1 //! Lowers intrinsic calls
3 use crate::transform::MirPass;
4 use rustc_middle::mir::*;
5 use rustc_middle::ty::subst::SubstsRef;
6 use rustc_middle::ty::{self, Ty, TyCtxt};
7 use rustc_span::symbol::{sym, Symbol};
8 use rustc_target::spec::abi::Abi;
10 pub struct LowerIntrinsics;
12 impl<'tcx> MirPass<'tcx> for LowerIntrinsics {
13 fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
14 let (basic_blocks, local_decls) = body.basic_blocks_and_local_decls_mut();
15 for block in basic_blocks {
16 let terminator = block.terminator.as_mut().unwrap();
17 if let TerminatorKind::Call { func, args, destination, .. } = &mut terminator.kind {
18 let func_ty = func.ty(local_decls, tcx);
19 let (intrinsic_name, substs) = match resolve_rust_intrinsic(tcx, func_ty) {
23 match intrinsic_name {
25 terminator.kind = TerminatorKind::Unreachable;
28 if let Some((destination, target)) = *destination {
29 block.statements.push(Statement {
30 source_info: terminator.source_info,
31 kind: StatementKind::Assign(box (
33 Rvalue::Use(Operand::Constant(box Constant {
34 span: terminator.source_info.span,
36 literal: ty::Const::zero_sized(tcx, tcx.types.unit),
40 terminator.kind = TerminatorKind::Goto { target };
43 sym::wrapping_add | sym::wrapping_sub | sym::wrapping_mul => {
44 if let Some((destination, target)) = *destination {
48 let mut args = args.drain(..);
49 lhs = args.next().unwrap();
50 rhs = args.next().unwrap();
52 let bin_op = match intrinsic_name {
53 sym::wrapping_add => BinOp::Add,
54 sym::wrapping_sub => BinOp::Sub,
55 sym::wrapping_mul => BinOp::Mul,
56 _ => bug!("unexpected intrinsic"),
58 block.statements.push(Statement {
59 source_info: terminator.source_info,
60 kind: StatementKind::Assign(box (
62 Rvalue::BinaryOp(bin_op, lhs, rhs),
65 terminator.kind = TerminatorKind::Goto { target };
68 sym::add_with_overflow | sym::sub_with_overflow | sym::mul_with_overflow => {
69 // The checked binary operations are not suitable target for lowering here,
70 // since their semantics depend on the value of overflow-checks flag used
71 // during codegen. Issue #35310.
74 if let Some((destination, target)) = *destination {
75 let tp_ty = substs.type_at(0);
76 block.statements.push(Statement {
77 source_info: terminator.source_info,
78 kind: StatementKind::Assign(box (
80 Rvalue::NullaryOp(NullOp::SizeOf, tp_ty),
83 terminator.kind = TerminatorKind::Goto { target };
86 sym::discriminant_value => {
87 if let (Some((destination, target)), Some(arg)) =
88 (*destination, args[0].place())
90 let arg = tcx.mk_place_deref(arg);
91 block.statements.push(Statement {
92 source_info: terminator.source_info,
93 kind: StatementKind::Assign(box (
95 Rvalue::Discriminant(arg),
98 terminator.kind = TerminatorKind::Goto { target };
108 fn resolve_rust_intrinsic(
111 ) -> Option<(Symbol, SubstsRef<'tcx>)> {
112 if let ty::FnDef(def_id, substs) = *func_ty.kind() {
113 let fn_sig = func_ty.fn_sig(tcx);
114 if fn_sig.abi() == Abi::RustIntrinsic {
115 return Some((tcx.item_name(def_id), substs));