Rollup merge of #73613 - oli-obk:const_prop_miscompile, r=wesleywiser

The const propagator cannot trace references.

Thus we avoid propagation of a local the moment we encounter references to it.

fixes #73609

cc @RalfJung

r? @wesleywiser

7 files changed, 166 insertions, 40 deletions

diff --git a/src/test/mir-opt/const_prop/bad_op_unsafe_oob_for_slices/32bit/rustc.main.ConstProp.diff b/src/test/mir-opt/const_prop/bad_op_unsafe_oob_for_slices/32bit/rustc.main.ConstProp.diff
index 7071f31dbf1..7ceec94d81e 100644
--- a/src/test/mir-opt/const_prop/bad_op_unsafe_oob_for_slices/32bit/rustc.main.ConstProp.diff
+++ b/src/test/mir-opt/const_prop/bad_op_unsafe_oob_for_slices/32bit/rustc.main.ConstProp.diff
@@ -46,22 +46,8 @@
                                            // mir::Constant
                                            // + span: $DIR/bad_op_unsafe_oob_for_slices.rs:7:23: 7:24
                                            // + literal: Const { ty: usize, val: Value(Scalar(0x00000003)) }
--         _7 = Len((*_1));                 // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
--         _8 = Lt(_6, _7);                 // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
-+         _7 = const 3usize;               // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
-+                                          // ty::Const
-+                                          // + ty: usize
-+                                          // + val: Value(Scalar(0x00000003))
-+                                          // mir::Constant
-+                                          // + span: $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
-+                                          // + literal: Const { ty: usize, val: Value(Scalar(0x00000003)) }
-+         _8 = const false;                // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
-+                                          // ty::Const
-+                                          // + ty: bool
-+                                          // + val: Value(Scalar(0x00))
-+                                          // mir::Constant
-+                                          // + span: $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
-+                                          // + literal: Const { ty: bool, val: Value(Scalar(0x00)) }
+          _7 = Len((*_1));                 // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
+          _8 = Lt(_6, _7);                 // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
           assert(move _8, "index out of bounds: the len is {} but the index is {}", move _7, _6) -> bb1; // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
       }
   
diff --git a/src/test/mir-opt/const_prop/bad_op_unsafe_oob_for_slices/64bit/rustc.main.ConstProp.diff b/src/test/mir-opt/const_prop/bad_op_unsafe_oob_for_slices/64bit/rustc.main.ConstProp.diff
index 15995ab0700..483a6f232ef 100644
--- a/src/test/mir-opt/const_prop/bad_op_unsafe_oob_for_slices/64bit/rustc.main.ConstProp.diff
+++ b/src/test/mir-opt/const_prop/bad_op_unsafe_oob_for_slices/64bit/rustc.main.ConstProp.diff
@@ -46,22 +46,8 @@
                                            // mir::Constant
                                            // + span: $DIR/bad_op_unsafe_oob_for_slices.rs:7:23: 7:24
                                            // + literal: Const { ty: usize, val: Value(Scalar(0x0000000000000003)) }
--         _7 = Len((*_1));                 // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
--         _8 = Lt(_6, _7);                 // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
-+         _7 = const 3usize;               // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
-+                                          // ty::Const
-+                                          // + ty: usize
-+                                          // + val: Value(Scalar(0x0000000000000003))
-+                                          // mir::Constant
-+                                          // + span: $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
-+                                          // + literal: Const { ty: usize, val: Value(Scalar(0x0000000000000003)) }
-+         _8 = const false;                // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
-+                                          // ty::Const
-+                                          // + ty: bool
-+                                          // + val: Value(Scalar(0x00))
-+                                          // mir::Constant
-+                                          // + span: $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
-+                                          // + literal: Const { ty: bool, val: Value(Scalar(0x00)) }
+          _7 = Len((*_1));                 // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
+          _8 = Lt(_6, _7);                 // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
           assert(move _8, "index out of bounds: the len is {} but the index is {}", move _7, _6) -> bb1; // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
       }
   
