool>
                                            // + val: Value(Scalar(0x01))
                                            // mir::Constant
--                                          // + span: $DIR/discriminant.rs:6:39: 6:43
+-                                          // + span: $DIR/discriminant.rs:11:39: 11:43
 -                                          // + literal: Const { ty: bool, val: Value(Scalar(0x01)) }
--         _4 = discriminant(_3);           // scope 0 at $DIR/discriminant.rs:6:21: 6:31
--         switchInt(move _4) -> [1isize: bb2, otherwise: bb1]; // scope 0 at $DIR/discriminant.rs:6:21: 6:31
-+                                          // + span: $DIR/discriminant.rs:6:34: 6:44
+-         _4 = discriminant(_3);           // scope 0 at $DIR/discriminant.rs:11:21: 11:31
+-         switchInt(move _4) -> [1isize: bb2, otherwise: bb1]; // scope 0 at $DIR/discriminant.rs:11:21: 11:31
++                                          // + span: $DIR/discriminant.rs:11:34: 11:44
 +                                          // + literal: Const { ty: std::option::Option<bool>, val: Value(Scalar(0x01)) }
-+         _4 = const 1isize;               // scope 0 at $DIR/discriminant.rs:6:21: 6:31
++         _4 = const 1isize;               // scope 0 at $DIR/discriminant.rs:11:21: 11:31
 +                                          // ty::Const
 +                                          // + ty: isize
 +                                          // + val: Value(Scalar(0x00000001))
 +                                          // mir::Constant
-+                                          // + span: $DIR/discriminant.rs:6:21: 6:31
++                                          // + span: $DIR/discriminant.rs:11:21: 11:31
 +                                          // + literal: Const { ty: isize, val: Value(Scalar(0x00000001)) }
-+         switchInt(const 1isize) -> [1isize: bb2, otherwise: bb1]; // scope 0 at $DIR/discriminant.rs:6:21: 6:31
++         switchInt(const 1isize) -> [1isize: bb2, otherwise: bb1]; // scope 0 at $DIR/discriminant.rs:11:21: 11:31
 +                                          // ty::Const
 +                                          // + ty: isize
 +                                          // + val: Value(Scalar(0x00000001))
 +                                          // mir::Constant
-+                                          // + span: $DIR/discriminant.rs:6:21: 6:31
++                                          // + span: $DIR/discriminant.rs:11:21: 11:31
 +                                          // + literal: Const { ty: isize, val: Value(Scalar(0x00000001)) }
       }
   
       bb1: {
-          _2 = const 10i32;                // scope 0 at $DIR/discriminant.rs:6:59: 6:61
+          _2 = const 10i32;                // scope 0 at $DIR/discriminant.rs:11:59: 11:61
                                            // ty::Const
                                            // + ty: i32
                                            // + val: Value(Scalar(0x0000000a))
                                            // mir::Constant
-                                           // + span: $DIR/discriminant.rs:6:59: 6:61
+                                           // + span: $DIR/discriminant.rs:11:59: 11:61
                                            // + literal: Const { ty: i32, val: Value(Scalar(0x0000000a)) }
-          goto -> bb4;                     // scope 0 at $DIR/discriminant.rs:6:13: 6:64
+          goto -> bb4;                     // scope 0 at $DIR/discriminant.rs:11:13: 11:64
       }
   
       bb2: {
--         switchInt(((_3 as Some).0: bool)) -> [false: bb1, otherwise: bb3]; // scope 0 at $DIR/discriminant.rs:6:26: 6:30
-+         switchInt(const true) -> [false: bb1, otherwise: bb3]; // scope 0 at $DIR/discriminant.rs:6:26: 6:30
-+                                          // ty::Const
-+                                          // + ty: bool
-+                                          // + val: Value(Scalar(0x01))
-+                                          // mir::Constant
-+                                          // + span: $DIR/discriminant.rs:6:26: 6:30
-+                                          // + literal: Const { ty: bool, val: Value(Scalar(0x01)) }
+          switchInt(((_3 as Some).0: bool)) -> [false: bb1, otherwise: bb3]; // scope 0 at $DIR/discriminant.rs:11:26: 11:30
       }
   
