Copyright 2000 Free Software Foundation, Inc. This file is part of the GNU MP Library. The GNU MP Library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. The GNU MP Library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with the GNU MP Library; see the file COPYING.LIB. If not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. Terms Used In This Document: ISA = Instruction Set Architecture. The instructions the current processor provides. ABI = Application Binary Interface. Specifies calling convention, type sizes, etc. AR64 = Arithmetic operations are 64-bit using 64-bit instructions (E.g., addition, subtraction, load, store, of 64-bit integer types are done with single instructions, not 32 bits at a time.) Environment = The operating system and compiler. GMP is a very complex package to build since its speed is very sensitive to the ISA and ABI. For example, if the ISA provides 64-bit instructions, it is crucial that GMP is configured to use them. Most environments that run on a 64-bit ISA provide more than one ABI. Typically one of the supported ABI's is a backward compatible 32-bit ABI, and one ABI provides 64-bit addressing and `long' (sometimes known as LP64). But a few environments (IRIX, HP-UX) provide intermediate ABI's using 32-bit addressing but allow efficient 64-bit operations through a `long long' type. For the latter to be useful to GMP, the ABI must allow operations using the native 64-bit instructions provided by the ISA, and allow passing of 64-bit quantities atomically. The ABI is typically chosen by means of command line options to the compiler tools (gcc, cc, c89, nm, ar, ld, as). Different environments use different defaults, but as of this writing (May 2000) the dominating default is to the plain 32-bit ABI in its most arcane form. The GMP 3.0.x approach was to compile using the ABI that gives the best performance. That places the burden on users to pass special options to the compiler when they compile their GMP applications. That approach has its advantages and disadvantages. The main advantage is that users don't unknowingly get bad GMP performance. The main disadvantage is that users' compiles (actually links) will fail unless they pass special compiler options. ** SPARC System vendors often confuse ABI, ISA, and implementation. The worst case is Solaris, were the unbundled compiler confuses ISA and ABI, and the options have very confusing names. option interpretation ====== ============== cc -xarch=v8plus ISA=sparcv9, ABI=V8plus (PTR=32, see below) gcc -mv8plus ISA=sparcv9, ABI=V8plus (see below) cc -xarch=v9 ISA=sparcv9, ABI=V9 (implying AR=64, PTR=64) It's hard to believe, but the option v8plus really means ISA=V9! Solaris releases prior to version 7 running on a V9 CPU fails to save/restore the upper 32 bits of the `i' and `l' registers. The `v8plus' option generates code that use as many V9 features as possible under such circumstances. ** MIPS The IRIX 6 compilers gets things right. They have a clear understanding of the differences between ABI and ISA. The option names are descriptive. option interpretation ====== ============== cc -n32 ABI=n32 (implying AR=64, PTR=32) gcc -mabi=n32 ABI=n32 (implying AR=64, PTR=32) cc -64 ABI=64 (implying AR=64, PTR=64) gcc -mabi=64 ABI=64 (implying AR=64, PTR=64) cc -mips3 ISA=mips3 gcc -mips3 ISA=mips3 cc -mips4 ISA=mips4 gcc -mips4 ISA=mips4 ** HP-PA HP-UX is somewhat weird, but not as broken as Solaris. option interpretation ====== ============== cc +DA2.0 ABI=32bit (implying AR=64, PTR=32) cc +DD64 ABI=64bit (implying AR=64, PTR=64) Code performing 64-bit arithmetic in the HP-UX 32-bit is not compatible with the 64-bit ABI; the former has a calling convention that passes/returns 64-bit integer quantities as two 32-bit chunks. ** PowerPC While the PowerPC ABI's are capable of supporting 64-bit registers/operations, the compilers under AIX are similar to Solaris' cc in that they don't currently provide any 32-bit addressing with 64-bit arithmetic. option interpretation ====== ============== cc -q64 ABI=64bit (implying AR=64, PTR=64) gcc -maix64 -mpowerpc64 ABI=64bit (implying AR=64, PTR=64)