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use crate::abi::call::{ArgAbi, FnAbi, Reg, RegKind, Uniform};
use crate::abi::{HasDataLayout, TyAbiInterface};
/// Given integer-types M and register width N (e.g. M=u16 and N=32 bits), the
/// `ParamExtension` policy specifies how a uM value should be treated when
/// passed via register or stack-slot of width N. See also rust-lang/rust#97463.
#[derive(Copy, Clone, PartialEq)]
pub enum ParamExtension {
/// Indicates that when passing an i8/i16, either as a function argument or
/// as a return value, it must be sign-extended to 32 bits, and likewise a
/// u8/u16 must be zero-extended to 32-bits. (This variant is here to
/// accommodate Apple's deviation from the usual AArch64 ABI as defined by
/// ARM.)
///
/// See also: <https://developer.apple.com/documentation/xcode/writing-arm64-code-for-apple-platforms#Pass-Arguments-to-Functions-Correctly>
ExtendTo32Bits,
/// Indicates that no sign- nor zero-extension is performed: if a value of
/// type with bitwidth M is passed as function argument or return value,
/// then M bits are copied into the least significant M bits, and the
/// remaining bits of the register (or word of memory) are untouched.
NoExtension,
}
fn is_homogeneous_aggregate<'a, Ty, C>(cx: &C, arg: &mut ArgAbi<'a, Ty>) -> Option<Uniform>
where
Ty: TyAbiInterface<'a, C> + Copy,
C: HasDataLayout,
{
arg.layout.homogeneous_aggregate(cx).ok().and_then(|ha| ha.unit()).and_then(|unit| {
let size = arg.layout.size;
// Ensure we have at most four uniquely addressable members.
if size > unit.size.checked_mul(4, cx).unwrap() {
return None;
}
let valid_unit = match unit.kind {
RegKind::Integer => false,
RegKind::Float => true,
RegKind::Vector => size.bits() == 64 || size.bits() == 128,
};
valid_unit.then_some(Uniform { unit, total: size })
})
}
fn classify_ret<'a, Ty, C>(cx: &C, ret: &mut ArgAbi<'a, Ty>, param_policy: ParamExtension)
where
Ty: TyAbiInterface<'a, C> + Copy,
C: HasDataLayout,
{
if !ret.layout.is_aggregate() {
match param_policy {
ParamExtension::ExtendTo32Bits => ret.extend_integer_width_to(32),
ParamExtension::NoExtension => {}
}
return;
}
if let Some(uniform) = is_homogeneous_aggregate(cx, ret) {
ret.cast_to(uniform);
return;
}
let size = ret.layout.size;
let bits = size.bits();
if bits <= 128 {
ret.cast_to(Uniform { unit: Reg::i64(), total: size });
return;
}
ret.make_indirect();
}
fn classify_arg<'a, Ty, C>(cx: &C, arg: &mut ArgAbi<'a, Ty>, param_policy: ParamExtension)
where
Ty: TyAbiInterface<'a, C> + Copy,
C: HasDataLayout,
{
if !arg.layout.is_aggregate() {
match param_policy {
ParamExtension::ExtendTo32Bits => arg.extend_integer_width_to(32),
ParamExtension::NoExtension => {}
}
return;
}
if let Some(uniform) = is_homogeneous_aggregate(cx, arg) {
arg.cast_to(uniform);
return;
}
let size = arg.layout.size;
let bits = size.bits();
if bits <= 128 {
arg.cast_to(Uniform { unit: Reg::i64(), total: size });
return;
}
arg.make_indirect();
}
pub fn compute_abi_info<'a, Ty, C>(cx: &C, fn_abi: &mut FnAbi<'a, Ty>, param_policy: ParamExtension)
where
Ty: TyAbiInterface<'a, C> + Copy,
C: HasDataLayout,
{
if !fn_abi.ret.is_ignore() {
classify_ret(cx, &mut fn_abi.ret, param_policy);
}
for arg in fn_abi.args.iter_mut() {
if arg.is_ignore() {
continue;
}
classify_arg(cx, arg, param_policy);
}
}
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