Rollup merge of rust-lang#49216 - bjorn3:patch-1, r=estebank

Don't check interpret_interner when accessing a static to fix miri mutable statics

Mutable statics don't work in my PR to fix the standalone [miri](https://github.com/solson/miri), as init_static didn't get called when the interpret_interner already contained a entry for the static, which is always immutable.

cc rust-lang/miri#364

Author: kennytm

src/librustc_mir/interpret/const_eval.rs

@@ -339,6 +339,14 @@ impl<'mir, 'tcx> super::Machine<'mir, 'tcx> for CompileTimeEvaluator {
         ecx: &mut EvalContext<'a, 'mir, 'tcx, Self>,
         cid: GlobalId<'tcx>,
     ) -> EvalResult<'tcx, AllocId> {
+        let alloc = ecx
+                    .tcx
+                    .interpret_interner
+                    .get_cached(cid.instance.def_id());
+        // Don't evaluate when already cached to prevent cycles
+        if let Some(alloc) = alloc {
+            return Ok(alloc)
+        }
         // ensure the static is computed
         ecx.const_eval(cid)?;
         Ok(ecx

src/librustc_mir/interpret/place.rs

@@ -197,29 +197,17 @@ impl<'a, 'mir, 'tcx, M: Machine<'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M> {
             },
 
             Static(ref static_) => {
-                let alloc = self
-                    .tcx
-                    .interpret_interner
-                    .get_cached(static_.def_id);
                 let layout = self.layout_of(self.place_ty(mir_place))?;
-                if let Some(alloc) = alloc {
-                    Place::Ptr {
-                        ptr: MemoryPointer::new(alloc, 0).into(),
-                        align: layout.align,
-                        extra: PlaceExtra::None,
-                    }
-                } else {
-                    let instance = ty::Instance::mono(*self.tcx, static_.def_id);
-                    let cid = GlobalId {
-                        instance,
-                        promoted: None
-                    };
-                    let alloc = Machine::init_static(self, cid)?;
-                    Place::Ptr {
-                        ptr: MemoryPointer::new(alloc, 0).into(),
-                        align: layout.align,
-                        extra: PlaceExtra::None,
-                    }
+                let instance = ty::Instance::mono(*self.tcx, static_.def_id);
+                let cid = GlobalId {
+                    instance,
+                    promoted: None
+                };
+                let alloc = Machine::init_static(self, cid)?;
+                Place::Ptr {
+                    ptr: MemoryPointer::new(alloc, 0).into(),
+                    align: layout.align,
+                    extra: PlaceExtra::None,
                 }
             }