rustc_smir/
builder.rs

1//! Logic required to produce a monomorphic stable body.
2//!
3//! We first retrieve and monomorphize the rustc body representation, i.e., we generate a
4//! monomorphic body using internal representation.
5//! After that, we convert the internal representation into a stable one.
6
7use rustc_hir::def::DefKind;
8use rustc_middle::mir;
9use rustc_middle::mir::visit::MutVisitor;
10use rustc_middle::ty::{self, TyCtxt};
11
12/// Builds a monomorphic body for a given instance.
13pub(crate) struct BodyBuilder<'tcx> {
14    tcx: TyCtxt<'tcx>,
15    instance: ty::Instance<'tcx>,
16}
17
18impl<'tcx> BodyBuilder<'tcx> {
19    pub(crate) fn new(tcx: TyCtxt<'tcx>, instance: ty::Instance<'tcx>) -> Self {
20        let instance = match instance.def {
21            // To get the fallback body of an intrinsic, we need to convert it to an item.
22            ty::InstanceKind::Intrinsic(def_id) => ty::Instance::new_raw(def_id, instance.args),
23            _ => instance,
24        };
25        BodyBuilder { tcx, instance }
26    }
27
28    /// Build a stable monomorphic body for a given instance based on the MIR body.
29    ///
30    /// All constants are also evaluated.
31    pub(crate) fn build(mut self) -> mir::Body<'tcx> {
32        let body = self.tcx.instance_mir(self.instance.def).clone();
33        let mono_body = if !self.instance.args.is_empty()
34            // Without the `generic_const_exprs` feature gate, anon consts in signatures do not
35            // get generic parameters. Which is wrong, but also not a problem without
36            // generic_const_exprs
37            || self.tcx.def_kind(self.instance.def_id()) != DefKind::AnonConst
38        {
39            let mut mono_body = self.instance.instantiate_mir_and_normalize_erasing_regions(
40                self.tcx,
41                ty::TypingEnv::fully_monomorphized(),
42                ty::EarlyBinder::bind(body),
43            );
44            self.visit_body(&mut mono_body);
45            mono_body
46        } else {
47            // Already monomorphic.
48            body
49        };
50
51        mono_body
52    }
53}
54
55impl<'tcx> MutVisitor<'tcx> for BodyBuilder<'tcx> {
56    fn visit_const_operand(
57        &mut self,
58        constant: &mut mir::ConstOperand<'tcx>,
59        location: mir::Location,
60    ) {
61        let const_ = constant.const_;
62        let val = match const_.eval(self.tcx, ty::TypingEnv::fully_monomorphized(), constant.span) {
63            Ok(v) => v,
64            Err(mir::interpret::ErrorHandled::Reported(..)) => return,
65            Err(mir::interpret::ErrorHandled::TooGeneric(..)) => {
66                unreachable!("Failed to evaluate instance constant: {:?}", const_)
67            }
68        };
69        let ty = constant.ty();
70        constant.const_ = mir::Const::Val(val, ty);
71        self.super_const_operand(constant, location);
72    }
73
74    fn tcx(&self) -> TyCtxt<'tcx> {
75        self.tcx
76    }
77}
rustc_smir/builder.rs

rustc_smir/
builder.rs