       bb3: {
-          _2 = const 42i32;                // scope 0 at $DIR/discriminant.rs:6:47: 6:49
+          _2 = const 42i32;                // scope 0 at $DIR/discriminant.rs:11:47: 11:49
                                            // ty::Const
                                            // + ty: i32
                                            // + val: Value(Scalar(0x0000002a))
                                            // mir::Constant
-                                           // + span: $DIR/discriminant.rs:6:47: 6:49
+                                           // + span: $DIR/discriminant.rs:11:47: 11:49
                                            // + literal: Const { ty: i32, val: Value(Scalar(0x0000002a)) }
-          goto -> bb4;                     // scope 0 at $DIR/discriminant.rs:6:13: 6:64
+          goto -> bb4;                     // scope 0 at $DIR/discriminant.rs:11:13: 11:64
       }
   
       bb4: {
-          _1 = Add(move _2, const 0i32);   // scope 0 at $DIR/discriminant.rs:6:13: 6:68
+          _1 = Add(move _2, const 0i32);   // scope 0 at $DIR/discriminant.rs:11:13: 11:68
                                            // ty::Const
                                            // + ty: i32
                                            // + val: Value(Scalar(0x00000000))
                                            // mir::Constant
-                                           // + span: $DIR/discriminant.rs:6:67: 6:68
+                                           // + span: $DIR/discriminant.rs:11:67: 11:68
                                            // + literal: Const { ty: i32, val: Value(Scalar(0x00000000)) }
-          StorageDead(_2);                 // scope 0 at $DIR/discriminant.rs:6:67: 6:68
-          StorageDead(_3);                 // scope 0 at $DIR/discriminant.rs:6:68: 6:69
-          _0 = const ();                   // scope 0 at $DIR/discriminant.rs:5:11: 7:2
+          StorageDead(_2);                 // scope 0 at $DIR/discriminant.rs:11:67: 11:68
+          StorageDead(_3);                 // scope 0 at $DIR/discriminant.rs:11:68: 11:69
+          _0 = const ();                   // scope 0 at $DIR/discriminant.rs:10:11: 12:2
                                            // ty::Const
                                            // + ty: ()
                                            // + val: Value(Scalar(<ZST>))
                                            // mir::Constant
-                                           // + span: $DIR/discriminant.rs:5:11: 7:2
+                                           // + span: $DIR/discriminant.rs:10:11: 12:2
                                            // + literal: Const { ty: (), val: Value(Scalar(<ZST>)) }
-          StorageDead(_1);                 // scope 0 at $DIR/discriminant.rs:7:1: 7:2
-          return;                          // scope 0 at $DIR/discriminant.rs:7:2: 7:2
+          StorageDead(_1);                 // scope 0 at $DIR/discriminant.rs:12:1: 12:2
+          return;                          // scope 0 at $DIR/discriminant.rs:12:2: 12:2
       }
   }
   
diff --git a/src/test/mir-opt/const_prop/discriminant/64bit/rustc.main.ConstProp.diff b/src/test/mir-opt/const_prop/discriminant/64bit/rustc.main.ConstProp.diff
index ec0341e3de2..75b4b7e5a62 100644
--- a/src/test/mir-opt/const_prop/discriminant/64bit/rustc.main.ConstProp.diff
+++ b/src/test/mir-opt/const_prop/discriminant/64bit/rustc.main.ConstProp.diff
@@ -2,100 +2,93 @@
 + // MIR for `main` after ConstProp
   
   fn main() -> () {
-      let mut _0: ();                      // return place in scope 0 at $DIR/discriminant.rs:5:11: 5:11
-      let _1: i32;                         // in scope 0 at $DIR/discriminant.rs:6:9: 6:10
-      let mut _2: i32;                     // in scope 0 at $DIR/discriminant.rs:6:13: 6:64
-      let mut _3: std::option::Option<bool>; // in scope 0 at $DIR/discriminant.rs:6:34: 6:44
-      let mut _4: isize;                   // in scope 0 at $DIR/discriminant.rs:6:21: 6:31
+      let mut _0: ();                      // return place in scope 0 at $DIR/discriminant.rs:10:11: 10:11
+      let _1: i32;                         // in scope 0 at $DIR/discriminant.rs:11:9: 11:10
+      let mut _2: i32;                     // in scope 0 at $DIR/discriminant.rs:11:13: 11:64
+      let mut _3: std::option::Option<bool>; // in scope 0 at $DIR/discriminant.rs:11:34: 11:44
+      let mut _4: isize;                   // in scope 0 at $DIR/discriminant.rs:11:21: 11:31
       scope 1 {
-          debug x => _1;                   // in scope 1 at $DIR/discriminant.rs:6:9: 6:10
+          debug x => _1;                   // in scope 1 at $DIR/discriminant.rs:11:9: 11:10
       }
   
