mod.rs

// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

use abi::{self, Abi, Align, FieldPlacement, Size};
use abi::{HasDataLayout, LayoutOf, TyLayout, TyLayoutMethods};
use spec::HasTargetSpec;

mod aarch64;
mod amdgpu;
mod arm;
mod asmjs;
mod hexagon;
mod mips;
mod mips64;
mod msp430;
mod nvptx;
mod nvptx64;
mod powerpc;
mod powerpc64;
mod riscv;
mod s390x;
mod sparc;
mod sparc64;
mod x86;
mod x86_64;
mod x86_win64;
mod wasm32;

#[derive(Clone, Copy, PartialEq, Eq, Debug)]
pub enum PassMode {
    /// Ignore the argument (useful for empty struct).
    Ignore,
    /// Pass the argument directly.
    Direct(ArgAttributes),
    /// Pass a pair's elements directly in two arguments.
    Pair(ArgAttributes, ArgAttributes),
    /// Pass the argument after casting it, to either
    /// a single uniform or a pair of registers.
    Cast(CastTarget),
    /// Pass the argument indirectly via a hidden pointer.
    /// The second value, if any, is for the extra data (vtable or length)
    /// which indicates that it refers to an unsized rvalue.
    Indirect(ArgAttributes, Option<ArgAttributes>),
}

// Hack to disable non_upper_case_globals only for the bitflags! and not for the rest
// of this module
pub use self::attr_impl::ArgAttribute;

#[allow(non_upper_case_globals)]
#[allow(unused)]
mod attr_impl {
    // The subset of llvm::Attribute needed for arguments, packed into a bitfield.
    bitflags! {
        #[derive(Default)]
        pub struct ArgAttribute: u16 {
            const ByVal     = 1 << 0;
            const NoAlias   = 1 << 1;
            const NoCapture = 1 << 2;
            const NonNull   = 1 << 3;
            const ReadOnly  = 1 << 4;
            const SExt      = 1 << 5;
            const StructRet = 1 << 6;
            const ZExt      = 1 << 7;
            const InReg     = 1 << 8;
        }
    }
}

/// A compact representation of LLVM attributes (at least those relevant for this module)
/// that can be manipulated without interacting with LLVM's Attribute machinery.
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
pub struct ArgAttributes {
    pub regular: ArgAttribute,
    pub pointee_size: Size,
    pub pointee_align: Option<Align>
}

impl ArgAttributes {
    pub fn new() -> Self {
        ArgAttributes {
            regular: ArgAttribute::default(),
            pointee_size: Size::ZERO,
            pointee_align: None,
        }
    }

    pub fn set(&mut self, attr: ArgAttribute) -> &mut Self {
        self.regular |= attr;
        self
    }

    pub fn contains(&self, attr: ArgAttribute) -> bool {
        self.regular.contains(attr)
    }
}

#[derive(Copy, Clone, PartialEq, Eq, Debug)]
pub enum RegKind {
    Integer,
    Float,
    Vector
}

#[derive(Copy, Clone, PartialEq, Eq, Debug)]
pub struct Reg {
    pub kind: RegKind,
    pub size: Size,
}

macro_rules! reg_ctor {
    ($name:ident, $kind:ident, $bits:expr) => {
        pub fn $name() -> Reg {
            Reg {
                kind: RegKind::$kind,
                size: Size::from_bits($bits)
            }
        }
    }
}

impl Reg {
    reg_ctor!(i8, Integer, 8);
    reg_ctor!(i16, Integer, 16);
    reg_ctor!(i32, Integer, 32);
    reg_ctor!(i64, Integer, 64);

    reg_ctor!(f32, Float, 32);
    reg_ctor!(f64, Float, 64);
}

impl Reg {
    pub fn align<C: HasDataLayout>(&self, cx: &C) -> Align {
        let dl = cx.data_layout();
        match self.kind {
            RegKind::Integer => {
                match self.size.bits() {
                    1 => dl.i1_align.abi,
                    2..=8 => dl.i8_align.abi,
                    9..=16 => dl.i16_align.abi,
                    17..=32 => dl.i32_align.abi,
                    33..=64 => dl.i64_align.abi,
                    65..=128 => dl.i128_align.abi,
                    _ => panic!("unsupported integer: {:?}", self)
                }
            }
            RegKind::Float => {
                match self.size.bits() {
                    32 => dl.f32_align.abi,
                    64 => dl.f64_align.abi,
                    _ => panic!("unsupported float: {:?}", self)
                }
            }
            RegKind::Vector => dl.vector_align(self.size).abi,
        }
    }
}

