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use rustc_abi::{Align, HasDataLayout, Reg, TyAbiInterface};
use crate::callconv::FnAbi;
use crate::spec::HasTargetSpec;
pub(crate) fn compute_abi_info<'a, Ty, C>(
cx: &C,
fn_abi: &mut FnAbi<'a, Ty>,
opts: super::x86::X86Options,
) where
Ty: TyAbiInterface<'a, C> + Copy,
C: HasDataLayout + HasTargetSpec,
{
if !fn_abi.ret.is_ignore() {
if fn_abi.ret.layout.is_aggregate() && fn_abi.ret.layout.is_sized() {
// Returning a structure. Most often, this will use
// a hidden first argument. On some platforms, though,
// small structs are returned as integers.
//
// Some links:
// https://www.angelcode.com/dev/callconv/callconv.html
// Clang's ABI handling is in lib/CodeGen/TargetInfo.cpp
let t = cx.target_spec();
// MSVC does not special-case 1-element float aggregates, unlike others.
// GCC used to apply the SysV rule here, breaking windows-gnu's ABI, but was fixed:
// - reported in https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82028
// - fixed in https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85667
if t.abi_return_struct_as_int || opts.reg_struct_return {
match fn_abi.ret.layout.size.bytes() {
1 => fn_abi.ret.cast_to(Reg::i8()),
2 => fn_abi.ret.cast_to(Reg::i16()),
4 => fn_abi.ret.cast_to(Reg::i32()),
8 => fn_abi.ret.cast_to(Reg::i64()),
_ => fn_abi.ret.make_indirect(),
}
} else {
fn_abi.ret.make_indirect();
}
} else {
fn_abi.ret.extend_integer_width_to(32);
}
}
for arg in fn_abi.args.iter_mut() {
if arg.is_ignore() || !arg.layout.is_sized() {
continue;
}
// FIXME: MSVC 2015+ will pass the first 3 vector arguments in [XYZ]MM0-2
// See https://reviews.llvm.org/D72114 for Clang behavior
let align_4 = Align::from_bytes(4).unwrap();
if arg.layout.is_adt()
&& let Some(max_repr_align) = arg.layout.max_repr_align
&& max_repr_align > align_4
{
// MSVC has special rules for overaligned arguments: https://reviews.llvm.org/D72114.
// Summarized here:
// - Arguments with _requested_ alignment > 4 are passed indirectly.
// - For backwards compatibility, arguments with natural alignment > 4 are still passed
// on stack (via `byval`). For example, this includes `double`, `int64_t`,
// and structs containing them, provided they lack an explicit alignment attribute.
assert!(
arg.layout.align.abi >= max_repr_align,
"abi alignment {:?} less than requested alignment {max_repr_align:?}",
arg.layout.align.abi,
);
arg.make_indirect();
} else if arg.layout.is_aggregate() {
// Alignment of the `byval` argument.
// The rules can be found in `X86_32ABIInfo::getTypeStackAlignInBytes` in Clang's `TargetInfo.cpp`.
let byval_align = align_4;
arg.pass_by_stack_offset(Some(byval_align));
} else {
arg.extend_integer_width_to(32);
}
}
super::x86::fill_inregs(cx, fn_abi, opts, false);
}
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