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Clean up special function const checks

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Mark them as const and `#[rustc_do_not_const_check]` instead of hard-coding
them in const-eval checks.
This commit is contained in:
Gary Guo 2021-10-25 17:07:16 +01:00
parent 235d9853d8
commit cc4345a1c5
8 changed files with 53 additions and 87 deletions
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52
compiler/rustc_const_eval/src/const_eval/machine.rs
View file

@ -30,34 +30,25 @@ impl<'mir, 'tcx> InterpCx<'mir, 'tcx, CompileTimeInterpreter<'mir, 'tcx>> {
&mut self,
instance: ty::Instance<'tcx>,
args: &[OpTy<'tcx>],
is_const_fn: bool,
) -> InterpResult<'tcx, Option<ty::Instance<'tcx>>> {
// The list of functions we handle here must be in sync with
// `is_lang_special_const_fn` in `transform/check_consts/mod.rs`.
// All `#[rustc_do_not_const_check]` functions should be hooked here.
let def_id = instance.def_id();
if is_const_fn {
if Some(def_id) == self.tcx.lang_items().const_eval_select() {
// redirect to const_eval_select_ct
if let Some(const_eval_select) = self.tcx.lang_items().const_eval_select_ct() {
return Ok(Some(
ty::Instance::resolve(
*self.tcx,
ty::ParamEnv::reveal_all(),
const_eval_select,
instance.substs,
)
.unwrap()
.unwrap(),
));
}
if Some(def_id) == self.tcx.lang_items().const_eval_select() {
// redirect to const_eval_select_ct
if let Some(const_eval_select) = self.tcx.lang_items().const_eval_select_ct() {
return Ok(Some(
ty::Instance::resolve(
*self.tcx,
ty::ParamEnv::reveal_all(),
const_eval_select,
instance.substs,
)
.unwrap()
.unwrap(),
));
}
return Ok(None);
}
if Some(def_id) == self.tcx.lang_items().panic_fn()
|| Some(def_id) == self.tcx.lang_items().panic_str()
|| Some(def_id) == self.tcx.lang_items().panic_display()
} else if Some(def_id) == self.tcx.lang_items().panic_display()
|| Some(def_id) == self.tcx.lang_items().begin_panic_fn()
{
// &str or &&str
@ -286,19 +277,16 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
}
}
// Some functions we support even if they are non-const -- but avoid testing
// that for const fn!
// `const_eval_select` is a const fn because it must use const trait bounds.
if let Some(new_instance) = ecx.hook_special_const_fn(instance, args, is_const_fn)? {
// We call another const fn instead.
return Self::find_mir_or_eval_fn(ecx, new_instance, _abi, args, _ret, _unwind);
}
if !is_const_fn {
// We certainly do *not* want to actually call the fn
// though, so be sure we return here.
throw_unsup_format!("calling non-const function `{}`", instance)
}
if let Some(new_instance) = ecx.hook_special_const_fn(instance, args)? {
// We call another const fn instead.
return Self::find_mir_or_eval_fn(ecx, new_instance, _abi, args, _ret, _unwind);
}
}
// This is a const fn. Call it.
Ok(Some(ecx.load_mir(instance.def, None)?))

