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