And please be careful not to confuse anyone with the name ftoi: the ftoi below and the MASM (and perhaps other assemblers') pseudo intstruction FTOI are not the same. http://www-zeuthen.desy.de/apewww/APE/software/asm/anext/MASM/conversion/ftoi_masm.php MASM FTOI takes the integer part of the floating point number and converts it to an integer. The ftoi function below (not part of any standard library that I know of, nor could find on a short google search), just gets the bits, not the integer portion. --Dean On Wed, 27 May 2009, Michael Meissner wrote: > On Tue, May 26, 2009 at 09:42:40PM -0700, me22 wrote: > > 2009/5/26 Florian Weimer <fw@xxxxxxxxxxxxx>: > > > * Michael Meissner: > > > > > >> On Sat, May 23, 2009 at 03:55:34PM +0200, Florian Weimer wrote: > > >>> It seems to me that x86_64 supports direct moves from XMM to > > >>> general-purpose registers, so that it's possible to access the > > >>> representation of a floating point value without going through memory: > > >>> > > >>> long getbits(double src) > > >>> { > > >>> long result; > > >>> __asm__ ("movq %1, %0" : "=q" (result) : "x" (src)); > > >>> return result; > > >>> } > > >>> > > >>> Is this functionally available as some sort of built-in? > > >> > > >> Well you typically can use a union to get the bits. > > > > > > Okay. I didn't realize that GCC was smart enough to avoid the > > > round-trip through memory. > > > > > > > In my experience compilers are often even smart enough to have this > > avoid the memory roundtrip, and it's undeniably legal: > > > > int ftoi(float x) { > > int i; > > memcpy(&i, &x, 4); > > return i; > > } > > Well from a pedantic point of view, it is only legal if sizeof (i) == sizeof > (x) == 4, but you presumably already know that. > > -- Av8 Internet Prepared to pay a premium for better service? www.av8.net faster, more reliable, better service 617 344 9000
