Auto merge of #95562 - lcnr:attr-no-encode, r=davidtwco

don't encode only locally used attrs

Part of rust-lang/compiler-team#505.

We now filter builtin attributes before encoding them in the crate metadata in case they should only be used in the local crate. To prevent accidental misuse `get_attrs` now requires the caller to state which attribute they are interested in. For places where that isn't trivially possible, I've added a method `fn get_attrs_unchecked` which I intend to remove in a followup PR.

After this pull request landed, we can then slowly move all attributes to only be used in the local crate while being certain that we don't accidentally try to access them from extern crates.

cc #94963 (comment)

Author: bors

compiler/rustc_attr/src/builtin.rs

@@ -6,6 +6,7 @@ use rustc_hir::def_id::DefId;
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use rustc_middle::ty::{self, TyCtxt};
 use rustc_session::config::OptLevel;
+use rustc_span::symbol::sym;
 use rustc_target::spec::abi::Abi;
 use rustc_target::spec::{FramePointer, SanitizerSet, StackProbeType, StackProtector};
 use smallvec::SmallVec;
@@ -329,9 +330,7 @@ pub fn from_fn_attrs<'ll, 'tcx>(
     ) {
         let span = cx
             .tcx
-            .get_attrs(instance.def_id())
-            .iter()
-            .find(|a| a.has_name(rustc_span::sym::target_feature))
+            .get_attr(instance.def_id(), sym::target_feature)
             .map_or_else(|| cx.tcx.def_span(instance.def_id()), |a| a.span);
         let msg = format!(
             "the target features {} must all be either enabled or disabled together",