Auto merge of #116564 - oli-obk:evaluated_static_in_metadata, r=RalfJung,cjgillot

Store static initializers in metadata instead of the MIR of statics.

This means that adding generic statics would be even more difficult, as we can't evaluate statics from other crates anymore, but the subtle issue I have encountered make me think that having this be an explicit problem is better.

The issue is that

```rust
static mut FOO: &mut u32 = &mut 42;
static mut BAR = unsafe { FOO };
```

gets different allocations, instead of referring to the same one. This is also true for non-static mut, but promotion makes `static FOO: &u32 = &42;` annoying to demo.

Fixes https://github.com/rust-lang/rust/issues/61345

## Why is this being done?

In order to ensure all crates see the same nested allocations (which is the last issue that needs fixing before we can stabilize [`const_mut_refs`](https://github.com/rust-lang/rust/issues/57349)), I am working on creating anonymous (from the Rust side, to LLVM it's like a regular static item) static items for the nested allocations in a static. If we evaluate the static item in a downstream crate again, we will end up duplicating its nested allocations (and in some cases, like the `match` case, even duplicate the main allocation).

1 files changed, 4 insertions, 4 deletions

diff --git a/compiler/rustc_const_eval/src/interpret/step.rs b/compiler/rustc_const_eval/src/interpret/step.rs
index 23f3d7eb67d..d4c96f4573d 100644
--- a/compiler/rustc_const_eval/src/interpret/step.rs
+++ b/compiler/rustc_const_eval/src/interpret/step.rs
@@ -151,12 +151,12 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             Use(ref operand) => {
                 // Avoid recomputing the layout
                 let op = self.eval_operand(operand, Some(dest.layout))?;
-                self.copy_op(&op, &dest, /*allow_transmute*/ false)?;
+                self.copy_op(&op, &dest)?;
             }
 
             CopyForDeref(place) => {
                 let op = self.eval_place_to_op(place, Some(dest.layout))?;
-                self.copy_op(&op, &dest, /* allow_transmute*/ false)?;
+                self.copy_op(&op, &dest)?;
             }
 
             BinaryOp(bin_op, box (ref left, ref right)) => {
@@ -316,7 +316,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             let field_index = active_field_index.unwrap_or(field_index);
             let field_dest = self.project_field(&variant_dest, field_index.as_usize())?;
             let op = self.eval_operand(operand, Some(field_dest.layout))?;
-            self.copy_op(&op, &field_dest, /*allow_transmute*/ false)?;
+            self.copy_op(&op, &field_dest)?;
         }
         self.write_discriminant(variant_index, dest)
     }
@@ -339,7 +339,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         } else {
             // Write the src to the first element.
             let first = self.project_index(&dest, 0)?;
-            self.copy_op(&src, &first, /*allow_transmute*/ false)?;
+            self.copy_op(&src, &first)?;
 
             // This is performance-sensitive code for big static/const arrays! So we
             // avoid writing each operand individually and instead just make many copies