On Android platform aarch64 ABI does not return vec4 correctly

[jilinxiaohuo]

System Details

platform: x86_64-pc-mingw64
toolchain: aarch64-unknown-linux-android
compiler: clang version 12.0.5

Problems Description

When calling the C++ member function glm::vec4 imageview::get_background_color() through ffi, the returnvalue parameter of the ffi_call can only get the first member (x) of vec4, and through debug, it is found that the st4 { v0.s, v1.s, v2.s, v3.s }[0], [x3] instructions used in sysV.S copy the return value. I debugged in lldb and found that the four members of vec4 are placed in the v0 register, not v0, v1, v2, v3 each stored in a float, changed to stp x0, x1, [x3] instructions can correctly get the return value. I also tried to return to vec3, and found that the three members of vec3 have stored v0, v1, v2 registers respectively, which can work correctly. Is there a way to get st4 to work correctly?

PS: the type of returnvalue passed to the ffi_call is:
type = new ffi_type;
memset(type, 0, sizeof(ffi_type));
type->type = FFI_TYPE_STRUCT;
type->elements = new ffi_type * [5];
type->elements[0] = &ffi_type_float;
type->elements[1] = &ffi_type_float;
type->elements[2] = &ffi_type_float;
type->elements[3] = &ffi_type_float;
type->elements[4] = nullptr;

[atgreen]

I added two tests: 2d63cee

Can you please validate that I wrote them correctly for this problem?
They are passing on aarch64 Linux, so this must be an ABI difference on Android (or the tests are wrong).

[jilinxiaohuo]

They are passing on my Android aarch64 platform.
There are some differences between your tests and my case.
The underlying type of glm::vec4 is float32x4_t( float32_t attribute((ext_vector_type(4))) ), which is defined in arm_neon.h.
I don't know how to describe float32x4_t with ffi_type_xxx.

[atgreen]

Ok, got it. There was work in progress for this feature. It stalled, but you might want to look to see how close it is: #414