Auto merge of #123781 - RalfJung:miri-fn-identity, r=oli-obk

Miri function identity hack: account for possible inlining

Having a non-lifetime generic is not the only reason a function can be duplicated. Another possibility is that the function may be eligible for cross-crate inlining. So also take into account the inlining attribute in this Miri hack for function pointer identity.

That said, `cross_crate_inlinable` will still sometimes return true even for `inline(never)` functions:
- when they are `DefKind::Ctor(..) | DefKind::Closure` -- I assume those cannot be `InlineAttr::Never` anyway?
- when `cross_crate_inline_threshold == InliningThreshold::Always`

so maybe this is still not quite the right criterion to use for function pointer identity.

compiler/rustc_passes/src/reachable.rs

@@ -310,7 +310,7 @@ impl<'tcx> ReachableContext<'tcx> {
                 GlobalAlloc::Static(def_id) => {
                     self.propagate_item(Res::Def(self.tcx.def_kind(def_id), def_id))
                 }
-                GlobalAlloc::Function(instance) => {
+                GlobalAlloc::Function { instance, .. } => {
                     // Manually visit to actually see the instance's `DefId`. Type visitors won't see it
                     self.propagate_item(Res::Def(
                         self.tcx.def_kind(instance.def_id()),