Re: calculation of pi

[Mischa Baars <mjbaars1977 at gmail dot com>]

On 11/02/2012 07:11 PM, Ian Lance Taylor wrote:
> On Fri, Nov 2, 2012 at 8:13 AM, Mischa Baars <mjbaars1977@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.

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.

Mischa.