bjoernager/rust
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Auto merge of #122505 - oli-obk:visit_nested_body2, r=tmiasko

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Don't walk the bodies of free constants for reachability.

follow-up to #122371

cc #119214

This avoids codegening items (e.g. functions) that are only used during const eval, but do not reach their final constant value (e.g. via function pointers).

r? `@tmiasko`
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bors 2024-06-06 01:33:14 +00:00
commit d0ccb5413e
3 changed files with 55 additions and 8 deletions
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26
compiler/rustc_middle/src/mir/interpret/queries.rs
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@ -1,4 +1,6 @@
use super::{ErrorHandled, EvalToConstValueResult, EvalToValTreeResult, GlobalId};
use super::{
ErrorHandled, EvalToAllocationRawResult, EvalToConstValueResult, EvalToValTreeResult, GlobalId,
};
use crate::mir;
use crate::query::TyCtxtEnsure;
@ -13,7 +15,7 @@ use tracing::{debug, instrument};
impl<'tcx> TyCtxt<'tcx> {
/// Evaluates a constant without providing any generic parameters. This is useful to evaluate consts
/// that can't take any generic arguments like statics, const items or enum discriminants. If a
/// that can't take any generic arguments like const items or enum discriminants. If a
/// generic parameter is used within the constant `ErrorHandled::ToGeneric` will be returned.
#[instrument(skip(self), level = "debug")]
pub fn const_eval_poly(self, def_id: DefId) -> EvalToConstValueResult<'tcx> {
@ -27,6 +29,24 @@ impl<'tcx> TyCtxt<'tcx> {
let param_env = self.param_env(def_id).with_reveal_all_normalized(self);
self.const_eval_global_id(param_env, cid, DUMMY_SP)
}
/// Evaluates a constant without providing any generic parameters. This is useful to evaluate consts
/// that can't take any generic arguments like const items or enum discriminants. If a
/// generic parameter is used within the constant `ErrorHandled::ToGeneric` will be returned.
#[instrument(skip(self), level = "debug")]
pub fn const_eval_poly_to_alloc(self, def_id: DefId) -> EvalToAllocationRawResult<'tcx> {
// In some situations def_id will have generic parameters within scope, but they aren't allowed
// to be used. So we can't use `Instance::mono`, instead we feed unresolved generic parameters
// into `const_eval` which will return `ErrorHandled::ToGeneric` if any of them are
// encountered.
let args = GenericArgs::identity_for_item(self, def_id);
let instance = ty::Instance::new(def_id, args);
let cid = GlobalId { instance, promoted: None };
let param_env = self.param_env(def_id).with_reveal_all_normalized(self);
let inputs = self.erase_regions(param_env.and(cid));
self.eval_to_allocation_raw(inputs)
}
/// Resolves and evaluates a constant.
///
/// The constant can be located on a trait like `<A as B>::C`, in which case the given
@ -177,7 +197,7 @@ impl<'tcx> TyCtxt<'tcx> {
impl<'tcx> TyCtxtEnsure<'tcx> {
/// Evaluates a constant without providing any generic parameters. This is useful to evaluate consts
/// that can't take any generic arguments like statics, const items or enum discriminants. If a
/// that can't take any generic arguments like const items or enum discriminants. If a
/// generic parameter is used within the constant `ErrorHandled::ToGeneric` will be returned.
#[instrument(skip(self), level = "debug")]
pub fn const_eval_poly(self, def_id: DefId) {