rustc_codegen_ssa/mir/

intrinsic.rs

use rustc_abi::WrappingRange;
use rustc_middle::ty::{self, Ty, TyCtxt};
use rustc_middle::{bug, span_bug};
use rustc_session::config::OptLevel;
use rustc_span::{Span, sym};
use rustc_target::callconv::{FnAbi, PassMode};

use super::FunctionCx;
use super::operand::OperandRef;
use super::place::PlaceRef;
use crate::errors::InvalidMonomorphization;
use crate::traits::*;
use crate::{MemFlags, errors, meth, size_of_val};

fn copy_intrinsic<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
    bx: &mut Bx,
    allow_overlap: bool,
    volatile: bool,
    ty: Ty<'tcx>,
    dst: Bx::Value,
    src: Bx::Value,
    count: Bx::Value,
) {
    let layout = bx.layout_of(ty);
    let size = layout.size;
    let align = layout.align.abi;
    let size = bx.mul(bx.const_usize(size.bytes()), count);
    let flags = if volatile { MemFlags::VOLATILE } else { MemFlags::empty() };
    if allow_overlap {
        bx.memmove(dst, align, src, align, size, flags);
    } else {
        bx.memcpy(dst, align, src, align, size, flags);
    }
}

fn memset_intrinsic<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
    bx: &mut Bx,
    volatile: bool,
    ty: Ty<'tcx>,
    dst: Bx::Value,
    val: Bx::Value,
    count: Bx::Value,
) {
    let layout = bx.layout_of(ty);
    let size = layout.size;
    let align = layout.align.abi;
    let size = bx.mul(bx.const_usize(size.bytes()), count);
    let flags = if volatile { MemFlags::VOLATILE } else { MemFlags::empty() };
    bx.memset(dst, val, size, align, flags);
}

impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
    /// In the `Err` case, returns the instance that should be called instead.
    pub fn codegen_intrinsic_call(
        bx: &mut Bx,
        instance: ty::Instance<'tcx>,
        fn_abi: &FnAbi<'tcx, Ty<'tcx>>,
        args: &[OperandRef<'tcx, Bx::Value>],
        llresult: Bx::Value,
        span: Span,
    ) -> Result<(), ty::Instance<'tcx>> {
        let callee_ty = instance.ty(bx.tcx(), bx.typing_env());

        let ty::FnDef(def_id, fn_args) = *callee_ty.kind() else {
            bug!("expected fn item type, found {}", callee_ty);
        };

        let sig = callee_ty.fn_sig(bx.tcx());
        let sig = bx.tcx().normalize_erasing_late_bound_regions(bx.typing_env(), sig);
        let arg_tys = sig.inputs();
        let ret_ty = sig.output();
        let name = bx.tcx().item_name(def_id);
        let name_str = name.as_str();

        // If we're swapping something that's *not* an `OperandValue::Ref`,
        // then we can do it directly and avoid the alloca.
        // Otherwise, we'll let the fallback MIR body take care of it.
        if let sym::typed_swap = name {
            let pointee_ty = fn_args.type_at(0);
            let pointee_layout = bx.layout_of(pointee_ty);
            if !bx.is_backend_ref(pointee_layout)
                // But if we're not going to optimize, trying to use the fallback
                // body just makes things worse, so don't bother.
                || bx.sess().opts.optimize == OptLevel::No
                // NOTE(eddyb) SPIR-V's Logical addressing model doesn't allow for arbitrary
                // reinterpretation of values as (chunkable) byte arrays, and the loop in the
                // block optimization in `ptr::swap_nonoverlapping` is hard to rewrite back
                // into the (unoptimized) direct swapping implementation, so we disable it.
                || bx.sess().target.arch == "spirv"
            {
                let align = pointee_layout.align.abi;
                let x_place = args[0].val.deref(align);
                let y_place = args[1].val.deref(align);
                bx.typed_place_swap(x_place, y_place, pointee_layout);
                return Ok(());
            }
        }

