remove spin_loop hint intrinsics we no longer need

src/shims/aarch64.rs

@@ -19,20 +19,6 @@ pub(super) trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
  // Prefix should have already been checked.
  let unprefixed_name = link_name.as_str().strip_prefix("llvm.aarch64.").unwrap();
  match unprefixed_name {
- "isb" => {
- let [arg] = this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
- let arg = this.read_scalar(arg)?.to_i32()?;
- match arg {
- // SY ("full system scope")
- 15 => {
- this.yield_active_thread();
- }
- _ => {
- throw_unsup_format!("unsupported llvm.aarch64.isb argument {}", arg);
- }
- }
- }
-
  // Used to implement the vpmaxq_u8 function.
  // Computes the maximum of adjacent pairs; the first half of the output is produced from the
  // `left` input, the second half of the output from the `right` input.

src/shims/foreign_items.rs

@@ -813,22 +813,6 @@ trait EvalContextExtPriv<'tcx>: crate::MiriInterpCxExt<'tcx> {
  this, link_name, abi, args, dest,
  );
  }
- // FIXME: Move this to an `arm` submodule.
- "llvm.arm.hint" if this.tcx.sess.target.arch == Arch::Arm => {
- let [arg] = this.check_shim_sig_lenient(abi, CanonAbi::C, link_name, args)?;
- let arg = this.read_scalar(arg)?.to_i32()?;
- // Note that different arguments might have different target feature requirements.
- match arg {
- // YIELD
- 1 => {
- this.expect_target_feature_for_intrinsic(link_name, "v6")?;
- this.yield_active_thread();
- }
- _ => {
- throw_unsup_format!("unsupported llvm.arm.hint argument {}", arg);
- }
- }
- }
 
  // Fallback to shims in submodules.
  _ => {