Remove an old workaround that was kept around for ABI-compatibility on x86-64 between different LLVM versions. This means LLVM r67588 is required if you want to compile for x86-64, otherwise the backend will assert when you try to return e.g. struct { int i; char c; } from a function. (In particular, this is no longer compatible with LLVM 2.5) It also means that any code returning small structs on x86-64 will probably need to be recompiled in order to be linkable to code compiled with this change.

int foo()
{
    version(X86)
    {
      asm { mov EAX, 42; }
    } else version(X86_64)
    {
      asm { movq RAX, 42; }
    }
    else static assert(0, "todo");
}

ulong bar()
{
    version(X86)
    {
      asm { mov EAX, 0xFF; mov EDX, 0xAA; }
    } else version(X86_64)
    {
      asm { movq RAX, 0xAA000000FF; }
    }
    else static assert(0, "todo");
}

void main()
{
    long l = 1;
    l = 2;
    l = 4;
    l = 8;
    assert(foo() == 42);
    assert(bar() == 0xAA000000FF);
}