       bb0: {
-          StorageLive(_1);                 // scope 0 at $DIR/discriminant.rs:6:9: 6:10
-          StorageLive(_2);                 // scope 0 at $DIR/discriminant.rs:6:13: 6:64
-          StorageLive(_3);                 // scope 0 at $DIR/discriminant.rs:6:34: 6:44
--         _3 = std::option::Option::<bool>::Some(const true); // scope 0 at $DIR/discriminant.rs:6:34: 6:44
-+         _3 = const std::option::Option::<bool>::Some(true); // scope 0 at $DIR/discriminant.rs:6:34: 6:44
+          StorageLive(_1);                 // scope 0 at $DIR/discriminant.rs:11:9: 11:10
+          StorageLive(_2);                 // scope 0 at $DIR/discriminant.rs:11:13: 11:64
+          StorageLive(_3);                 // scope 0 at $DIR/discriminant.rs:11:34: 11:44
+-         _3 = std::option::Option::<bool>::Some(const true); // scope 0 at $DIR/discriminant.rs:11:34: 11:44
++         _3 = const std::option::Option::<bool>::Some(true); // scope 0 at $DIR/discriminant.rs:11:34: 11:44
                                            // ty::Const
 -                                          // + ty: bool
 +                                          // + ty: std::option::Option<bool>
                                            // + val: Value(Scalar(0x01))
                                            // mir::Constant
--                                          // + span: $DIR/discriminant.rs:6:39: 6:43
+-                                          // + span: $DIR/discriminant.rs:11:39: 11:43
 -                                          // + literal: Const { ty: bool, val: Value(Scalar(0x01)) }
--         _4 = discriminant(_3);           // scope 0 at $DIR/discriminant.rs:6:21: 6:31
--         switchInt(move _4) -> [1isize: bb2, otherwise: bb1]; // scope 0 at $DIR/discriminant.rs:6:21: 6:31
-+                                          // + span: $DIR/discriminant.rs:6:34: 6:44
+-         _4 = discriminant(_3);           // scope 0 at $DIR/discriminant.rs:11:21: 11:31
+-         switchInt(move _4) -> [1isize: bb2, otherwise: bb1]; // scope 0 at $DIR/discriminant.rs:11:21: 11:31
++                                          // + span: $DIR/discriminant.rs:11:34: 11:44
 +                                          // + literal: Const { ty: std::option::Option<bool>, val: Value(Scalar(0x01)) }
-+         _4 = const 1isize;               // scope 0 at $DIR/discriminant.rs:6:21: 6:31
++         _4 = const 1isize;               // scope 0 at $DIR/discriminant.rs:11:21: 11:31
 +                                          // ty::Const
 +                                          // + ty: isize
 +                                          // + val: Value(Scalar(0x0000000000000001))
 +                                          // mir::Constant
-+                                          // + span: $DIR/discriminant.rs:6:21: 6:31
++                                          // + span: $DIR/discriminant.rs:11:21: 11:31
 +                                          // + literal: Const { ty: isize, val: Value(Scalar(0x0000000000000001)) }
-+         switchInt(const 1isize) -> [1isize: bb2, otherwise: bb1]; // scope 0 at $DIR/discriminant.rs:6:21: 6:31
++         switchInt(const 1isize) -> [1isize: bb2, otherwise: bb1]; // scope 0 at $DIR/discriminant.rs:11:21: 11:31
 +                                          // ty::Const
 +                                          // + ty: isize
 +                                          // + val: Value(Scalar(0x0000000000000001))
 +                                          // mir::Constant
-+                                          // + span: $DIR/discriminant.rs:6:21: 6:31
++                                          // + span: $DIR/discriminant.rs:11:21: 11:31
 +                                          // + literal: Const { ty: isize, val: Value(Scalar(0x0000000000000001)) }
       }
   
