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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.
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.

GCC is recommended for compiling GMP, but the resulting DLL can be used with any compiler. On mingw only the standard Windows libraries will be needed, on Cygwin the usual cygwin runtime will be required.

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.
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.

x86 GCC -march=pentiumpro
GCC 2.95.2 and 2.95.3 miscompiled some versions of mpz/powm.c when -march=pentiumpro was used, so for relevant CPUs that option is only in the default CFLAGS for GCC 2.95.4 and up.