/// An argument passed entirely registers with the
/// same kind (e.g., HFA / HVA on PPC64 and AArch64).
#[derive(Clone, Copy, PartialEq, Eq, Debug)]
pub struct Uniform {
    pub unit: Reg,

    /// The total size of the argument, which can be:
    /// * equal to `unit.size` (one scalar/vector)
    /// * a multiple of `unit.size` (an array of scalar/vectors)
    /// * if `unit.kind` is `Integer`, the last element
    ///   can be shorter, i.e., `{ i64, i64, i32 }` for
    ///   64-bit integers with a total size of 20 bytes
    pub total: Size,
}

impl From<Reg> for Uniform {
    fn from(unit: Reg) -> Uniform {
        Uniform {
            unit,
            total: unit.size
        }
    }
}

impl Uniform {
    pub fn align<C: HasDataLayout>(&self, cx: &C) -> Align {
        self.unit.align(cx)
    }
}

#[derive(Clone, Copy, PartialEq, Eq, Debug)]
pub struct CastTarget {
    pub prefix: [Option<RegKind>; 8],
    pub prefix_chunk: Size,
    pub rest: Uniform,
}

impl From<Reg> for CastTarget {
    fn from(unit: Reg) -> CastTarget {
        CastTarget::from(Uniform::from(unit))
    }
}

impl From<Uniform> for CastTarget {
    fn from(uniform: Uniform) -> CastTarget {
        CastTarget {
            prefix: [None; 8],
            prefix_chunk: Size::ZERO,
            rest: uniform
        }
    }
}

impl CastTarget {
    pub fn pair(a: Reg, b: Reg) -> CastTarget {
        CastTarget {
            prefix: [Some(a.kind), None, None, None, None, None, None, None],
            prefix_chunk: a.size,
            rest: Uniform::from(b)
        }
    }

    pub fn size<C: HasDataLayout>(&self, cx: &C) -> Size {
        (self.prefix_chunk * self.prefix.iter().filter(|x| x.is_some()).count() as u64)
             .align_to(self.rest.align(cx)) + self.rest.total
    }

    pub fn align<C: HasDataLayout>(&self, cx: &C) -> Align {
        self.prefix.iter()
            .filter_map(|x| x.map(|kind| Reg { kind, size: self.prefix_chunk }.align(cx)))
            .fold(cx.data_layout().aggregate_align.abi.max(self.rest.align(cx)),
                |acc, align| acc.max(align))
    }
}

impl<'a, Ty> TyLayout<'a, Ty> {
    fn is_aggregate(&self) -> bool {
        match self.abi {
            Abi::Uninhabited |
            Abi::Scalar(_) |
            Abi::Vector { .. } => false,
            Abi::ScalarPair(..) |
            Abi::Aggregate { .. } => true
        }
    }

    fn homogeneous_aggregate<C>(&self, cx: &C) -> Option<Reg>
        where Ty: TyLayoutMethods<'a, C> + Copy, C: LayoutOf<Ty = Ty, TyLayout = Self>
    {
        match self.abi {
            Abi::Uninhabited => None,

            // The primitive for this algorithm.
            Abi::Scalar(ref scalar) => {
                let kind = match scalar.value {
                    abi::Int(..) |
                    abi::Pointer => RegKind::Integer,
                    abi::Float(_) => RegKind::Float,
                };
                Some(Reg {
                    kind,
                    size: self.size
                })
            }

            Abi::Vector { .. } => {
                Some(Reg {
                    kind: RegKind::Vector,
                    size: self.size
                })
            }