        let llret_ty = bx.backend_type(bx.layout_of(ret_ty));
        let result = PlaceRef::new_sized(llresult, fn_abi.ret.layout);

        let llval = match name {
            sym::abort => {
                bx.abort();
                return Ok(());
            }

            sym::va_start => bx.va_start(args[0].immediate()),
            sym::va_end => bx.va_end(args[0].immediate()),
            sym::size_of_val => {
                let tp_ty = fn_args.type_at(0);
                let (_, meta) = args[0].val.pointer_parts();
                let (llsize, _) = size_of_val::size_and_align_of_dst(bx, tp_ty, meta);
                llsize
            }
            sym::min_align_of_val => {
                let tp_ty = fn_args.type_at(0);
                let (_, meta) = args[0].val.pointer_parts();
                let (_, llalign) = size_of_val::size_and_align_of_dst(bx, tp_ty, meta);
                llalign
            }
            sym::vtable_size | sym::vtable_align => {
                let vtable = args[0].immediate();
                let idx = match name {
                    sym::vtable_size => ty::COMMON_VTABLE_ENTRIES_SIZE,
                    sym::vtable_align => ty::COMMON_VTABLE_ENTRIES_ALIGN,
                    _ => bug!(),
                };
                let value = meth::VirtualIndex::from_index(idx).get_usize(bx, vtable, callee_ty);
                match name {
                    // Size is always <= isize::MAX.
                    sym::vtable_size => {
                        let size_bound = bx.data_layout().ptr_sized_integer().signed_max() as u128;
                        bx.range_metadata(value, WrappingRange { start: 0, end: size_bound });
                    }
                    // Alignment is always nonzero.
                    sym::vtable_align => {
                        bx.range_metadata(value, WrappingRange { start: 1, end: !0 })
                    }
                    _ => {}
                }
                value
            }
            sym::pref_align_of
            | sym::needs_drop
            | sym::type_id
            | sym::type_name
            | sym::variant_count => {
                let value = bx.tcx().const_eval_instance(bx.typing_env(), instance, span).unwrap();
                OperandRef::from_const(bx, value, ret_ty).immediate_or_packed_pair(bx)
            }
            sym::arith_offset => {
                let ty = fn_args.type_at(0);
                let layout = bx.layout_of(ty);
                let ptr = args[0].immediate();
                let offset = args[1].immediate();
                bx.gep(bx.backend_type(layout), ptr, &[offset])
            }
            sym::copy => {
                copy_intrinsic(
                    bx,
                    true,
                    false,
                    fn_args.type_at(0),
                    args[1].immediate(),
                    args[0].immediate(),
                    args[2].immediate(),
                );
                return Ok(());
            }
            sym::write_bytes => {
                memset_intrinsic(
                    bx,
                    false,
                    fn_args.type_at(0),
                    args[0].immediate(),
                    args[1].immediate(),
                    args[2].immediate(),
                );
                return Ok(());
            }

