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|
use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
use rustc_data_structures::stack::ensure_sufficient_stack;
use rustc_data_structures::unord::UnordSet;
use rustc_hir::def_id::{DefId, LocalDefId};
use rustc_middle::mir::TerminatorKind;
use rustc_middle::ty::{self, GenericArgsRef, InstanceKind, TyCtxt, TypeVisitableExt};
use rustc_session::Limit;
use rustc_span::sym;
use tracing::{instrument, trace};
#[instrument(level = "debug", skip(tcx), ret)]
fn should_recurse<'tcx>(tcx: TyCtxt<'tcx>, callee: ty::Instance<'tcx>) -> bool {
match callee.def {
// If there is no MIR available (either because it was not in metadata or
// because it has no MIR because it's an extern function), then the inliner
// won't cause cycles on this.
InstanceKind::Item(_) => {
if !tcx.is_mir_available(callee.def_id()) {
return false;
}
}
// These have no own callable MIR.
InstanceKind::Intrinsic(_) | InstanceKind::Virtual(..) => return false,
// These have MIR and if that MIR is inlined, instantiated and then inlining is run
// again, a function item can end up getting inlined. Thus we'll be able to cause
// a cycle that way
InstanceKind::VTableShim(_)
| InstanceKind::ReifyShim(..)
| InstanceKind::FnPtrShim(..)
| InstanceKind::ClosureOnceShim { .. }
| InstanceKind::ConstructCoroutineInClosureShim { .. }
| InstanceKind::ThreadLocalShim { .. }
| InstanceKind::CloneShim(..) => {}
// This shim does not call any other functions, thus there can be no recursion.
InstanceKind::FnPtrAddrShim(..) => return false,
// FIXME: A not fully instantiated drop shim can cause ICEs if one attempts to
// have its MIR built. Likely oli-obk just screwed up the `ParamEnv`s, so this
// needs some more analysis.
InstanceKind::DropGlue(..)
| InstanceKind::FutureDropPollShim(..)
| InstanceKind::AsyncDropGlue(..)
| InstanceKind::AsyncDropGlueCtorShim(..) => {
if callee.has_param() {
return false;
}
}
}
crate::pm::should_run_pass(tcx, &crate::inline::Inline, crate::pm::Optimizations::Allowed)
|| crate::inline::ForceInline::should_run_pass_for_callee(tcx, callee.def.def_id())
}
#[instrument(
level = "debug",
skip(tcx, typing_env, seen, involved, recursion_limiter, recursion_limit),
ret
)]
fn process<'tcx>(
tcx: TyCtxt<'tcx>,
typing_env: ty::TypingEnv<'tcx>,
caller: ty::Instance<'tcx>,
target: LocalDefId,
seen: &mut FxHashMap<ty::Instance<'tcx>, bool>,
involved: &mut FxHashSet<LocalDefId>,
recursion_limiter: &mut FxHashMap<DefId, usize>,
recursion_limit: Limit,
) -> bool {
trace!(%caller);
let mut reaches_root = false;
for &(callee_def_id, args) in tcx.mir_inliner_callees(caller.def) {
let Ok(args) = caller.try_instantiate_mir_and_normalize_erasing_regions(
tcx,
typing_env,
ty::EarlyBinder::bind(args),
) else {
trace!(?caller, ?typing_env, ?args, "cannot normalize, skipping");
continue;
};
let Ok(Some(callee)) = ty::Instance::try_resolve(tcx, typing_env, callee_def_id, args)
else {
trace!(?callee_def_id, "cannot resolve, skipping");
continue;
};
// Found a path.
if callee.def_id() == target.to_def_id() {
reaches_root = true;
seen.insert(callee, true);
continue;
}
if tcx.is_constructor(callee.def_id()) {
trace!("constructors always have MIR");
// Constructor functions cannot cause a query cycle.
continue;
}
if !should_recurse(tcx, callee) {
continue;
}
let callee_reaches_root = if let Some(&c) = seen.get(&callee) {
// Even if we have seen this callee before, and thus don't need
// to recurse into it, we still need to propagate whether it reaches
// the root so that we can mark all the involved callers, in case we
// end up reaching that same recursive callee through some *other* cycle.
c
} else {
seen.insert(callee, false);
let recursion = recursion_limiter.entry(callee.def_id()).or_default();
trace!(?callee, recursion = *recursion);
let callee_reaches_root = if recursion_limit.value_within_limit(*recursion) {
*recursion += 1;
ensure_sufficient_stack(|| {
process(
tcx,
typing_env,
callee,
target,
seen,
involved,
recursion_limiter,
recursion_limit,
)
})
} else {
// Pessimistically assume that there could be recursion.
true
};
seen.insert(callee, callee_reaches_root);
callee_reaches_root
};
if callee_reaches_root {
if let Some(callee_def_id) = callee.def_id().as_local() {
// Calling `optimized_mir` of a non-local definition cannot cycle.
involved.insert(callee_def_id);
}
reaches_root = true;
}
}
reaches_root
}
#[instrument(level = "debug", skip(tcx), ret)]
pub(crate) fn mir_callgraph_cyclic<'tcx>(
tcx: TyCtxt<'tcx>,
root: LocalDefId,
) -> UnordSet<LocalDefId> {
assert!(
!tcx.is_constructor(root.to_def_id()),
"you should not call `mir_callgraph_reachable` on enum/struct constructor functions"
);
// FIXME(-Znext-solver=no): Remove this hack when trait solver overflow can return an error.
// In code like that pointed out in #128887, the type complexity we ask the solver to deal with
// grows as we recurse into the call graph. If we use the same recursion limit here and in the
// solver, the solver hits the limit first and emits a fatal error. But if we use a reduced
// limit, we will hit the limit first and give up on looking for inlining. And in any case,
// the default recursion limits are quite generous for us. If we need to recurse 64 times
// into the call graph, we're probably not going to find any useful MIR inlining.
let recursion_limit = tcx.recursion_limit() / 2;
let mut involved = FxHashSet::default();
let typing_env = ty::TypingEnv::post_analysis(tcx, root);
let root_instance =
ty::Instance::new_raw(root.to_def_id(), ty::GenericArgs::identity_for_item(tcx, root));
if !should_recurse(tcx, root_instance) {
trace!("cannot walk, skipping");
return involved.into();
}
process(
tcx,
typing_env,
root_instance,
root,
&mut FxHashMap::default(),
&mut involved,
&mut FxHashMap::default(),
recursion_limit,
);
involved.into()
}
pub(crate) fn mir_inliner_callees<'tcx>(
tcx: TyCtxt<'tcx>,
instance: ty::InstanceKind<'tcx>,
) -> &'tcx [(DefId, GenericArgsRef<'tcx>)] {
let steal;
let guard;
let body = match (instance, instance.def_id().as_local()) {
(InstanceKind::Item(_), Some(def_id)) => {
steal = tcx.mir_promoted(def_id).0;
guard = steal.borrow();
&*guard
}
// Functions from other crates and MIR shims
_ => 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, args: call_args, .. } = &terminator.kind {
let ty = func.ty(&body.local_decls, tcx);
let ty::FnDef(def_id, generic_args) = ty.kind() else {
continue;
};
let call = if tcx.is_intrinsic(*def_id, sym::const_eval_select) {
let func = &call_args[2].node;
let ty = func.ty(&body.local_decls, tcx);
let ty::FnDef(def_id, generic_args) = ty.kind() else {
continue;
};
(*def_id, *generic_args)
} else {
(*def_id, *generic_args)
};
calls.insert(call);
}
}
tcx.arena.alloc_from_iter(calls.iter().copied())
}
|
