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5bbaeadc01
The first PR for https://github.com/rust-lang/compiler-team/issues/606 This is just the move-and-rename, because it's plenty big-and-bitrotty already. Future PRs will start using `FieldIdx` more broadly, and concomitantly removing `FieldIdx::new`s.
281 lines
14 KiB
Rust
281 lines
14 KiB
Rust
//! Lowers intrinsic calls
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use crate::MirPass;
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use rustc_middle::mir::*;
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use rustc_middle::ty::subst::SubstsRef;
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use rustc_middle::ty::{self, Ty, TyCtxt};
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use rustc_span::symbol::{sym, Symbol};
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use rustc_span::Span;
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use rustc_target::abi::{FieldIdx, VariantIdx};
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pub struct LowerIntrinsics;
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impl<'tcx> MirPass<'tcx> for LowerIntrinsics {
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fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
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let local_decls = &body.local_decls;
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for block in body.basic_blocks.as_mut() {
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let terminator = block.terminator.as_mut().unwrap();
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if let TerminatorKind::Call { func, args, destination, target, .. } =
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&mut terminator.kind
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{
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let func_ty = func.ty(local_decls, tcx);
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let Some((intrinsic_name, substs)) = resolve_rust_intrinsic(tcx, func_ty) else {
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continue;
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};
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match intrinsic_name {
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sym::unreachable => {
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terminator.kind = TerminatorKind::Unreachable;
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}
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sym::forget => {
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if let Some(target) = *target {
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block.statements.push(Statement {
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source_info: terminator.source_info,
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kind: StatementKind::Assign(Box::new((
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*destination,
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Rvalue::Use(Operand::Constant(Box::new(Constant {
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span: terminator.source_info.span,
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user_ty: None,
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literal: ConstantKind::zero_sized(tcx.types.unit),
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}))),
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))),
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});
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terminator.kind = TerminatorKind::Goto { target };
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}
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}
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sym::copy_nonoverlapping => {
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let target = target.unwrap();
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let mut args = args.drain(..);
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block.statements.push(Statement {
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source_info: terminator.source_info,
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kind: StatementKind::Intrinsic(Box::new(
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NonDivergingIntrinsic::CopyNonOverlapping(
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rustc_middle::mir::CopyNonOverlapping {
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src: args.next().unwrap(),
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dst: args.next().unwrap(),
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count: args.next().unwrap(),
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},
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),
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)),
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});
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assert_eq!(
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args.next(),
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None,
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"Extra argument for copy_non_overlapping intrinsic"
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);
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drop(args);
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terminator.kind = TerminatorKind::Goto { target };
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}
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sym::assume => {
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let target = target.unwrap();
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let mut args = args.drain(..);
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block.statements.push(Statement {
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source_info: terminator.source_info,
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kind: StatementKind::Intrinsic(Box::new(
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NonDivergingIntrinsic::Assume(args.next().unwrap()),
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)),
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});
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assert_eq!(
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args.next(),
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None,
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"Extra argument for copy_non_overlapping intrinsic"
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);
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drop(args);
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terminator.kind = TerminatorKind::Goto { target };
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}
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sym::wrapping_add | sym::wrapping_sub | sym::wrapping_mul => {
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if let Some(target) = *target {
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let lhs;
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let rhs;
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{
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let mut args = args.drain(..);
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lhs = args.next().unwrap();
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rhs = args.next().unwrap();
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}
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let bin_op = match intrinsic_name {
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sym::wrapping_add => BinOp::Add,
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sym::wrapping_sub => BinOp::Sub,
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sym::wrapping_mul => BinOp::Mul,
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_ => bug!("unexpected intrinsic"),
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};
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block.statements.push(Statement {
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source_info: terminator.source_info,
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kind: StatementKind::Assign(Box::new((
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*destination,
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Rvalue::BinaryOp(bin_op, Box::new((lhs, rhs))),
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))),
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});
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terminator.kind = TerminatorKind::Goto { target };
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}
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}
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sym::add_with_overflow | sym::sub_with_overflow | sym::mul_with_overflow => {
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if let Some(target) = *target {
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let lhs;
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let rhs;
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{
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let mut args = args.drain(..);
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lhs = args.next().unwrap();
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rhs = args.next().unwrap();
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}
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let bin_op = match intrinsic_name {
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sym::add_with_overflow => BinOp::Add,
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sym::sub_with_overflow => BinOp::Sub,
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sym::mul_with_overflow => BinOp::Mul,
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_ => bug!("unexpected intrinsic"),
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};
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block.statements.push(Statement {
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source_info: terminator.source_info,
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kind: StatementKind::Assign(Box::new((
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*destination,
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Rvalue::CheckedBinaryOp(bin_op, Box::new((lhs, rhs))),
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))),
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});
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terminator.kind = TerminatorKind::Goto { target };
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}
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}
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sym::size_of | sym::min_align_of => {
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if let Some(target) = *target {
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let tp_ty = substs.type_at(0);
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let null_op = match intrinsic_name {
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sym::size_of => NullOp::SizeOf,
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sym::min_align_of => NullOp::AlignOf,
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_ => bug!("unexpected intrinsic"),
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};
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block.statements.push(Statement {
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source_info: terminator.source_info,
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kind: StatementKind::Assign(Box::new((
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*destination,
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Rvalue::NullaryOp(null_op, tp_ty),
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))),
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});
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terminator.kind = TerminatorKind::Goto { target };
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}
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}
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sym::read_via_copy => {
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let [arg] = args.as_slice() else {
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span_bug!(terminator.source_info.span, "Wrong number of arguments");
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};
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let derefed_place =
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if let Some(place) = arg.place() && let Some(local) = place.as_local() {
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tcx.mk_place_deref(local.into())
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} else {
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span_bug!(terminator.source_info.span, "Only passing a local is supported");
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};
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terminator.kind = match *target {
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None => {
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// No target means this read something uninhabited,
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// so it must be unreachable, and we don't need to
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// preserve the assignment either.
