Auto merge of rust-lang#133474 - RalfJung:gvn-miscompile, r=<try>

Do not unify dereferences of shared borrows in GVN

Repost of rust-lang#132461, the last commit applies my suggestions.

Fixes rust-lang#130853

Author: bors

compiler/rustc_mir_transform/src/gvn.rs

@@ -638,7 +638,9 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
         let proj = match proj {
             ProjectionElem::Deref => {
                 let ty = place.ty(self.local_decls, self.tcx).ty;
-                if let Some(Mutability::Not) = ty.ref_mutability()
+                // unsound: https://github.com/rust-lang/rust/issues/130853
+                if self.tcx.sess.opts.unstable_opts.unsound_mir_opts
+                    && let Some(Mutability::Not) = ty.ref_mutability()
                     && let Some(pointee_ty) = ty.builtin_deref(true)
                     && pointee_ty.is_freeze(self.tcx, self.typing_env())
                 {

tests/coverage/closure.cov-map

@@ -140,17 +140,19 @@ Number of file 0 mappings: 6
 - Code(Counter(0)) at (prev + 2, 9) to (start + 0, 10)
 Highest counter ID seen: c1
 
-Function name: closure::main::{closure#18} (unused)
-Raw bytes (24): 0x[01, 01, 00, 04, 00, 19, 0d, 02, 1c, 00, 02, 1d, 02, 12, 00, 02, 11, 00, 12, 00, 01, 11, 01, 0e]
+Function name: closure::main::{closure#18}
+Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 19, 0d, 02, 1c, 05, 02, 1d, 02, 12, 02, 02, 11, 00, 12, 01, 01, 11, 01, 0e]
 Number of files: 1
 - file 0 => global file 1
-Number of expressions: 0
+Number of expressions: 1
+- expression 0 operands: lhs = Counter(0), rhs = Counter(1)
 Number of file 0 mappings: 4
-- Code(Zero) at (prev + 25, 13) to (start + 2, 28)
-- Code(Zero) at (prev + 2, 29) to (start + 2, 18)
-- Code(Zero) at (prev + 2, 17) to (start + 0, 18)
-- Code(Zero) at (prev + 1, 17) to (start + 1, 14)
-Highest counter ID seen: (none)
+- Code(Counter(0)) at (prev + 25, 13) to (start + 2, 28)
+- Code(Counter(1)) at (prev + 2, 29) to (start + 2, 18)
+- Code(Expression(0, Sub)) at (prev + 2, 17) to (start + 0, 18)
+    = (c0 - c1)
+- Code(Counter(0)) at (prev + 1, 17) to (start + 1, 14)
+Highest counter ID seen: c1
 
 Function name: closure::main::{closure#19}
 Raw bytes (26): 0x[01, 01, 01, 01, 05, 04, 01, 43, 0d, 02, 1c, 05, 02, 1d, 02, 12, 02, 02, 11, 00, 12, 01, 01, 11, 01, 0e]

tests/coverage/issue-84561.cov-map

@@ -14,23 +14,19 @@
 
       bb0: {
           StorageLive(_1);
--         StorageLive(_2);
+          StorageLive(_2);
 -         StorageLive(_3);
-+         nop;
 +         nop;
           _3 = const {ALLOC0: &u8};
--         _2 = copy (*_3);
-+         _2 = const 2_u8;
+          _2 = copy (*_3);
           StorageLive(_4);
           StorageLive(_5);
           _5 = const {ALLOC0: &u8};
 -         _4 = copy (*_5);
--         _1 = Add(move _2, move _4);
-+         _4 = const 2_u8;
-+         _1 = const 4_u8;
++         _4 = copy (*_3);
+          _1 = Add(move _2, move _4);
           StorageDead(_4);
--         StorageDead(_2);
-+         nop;
+          StorageDead(_2);
           StorageDead(_5);
 -         StorageDead(_3);
 +         nop;

