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|
//! Argument passing
use crate::prelude::*;
pub(super) use EmptySinglePair::*;
#[derive(Copy, Clone, Debug)]
pub(super) enum PassMode {
NoPass,
ByVal(Type),
ByValPair(Type, Type),
ByRef { size: Option<Size> },
}
#[derive(Copy, Clone, Debug)]
pub(super) enum EmptySinglePair<T> {
Empty,
Single(T),
Pair(T, T),
}
impl<T> EmptySinglePair<T> {
pub(super) fn into_iter(self) -> EmptySinglePairIter<T> {
EmptySinglePairIter(self)
}
pub(super) fn map<U>(self, mut f: impl FnMut(T) -> U) -> EmptySinglePair<U> {
match self {
Empty => Empty,
Single(v) => Single(f(v)),
Pair(a, b) => Pair(f(a), f(b)),
}
}
}
pub(super) struct EmptySinglePairIter<T>(EmptySinglePair<T>);
impl<T> Iterator for EmptySinglePairIter<T> {
type Item = T;
fn next(&mut self) -> Option<T> {
match std::mem::replace(&mut self.0, Empty) {
Empty => None,
Single(v) => Some(v),
Pair(a, b) => {
self.0 = Single(b);
Some(a)
}
}
}
}
impl<T: std::fmt::Debug> EmptySinglePair<T> {
pub(super) fn assert_single(self) -> T {
match self {
Single(v) => v,
_ => panic!("Called assert_single on {:?}", self),
}
}
pub(super) fn assert_pair(self) -> (T, T) {
match self {
Pair(a, b) => (a, b),
_ => panic!("Called assert_pair on {:?}", self),
}
}
}
impl PassMode {
pub(super) fn get_param_ty(self, tcx: TyCtxt<'_>) -> EmptySinglePair<Type> {
match self {
PassMode::NoPass => Empty,
PassMode::ByVal(clif_type) => Single(clif_type),
PassMode::ByValPair(a, b) => Pair(a, b),
PassMode::ByRef { size: Some(_) } => Single(pointer_ty(tcx)),
PassMode::ByRef { size: None } => Pair(pointer_ty(tcx), pointer_ty(tcx)),
}
}
}
pub(super) fn get_pass_mode<'tcx>(tcx: TyCtxt<'tcx>, layout: TyAndLayout<'tcx>) -> PassMode {
if layout.is_zst() {
// WARNING zst arguments must never be passed, as that will break CastKind::ClosureFnPointer
PassMode::NoPass
} else {
match &layout.abi {
Abi::Uninhabited => PassMode::NoPass,
Abi::Scalar(scalar) => PassMode::ByVal(scalar_to_clif_type(tcx, scalar.clone())),
Abi::ScalarPair(a, b) => {
let a = scalar_to_clif_type(tcx, a.clone());
let b = scalar_to_clif_type(tcx, b.clone());
if a == types::I128 && b == types::I128 {
// Returning (i128, i128) by-val-pair would take 4 regs, while only 3 are
// available on x86_64. Cranelift gets confused when too many return params
// are used.
PassMode::ByRef {
size: Some(layout.size),
}
} else {
PassMode::ByValPair(a, b)
}
}
// FIXME implement Vector Abi in a cg_llvm compatible way
Abi::Vector { .. } => {
if let Some(vector_ty) = crate::intrinsics::clif_vector_type(tcx, layout) {
PassMode::ByVal(vector_ty)
} else {
PassMode::ByRef {
size: Some(layout.size),
}
}
}
Abi::Aggregate { sized: true } => PassMode::ByRef {
size: Some(layout.size),
},
Abi::Aggregate { sized: false } => PassMode::ByRef { size: None },
}
}
}
/// Get a set of values to be passed as function arguments.
pub(super) fn adjust_arg_for_abi<'tcx>(
fx: &mut FunctionCx<'_, 'tcx, impl Module>,
arg: CValue<'tcx>,
) -> EmptySinglePair<Value> {
match get_pass_mode(fx.tcx, arg.layout()) {
PassMode::NoPass => Empty,
PassMode::ByVal(_) => Single(arg.load_scalar(fx)),
PassMode::ByValPair(_, _) => {
let (a, b) = arg.load_scalar_pair(fx);
Pair(a, b)
}
PassMode::ByRef { size: _ } => match arg.force_stack(fx) {
(ptr, None) => Single(ptr.get_addr(fx)),
(ptr, Some(meta)) => Pair(ptr.get_addr(fx), meta),
},
}
}
/// Create a [`CValue`] containing the value of a function parameter adding clif function parameters
/// as necessary.
pub(super) fn cvalue_for_param<'tcx>(
fx: &mut FunctionCx<'_, 'tcx, impl Module>,
start_block: Block,
#[cfg_attr(not(debug_assertions), allow(unused_variables))] local: Option<mir::Local>,
#[cfg_attr(not(debug_assertions), allow(unused_variables))] local_field: Option<usize>,
arg_ty: Ty<'tcx>,
) -> Option<CValue<'tcx>> {
let layout = fx.layout_of(arg_ty);
let pass_mode = get_pass_mode(fx.tcx, layout);
if let PassMode::NoPass = pass_mode {
return None;
}
let clif_types = pass_mode.get_param_ty(fx.tcx);
let block_params = clif_types.map(|t| fx.bcx.append_block_param(start_block, t));
#[cfg(debug_assertions)]
crate::abi::comments::add_arg_comment(
fx,
"arg",
local,
local_field,
block_params,
pass_mode,
arg_ty,
);
match pass_mode {
PassMode::NoPass => unreachable!(),
PassMode::ByVal(_) => Some(CValue::by_val(block_params.assert_single(), layout)),
PassMode::ByValPair(_, _) => {
let (a, b) = block_params.assert_pair();
Some(CValue::by_val_pair(a, b, layout))
}
PassMode::ByRef { size: Some(_) } => Some(CValue::by_ref(
Pointer::new(block_params.assert_single()),
layout,
)),
PassMode::ByRef { size: None } => {
let (ptr, meta) = block_params.assert_pair();
Some(CValue::by_ref_unsized(Pointer::new(ptr), meta, layout))
}
}
}
|
