On Sat, Nov 3, 2012 at 12:55 AM, Mischa Baars <mjbaars1...@gmail.com> wrote: > On 11/02/2012 07:11 PM, Ian Lance Taylor wrote: >> >> On Fri, Nov 2, 2012 at 8:13 AM, Mischa Baars <mjbaars1...@gmail.com> >> wrote: >>> >>> I have been writing this piece of example code, but it seems that someone >>> has been modifying the compiler in the meantime such that arguments are >>> now >>> passed in xmm registers instead of over the stack. Also the npx top of >>> stack >>> pointer isn't handled alike for all three different types of real numbers >>> on >>> function return any more. >> >> I have not looked at your code. However, I can tell you that on >> 32-bit x86 floating point function arguments are normally passed on >> the stack and on 64-bit x86 floating point arguments are normally >> passed in the xmm registers. There are various ways that you can >> change this default behaviour, but if you are seeing an unexpected >> change then I would guess that you changed from 32-bit compilation to >> 64-bit compilation. >> >> Ian > > > By the way, it seems this only holds for single and double real numbers. > These are indeed passed in xmm registers, the long double however is still > passed over the stack.
Yes. > Do we have any compiler options that change this behaviour back to the > original? The default behaviour in 64-bit mode is not even the same for all > real number types. There is no "original." The 32-bit and 64-bit ABIs are different. The 64-bit ABI has always passed arguments in registers. There is no option to force the 64-bit compiler to pass arguments on the stack. Ian