diff --git a/src/test/mir-opt/const_prop_miscompile.rs b/src/test/mir-opt/const_prop_miscompile.rs
new file mode 100644
index 00000000000..043b22870f4
--- /dev/null
+++ b/src/test/mir-opt/const_prop_miscompile.rs
@@ -0,0 +1,22 @@
+#![feature(raw_ref_op)]
+
+// EMIT_MIR rustc.foo.ConstProp.diff
+fn foo() {
+    let mut u = (1,);
+    *&mut u.0 = 5;
+    let y = { u.0 } == 5;
+}
+
+// EMIT_MIR rustc.bar.ConstProp.diff
+fn bar() {
+    let mut v = (1,);
+    unsafe {
+        *&raw mut v.0 = 5;
+    }
+    let y = { v.0 } == 5;
+}
+
+fn main() {
+    foo();
+    bar();
+}
diff --git a/src/test/mir-opt/const_prop_miscompile/rustc.bar.ConstProp.diff b/src/test/mir-opt/const_prop_miscompile/rustc.bar.ConstProp.diff
new file mode 100644
index 00000000000..c87f67bf9f5
--- /dev/null
+++ b/src/test/mir-opt/const_prop_miscompile/rustc.bar.ConstProp.diff
@@ -0,0 +1,75 @@
+- // MIR for `bar` before ConstProp
++ // MIR for `bar` after ConstProp
+  
+  fn bar() -> () {
+      let mut _0: ();                      // return place in scope 0 at $DIR/const_prop_miscompile.rs:11:10: 11:10
+      let mut _1: (i32,);                  // in scope 0 at $DIR/const_prop_miscompile.rs:12:9: 12:14
+      let _2: ();                          // in scope 0 at $DIR/const_prop_miscompile.rs:13:5: 15:6
+      let mut _3: *mut i32;                // in scope 0 at $DIR/const_prop_miscompile.rs:14:10: 14:22
+      let mut _5: i32;                     // in scope 0 at $DIR/const_prop_miscompile.rs:16:13: 16:20
+      scope 1 {
+          debug v => _1;                   // in scope 1 at $DIR/const_prop_miscompile.rs:12:9: 12:14
+          let _4: bool;                    // in scope 1 at $DIR/const_prop_miscompile.rs:16:9: 16:10
+          scope 2 {
+          }
+          scope 3 {
+              debug y => _4;               // in scope 3 at $DIR/const_prop_miscompile.rs:16:9: 16:10
+          }
+      }
+  
+      bb0: {
+          StorageLive(_1);                 // scope 0 at $DIR/const_prop_miscompile.rs:12:9: 12:14
+-         _1 = (const 1i32,);              // scope 0 at $DIR/const_prop_miscompile.rs:12:17: 12:21
++         _1 = const (1i32,);              // scope 0 at $DIR/const_prop_miscompile.rs:12:17: 12:21
+                                           // ty::Const
+-                                          // + ty: i32
++                                          // + ty: (i32,)
+                                           // + val: Value(Scalar(0x00000001))
+                                           // mir::Constant
+-                                          // + span: $DIR/const_prop_miscompile.rs:12:18: 12:19
+-                                          // + literal: Const { ty: i32, val: Value(Scalar(0x00000001)) }
++                                          // + span: $DIR/const_prop_miscompile.rs:12:17: 12:21
++                                          // + literal: Const { ty: (i32,), val: Value(Scalar(0x00000001)) }
+          StorageLive(_2);                 // scope 1 at $DIR/const_prop_miscompile.rs:13:5: 15:6
+          StorageLive(_3);                 // scope 2 at $DIR/const_prop_miscompile.rs:14:10: 14:22
+          _3 = &raw mut (_1.0: i32);       // scope 2 at $DIR/const_prop_miscompile.rs:14:10: 14:22
+          (*_3) = const 5i32;              // scope 2 at $DIR/const_prop_miscompile.rs:14:9: 14:26
+                                           // ty::Const
+                                           // + ty: i32
+                                           // + val: Value(Scalar(0x00000005))
+                                           // mir::Constant
+                                           // + span: $DIR/const_prop_miscompile.rs:14:25: 14:26
+                                           // + literal: Const { ty: i32, val: Value(Scalar(0x00000005)) }
+          StorageDead(_3);                 // scope 2 at $DIR/const_prop_miscompile.rs:14:26: 14:27
+          _2 = const ();                   // scope 2 at $DIR/const_prop_miscompile.rs:13:5: 15:6
+                                           // ty::Const
+                                           // + ty: ()
