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use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
use rustc_data_structures::stack::ensure_sufficient_stack;
use rustc_hir::def_id::{DefId, LocalDefId};
use rustc_middle::mir::TerminatorKind;
use rustc_middle::ty::TypeVisitable;
use rustc_middle::ty::{self, subst::SubstsRef, InstanceDef, TyCtxt};
use rustc_session::Limit;
#[instrument(level = "debug", skip(tcx, root, target))]
pub(crate) fn mir_callgraph_reachable<'tcx>(
tcx: TyCtxt<'tcx>,
(root, target): (ty::Instance<'tcx>, LocalDefId),
) -> bool {
trace!(%root, target = %tcx.def_path_str(target.to_def_id()));
let param_env = tcx.param_env_reveal_all_normalized(target);
assert_ne!(
root.def_id().expect_local(),
target,
"you should not call `mir_callgraph_reachable` on immediate self recursion"
);
assert!(
matches!(root.def, InstanceDef::Item(_)),
"you should not call `mir_callgraph_reachable` on shims"
);
assert!(
!tcx.is_constructor(root.def_id()),
"you should not call `mir_callgraph_reachable` on enum/struct constructor functions"
);
#[instrument(
level = "debug",
skip(tcx, param_env, target, stack, seen, recursion_limiter, caller, recursion_limit)
)]
fn process<'tcx>(
tcx: TyCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
caller: ty::Instance<'tcx>,
target: LocalDefId,
stack: &mut Vec<ty::Instance<'tcx>>,
seen: &mut FxHashSet<ty::Instance<'tcx>>,
recursion_limiter: &mut FxHashMap<DefId, usize>,
recursion_limit: Limit,
) -> bool {
trace!(%caller);
for &(callee, substs) in tcx.mir_inliner_callees(caller.def) {
let Ok(substs) = caller.try_subst_mir_and_normalize_erasing_regions(tcx, param_env, substs) else {
trace!(?caller, ?param_env, ?substs, "cannot normalize, skipping");
continue;
};
let Ok(Some(callee)) = ty::Instance::resolve(tcx, param_env, callee, substs) else {
trace!(?callee, "cannot resolve, skipping");
continue;
};
if callee.def_id() == target.to_def_id() {
return true;
}
if tcx.is_constructor(callee.def_id()) {
trace!("constructors always have MIR");
continue;
}
match callee.def {
InstanceDef::Item(_) => {
if !tcx.is_mir_available(callee.def_id()) {
trace!(?callee, "no mir available, skipping");
continue;
}
}
InstanceDef::Intrinsic(_) | InstanceDef::Virtual(..) => continue,
InstanceDef::VTableShim(_)
| InstanceDef::ReifyShim(_)
| InstanceDef::FnPtrShim(..)
| InstanceDef::ClosureOnceShim { .. }
| InstanceDef::CloneShim(..) => {}
InstanceDef::DropGlue(..) => {
if callee.needs_subst() {
continue;
}
}
}
if seen.insert(callee) {
let recursion = recursion_limiter.entry(callee.def_id()).or_default();
trace!(?callee, recursion = *recursion);
if recursion_limit.value_within_limit(*recursion) {
*recursion += 1;
stack.push(callee);
let found_recursion = ensure_sufficient_stack(|| {
process(
tcx,
param_env,
callee,
target,
stack,
seen,
recursion_limiter,
recursion_limit,
)
});
if found_recursion {
return true;
}
stack.pop();
} else {
return true;
}
}
}
false
}
process(
tcx,
param_env,
root,
target,
&mut Vec::new(),
&mut FxHashSet::default(),
&mut FxHashMap::default(),
tcx.recursion_limit(),
)
}
pub(crate) fn mir_inliner_callees<'tcx>(
tcx: TyCtxt<'tcx>,
instance: ty::InstanceDef<'tcx>,
) -> &'tcx [(DefId, SubstsRef<'tcx>)] {
let steal;
let guard;
let body = match (instance, instance.def_id().as_local()) {
(InstanceDef::Item(_), Some(def_id)) => {
let def = ty::WithOptConstParam::unknown(def_id);
steal = tcx.mir_promoted(def).0;
guard = steal.borrow();
&*guard
}
_ => tcx.instance_mir(instance),
};
let mut calls = FxIndexSet::default();
for bb_data in body.basic_blocks.iter() {
let terminator = bb_data.terminator();
if let TerminatorKind::Call { func, .. } = &terminator.kind {
let ty = func.ty(&body.local_decls, tcx);
let call = match ty.kind() {
ty::FnDef(def_id, substs) => (*def_id, *substs),
_ => continue,
};
calls.insert(call);
}
}
tcx.arena.alloc_from_iter(calls.iter().copied())
}