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use crate::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_span::Span;
pub struct LowerIntrinsics;
impl<'tcx> MirPass<'tcx> for LowerIntrinsics {
fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
let local_decls = &body.local_decls;
for block in body.basic_blocks.as_mut() {
let terminator = block.terminator.as_mut().unwrap();
if let TerminatorKind::Call { func, args, destination, target, .. } =
&mut terminator.kind
{
let func_ty = func.ty(local_decls, tcx);
let Some((intrinsic_name, substs)) = resolve_rust_intrinsic(tcx, func_ty) else {
continue;
};
match intrinsic_name {
sym::unreachable => {
terminator.kind = TerminatorKind::Unreachable;
}
sym::forget => {
if let Some(target) = *target {
block.statements.push(Statement {
source_info: terminator.source_info,
kind: StatementKind::Assign(Box::new((
*destination,
Rvalue::Use(Operand::Constant(Box::new(Constant {
span: terminator.source_info.span,
user_ty: None,
literal: ConstantKind::zero_sized(tcx.types.unit),
}))),
))),
});
terminator.kind = TerminatorKind::Goto { target };
}
}
sym::copy_nonoverlapping => {
let target = target.unwrap();
let mut args = args.drain(..);
block.statements.push(Statement {
source_info: terminator.source_info,
kind: StatementKind::Intrinsic(Box::new(
NonDivergingIntrinsic::CopyNonOverlapping(
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::assume => {
let target = target.unwrap();
let mut args = args.drain(..);
block.statements.push(Statement {
source_info: terminator.source_info,
kind: StatementKind::Intrinsic(Box::new(
NonDivergingIntrinsic::Assume(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(target) = *target {
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::new((
*destination,
Rvalue::BinaryOp(bin_op, Box::new((lhs, rhs))),
))),
});
terminator.kind = TerminatorKind::Goto { target };
}
}
sym::add_with_overflow | sym::sub_with_overflow | sym::mul_with_overflow => {
if let Some(target) = *target {
let lhs;
let rhs;
{
let mut args = args.drain(..);
lhs = args.next().unwrap();
rhs = args.next().unwrap();
}
let bin_op = match intrinsic_name {
sym::add_with_overflow => BinOp::Add,
sym::sub_with_overflow => BinOp::Sub,
sym::mul_with_overflow => BinOp::Mul,
_ => bug!("unexpected intrinsic"),
};
block.statements.push(Statement {
source_info: terminator.source_info,
kind: StatementKind::Assign(Box::new((
*destination,
Rvalue::CheckedBinaryOp(bin_op, Box::new((lhs, rhs))),
))),
});
terminator.kind = TerminatorKind::Goto { target };
}
}
sym::size_of | sym::min_align_of => {
if let Some(target) = *target {
let tp_ty = substs.type_at(0);
let null_op = match intrinsic_name {
sym::size_of => NullOp::SizeOf,
sym::min_align_of => NullOp::AlignOf,
_ => bug!("unexpected intrinsic"),
};
block.statements.push(Statement {
source_info: terminator.source_info,
kind: StatementKind::Assign(Box::new((
*destination,
Rvalue::NullaryOp(null_op, tp_ty),
))),
});
terminator.kind = TerminatorKind::Goto { target };
}
}
sym::read_via_copy => {
let [arg] = args.as_slice() else {
span_bug!(terminator.source_info.span, "Wrong number of arguments");
};
let derefed_place =
if let Some(place) = arg.place() && let Some(local) = place.as_local() {
tcx.mk_place_deref(local.into())
} else {
span_bug!(terminator.source_info.span, "Only passing a local is supported");
};
terminator.kind = match *target {
None => {
TerminatorKind::Unreachable
}
Some(target) => {
block.statements.push(Statement {
source_info: terminator.source_info,
kind: StatementKind::Assign(Box::new((
*destination,
Rvalue::Use(Operand::Copy(derefed_place)),
))),
});
TerminatorKind::Goto { target }
}
}
}
sym::discriminant_value => {
if let (Some(target), Some(arg)) = (*target, args[0].place()) {
let arg = tcx.mk_place_deref(arg);
block.statements.push(Statement {
source_info: terminator.source_info,
kind: StatementKind::Assign(Box::new((
*destination,
Rvalue::Discriminant(arg),
))),
});
terminator.kind = TerminatorKind::Goto { target };
}
}
_ if intrinsic_name.as_str().starts_with("simd_shuffle") => {
validate_simd_shuffle(tcx, args, terminator.source_info.span);
}
_ => {}
}
}
}
}
}
fn resolve_rust_intrinsic<'tcx>(
tcx: TyCtxt<'tcx>,
func_ty: Ty<'tcx>,
) -> Option<(Symbol, SubstsRef<'tcx>)> {
if let ty::FnDef(def_id, substs) = *func_ty.kind() {
if tcx.is_intrinsic(def_id) {
return Some((tcx.item_name(def_id), substs));
}
}
None
}
fn validate_simd_shuffle<'tcx>(tcx: TyCtxt<'tcx>, args: &[Operand<'tcx>], span: Span) {
match &args[2] {
Operand::Constant(_) => {} _ => {
let msg = "last argument of `simd_shuffle` is required to be a `const` item";
tcx.sess.span_err(span, msg);
}
}
}