bjoernager/rust
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Auto merge of #89247 - fee1-dead:const-eval-select, r=oli-obk

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Add `const_eval_select` intrinsic

Adds an intrinsic that calls a given function when evaluated at compiler time, but generates a call to another function when called at runtime.

See https://github.com/rust-lang/const-eval/issues/7 for previous discussion.

r? `@oli-obk.`
This commit is contained in:
bors 2021-10-14 10:06:30 +00:00
commit c34ac8747c
22 changed files with 372 additions and 39 deletions
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6
compiler/rustc_typeck/src/check/callee.rs
View file

@ -17,7 +17,7 @@ use rustc_infer::{
use rustc_middle::ty::adjustment::{
Adjust, Adjustment, AllowTwoPhase, AutoBorrow, AutoBorrowMutability,
};
use rustc_middle::ty::subst::SubstsRef;
use rustc_middle::ty::subst::{Subst, SubstsRef};
use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable};
use rustc_span::symbol::{sym, Ident};
use rustc_span::Span;
@ -317,6 +317,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
) -> Ty<'tcx> {
let (fn_sig, def_id) = match *callee_ty.kind() {
ty::FnDef(def_id, subst) => {
let fn_sig = self.tcx.fn_sig(def_id).subst(self.tcx, subst);
// Unit testing: function items annotated with
// `#[rustc_evaluate_where_clauses]` trigger special output
// to let us test the trait evaluation system.
@ -342,7 +344,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
.emit();
}
}
(callee_ty.fn_sig(self.tcx), Some(def_id))
(fn_sig, Some(def_id))
}
ty::FnPtr(sig) => (sig, None),
ref t => {

2
compiler/rustc_typeck/src/check/intrinsic.rs
View file

@ -390,6 +390,8 @@ pub fn check_intrinsic_type(tcx: TyCtxt<'_>, it: &hir::ForeignItem<'_>) {
sym::black_box => (1, vec![param(0)], param(0)),
sym::const_eval_select => (4, vec![param(0), param(1), param(2)], param(3)),
other => {
tcx.sess.emit_err(UnrecognizedIntrinsicFunction { span: it.span, name: other });
return;