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| 1 | +use rustc_abi::{Align, HasDataLayout, Reg, TyAbiInterface}; |
| 2 | + |
| 3 | +use crate::callconv::FnAbi; |
| 4 | +use crate::spec::HasTargetSpec; |
| 5 | + |
| 6 | +pub(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 | +} |
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