1Copyright 2000 Free Software Foundation, Inc. 2 3This file is part of the GNU MP Library. 4 5The GNU MP Library is free software; you can redistribute it and/or modify 6it under the terms of the GNU Lesser General Public License as published by 7the Free Software Foundation; either version 3 of the License, or (at your 8option) any later version. 9 10The GNU MP Library is distributed in the hope that it will be useful, but 11WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 12or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 13License for more details. 14 15You should have received a copy of the GNU Lesser General Public License 16along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. 17 18 19 20 21Terms Used In This Document: 22 ISA = Instruction Set Architecture. The instructions the current 23 processor provides. 24 ABI = Application Binary Interface. Specifies calling convention, 25 type sizes, etc. 26 AR64 = Arithmetic operations are 64-bit using 64-bit instructions 27 (E.g., addition, subtraction, load, store, of 64-bit integer types 28 are done with single instructions, not 32 bits at a time.) 29 Environment = The operating system and compiler. 30 31GMP is a very complex package to build since its speed is very 32sensitive to the ISA and ABI. For example, if the ISA provides 64-bit 33instructions, it is crucial that GMP is configured to use them. 34 35Most environments that run on a 64-bit ISA provide more than one ABI. 36Typically one of the supported ABI's is a backward compatible 32-bit 37ABI, and one ABI provides 64-bit addressing and `long' (sometimes 38known as LP64). But a few environments (IRIX, HP-UX) provide 39intermediate ABI's using 32-bit addressing but allow efficient 64-bit 40operations through a `long long' type. For the latter to be useful to 41GMP, the ABI must allow operations using the native 64-bit 42instructions provided by the ISA, and allow passing of 64-bit 43quantities atomically. 44 45The ABI is typically chosen by means of command line options to the 46compiler tools (gcc, cc, c89, nm, ar, ld, as). Different environments 47use different defaults, but as of this writing (May 2000) the 48dominating default is to the plain 32-bit ABI in its most arcane form. 49 50The GMP 3.0.x approach was to compile using the ABI that gives the 51best performance. That places the burden on users to pass special 52options to the compiler when they compile their GMP applications. 53That approach has its advantages and disadvantages. The main 54advantage is that users don't unknowingly get bad GMP performance. 55The main disadvantage is that users' compiles (actually links) will 56fail unless they pass special compiler options. 57 58** SPARC 59 60System vendors often confuse ABI, ISA, and implementation. The worst 61case is Solaris, were the unbundled compiler confuses ISA and ABI, and 62the options have very confusing names. 63 64 option interpretation 65 ====== ============== 66cc -xarch=v8plus ISA=sparcv9, ABI=V8plus (PTR=32, see below) 67gcc -mv8plus ISA=sparcv9, ABI=V8plus (see below) 68cc -xarch=v9 ISA=sparcv9, ABI=V9 (implying AR=64, PTR=64) 69 70It's hard to believe, but the option v8plus really means ISA=V9! 71 72Solaris releases prior to version 7 running on a V9 CPU fails to 73save/restore the upper 32 bits of the `i' and `l' registers. The 74`v8plus' option generates code that use as many V9 features as 75possible under such circumstances. 76 77** MIPS 78 79The IRIX 6 compilers gets things right. They have a clear 80understanding of the differences between ABI and ISA. The option 81names are descriptive. 82 83 option interpretation 84 ====== ============== 85cc -n32 ABI=n32 (implying AR=64, PTR=32) 86gcc -mabi=n32 ABI=n32 (implying AR=64, PTR=32) 87cc -64 ABI=64 (implying AR=64, PTR=64) 88gcc -mabi=64 ABI=64 (implying AR=64, PTR=64) 89cc -mips3 ISA=mips3 90gcc -mips3 ISA=mips3 91cc -mips4 ISA=mips4 92gcc -mips4 ISA=mips4 93 94** HP-PA 95 96HP-UX is somewhat weird, but not as broken as Solaris. 97 98 option interpretation 99 ====== ============== 100cc +DA2.0 ABI=32bit (implying AR=64, PTR=32) 101cc +DD64 ABI=64bit (implying AR=64, PTR=64) 102 103Code performing 64-bit arithmetic in the HP-UX 32-bit is not 104compatible with the 64-bit ABI; the former has a calling convention 105that passes/returns 64-bit integer quantities as two 32-bit chunks. 106 107** PowerPC 108 109While the PowerPC ABI's are capable of supporting 64-bit 110registers/operations, the compilers under AIX are similar to Solaris' 111cc in that they don't currently provide any 32-bit addressing with 11264-bit arithmetic. 113 114 option interpretation 115 ====== ============== 116cc -q64 ABI=64bit (implying AR=64, PTR=64) 117gcc -maix64 -mpowerpc64 ABI=64bit (implying AR=64, PTR=64) 118