            Abi::ScalarPair(..) |
            Abi::Aggregate { .. } => {
                let mut total = Size::ZERO;
                let mut result = None;

                let is_union = match self.fields {
                    FieldPlacement::Array { count, .. } => {
                        if count > 0 {
                            return self.field(cx, 0).homogeneous_aggregate(cx);
                        } else {
                            return None;
                        }
                    }
                    FieldPlacement::Union(_) => true,
                    FieldPlacement::Arbitrary { .. } => false
                };

                for i in 0..self.fields.count() {
                    if !is_union && total != self.fields.offset(i) {
                        return None;
                    }

                    let field = self.field(cx, i);
                    match (result, field.homogeneous_aggregate(cx)) {
                        // The field itself must be a homogeneous aggregate.
                        (_, None) => return None,
                        // If this is the first field, record the unit.
                        (None, Some(unit)) => {
                            result = Some(unit);
                        }
                        // For all following fields, the unit must be the same.
                        (Some(prev_unit), Some(unit)) => {
                            if prev_unit != unit {
                                return None;
                            }
                        }
                    }

                    // Keep track of the offset (without padding).
                    let size = field.size;
                    if is_union {
                        total = total.max(size);
                    } else {
                        total += size;
                    }
                }

                // There needs to be no padding.
                if total != self.size {
                    None
                } else {
                    result
                }
            }
        }
    }
}

/// Information about how to pass an argument to,
/// or return a value from, a function, under some ABI.
#[derive(Debug)]
pub struct ArgType<'a, Ty> {
    pub layout: TyLayout<'a, Ty>,

    /// Dummy argument, which is emitted before the real argument.
    pub pad: Option<Reg>,

    pub mode: PassMode,
}

impl<'a, Ty> ArgType<'a, Ty> {
    pub fn new(layout: TyLayout<'a, Ty>) -> Self {
        ArgType {
            layout,
            pad: None,
            mode: PassMode::Direct(ArgAttributes::new()),
        }
    }

    pub fn make_indirect(&mut self) {
        assert_eq!(self.mode, PassMode::Direct(ArgAttributes::new()));

        // Start with fresh attributes for the pointer.
        let mut attrs = ArgAttributes::new();

        // For non-immediate arguments the callee gets its own copy of
        // the value on the stack, so there are no aliases. It's also
        // program-invisible so can't possibly capture
        attrs.set(ArgAttribute::NoAlias)
             .set(ArgAttribute::NoCapture)
             .set(ArgAttribute::NonNull);
        attrs.pointee_size = self.layout.size;
        // FIXME(eddyb) We should be doing this, but at least on
        // i686-pc-windows-msvc, it results in wrong stack offsets.
        // attrs.pointee_align = Some(self.layout.align.abi);

        let extra_attrs = if self.layout.is_unsized() {
            Some(ArgAttributes::new())
        } else {
            None
        };

        self.mode = PassMode::Indirect(attrs, extra_attrs);
    }

    pub fn make_indirect_byval(&mut self) {
        self.make_indirect();
        match self.mode {
            PassMode::Indirect(ref mut attrs, _) => {
                attrs.set(ArgAttribute::ByVal);
            }
            _ => unreachable!()
        }
    }

    pub fn extend_integer_width_to(&mut self, bits: u64) {
        // Only integers have signedness
        if let Abi::Scalar(ref scalar) = self.layout.abi {
            if let abi::Int(i, signed) = scalar.value {
                if i.size().bits() < bits {
                    if let PassMode::Direct(ref mut attrs) = self.mode {
                        attrs.set(if signed {
                            ArgAttribute::SExt
                        } else {
                            ArgAttribute::ZExt
                        });
                    }
                }
            }
        }
    }

    pub fn cast_to<T: Into<CastTarget>>(&mut self, target: T) {
        assert_eq!(self.mode, PassMode::Direct(ArgAttributes::new()));
        self.mode = PassMode::Cast(target.into());
    }