       bb1: {
-          _2 = const 10i32;                // scope 0 at $DIR/discriminant.rs:6:59: 6:61
+          _2 = const 10i32;                // scope 0 at $DIR/discriminant.rs:11:59: 11:61
                                            // ty::Const
                                            // + ty: i32
                                            // + val: Value(Scalar(0x0000000a))
                                            // mir::Constant
-                                           // + span: $DIR/discriminant.rs:6:59: 6:61
+                                           // + span: $DIR/discriminant.rs:11:59: 11:61
                                            // + literal: Const { ty: i32, val: Value(Scalar(0x0000000a)) }
-          goto -> bb4;                     // scope 0 at $DIR/discriminant.rs:6:13: 6:64
+          goto -> bb4;                     // scope 0 at $DIR/discriminant.rs:11:13: 11:64
       }
   
       bb2: {
--         switchInt(((_3 as Some).0: bool)) -> [false: bb1, otherwise: bb3]; // scope 0 at $DIR/discriminant.rs:6:26: 6:30
-+         switchInt(const true) -> [false: bb1, otherwise: bb3]; // scope 0 at $DIR/discriminant.rs:6:26: 6:30
-+                                          // ty::Const
-+                                          // + ty: bool
-+                                          // + val: Value(Scalar(0x01))
-+                                          // mir::Constant
-+                                          // + span: $DIR/discriminant.rs:6:26: 6:30
-+                                          // + literal: Const { ty: bool, val: Value(Scalar(0x01)) }
+          switchInt(((_3 as Some).0: bool)) -> [false: bb1, otherwise: bb3]; // scope 0 at $DIR/discriminant.rs:11:26: 11:30
       }
   
       bb3: {
-          _2 = const 42i32;                // scope 0 at $DIR/discriminant.rs:6:47: 6:49
+          _2 = const 42i32;                // scope 0 at $DIR/discriminant.rs:11:47: 11:49
                                            // ty::Const
                                            // + ty: i32
                                            // + val: Value(Scalar(0x0000002a))
                                            // mir::Constant
-                                           // + span: $DIR/discriminant.rs:6:47: 6:49
+                                           // + span: $DIR/discriminant.rs:11:47: 11:49
                                            // + literal: Const { ty: i32, val: Value(Scalar(0x0000002a)) }
-          goto -> bb4;                     // scope 0 at $DIR/discriminant.rs:6:13: 6:64
+          goto -> bb4;                     // scope 0 at $DIR/discriminant.rs:11:13: 11:64
       }
   
       bb4: {
-          _1 = Add(move _2, const 0i32);   // scope 0 at $DIR/discriminant.rs:6:13: 6:68
+          _1 = Add(move _2, const 0i32);   // scope 0 at $DIR/discriminant.rs:11:13: 11:68
                                            // ty::Const
                                            // + ty: i32
                                            // + val: Value(Scalar(0x00000000))
                                            // mir::Constant
-                                           // + span: $DIR/discriminant.rs:6:67: 6:68
+                                           // + span: $DIR/discriminant.rs:11:67: 11:68
                                            // + literal: Const { ty: i32, val: Value(Scalar(0x00000000)) }
-          StorageDead(_2);                 // scope 0 at $DIR/discriminant.rs:6:67: 6:68
-          StorageDead(_3);                 // scope 0 at $DIR/discriminant.rs:6:68: 6:69
-          _0 = const ();                   // scope 0 at $DIR/discriminant.rs:5:11: 7:2
+          StorageDead(_2);                 // scope 0 at $DIR/discriminant.rs:11:67: 11:68
+          StorageDead(_3);                 // scope 0 at $DIR/discriminant.rs:11:68: 11:69
+          _0 = const ();                   // scope 0 at $DIR/discriminant.rs:10:11: 12:2
                                            // ty::Const
                                            // + ty: ()
                                            // + val: Value(Scalar(<ZST>))
                                            // mir::Constant
-                                           // + span: $DIR/discriminant.rs:5:11: 7:2
+                                           // + span: $DIR/discriminant.rs:10:11: 12:2
                                            // + literal: Const { ty: (), val: Value(Scalar(<ZST>)) }
-          StorageDead(_1);                 // scope 0 at $DIR/discriminant.rs:7:1: 7:2
-          return;                          // scope 0 at $DIR/discriminant.rs:7:2: 7:2
+          StorageDead(_1);                 // scope 0 at $DIR/discriminant.rs:12:1: 12:2
+          return;                          // scope 0 at $DIR/discriminant.rs:12:2: 12:2
       }
   }