109 lines
4.7 KiB
Rust
109 lines
4.7 KiB
Rust
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//! Lowers intrinsic calls
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use crate::transform::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_target::spec::abi::Abi;
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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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for block in body.basic_blocks_mut() {
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let terminator = block.terminator.as_mut().unwrap();
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if let TerminatorKind::Call {
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func: Operand::Constant(box Constant { literal: ty::Const { ty: func_ty, .. }, .. }),
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args,
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destination,
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..
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} = &mut terminator.kind
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{
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let (intrinsic_name, substs) = match resolve_rust_intrinsic(tcx, func_ty) {
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None => continue,
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Some(it) => it,
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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((destination, target)) = *destination {
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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 (
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destination,
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Rvalue::Use(Operand::Constant(box Constant {
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span: terminator.source_info.span,
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user_ty: None,
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literal: ty::Const::zero_sized(tcx, 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::wrapping_add | sym::wrapping_sub | sym::wrapping_mul => {
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if let Some((destination, target)) = *destination {
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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 (
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destination,
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Rvalue::BinaryOp(bin_op, 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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// The checked binary operations are not suitable target for lowering here,
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// since their semantics depend on the value of overflow-checks flag used
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// during codegen. Issue #35310.
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}
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sym::size_of => {
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if let Some((destination, target)) = *destination {
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let tp_ty = substs.type_at(0);
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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 (
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destination,
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Rvalue::NullaryOp(NullOp::SizeOf, 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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_ => {}
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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(
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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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let fn_sig = func_ty.fn_sig(tcx);
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if fn_sig.abi() == Abi::RustIntrinsic {
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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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