+                                           // + val: Value(Scalar(<ZST>))
+                                           // mir::Constant
+                                           // + span: $DIR/const_prop_miscompile.rs:13:5: 15:6
+                                           // + literal: Const { ty: (), val: Value(Scalar(<ZST>)) }
+          StorageDead(_2);                 // scope 1 at $DIR/const_prop_miscompile.rs:15:5: 15:6
+          StorageLive(_4);                 // scope 1 at $DIR/const_prop_miscompile.rs:16:9: 16:10
+          StorageLive(_5);                 // scope 1 at $DIR/const_prop_miscompile.rs:16:13: 16:20
+          _5 = (_1.0: i32);                // scope 1 at $DIR/const_prop_miscompile.rs:16:15: 16:18
+          _4 = Eq(move _5, const 5i32);    // scope 1 at $DIR/const_prop_miscompile.rs:16:13: 16:25
+                                           // ty::Const
+                                           // + ty: i32
+                                           // + val: Value(Scalar(0x00000005))
+                                           // mir::Constant
+                                           // + span: $DIR/const_prop_miscompile.rs:16:24: 16:25
+                                           // + literal: Const { ty: i32, val: Value(Scalar(0x00000005)) }
+          StorageDead(_5);                 // scope 1 at $DIR/const_prop_miscompile.rs:16:24: 16:25
+          _0 = const ();                   // scope 0 at $DIR/const_prop_miscompile.rs:11:10: 17:2
+                                           // ty::Const
+                                           // + ty: ()
+                                           // + val: Value(Scalar(<ZST>))
+                                           // mir::Constant
+                                           // + span: $DIR/const_prop_miscompile.rs:11:10: 17:2
+                                           // + literal: Const { ty: (), val: Value(Scalar(<ZST>)) }
+          StorageDead(_4);                 // scope 1 at $DIR/const_prop_miscompile.rs:17:1: 17:2
+          StorageDead(_1);                 // scope 0 at $DIR/const_prop_miscompile.rs:17:1: 17:2
+          return;                          // scope 0 at $DIR/const_prop_miscompile.rs:17:2: 17:2
+      }
+  }
+  
diff --git a/src/test/mir-opt/const_prop_miscompile/rustc.foo.ConstProp.diff b/src/test/mir-opt/const_prop_miscompile/rustc.foo.ConstProp.diff
new file mode 100644
index 00000000000..8a6850d2fe3
--- /dev/null
+++ b/src/test/mir-opt/const_prop_miscompile/rustc.foo.ConstProp.diff
@@ -0,0 +1,63 @@
+- // MIR for `foo` before ConstProp
++ // MIR for `foo` after ConstProp
+  
+  fn foo() -> () {
+      let mut _0: ();                      // return place in scope 0 at $DIR/const_prop_miscompile.rs:4:10: 4:10
+      let mut _1: (i32,);                  // in scope 0 at $DIR/const_prop_miscompile.rs:5:9: 5:14
+      let mut _2: &mut i32;                // in scope 0 at $DIR/const_prop_miscompile.rs:6:6: 6:14
+      let mut _4: i32;                     // in scope 0 at $DIR/const_prop_miscompile.rs:7:13: 7:20
+      scope 1 {
+          debug u => _1;                   // in scope 1 at $DIR/const_prop_miscompile.rs:5:9: 5:14
+          let _3: bool;                    // in scope 1 at $DIR/const_prop_miscompile.rs:7:9: 7:10
+          scope 2 {
+              debug y => _3;               // in scope 2 at $DIR/const_prop_miscompile.rs:7:9: 7:10
+          }
+      }
+  
+      bb0: {
+          StorageLive(_1);                 // scope 0 at $DIR/const_prop_miscompile.rs:5:9: 5:14
+-         _1 = (const 1i32,);              // scope 0 at $DIR/const_prop_miscompile.rs:5:17: 5:21
++         _1 = const (1i32,);              // scope 0 at $DIR/const_prop_miscompile.rs:5:17: 5:21
+                                           // ty::Const
+-                                          // + ty: i32
++                                          // + ty: (i32,)
+                                           // + val: Value(Scalar(0x00000001))
+                                           // mir::Constant
+-                                          // + span: $DIR/const_prop_miscompile.rs:5:18: 5:19
