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|
//! Lowers intrinsic calls
use crate::transform::MirPass;
use rustc_middle::mir::*;
use rustc_middle::ty::subst::SubstsRef;
use rustc_middle::ty::{self, Ty, TyCtxt};
use rustc_span::symbol::{sym, Symbol};
use rustc_target::spec::abi::Abi;
pub struct LowerIntrinsics;
impl<'tcx> MirPass<'tcx> for LowerIntrinsics {
fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
let (basic_blocks, local_decls) = body.basic_blocks_and_local_decls_mut();
for block in basic_blocks {
let terminator = block.terminator.as_mut().unwrap();
if let TerminatorKind::Call { func, args, destination, .. } = &mut terminator.kind {
let func_ty = func.ty(local_decls, tcx);
let (intrinsic_name, substs) = match resolve_rust_intrinsic(tcx, func_ty) {
None => continue,
Some(it) => it,
};
match intrinsic_name {
sym::unreachable => {
terminator.kind = TerminatorKind::Unreachable;
}
sym::forget => {
if let Some((destination, target)) = *destination {
block.statements.push(Statement {
source_info: terminator.source_info,
kind: StatementKind::Assign(box (
destination,
Rvalue::Use(Operand::Constant(box Constant {
span: terminator.source_info.span,
user_ty: None,
literal: ty::Const::zero_sized(tcx, tcx.types.unit).into(),
})),
)),
});
terminator.kind = TerminatorKind::Goto { target };
}
}
sym::copy_nonoverlapping => {
let target = destination.unwrap().1;
let mut args = args.drain(..);
block.statements.push(Statement {
source_info: terminator.source_info,
kind: StatementKind::CopyNonOverlapping(
box rustc_middle::mir::CopyNonOverlapping {
src: args.next().unwrap(),
dst: args.next().unwrap(),
count: args.next().unwrap(),
},
),
});
assert_eq!(
args.next(),
None,
"Extra argument for copy_non_overlapping intrinsic"
);
drop(args);
terminator.kind = TerminatorKind::Goto { target };
}
sym::wrapping_add | sym::wrapping_sub | sym::wrapping_mul => {
if let Some((destination, target)) = *destination {
let lhs;
let rhs;
{
let mut args = args.drain(..);
lhs = args.next().unwrap();
rhs = args.next().unwrap();
}
let bin_op = match intrinsic_name {
sym::wrapping_add => BinOp::Add,
sym::wrapping_sub => BinOp::Sub,
sym::wrapping_mul => BinOp::Mul,
_ => bug!("unexpected intrinsic"),
};
block.statements.push(Statement {
source_info: terminator.source_info,
kind: StatementKind::Assign(box (
destination,
Rvalue::BinaryOp(bin_op, box (lhs, rhs)),
)),
});
terminator.kind = TerminatorKind::Goto { target };
}
}
sym::add_with_overflow | sym::sub_with_overflow | sym::mul_with_overflow => {
// The checked binary operations are not suitable target for lowering here,
// since their semantics depend on the value of overflow-checks flag used
// during codegen. Issue #35310.
}
sym::size_of => {
if let Some((destination, target)) = *destination {
let tp_ty = substs.type_at(0);
block.statements.push(Statement {
source_info: terminator.source_info,
kind: StatementKind::Assign(box (
destination,
Rvalue::NullaryOp(NullOp::SizeOf, tp_ty),
)),
});
terminator.kind = TerminatorKind::Goto { target };
}
}
sym::discriminant_value => {
if let (Some((destination, target)), Some(arg)) =
(*destination, args[0].place())
{
let arg = tcx.mk_place_deref(arg);
block.statements.push(Statement {
source_info: terminator.source_info,
kind: StatementKind::Assign(box (
destination,
Rvalue::Discriminant(arg),
)),
});
terminator.kind = TerminatorKind::Goto { target };
}
}
_ => {}
}
}
}
}
}
fn resolve_rust_intrinsic(
tcx: TyCtxt<'tcx>,
func_ty: Ty<'tcx>,
) -> Option<(Symbol, SubstsRef<'tcx>)> {
if let ty::FnDef(def_id, substs) = *func_ty.kind() {
let fn_sig = func_ty.fn_sig(tcx);
if fn_sig.abi() == Abi::RustIntrinsic {
return Some((tcx.item_name(def_id), substs));
}
}
None
}
|
