Currently complex types are not passed in accordance with the
System V ABI when using extern(C) on linux x64, (dmd git master,
no flags):
extern(C):
cfloat cf(cfloat a)
{
return a;
}
// a is expected on the stack (not the fpu stack) and returned in
XMM0:XMM1 (real in one, imaginary in the other I presume. Lots of
empty space.)
cdouble cd(cdouble a)
{
return a;
}
// a is expected in XMM0:XMM1, a hidden pointer argument to some
stack space is expected in RDI, filled from a and is returned in
RAX
creal cr(creal a)
{
return a;
}
// a is expected on the stack (not fpu stack), a hidden pointer
argument to some stack space is passed in RDI, filled from a and
is returned in RAX.
/*********
Would it not be better to make these compliant with the
equivalent types specified in the System V ABI (when using
extern(C) on linux x64)? It would ease interactions with other
languages.
*********/
As specified here:
http://refspecs.linuxfoundation.org/elf/x86_64-abi-0.95.pdf
cfloat would be passed as real -> XMM<n> and imag -> XMM<n+1>
and returned identically
cdouble would be passed as real -> XMM<n> and imag -> XMM<n+1>
and returned identically
creal would be passed on the stack (not fpu)
and returned as real -> ST<n> and imag -> ST<n+1>
I recognise that these types are supposed to be phased out in
favour of std.complex. However, seeing as that doesn't seem to be
happening any time soon, getting the ABI right would be good for
now.
