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69 lines
1.9 KiB
ArmAsm
69 lines
1.9 KiB
ArmAsm
/* Subtract two limb vectors of equal, non-zero length for PowerPC.
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Copyright (C) 1997-2020 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <sysdep.h>
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/* mp_limb_t mpn_sub_n (mp_ptr res_ptr, mp_srcptr s1_ptr, mp_srcptr s2_ptr,
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mp_size_t size)
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Calculate s1-s2 and put result in res_ptr; return borrow, 0 or 1. */
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/* Note on optimisation: This code is optimal for the 601. Almost every other
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possible 2-unrolled inner loop will not be. Also, watch out for the
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alignment... */
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EALIGN (__mpn_sub_n, 3, 1)
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/* Set up for loop below. */
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mtcrf 0x01,r6
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srwi. r7,r6,1
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mtctr r7
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bt 31,L(2)
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/* Set the carry (clear the borrow). */
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subfc r0,r0,r0
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/* Adjust pointers for loop. */
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addi r3,r3,-4
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addi r4,r4,-4
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addi r5,r5,-4
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b L(0)
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L(2): lwz r7,0(r5)
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lwz r6,0(r4)
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subfc r6,r7,r6
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stw r6,0(r3)
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beq L(1)
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/* Align start of loop to an odd word boundary to guarantee that the
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last two words can be fetched in one access (for 601). This turns
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out to be important. */
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L(0):
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lwz r9,4(r4)
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lwz r8,4(r5)
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lwzu r6,8(r4)
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lwzu r7,8(r5)
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subfe r8,r8,r9
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stw r8,4(r3)
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subfe r6,r7,r6
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stwu r6,8(r3)
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bdnz L(0)
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/* Return the borrow. */
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L(1): subfe r3,r3,r3
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neg r3,r3
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blr
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END (__mpn_sub_n)
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