            sym::volatile_copy_nonoverlapping_memory => {
                copy_intrinsic(
                    bx,
                    false,
                    true,
                    fn_args.type_at(0),
                    args[0].immediate(),
                    args[1].immediate(),
                    args[2].immediate(),
                );
                return Ok(());
            }
            sym::volatile_copy_memory => {
                copy_intrinsic(
                    bx,
                    true,
                    true,
                    fn_args.type_at(0),
                    args[0].immediate(),
                    args[1].immediate(),
                    args[2].immediate(),
                );
                return Ok(());
            }
            sym::volatile_set_memory => {
                memset_intrinsic(
                    bx,
                    true,
                    fn_args.type_at(0),
                    args[0].immediate(),
                    args[1].immediate(),
                    args[2].immediate(),
                );
                return Ok(());
            }
            sym::volatile_store => {
                let dst = args[0].deref(bx.cx());
                args[1].val.volatile_store(bx, dst);
                return Ok(());
            }
            sym::unaligned_volatile_store => {
                let dst = args[0].deref(bx.cx());
                args[1].val.unaligned_volatile_store(bx, dst);
                return Ok(());
            }
            sym::exact_div => {
                let ty = arg_tys[0];
                match int_type_width_signed(ty, bx.tcx()) {
                    Some((_width, signed)) => {
                        if signed {
                            bx.exactsdiv(args[0].immediate(), args[1].immediate())
                        } else {
                            bx.exactudiv(args[0].immediate(), args[1].immediate())
                        }
                    }
                    None => {
                        bx.tcx().dcx().emit_err(InvalidMonomorphization::BasicIntegerType {
                            span,
                            name,
                            ty,
                        });
                        return Ok(());
                    }
                }
            }
            sym::fadd_fast | sym::fsub_fast | sym::fmul_fast | sym::fdiv_fast | sym::frem_fast => {
                match float_type_width(arg_tys[0]) {
                    Some(_width) => match name {
                        sym::fadd_fast => bx.fadd_fast(args[0].immediate(), args[1].immediate()),
                        sym::fsub_fast => bx.fsub_fast(args[0].immediate(), args[1].immediate()),
                        sym::fmul_fast => bx.fmul_fast(args[0].immediate(), args[1].immediate()),
                        sym::fdiv_fast => bx.fdiv_fast(args[0].immediate(), args[1].immediate()),
                        sym::frem_fast => bx.frem_fast(args[0].immediate(), args[1].immediate()),
                        _ => bug!(),
                    },
                    None => {
                        bx.tcx().dcx().emit_err(InvalidMonomorphization::BasicFloatType {
                            span,
                            name,
                            ty: arg_tys[0],
                        });
                        return Ok(());
                    }
                }
            }
            sym::fadd_algebraic
            | sym::fsub_algebraic
            | sym::fmul_algebraic
            | sym::fdiv_algebraic
            | sym::frem_algebraic => match float_type_width(arg_tys[0]) {
                Some(_width) => match name {
                    sym::fadd_algebraic => {
                        bx.fadd_algebraic(args[0].immediate(), args[1].immediate())
                    }
                    sym::fsub_algebraic => {
                        bx.fsub_algebraic(args[0].immediate(), args[1].immediate())
                    }
                    sym::fmul_algebraic => {
                        bx.fmul_algebraic(args[0].immediate(), args[1].immediate())
                    }
                    sym::fdiv_algebraic => {
                        bx.fdiv_algebraic(args[0].immediate(), args[1].immediate())
                    }
                    sym::frem_algebraic => {
                        bx.frem_algebraic(args[0].immediate(), args[1].immediate())
                    }
                    _ => bug!(),
                },
                None => {
                    bx.tcx().dcx().emit_err(InvalidMonomorphization::BasicFloatType {
                        span,
                        name,
                        ty: arg_tys[0],
                    });
                    return Ok(());
                }
            },

            sym::float_to_int_unchecked => {
                if float_type_width(arg_tys[0]).is_none() {
                    bx.tcx().dcx().emit_err(InvalidMonomorphization::FloatToIntUnchecked {
                        span,
                        ty: arg_tys[0],
                    });
                    return Ok(());
                }
                let Some((_width, signed)) = int_type_width_signed(ret_ty, bx.tcx()) else {
                    bx.tcx().dcx().emit_err(InvalidMonomorphization::FloatToIntUnchecked {
                        span,
                        ty: ret_ty,
                    });
                    return Ok(());
                };
                if signed {
                    bx.fptosi(args[0].immediate(), llret_ty)
                } else {
                    bx.fptoui(args[0].immediate(), llret_ty)
                }
            }

            sym::discriminant_value => {
                if ret_ty.is_integral() {
                    args[0].deref(bx.cx()).codegen_get_discr(bx, ret_ty)
                } else {
                    span_bug!(span, "Invalid discriminant type for `{:?}`", arg_tys[0])
                }
            }