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TerminatorKind::Unreachable
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}
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Some(target) => {
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block.statements.push(Statement {
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source_info: terminator.source_info,
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kind: StatementKind::Assign(Box::new((
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*destination,
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Rvalue::Use(Operand::Copy(derefed_place)),
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))),
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});
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TerminatorKind::Goto { target }
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}
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}
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}
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sym::discriminant_value => {
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if let (Some(target), Some(arg)) = (*target, args[0].place()) {
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let arg = tcx.mk_place_deref(arg);
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block.statements.push(Statement {
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source_info: terminator.source_info,
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kind: StatementKind::Assign(Box::new((
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*destination,
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Rvalue::Discriminant(arg),
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))),
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});
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terminator.kind = TerminatorKind::Goto { target };
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}
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}
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sym::option_payload_ptr => {
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if let (Some(target), Some(arg)) = (*target, args[0].place()) {
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let ty::RawPtr(ty::TypeAndMut { ty: dest_ty, .. }) =
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destination.ty(local_decls, tcx).ty.kind()
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else { bug!(); };
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block.statements.push(Statement {
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source_info: terminator.source_info,
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kind: StatementKind::Assign(Box::new((
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*destination,
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Rvalue::AddressOf(
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Mutability::Not,
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arg.project_deeper(
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&[
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PlaceElem::Deref,
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PlaceElem::Downcast(
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Some(sym::Some),
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VariantIdx::from_u32(1),
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),
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PlaceElem::Field(FieldIdx::from_u32(0), *dest_ty),
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],
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tcx,
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),
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),
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))),
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});
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terminator.kind = TerminatorKind::Goto { target };
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}
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}
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sym::transmute => {
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let dst_ty = destination.ty(local_decls, tcx).ty;
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let Ok([arg]) = <[_; 1]>::try_from(std::mem::take(args)) else {
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span_bug!(
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terminator.source_info.span,
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"Wrong number of arguments for transmute intrinsic",
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);
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};
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// Always emit the cast, even if we transmute to an uninhabited type,
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// because that lets CTFE and codegen generate better error messages
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// when such a transmute actually ends up reachable.
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block.statements.push(Statement {
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source_info: terminator.source_info,
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kind: StatementKind::Assign(Box::new((
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*destination,
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Rvalue::Cast(CastKind::Transmute, arg, dst_ty),
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))),
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});
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if let Some(target) = *target {
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terminator.kind = TerminatorKind::Goto { target };
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} else {
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terminator.kind = TerminatorKind::Unreachable;
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}
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}
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_ if intrinsic_name.as_str().starts_with("simd_shuffle") => {
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validate_simd_shuffle(tcx, args, terminator.source_info.span);
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}
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_ => {}
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}
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}
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}
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}
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}
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fn resolve_rust_intrinsic<'tcx>(
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tcx: TyCtxt<'tcx>,
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func_ty: Ty<'tcx>,
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) -> Option<(Symbol, SubstsRef<'tcx>)> {
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if let ty::FnDef(def_id, substs) = *func_ty.kind() {
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if tcx.is_intrinsic(def_id) {
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return Some((tcx.item_name(def_id), substs));
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}
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}
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None
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}
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fn validate_simd_shuffle<'tcx>(tcx: TyCtxt<'tcx>, args: &[Operand<'tcx>], span: Span) {
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match &args[2] {
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Operand::Constant(_) => {} // all good
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_ => {
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let msg = "last argument of `simd_shuffle` is required to be a `const` item";
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tcx.sess.span_err(span, msg);
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}
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}
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}
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