+-                                          // + literal: Const { ty: i32, val: Value(Scalar(0x00000001)) }
++                                          // + span: $DIR/const_prop_miscompile.rs:5:17: 5:21
++                                          // + literal: Const { ty: (i32,), val: Value(Scalar(0x00000001)) }
+          StorageLive(_2);                 // scope 1 at $DIR/const_prop_miscompile.rs:6:6: 6:14
+          _2 = &mut (_1.0: i32);           // scope 1 at $DIR/const_prop_miscompile.rs:6:6: 6:14
+          (*_2) = const 5i32;              // scope 1 at $DIR/const_prop_miscompile.rs:6:5: 6:18
+                                           // ty::Const
+                                           // + ty: i32
+                                           // + val: Value(Scalar(0x00000005))
+                                           // mir::Constant
+                                           // + span: $DIR/const_prop_miscompile.rs:6:17: 6:18
+                                           // + literal: Const { ty: i32, val: Value(Scalar(0x00000005)) }
+          StorageDead(_2);                 // scope 1 at $DIR/const_prop_miscompile.rs:6:18: 6:19
+          StorageLive(_3);                 // scope 1 at $DIR/const_prop_miscompile.rs:7:9: 7:10
+          StorageLive(_4);                 // scope 1 at $DIR/const_prop_miscompile.rs:7:13: 7:20
+          _4 = (_1.0: i32);                // scope 1 at $DIR/const_prop_miscompile.rs:7:15: 7:18
+          _3 = Eq(move _4, const 5i32);    // scope 1 at $DIR/const_prop_miscompile.rs:7:13: 7:25
+                                           // ty::Const
+                                           // + ty: i32
+                                           // + val: Value(Scalar(0x00000005))
+                                           // mir::Constant
+                                           // + span: $DIR/const_prop_miscompile.rs:7:24: 7:25
+                                           // + literal: Const { ty: i32, val: Value(Scalar(0x00000005)) }
+          StorageDead(_4);                 // scope 1 at $DIR/const_prop_miscompile.rs:7:24: 7:25
+          _0 = const ();                   // scope 0 at $DIR/const_prop_miscompile.rs:4:10: 8:2
+                                           // ty::Const
+                                           // + ty: ()
+                                           // + val: Value(Scalar(<ZST>))
+                                           // mir::Constant
+                                           // + span: $DIR/const_prop_miscompile.rs:4:10: 8:2
+                                           // + literal: Const { ty: (), val: Value(Scalar(<ZST>)) }
+          StorageDead(_3);                 // scope 1 at $DIR/const_prop_miscompile.rs:8:1: 8:2
+          StorageDead(_1);                 // scope 0 at $DIR/const_prop_miscompile.rs:8:1: 8:2
+          return;                          // scope 0 at $DIR/const_prop_miscompile.rs:8:2: 8:2
+      }
+  }
+  
diff --git a/src/test/ui/mir/mir_detects_invalid_ops.rs b/src/test/ui/mir/mir_detects_invalid_ops.rs
index 0940dbe6a5e..136c03cd9f1 100644
--- a/src/test/ui/mir/mir_detects_invalid_ops.rs
+++ b/src/test/ui/mir/mir_detects_invalid_ops.rs
@@ -19,6 +19,6 @@ fn mod_by_zero() {
 fn oob_error_for_slices() {
     let a: *const [_] = &[1, 2, 3];
     unsafe {
-        let _b = (*a)[3]; //~ ERROR this operation will panic at runtime [unconditional_panic]
+        let _b = (*a)[3];
     }
 }
diff --git a/src/test/ui/mir/mir_detects_invalid_ops.stderr b/src/test/ui/mir/mir_detects_invalid_ops.stderr
index 41f03789f23..0b6dbfd7c3d 100644
--- a/src/test/ui/mir/mir_detects_invalid_ops.stderr
+++ b/src/test/ui/mir/mir_detects_invalid_ops.stderr
@@ -12,11 +12,5 @@ error: this operation will panic at runtime
 LL |     let _z = 1 % y;
    |              ^^^^^ attempt to calculate the remainder with a divisor of zero
 
-error: this operation will panic at runtime
-  --> $DIR/mir_detects_invalid_ops.rs:22:18
-   |
-LL |         let _b = (*a)[3];
-   |                  ^^^^^^^ index out of bounds: the len is 3 but the index is 3
-
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors