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GNU MP 4.1.2

2.4 Notes for Particular Systems

AIX 3 and 4

On systems `*-*-aix[34]*' shared libraries are disabled by default, since some versions of the native ar fail on the convenience libraries used. A shared build can be attempted with

./configure --enable-shared --disable-static

Note that the `--disable-static' is necessary because in a shared build libtool makes `libgmp.a' a symlink to `libgmp.so', apparently for the benefit of old versions of ld which only recognise `.a', but unfortunately this is done even if a fully functional ld is available.

ARM

On systems `arm*-*-*', versions of GCC up to and including 2.95.3 have a bug in unsigned division, giving wrong results for some operands. GMP `./configure' will demand GCC 2.95.4 or later.

Compaq C++

Compaq C++ on OSF 5.1 has two flavours of iostream, a standard one and an old pre-standard one (see `man iostream_intro'). GMP can only use the standard one, which unfortunately is not the default but must be selected by defining __USE_STD_IOSTREAM. Configure with for instance

./configure --enable-cxx CPPFLAGS=-D__USE_STD_IOSTREAM

Microsoft Windows

On systems `*-*-cygwin*', `*-*-mingw*' and `*-*-pw32*' by default GMP builds only a static library, but a DLL can be built instead using

./configure --disable-static --enable-shared

Static and DLL libraries can't both be built, since certain export directives in `gmp.h' must be different. `--enable-cxx' cannot be used when building a DLL, since libtool doesn't currently support C++ DLLs. This might change in the future.

Microsoft C

A MINGW DLL build of GMP can be used with Microsoft C. Libtool doesn't install `.lib' and `.exp' files, but they can be created with the following commands, where `/my/inst/dir' is the install directory (with a `lib' subdirectory).

lib /machine:IX86 /def:_libs/libgmp-3.dll-def cp libgmp-3.lib /my/inst/dir/lib cp _libs/libgmp-3.dll-exp /my/inst/dir/lib/libgmp-3.exp

MINGW uses `msvcrt.dll' for I/O, so applications wanting to use the GMP I/O routines must be compiled with `cl /MD' to do the same. If one of the other I/O choices provided by MS C is desired then the suggestion is to use the GMP string functions and confine I/O to the application.

Motorola 68k CPU Types

`m68k' is taken to mean 68000. `m68020' or higher will give a performance boost on applicable CPUs. `m68360' can be used for CPU32 series chips. `m68302' can be used for "Dragonball" series chips, though this is merely a synonym for `m68000'.

OpenBSD 2.6

m4 in this release of OpenBSD has a bug in eval that makes it unsuitable for `.asm' file processing. `./configure' will detect the problem and either abort or choose another m4 in the PATH. The bug is fixed in OpenBSD 2.7, so either upgrade or use GNU m4.

Power CPU Types

In GMP, CPU types `power*' and `powerpc*' will each use instructions not available on the other, so it's important to choose the right one for the CPU that will be used. Currently GMP has no assembler code support for using just the common instruction subset. To get executables that run on both, the current suggestion is to use the generic C code (CPU `none'), possibly with appropriate compiler options (like `-mcpu=common' for gcc). CPU `rs6000' (which is not a CPU but a family of workstations) is accepted by `config.sub', but is currently equivalent to `none'.

Sparc CPU Types

`sparcv8' or `supersparc' on relevant systems will give a significant performance increase over the V7 code.

Sparc App Regs

The GMP assembler code for both 32-bit and 64-bit Sparc clobbers the "application registers" g2, g3 and g4, the same way that the GCC default `-mapp-regs' does (see section `SPARC Options' in Using the GNU Compiler Collection (GCC)).

This makes that code unsuitable for use with the special V9 `-mcmodel=embmedany' (which uses g4 as a data segment pointer), and for applications wanting to use those registers for special purposes. In these cases the only suggestion currently is to build GMP with CPU `none' to avoid the assembler code.

SunOS 4

/usr/bin/m4 lacks various features needed to process `.asm' files, and instead `./configure' will automatically use /usr/5bin/m4, which we believe is always available (if not then use GNU m4).

x86 CPU Types

`i386' selects generic code which will run reasonably well on all x86 chips.

`i586', `pentium' or `pentiummmx' code is good for the intended P5 Pentium chips, but quite slow when run on Intel P6 class chips (PPro, P-II, P-III). `i386' is a better choice when making binaries that must run on both.

`pentium4' and an SSE2 capable assembler are important for best results on Pentium 4. The specific code is for instance roughly a 2x to 3x speedup over the generic `i386' code.

x86 MMX and SSE2 Code

If the CPU selected has MMX code but the assembler doesn't support it, a warning is given and non-MMX code is used instead. This will be an inferior build, since the MMX code that's present is there because it's faster than the corresponding plain integer code. The same applies to SSE2.

Old versions of `gas' don't support MMX instructions, in particular version 1.92.3 that comes with FreeBSD 2.2.8 doesn't (and unfortunately there's no newer assembler for that system).

Solaris 2.6 and 2.7 as generate incorrect object code for register to register movq instructions, and so can't be used for MMX code. Install a recent gas if MMX code is wanted on these systems.