tests/mir-opt/const_prop/read_immutable_static.main.GVN.diff

@@ -6,6 +6,7 @@ static FOO: u8 = 2;
 fn main() {
     // CHECK-LABEL: fn main(
     // CHECK: debug x => [[x:_.*]];
-    // CHECK: [[x]] = const 4_u8;
+    // Disabled due to <https://github.com/rust-lang/rust/issues/130853>
+    // COM: CHECK: [[x]] = const 4_u8;
     let x = FOO + FOO;
 }

tests/mir-opt/const_prop/read_immutable_static.rs

@@ -16,8 +16,7 @@
           StorageLive(_2);
           _4 = const main::promoted[0];
           _2 = &(*_4);
--         _1 = copy (*_2);
-+         _1 = const 4_i32;
+          _1 = copy (*_2);
           StorageDead(_2);
           _0 = const ();
           StorageDead(_1);

tests/mir-opt/const_prop/ref_deref.main.GVN.diff

@@ -16,8 +16,7 @@
           StorageLive(_2);
           _4 = const main::promoted[0];
           _2 = &((*_4).1: i32);
--         _1 = copy (*_2);
-+         _1 = const 5_i32;
+          _1 = copy (*_2);
           StorageDead(_2);
           _0 = const ();
           StorageDead(_1);

tests/mir-opt/const_prop/ref_deref_project.main.GVN.diff

@@ -5,6 +5,7 @@
 fn main() {
     // CHECK-LABEL: fn main(
     // CHECK: debug a => [[a:_.*]];
-    // CHECK: [[a]] = const 5_i32;
+    // Disabled due to <https://github.com/rust-lang/rust/issues/130853>
+    // COM: CHECK: [[a]] = const 5_i32;
     let a = *(&(4, 5).1);
 }

tests/mir-opt/const_prop/ref_deref_project.rs

@@ -30,17 +30,16 @@
           StorageDead(_3);
           StorageLive(_6);
           _6 = const 1_usize;
--         _7 = Len((*_2));
+          _7 = Len((*_2));
 -         _8 = Lt(copy _6, copy _7);
 -         assert(move _8, "index out of bounds: the length is {} but the index is {}", move _7, copy _6) -> [success: bb1, unwind unreachable];
-+         _7 = const 3_usize;
-+         _8 = const true;
-+         assert(const true, "index out of bounds: the length is {} but the index is {}", const 3_usize, const 1_usize) -> [success: bb1, unwind unreachable];
++         _8 = Lt(const 1_usize, copy _7);
++         assert(move _8, "index out of bounds: the length is {} but the index is {}", move _7, const 1_usize) -> [success: bb1, unwind unreachable];
       }
 
       bb1: {
 -         _1 = copy (*_2)[_6];
-+         _1 = const 2_u32;
++         _1 = copy (*_2)[1 of 2];
           StorageDead(_6);
           StorageDead(_4);
           StorageDead(_2);

tests/mir-opt/const_prop/slice_len.main.GVN.32bit.panic-abort.diff

@@ -30,17 +30,16 @@
           StorageDead(_3);
           StorageLive(_6);
           _6 = const 1_usize;
--         _7 = Len((*_2));
+          _7 = Len((*_2));
 -         _8 = Lt(copy _6, copy _7);
 -         assert(move _8, "index out of bounds: the length is {} but the index is {}", move _7, copy _6) -> [success: bb1, unwind continue];
-+         _7 = const 3_usize;
-+         _8 = const true;
-+         assert(const true, "index out of bounds: the length is {} but the index is {}", const 3_usize, const 1_usize) -> [success: bb1, unwind continue];
++         _8 = Lt(const 1_usize, copy _7);
++         assert(move _8, "index out of bounds: the length is {} but the index is {}", move _7, const 1_usize) -> [success: bb1, unwind continue];
       }
 
       bb1: {
 -         _1 = copy (*_2)[_6];
-+         _1 = const 2_u32;
++         _1 = copy (*_2)[1 of 2];
           StorageDead(_6);
           StorageDead(_4);
           StorageDead(_2);