Wrong alignment on vectors

[ilcheese2]

Since vectors are defined with type aliases they have an incorrect alignment.

For example this has an alignment of 8

typedef float float2 __attribute__((vector_size(2 * sizeof(float))));

The generated bindgen code is

pub type float2 = [f32; 2usize];

which has an alignment of 4 instead of the expected 8.

[rich-ayr]

__vector_size__/ext_vector_type should work, is vector_size standard/documented syntax?

rust-bindgen/bindgen-tests/tests/headers/vector.hpp

Lines 1 to 3 in 97ab915

	struct foo {
	__attribute__((__vector_size__(1 * sizeof(long long)))) long long mMember;
	};

rust-bindgen/bindgen-tests/tests/headers/opencl_vector.h

Lines 1 to 2 in 97ab915

	typedef float float4 __attribute__((ext_vector_type(4)));
	typedef float float2 __attribute__((ext_vector_type(2)));

Could just be an uncaught variant, some of the work done here is only 2 weeks old.

[ilcheese2]

The issue isn't specific to that syntax; using ext_vector_type would result in the same problem.
The current implementation for vectors represents them with an array which have a different alignment than the SIMD types.

rust-bindgen/bindgen/codegen/mod.rs

Lines 4369 to 4371 in 97ab915

	TypeKind::Array(item, len) | TypeKind::Vector(item, len) => {
	let ty = item.try_to_rust_ty(ctx, &())?;
	Ok(syn::parse_quote! { [ #ty ; #len ] })

A solution would be to wrap them in a struct to preserve alignment similar to what's being done for opaque arrays

rust-bindgen/bindgen/codegen/helpers.rs

Lines 105 to 109 in 97ab915

	if ctx.options().enable_cxx_namespaces {
	syn::parse_quote! { root::__BindgenOpaqueArray<#ty, #data_len> }
	} else {
	syn::parse_quote! { __BindgenOpaqueArray<#ty, #data_len> }
	}