On 2011-05-13 13:53:11 +0100, Jonathan Wakely wrote: > On 13 May 2011 13:19, Jonathan Wakely wrote: > > On 13 May 2011 11:20, Vincent Lefevre wrote: > >> On 2011-05-13 11:38:22 +0200, Axel Freyn wrote: > >>> Hi Vincent, > >>> On Fri, May 13, 2011 at 11:29:46AM +0200, Vincent Lefevre wrote: > >>> > https://www-304.ibm.com/support/docview.wss?rs=2030&uid=swg21245006 > >>> > says: > >>> > > >>> > GCC versions 4.0 and higher support 128-bit quad precision > >>> > floating point values. The XL compilers now provide the > >>> > -qfloat=gcclongdouble option to be compatible with GCC's > >>> > representation of 128-bit quad precision floating point > >>> > values. > >>> > > >>> > Anyone knows how to enable it? > >>> > > >>> > By default, I just get the double-double representation (yielding > >>> > 106-bit precision). > >>> the gcc online-docs say > >>> http://gcc.gnu.org/onlinedocs/gcc/Floating-Types.html > >>> "Not all targets support additional floating point types. __float80 and > >>> __float128 types are supported on i386, x86_64 and ia64 targets." > >>> (but I never tried it on PowerPC) > >> > >> Still, __float128 isn't a long double as said in the note above. > >> I now wonder whether the note is correct. > > > > Use --with-long-double-128 at configure time. This is how gcc is configured under Debian: ay:~> gcc -v Using built-in specs. Target: powerpc-linux-gnu Configured with: ../src/configure -v --with-pkgversion='Debian 4.4.5-8' --with-bugurl=file:///usr/share/doc/gcc-4.4/README.Bugs --enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-4.4 --enable-shared --enable-multiarch --enable-linker-build-id --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.4 --libdir=/usr/lib --enable-nls --enable-clocale=gnu --enable-libstdcxx-debug --enable-objc-gc --enable-secureplt --disable-softfloat --enable-targets=powerpc-linux,powerpc64-linux --with-cpu=default32 --with-long-double-128 --enable-checking=release --build=powerpc-linux-gnu --host=powerpc-linux-gnu --target=powerpc-linux-gnu Thread model: posix gcc version 4.4.5 (Debian 4.4.5-8) but I do not get quad precision (see below). > > See gcc/configure > > > > case "$target" in > > powerpc*-*-linux* | \ > > powerpc*-*-gnu* | \ > > sparc*-*-linux* | \ > > s390*-*-linux* | \ > > alpha*-*-linux*) > > > > It looks as though rs6000 and powerpc also support the > -mlong-double-128 option, although it's not documented It has no effect on PowerPC: ay:~> gcc -dM -E -xc /dev/null | grep LDBL #define __LDBL_MAX__ 1.79769313486231580793728971405301e+308L #define __LDBL_MAX_EXP__ 1024 #define __LDBL_HAS_INFINITY__ 1 #define __LDBL_MIN__ 2.00416836000897277799610805135016e-292L #define __LDBL_HAS_QUIET_NAN__ 1 #define __LDBL_HAS_DENORM__ 1 #define __LDBL_EPSILON__ 4.94065645841246544176568792868221e-324L #define __LDBL_MANT_DIG__ 106 #define __LDBL_MIN_EXP__ (-968) #define __LDBL_MAX_10_EXP__ 308 #define __LDBL_DENORM_MIN__ 4.94065645841246544176568792868221e-324L #define __LDBL_MIN_10_EXP__ (-291) #define __LDBL_DIG__ 31 ay:~> gcc -dM -E -xc /dev/null -mlong-double-128 | grep LDBL #define __LDBL_MAX__ 1.79769313486231580793728971405301e+308L #define __LDBL_MAX_EXP__ 1024 #define __LDBL_HAS_INFINITY__ 1 #define __LDBL_MIN__ 2.00416836000897277799610805135016e-292L #define __LDBL_HAS_QUIET_NAN__ 1 #define __LDBL_HAS_DENORM__ 1 #define __LDBL_EPSILON__ 4.94065645841246544176568792868221e-324L #define __LDBL_MANT_DIG__ 106 #define __LDBL_MIN_EXP__ (-968) #define __LDBL_MAX_10_EXP__ 308 #define __LDBL_DENORM_MIN__ 4.94065645841246544176568792868221e-324L #define __LDBL_MIN_10_EXP__ (-291) #define __LDBL_DIG__ 31 -- Vincent Lefèvre <vincent@xxxxxxxxxx> - Web: <http://www.vinc17.net/> 100% accessible validated (X)HTML - Blog: <http://www.vinc17.net/blog/> Work: CR INRIA - computer arithmetic / Arénaire project (LIP, ENS-Lyon)