            // This requires that atomic intrinsics follow a specific naming pattern:
            // "atomic_<operation>[_<ordering>]"
            name if let Some(atomic) = name_str.strip_prefix("atomic_") => {
                use crate::common::AtomicOrdering::*;
                use crate::common::{AtomicRmwBinOp, SynchronizationScope};

                let Some((instruction, ordering)) = atomic.split_once('_') else {
                    bx.sess().dcx().emit_fatal(errors::MissingMemoryOrdering);
                };

                let parse_ordering = |bx: &Bx, s| match s {
                    "unordered" => Unordered,
                    "relaxed" => Relaxed,
                    "acquire" => Acquire,
                    "release" => Release,
                    "acqrel" => AcquireRelease,
                    "seqcst" => SequentiallyConsistent,
                    _ => bx.sess().dcx().emit_fatal(errors::UnknownAtomicOrdering),
                };

                let invalid_monomorphization = |ty| {
                    bx.tcx().dcx().emit_err(InvalidMonomorphization::BasicIntegerType {
                        span,
                        name,
                        ty,
                    });
                };

                match instruction {
                    "cxchg" | "cxchgweak" => {
                        let Some((success, failure)) = ordering.split_once('_') else {
                            bx.sess().dcx().emit_fatal(errors::AtomicCompareExchange);
                        };
                        let ty = fn_args.type_at(0);
                        if int_type_width_signed(ty, bx.tcx()).is_some() || ty.is_unsafe_ptr() {
                            let weak = instruction == "cxchgweak";
                            let dst = args[0].immediate();
                            let cmp = args[1].immediate();
                            let src = args[2].immediate();
                            let (val, success) = bx.atomic_cmpxchg(
                                dst,
                                cmp,
                                src,
                                parse_ordering(bx, success),
                                parse_ordering(bx, failure),
                                weak,
                            );
                            let val = bx.from_immediate(val);
                            let success = bx.from_immediate(success);

                            let dest = result.project_field(bx, 0);
                            bx.store_to_place(val, dest.val);
                            let dest = result.project_field(bx, 1);
                            bx.store_to_place(success, dest.val);
                        } else {
                            invalid_monomorphization(ty);
                        }
                        return Ok(());
                    }

                    "load" => {
                        let ty = fn_args.type_at(0);
                        if int_type_width_signed(ty, bx.tcx()).is_some() || ty.is_unsafe_ptr() {
                            let layout = bx.layout_of(ty);
                            let size = layout.size;
                            let source = args[0].immediate();
                            bx.atomic_load(
                                bx.backend_type(layout),
                                source,
                                parse_ordering(bx, ordering),
                                size,
                            )
                        } else {
                            invalid_monomorphization(ty);
                            return Ok(());
                        }
                    }

                    "store" => {
                        let ty = fn_args.type_at(0);
                        if int_type_width_signed(ty, bx.tcx()).is_some() || ty.is_unsafe_ptr() {
                            let size = bx.layout_of(ty).size;
                            let val = args[1].immediate();
                            let ptr = args[0].immediate();
                            bx.atomic_store(val, ptr, parse_ordering(bx, ordering), size);
                        } else {
                            invalid_monomorphization(ty);
                        }
                        return Ok(());
                    }

                    "fence" => {
                        bx.atomic_fence(
                            parse_ordering(bx, ordering),
                            SynchronizationScope::CrossThread,
                        );
                        return Ok(());
                    }

                    "singlethreadfence" => {
                        bx.atomic_fence(
                            parse_ordering(bx, ordering),
                            SynchronizationScope::SingleThread,
                        );
                        return Ok(());
                    }

