Hi all,
I am trying to generate LLVM IR that calls an external C++ function
returning a structure by copy:
vec3 vec3::Cross(const vec3& iV) const;
Here is the LLVM IR that I am generating for win32 ABI, which says that the
first parameter should be a pointer to the return value:
%vec3 = type <{ float, float, float }>
define void @CPP_Return_Struct(%vec3* %v1, %vec3* %v2) inlinehint
alignstack(16) {
ENTRY:
%"@0" = alloca %vec3, align 4
call x86_thiscallcc void @vec3_Cross(%vec3* sret %"@0", %vec3* %v1, %vec3*
%v2)
ret void
}
declare x86_thiscallcc void @vec3_Cross(%vec3* sret, %vec3*, %vec3*) align 2
It seems that the code generated by the JIT takes the first parameter for
the this value because of the X86_thiscall calling convention. However, in
this particular case, the first parameter is the return value which is
tagged with the sret attribute.
I have manually modified the X86GenCallingConv.inc to treat the second
parameter as this value when the first has been tagged with sret attribute,
and it is working fine.
But I am not sure if it is a (known?) bug or if I do not generate the
correct LLVM IR.
I found nothing about this on the mailing list, I apologize if I missed any
important information.
Damien
