vasilito
ff4ff35918
Red Bear OS is a full fork. All sources must be available from git clone with zero network access. Removed gitignore rules that excluded fetched source trees under recipes/*/source/, local/recipes/kde/*/source/, local/recipes/qt/*/source/, and vendor source trees. Build artifacts (target/, build/, source.tar, *.o, *.so) remain excluded. 127291 files added — kernel, relibc, base, bootloader, pkgar, all KDE/Qt frameworks, mesa, wayland, DRM drivers, and every other recipe source.
89 lines
2.7 KiB
Plaintext
89 lines
2.7 KiB
Plaintext
Copyright 2011 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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There are 5 generations of 64-bit s390 processors, z900, z990, z9,
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z10, and z196. The current GMP code was optimised for the two oldest,
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z900 and z990.
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mpn_copyi
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This code makes use of a loop around MVC. It almost surely runs very
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close to optimally. A small improvement could be done by using one
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MVC for size 256 bytes, now we use two (we use an extra MVC when
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copying any multiple of 256 bytes).
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mpn_copyd
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We have tried several feed-in variants here, branch tree, jump table
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and computed goto. The fastest (on z990) turned out to be computed
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goto.
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An approach not tried is EX of LMG and STMG, modifying the register set
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on-the-fly. Using that trick, we could completely avoid using
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separate feed-in paths.
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mpn_lshift, mpn_rshift
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The current code runs at pipeline decode bandwidth on z990.
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mpn_add_n, mpn_sub_n
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The current code is 4-way unrolled. It should be unrolled more, at
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least 8x, in order to reach 2.5 c/l.
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mpn_mul_1, mpn_addmul_1, mpn_submul_1
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The current code is very naive, but due to the non-pipelined nature of
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MLGR on z900 and z990, more sophisticated code would not gain much.
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On z10 one would need to cluster at least 4 MLGR together, in order to
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reduce stalling.
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On z196, one surely want to use unrolling and pipelining, to perhaps
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reach around 12 c/l. A major issue here and on z10 is ALCGR's 3 cycle
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stalling.
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mpn_mul_2, mpn_addmul_2
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At least for older machines (z900, z990) with very slow MLGR, we
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should use Karatsuba's algorithm on 2-limb units, making mul_2 and
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addmul_2 the main multiplication primitives. The newer machines might
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benefit less from this approach, perhaps in particular z10, where MLGR
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clustering is more important.
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With Karatsuba, one could hope for around 16 cycles per accumulated
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128 cross product, on z990.
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