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128 lines
4.0 KiB
ArmAsm
128 lines
4.0 KiB
ArmAsm
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; mc88100 __mpn_mul_1 -- Multiply a limb vector with a single limb and
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; store the product in a second limb vector.
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; Copyright (C) 1992, 1994 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 General Public License as published by
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; the Free Software Foundation; either version 2, or (at your option)
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; any later version.
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; The GNU MP 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
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; GNU General Public License for more details.
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; You should have received a copy of the GNU General Public License
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; along with the GNU MP Library; see the file COPYING. If not, write to
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; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
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; INPUT PARAMETERS
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; res_ptr r2
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; s1_ptr r3
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; size r4
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; s2_limb r5
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; Common overhead is about 11 cycles/invocation.
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; The speed for S2_LIMB >= 0x10000 is approximately 21 cycles/limb. (The
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; pipeline stalls 2 cycles due to WB contention.)
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; The speed for S2_LIMB < 0x10000 is approximately 16 cycles/limb. (The
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; pipeline stalls 2 cycles due to WB contention and 1 cycle due to latency.)
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; To enhance speed:
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; 1. Unroll main loop 4-8 times.
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; 2. Schedule code to avoid WB contention. It might be tempting to move the
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; ld instruction in the loops down to save 2 cycles (less WB contention),
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; but that looses because the ultimate value will be read from outside
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; the allocated space. But if we handle the ultimate multiplication in
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; the tail, we can do this.
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; 3. Make the multiplication with less instructions. I think the code for
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; (S2_LIMB >= 0x10000) is not minimal.
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; With these techniques the (S2_LIMB >= 0x10000) case would run in 17 or
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; less cycles/limb; the (S2_LIMB < 0x10000) case would run in 11
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; cycles/limb. (Assuming infinite unrolling.)
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#include "sysdep.h"
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ENTRY (__mpn_mul_1)
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; Make S1_PTR and RES_PTR point at the end of their blocks
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; and negate SIZE.
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lda r3,r3[r4]
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lda r6,r2[r4] ; RES_PTR in r6 since r2 is retval
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subu r4,r0,r4
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addu.co r2,r0,r0 ; r2 = cy = 0
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ld r9,r3[r4]
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mask r7,r5,0xffff ; r7 = lo(S2_LIMB)
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extu r8,r5,16 ; r8 = hi(S2_LIMB)
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bcnd.n eq0,r8,Lsmall ; jump if (hi(S2_LIMB) == 0)
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subu r6,r6,4
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; General code for any value of S2_LIMB.
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; Make a stack frame and save r25 and r26
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subu r31,r31,16
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st.d r25,r31,8
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; Enter the loop in the middle
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br.n L1
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addu r4,r4,1
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Loop:
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ld r9,r3[r4]
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st r26,r6[r4]
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; bcnd ne0,r0,0 ; bubble
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addu r4,r4,1
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L1: mul r26,r9,r5 ; low word of product mul_1 WB ld
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mask r12,r9,0xffff ; r12 = lo(s1_limb) mask_1
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mul r11,r12,r7 ; r11 = prod_0 mul_2 WB mask_1
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mul r10,r12,r8 ; r10 = prod_1a mul_3
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extu r13,r9,16 ; r13 = hi(s1_limb) extu_1 WB mul_1
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mul r12,r13,r7 ; r12 = prod_1b mul_4 WB extu_1
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mul r25,r13,r8 ; r25 = prod_2 mul_5 WB mul_2
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extu r11,r11,16 ; r11 = hi(prod_0) extu_2 WB mul_3
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addu r10,r10,r11 ; addu_1 WB extu_2
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; bcnd ne0,r0,0 ; bubble WB addu_1
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addu.co r10,r10,r12 ; WB mul_4
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mask.u r10,r10,0xffff ; move the 16 most significant bits...
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addu.ci r10,r10,r0 ; ...to the low half of the word...
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rot r10,r10,16 ; ...and put carry in pos 16.
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addu.co r26,r26,r2 ; add old carry limb
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bcnd.n ne0,r4,Loop
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addu.ci r2,r25,r10 ; compute new carry limb
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st r26,r6[r4]
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ld.d r25,r31,8
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jmp.n r1
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addu r31,r31,16
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; Fast code for S2_LIMB < 0x10000
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Lsmall:
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; Enter the loop in the middle
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br.n SL1
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addu r4,r4,1
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SLoop:
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ld r9,r3[r4] ;
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st r8,r6[r4] ;
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addu r4,r4,1 ;
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SL1: mul r8,r9,r5 ; low word of product
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mask r12,r9,0xffff ; r12 = lo(s1_limb)
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extu r13,r9,16 ; r13 = hi(s1_limb)
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mul r11,r12,r7 ; r11 = prod_0
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mul r12,r13,r7 ; r12 = prod_1b
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addu.cio r8,r8,r2 ; add old carry limb
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extu r10,r11,16 ; r11 = hi(prod_0)
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addu r10,r10,r12 ;
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bcnd.n ne0,r4,SLoop
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extu r2,r10,16 ; r2 = new carry limb
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jmp.n r1
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st r8,r6[r4]
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