40
compiler/rustc_const_eval/src/transform/check_consts/check.rs
View file

@ -24,7 +24,7 @@ use std::ops::Deref;
use super::ops::{self, NonConstOp, Status};
use super::qualifs::{self, CustomEq, HasMutInterior, NeedsDrop, NeedsNonConstDrop};
use super::resolver::FlowSensitiveAnalysis;
use super::{is_lang_panic_fn, is_lang_special_const_fn, ConstCx, Qualif};
use super::{ConstCx, Qualif};
use crate::const_eval::is_unstable_const_fn;
// We are using `MaybeMutBorrowedLocals` as a proxy for whether an item may have been mutated
@ -918,31 +918,27 @@ impl Visitor<'tcx> for Checker<'mir, 'tcx> {
}
// At this point, we are calling a function, `callee`, whose `DefId` is known...
if is_lang_special_const_fn(tcx, callee) {
// `begin_panic` and `panic_display` are generic functions that accept
// types other than str. Check to enforce that only str can be used in
// const-eval.
// const-eval of the `begin_panic` fn assumes the argument is `&str`
if Some(callee) == tcx.lang_items().begin_panic_fn() {
match args[0].ty(&self.ccx.body.local_decls, tcx).kind() {
ty::Ref(_, ty, _) if ty.is_str() => (),
_ => self.check_op(ops::PanicNonStr),
}
// `begin_panic` and `panic_display` are generic functions that accept
// types other than str. Check to enforce that only str can be used in
// const-eval.
// const-eval of the `begin_panic` fn assumes the argument is `&str`
if Some(callee) == tcx.lang_items().begin_panic_fn() {
match args[0].ty(&self.ccx.body.local_decls, tcx).kind() {
ty::Ref(_, ty, _) if ty.is_str() => return,
_ => self.check_op(ops::PanicNonStr),
}
}
// const-eval of the `panic_display` fn assumes the argument is `&&str`
if Some(callee) == tcx.lang_items().panic_display() {
match args[0].ty(&self.ccx.body.local_decls, tcx).kind() {
ty::Ref(_, ty, _) if matches!(ty.kind(), ty::Ref(_, ty, _) if ty.is_str()) =>
{}
_ => self.check_op(ops::PanicNonStr),
// const-eval of the `panic_display` fn assumes the argument is `&&str`
if Some(callee) == tcx.lang_items().panic_display() {
match args[0].ty(&self.ccx.body.local_decls, tcx).kind() {
ty::Ref(_, ty, _) if matches!(ty.kind(), ty::Ref(_, ty, _) if ty.is_str()) =>
{
return;
}
}
if is_lang_panic_fn(tcx, callee) {
// run stability check on non-panic special const fns.
return;
_ => self.check_op(ops::PanicNonStr),
}
}

18
compiler/rustc_const_eval/src/transform/check_consts/mod.rs
View file

@ -72,24 +72,6 @@ impl ConstCx<'mir, 'tcx> {
}
}
/// Returns `true` if this `DefId` points to one of the official `panic` lang items.
pub fn is_lang_panic_fn(tcx: TyCtxt<'tcx>, def_id: DefId) -> bool {
Some(def_id) == tcx.lang_items().panic_fn()
|| Some(def_id) == tcx.lang_items().panic_str()
|| Some(def_id) == tcx.lang_items().panic_display()
|| Some(def_id) == tcx.lang_items().begin_panic_fn()
|| Some(def_id) == tcx.lang_items().panic_fmt()
}
/// Returns `true` if this `DefId` points to one of the lang items that will be handled differently
/// in const_eval.
pub fn is_lang_special_const_fn(tcx: TyCtxt<'tcx>, def_id: DefId) -> bool {
// We can allow calls to these functions because `hook_special_const_fn` in
// `const_eval/machine.rs` ensures the calls are handled specially.
// Keep in sync with what that function handles!
is_lang_panic_fn(tcx, def_id) || Some(def_id) == tcx.lang_items().const_eval_select()
}
pub fn rustc_allow_const_fn_unstable(
tcx: TyCtxt<'tcx>,
def_id: DefId,

6
compiler/rustc_const_eval/src/transform/promote_consts.rs
View file

@ -26,7 +26,7 @@ use rustc_index::vec::{Idx, IndexVec};
use std::cell::Cell;
use std::{cmp, iter, mem};
use crate::transform::check_consts::{is_lang_special_const_fn, qualifs, ConstCx};
use crate::transform::check_consts::{qualifs, ConstCx};
use crate::transform::MirPass;
/// A `MirPass` for promotion.
@ -656,9 +656,7 @@ impl<'tcx> Validator<'_, 'tcx> {
}
let is_const_fn = match *fn_ty.kind() {
ty::FnDef(def_id, _) => {
self.tcx.is_const_fn_raw(def_id) || is_lang_special_const_fn(self.tcx, def_id)
}
ty::FnDef(def_id, _) => self.tcx.is_const_fn_raw(def_id),
_ => false,
};
if !is_const_fn {