README
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- Copyright 1996 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 3 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. If not, see http://www.gnu.org/licenses/.
- This directory contains mpn functions optimized for MIPS3. Example of
- processors that implement MIPS3 are R4000, R4400, R4600, R4700, and R8000.
- RELEVANT OPTIMIZATION ISSUES
- 1. On the R4000 and R4400, branches, both the plain and the "likely" ones,
- take 3 cycles to execute. (The fastest possible loop will take 4 cycles,
- because of the delay insn.)
- On the R4600, branches takes a single cycle
- On the R8000, branches often take no noticable cycles, as they are
- executed in a separate function unit..
- 2. The R4000 and R4400 have a load latency of 4 cycles.
- 3. On the R4000 and R4400, multiplies take a data-dependent number of
- cycles, contrary to the SGI documentation. There seem to be 3 or 4
- possible latencies.
- 4. The R1x000 processors can issue one floating-point operation, two integer
- operations, and one memory operation per cycle. The FPU has very short
- latencies, while the integer multiply unit is non-pipelined. We should
- therefore write fp based mpn_Xmul_1.
- STATUS
- Good...