forked from M-Labs/nac3
core: Fix passing structure arguments to extern functions
All parameters with a structure type in extern functions are marked as `byref` instead of `byval`, as most ABIs require the first several arguments to be passed in registers before spilling into the stack. `byval` breaks this contract by explicitly requiring all arguments to be passed in the stack, breaking interop with libraries written in other languages.
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@ -365,6 +365,7 @@ impl<'ctx, 'a> CodeGenContext<'ctx, 'a> {
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let mut return_slot = None;
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if fun.count_params() > 0 {
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let sret_id = Attribute::get_named_enum_kind_id("sret");
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let byref_id = Attribute::get_named_enum_kind_id("byref");
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let byval_id = Attribute::get_named_enum_kind_id("byval");
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let offset = if fun.get_enum_attribute(AttributeLoc::Param(0), sret_id).is_some() {
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@ -376,7 +377,8 @@ impl<'ctx, 'a> CodeGenContext<'ctx, 'a> {
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0
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};
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for (i, param) in params.iter().enumerate() {
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if fun.get_enum_attribute(AttributeLoc::Param((i + offset) as u32), byval_id).is_some() {
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let loc = AttributeLoc::Param((i + offset) as u32);
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if fun.get_enum_attribute(loc, byref_id).is_some() || fun.get_enum_attribute(loc, byval_id).is_some() {
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// lazy update
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if loc_params.is_empty() {
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loc_params.extend(params[0..i+offset].iter().copied());
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@ -745,11 +747,11 @@ pub fn gen_call<'ctx, 'a, G: CodeGenerator>(
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Some(ctx.get_llvm_abi_type(generator, fun.0.ret))
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};
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let has_sret = ret_type.map_or(false, |ret_type| need_sret(ctx.ctx, ret_type));
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let mut byvals = Vec::new();
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let mut byrefs = Vec::new();
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let mut params = args.iter().enumerate()
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.map(|(i, arg)| match ctx.get_llvm_abi_type(generator, arg.ty) {
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BasicTypeEnum::StructType(ty) if is_extern => {
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byvals.push((i, ty));
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byrefs.push((i, ty));
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ty.ptr_type(AddressSpace::default()).into()
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},
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x => x
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@ -770,9 +772,19 @@ pub fn gen_call<'ctx, 'a, G: CodeGenerator>(
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} else {
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0
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};
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for (i, ty) in byvals {
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fun_val.add_attribute(AttributeLoc::Param((i as u32) + offset),
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ctx.ctx.create_type_attribute(Attribute::get_named_enum_kind_id("byval"), ty.as_any_type_enum()));
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// The attribute ID used to mark arguments of a structure type.
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// Structure-Typed parameters of extern functions must **not** be marked as `byval`, as
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// `byval` explicitly specifies that the argument is to be passed on the stack, which breaks
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// on most ABIs where the first several arguments are expected to be passed in registers.
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let passing_attr_id = Attribute::get_named_enum_kind_id(
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if is_extern { "byref" } else { "byval" }
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);
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for (i, ty) in byrefs {
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fun_val.add_attribute(
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AttributeLoc::Param((i as u32) + offset),
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ctx.ctx.create_type_attribute(passing_attr_id, ty.as_any_type_enum())
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);
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}
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fun_val
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});
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