                    // These are all AtomicRMW ops
                    op => {
                        let atom_op = match op {
                            "xchg" => AtomicRmwBinOp::AtomicXchg,
                            "xadd" => AtomicRmwBinOp::AtomicAdd,
                            "xsub" => AtomicRmwBinOp::AtomicSub,
                            "and" => AtomicRmwBinOp::AtomicAnd,
                            "nand" => AtomicRmwBinOp::AtomicNand,
                            "or" => AtomicRmwBinOp::AtomicOr,
                            "xor" => AtomicRmwBinOp::AtomicXor,
                            "max" => AtomicRmwBinOp::AtomicMax,
                            "min" => AtomicRmwBinOp::AtomicMin,
                            "umax" => AtomicRmwBinOp::AtomicUMax,
                            "umin" => AtomicRmwBinOp::AtomicUMin,
                            _ => bx.sess().dcx().emit_fatal(errors::UnknownAtomicOperation),
                        };

                        let ty = fn_args.type_at(0);
                        if int_type_width_signed(ty, bx.tcx()).is_some() || ty.is_unsafe_ptr() {
                            let ptr = args[0].immediate();
                            let val = args[1].immediate();
                            bx.atomic_rmw(atom_op, ptr, val, parse_ordering(bx, ordering))
                        } else {
                            invalid_monomorphization(ty);
                            return Ok(());
                        }
                    }
                }
            }

            sym::nontemporal_store => {
                let dst = args[0].deref(bx.cx());
                args[1].val.nontemporal_store(bx, dst);
                return Ok(());
            }

            sym::ptr_offset_from | sym::ptr_offset_from_unsigned => {
                let ty = fn_args.type_at(0);
                let pointee_size = bx.layout_of(ty).size;

                let a = args[0].immediate();
                let b = args[1].immediate();
                let a = bx.ptrtoint(a, bx.type_isize());
                let b = bx.ptrtoint(b, bx.type_isize());
                let pointee_size = bx.const_usize(pointee_size.bytes());
                if name == sym::ptr_offset_from {
                    // This is the same sequence that Clang emits for pointer subtraction.
                    // It can be neither `nsw` nor `nuw` because the input is treated as
                    // unsigned but then the output is treated as signed, so neither works.
                    let d = bx.sub(a, b);
                    // this is where the signed magic happens (notice the `s` in `exactsdiv`)
                    bx.exactsdiv(d, pointee_size)
                } else {
                    // The `_unsigned` version knows the relative ordering of the pointers,
                    // so can use `sub nuw` and `udiv exact` instead of dealing in signed.
                    let d = bx.unchecked_usub(a, b);
                    bx.exactudiv(d, pointee_size)
                }
            }

            sym::cold_path => {
                // This is a no-op. The intrinsic is just a hint to the optimizer.
                return Ok(());
            }

            _ => {
                // Need to use backend-specific things in the implementation.
                return bx.codegen_intrinsic_call(instance, fn_abi, args, llresult, span);
            }
        };

        if !fn_abi.ret.is_ignore() {
            if let PassMode::Cast { .. } = &fn_abi.ret.mode {
                bx.store_to_place(llval, result.val);
            } else {
                OperandRef::from_immediate_or_packed_pair(bx, llval, result.layout)
                    .val
                    .store(bx, result);
            }
        }
        Ok(())
    }
}

// Returns the width of an int Ty, and if it's signed or not
// Returns None if the type is not an integer
// FIXME: there’s multiple of this functions, investigate using some of the already existing
// stuffs.
fn int_type_width_signed(ty: Ty<'_>, tcx: TyCtxt<'_>) -> Option<(u64, bool)> {
    match ty.kind() {
        ty::Int(t) => {
            Some((t.bit_width().unwrap_or(u64::from(tcx.sess.target.pointer_width)), true))
        }
        ty::Uint(t) => {
            Some((t.bit_width().unwrap_or(u64::from(tcx.sess.target.pointer_width)), false))
        }
        _ => None,
    }
}

// Returns the width of a float Ty
// Returns None if the type is not a float
fn float_type_width(ty: Ty<'_>) -> Option<u64> {
    match ty.kind() {
        ty::Float(t) => Some(t.bit_width()),
        _ => None,
    }
}