    pub fn pad_with(&mut self, reg: Reg) {
        self.pad = Some(reg);
    }

    pub fn is_indirect(&self) -> bool {
        match self.mode {
            PassMode::Indirect(..) => true,
            _ => false
        }
    }

    pub fn is_sized_indirect(&self) -> bool {
        match self.mode {
            PassMode::Indirect(_, None) => true,
            _ => false
        }
    }

    pub fn is_unsized_indirect(&self) -> bool {
        match self.mode {
            PassMode::Indirect(_, Some(_)) => true,
            _ => false
        }
    }

    pub fn is_ignore(&self) -> bool {
        self.mode == PassMode::Ignore
    }
}

#[derive(Copy, Clone, PartialEq, Debug)]
pub enum Conv {
    C,

    ArmAapcs,

    Msp430Intr,

    PtxKernel,

    X86Fastcall,
    X86Intr,
    X86Stdcall,
    X86ThisCall,
    X86VectorCall,

    X86_64SysV,
    X86_64Win64,

    AmdGpuKernel,
}

/// Metadata describing how the arguments to a native function
/// should be passed in order to respect the native ABI.
///
/// I will do my best to describe this structure, but these
/// comments are reverse-engineered and may be inaccurate. -NDM
#[derive(Debug)]
pub struct FnType<'a, Ty> {
    /// The LLVM types of each argument.
    pub args: Vec<ArgType<'a, Ty>>,

    /// LLVM return type.
    pub ret: ArgType<'a, Ty>,

    pub variadic: bool,

    pub conv: Conv,
}

impl<'a, Ty> FnType<'a, Ty> {
    pub fn adjust_for_cabi<C>(&mut self, cx: &C, abi: ::spec::abi::Abi) -> Result<(), String>
        where Ty: TyLayoutMethods<'a, C> + Copy,
              C: LayoutOf<Ty = Ty, TyLayout = TyLayout<'a, Ty>> + HasDataLayout + HasTargetSpec
    {
        match &cx.target_spec().arch[..] {
            "x86" => {
                let flavor = if abi == ::spec::abi::Abi::Fastcall {
                    x86::Flavor::Fastcall
                } else {
                    x86::Flavor::General
                };
                x86::compute_abi_info(cx, self, flavor);
            },
            "x86_64" => if abi == ::spec::abi::Abi::SysV64 {
                x86_64::compute_abi_info(cx, self);
            } else if abi == ::spec::abi::Abi::Win64 || cx.target_spec().options.is_like_windows {
                x86_win64::compute_abi_info(self);
            } else {
                x86_64::compute_abi_info(cx, self);
            },
            "aarch64" => aarch64::compute_abi_info(cx, self),
            "amdgpu" => amdgpu::compute_abi_info(cx, self),
            "arm" => arm::compute_abi_info(cx, self),
            "mips" => mips::compute_abi_info(cx, self),
            "mips64" => mips64::compute_abi_info(cx, self),
            "powerpc" => powerpc::compute_abi_info(cx, self),
            "powerpc64" => powerpc64::compute_abi_info(cx, self),
            "s390x" => s390x::compute_abi_info(cx, self),
            "asmjs" => asmjs::compute_abi_info(cx, self),
            "wasm32" => {
                if cx.target_spec().llvm_target.contains("emscripten") {
                    asmjs::compute_abi_info(cx, self)
                } else {
                    wasm32::compute_abi_info(self)
                }
            }
            "msp430" => msp430::compute_abi_info(self),
            "sparc" => sparc::compute_abi_info(cx, self),
            "sparc64" => sparc64::compute_abi_info(cx, self),
            "nvptx" => nvptx::compute_abi_info(self),
            "nvptx64" => nvptx64::compute_abi_info(self),
            "hexagon" => hexagon::compute_abi_info(self),
            "riscv32" => riscv::compute_abi_info(self, 32),
            "riscv64" => riscv::compute_abi_info(self, 64),
            a => return Err(format!("unrecognized arch \"{}\" in target specification", a))
        }

        if let PassMode::Indirect(ref mut attrs, _) = self.ret.mode {
            attrs.set(ArgAttribute::StructRet);
        }

        Ok(())
    }
}