rustc_target/callconv/
x86_win32.rs

Help
1use rustc_abi::{Align, HasDataLayout, Reg, TyAbiInterface};
2
3use crate::callconv::FnAbi;
4use crate::spec::HasTargetSpec;
5
6pub(crate) fn compute_abi_info<'a, Ty, C>(
7    cx: &C,
8    fn_abi: &mut FnAbi<'a, Ty>,
9    opts: super::x86::X86Options,
10) where
11    Ty: TyAbiInterface<'a, C> + Copy,
12    C: HasDataLayout + HasTargetSpec,
13{
14    if !fn_abi.ret.is_ignore() {
15        if fn_abi.ret.layout.is_aggregate() && fn_abi.ret.layout.is_sized() {
16            // Returning a structure. Most often, this will use
17            // a hidden first argument. On some platforms, though,
18            // small structs are returned as integers.
19            //
20            // Some links:
21            // https://www.angelcode.com/dev/callconv/callconv.html
22            // Clang's ABI handling is in lib/CodeGen/TargetInfo.cpp
23            let t = cx.target_spec();
24            // MSVC does not special-case 1-element float aggregates, unlike others.
25            // GCC used to apply the SysV rule here, breaking windows-gnu's ABI, but was fixed:
26            // - reported in https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82028
27            // - fixed in https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85667
28            if t.abi_return_struct_as_int || opts.reg_struct_return {
29                match fn_abi.ret.layout.size.bytes() {
30                    1 => fn_abi.ret.cast_to(Reg::i8()),
31                    2 => fn_abi.ret.cast_to(Reg::i16()),
32                    4 => fn_abi.ret.cast_to(Reg::i32()),
33                    8 => fn_abi.ret.cast_to(Reg::i64()),
34                    _ => fn_abi.ret.make_indirect(),
35                }
36            } else {
37                fn_abi.ret.make_indirect();
38            }
39        } else {
40            fn_abi.ret.extend_integer_width_to(32);
41        }
42    }
43
44    for arg in fn_abi.args.iter_mut() {
45        if arg.is_ignore() || !arg.layout.is_sized() {
46            continue;
47        }
48
49        // FIXME: MSVC 2015+ will pass the first 3 vector arguments in [XYZ]MM0-2
50        // See https://reviews.llvm.org/D72114 for Clang behavior
51
52        let align_4 = Align::from_bytes(4).unwrap();
53
54        if arg.layout.is_adt()
55            && let Some(max_repr_align) = arg.layout.max_repr_align
56            && max_repr_align > align_4
57        {
58            // MSVC has special rules for overaligned arguments: https://reviews.llvm.org/D72114.
59            // Summarized here:
60            // - Arguments with _requested_ alignment > 4 are passed indirectly.
61            // - For backwards compatibility, arguments with natural alignment > 4 are still passed
62            //   on stack (via `byval`). For example, this includes `double`, `int64_t`,
63            //   and structs containing them, provided they lack an explicit alignment attribute.
64            assert!(
65                arg.layout.align.abi >= max_repr_align,
66                "abi alignment {:?} less than requested alignment {max_repr_align:?}",
67                arg.layout.align.abi,
68            );
69            arg.make_indirect();
70        } else if arg.layout.is_aggregate() {
71            // Alignment of the `byval` argument.
72            // The rules can be found in `X86_32ABIInfo::getTypeStackAlignInBytes` in Clang's `TargetInfo.cpp`.
73            let byval_align = align_4;
74            arg.pass_by_stack_offset(Some(byval_align));
75        } else {
76            arg.extend_integer_width_to(32);
77        }
78    }
79
80    super::x86::fill_inregs(cx, fn_abi, opts, false);
81}
rustc_target/callconv/x86_win32.rs

rustc_target/callconv/
x86_win32.rs
