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Old version was from 2012-05-06, 6.1.2 is from 2016-12-16 A lot of support for newer processors and speedups since then See gmp/NEWS for details
163 lines
3.4 KiB
Plaintext
163 lines
3.4 KiB
Plaintext
Copyright 1996, 1999, 2001, 2002, 2004 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 either:
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* the GNU Lesser General Public License as published by the Free
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Software Foundation; either version 3 of the License, or (at your
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option) any later version.
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or
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* the GNU General Public License as published by the Free Software
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Foundation; either version 2 of the License, or (at your option) any
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later version.
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or both in parallel, as here.
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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 General Public License
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for more details.
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You should have received copies of the GNU General Public License and the
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GNU Lesser General Public License along with the GNU MP Library. If not,
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see https://www.gnu.org/licenses/.
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This directory contains mpn functions for various HP PA-RISC chips. Code
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that runs faster on the PA7100 and later implementations, is in the pa7100
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directory.
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RELEVANT OPTIMIZATION ISSUES
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Load and Store timing
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On the PA7000 no memory instructions can issue the two cycles after a store.
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For the PA7100, this is reduced to one cycle.
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The PA7100 has a lookup-free cache, so it helps to schedule loads and the
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dependent instruction really far from each other.
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STATUS
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1. mpn_mul_1 could be improved to 6.5 cycles/limb on the PA7100, using the
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instructions below (but some sw pipelining is needed to avoid the
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xmpyu-fstds delay):
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fldds s1_ptr
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xmpyu
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fstds N(%r30)
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xmpyu
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fstds N(%r30)
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ldws N(%r30)
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ldws N(%r30)
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ldws N(%r30)
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ldws N(%r30)
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addc
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stws res_ptr
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addc
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stws res_ptr
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addib Loop
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2. mpn_addmul_1 could be improved from the current 10 to 7.5 cycles/limb
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(asymptotically) on the PA7100, using the instructions below. With proper
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sw pipelining and the unrolling level below, the speed becomes 8
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cycles/limb.
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fldds s1_ptr
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fldds s1_ptr
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xmpyu
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fstds N(%r30)
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xmpyu
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fstds N(%r30)
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xmpyu
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fstds N(%r30)
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xmpyu
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fstds N(%r30)
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ldws N(%r30)
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ldws N(%r30)
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ldws N(%r30)
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ldws N(%r30)
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ldws N(%r30)
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ldws N(%r30)
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ldws N(%r30)
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ldws N(%r30)
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addc
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addc
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addc
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addc
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addc %r0,%r0,cy-limb
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ldws res_ptr
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ldws res_ptr
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ldws res_ptr
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ldws res_ptr
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add
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stws res_ptr
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addc
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stws res_ptr
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addc
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stws res_ptr
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addc
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stws res_ptr
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addib
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3. For the PA8000 we have to stick to using 32-bit limbs before compiler
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support emerges. But we want to use 64-bit operations whenever possible,
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in particular for loads and stores. It is possible to handle mpn_add_n
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efficiently by rotating (when s1/s2 are aligned), masking+bit field
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inserting when (they are not). The speed should double compared to the
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code used today.
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LABEL SYNTAX
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The HP-UX assembler takes labels starting in column 0 with no colon,
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L$loop ldws,mb -4(0,%r25),%r22
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Gas on hppa GNU/Linux however requires a colon,
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L$loop: ldws,mb -4(0,%r25),%r22
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This is covered by using LDEF() from asm-defs.m4. An alternative would be
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to use ".label" which is accepted by both,
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.label L$loop
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ldws,mb -4(0,%r25),%r22
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but that's not as nice to look at, not if you're used to assembler code
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having labels in column 0.
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REFERENCES
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Hewlett Packard, "HP Assembler Reference Manual", 9th edition, June 1998,
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part number 92432-90012.
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----------------
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Local variables:
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mode: text
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fill-column: 76
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End:
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