mul_1.s
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- ; mc88100 __gmpn_mul_1 -- Multiply a limb vector with a single limb and
- ; store the product in a second limb vector.
- ; Copyright 1992, 1994, 1995, 2000 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/.
- ; INPUT PARAMETERS
- ; res_ptr r2
- ; s1_ptr r3
- ; size r4
- ; s2_limb r5
- ; Common overhead is about 11 cycles/invocation.
- ; The speed for S2_LIMB >= 0x10000 is approximately 21 cycles/limb. (The
- ; pipeline stalls 2 cycles due to WB contention.)
- ; The speed for S2_LIMB < 0x10000 is approximately 16 cycles/limb. (The
- ; pipeline stalls 2 cycles due to WB contention and 1 cycle due to latency.)
- ; To enhance speed:
- ; 1. Unroll main loop 4-8 times.
- ; 2. Schedule code to avoid WB contention. It might be tempting to move the
- ; ld instruction in the loops down to save 2 cycles (less WB contention),
- ; but that looses because the ultimate value will be read from outside
- ; the allocated space. But if we handle the ultimate multiplication in
- ; the tail, we can do this.
- ; 3. Make the multiplication with less instructions. I think the code for
- ; (S2_LIMB >= 0x10000) is not minimal.
- ; With these techniques the (S2_LIMB >= 0x10000) case would run in 17 or
- ; less cycles/limb; the (S2_LIMB < 0x10000) case would run in 11
- ; cycles/limb. (Assuming infinite unrolling.)
- text
- align 16
- global ___gmpn_mul_1
- ___gmpn_mul_1:
- ; Make S1_PTR and RES_PTR point at the end of their blocks
- ; and negate SIZE.
- lda r3,r3[r4]
- lda r6,r2[r4] ; RES_PTR in r6 since r2 is retval
- subu r4,r0,r4
- addu.co r2,r0,r0 ; r2 = cy = 0
- ld r9,r3[r4]
- mask r7,r5,0xffff ; r7 = lo(S2_LIMB)
- extu r8,r5,16 ; r8 = hi(S2_LIMB)
- bcnd.n eq0,r8,Lsmall ; jump if (hi(S2_LIMB) == 0)
- subu r6,r6,4
- ; General code for any value of S2_LIMB.
- ; Make a stack frame and save r25 and r26
- subu r31,r31,16
- st.d r25,r31,8
- ; Enter the loop in the middle
- br.n L1
- addu r4,r4,1
- Loop: ld r9,r3[r4]
- st r26,r6[r4]
- ; bcnd ne0,r0,0 ; bubble
- addu r4,r4,1
- L1: mul r26,r9,r5 ; low word of product mul_1 WB ld
- mask r12,r9,0xffff ; r12 = lo(s1_limb) mask_1
- mul r11,r12,r7 ; r11 = prod_0 mul_2 WB mask_1
- mul r10,r12,r8 ; r10 = prod_1a mul_3
- extu r13,r9,16 ; r13 = hi(s1_limb) extu_1 WB mul_1
- mul r12,r13,r7 ; r12 = prod_1b mul_4 WB extu_1
- mul r25,r13,r8 ; r25 = prod_2 mul_5 WB mul_2
- extu r11,r11,16 ; r11 = hi(prod_0) extu_2 WB mul_3
- addu r10,r10,r11 ; addu_1 WB extu_2
- ; bcnd ne0,r0,0 ; bubble WB addu_1
- addu.co r10,r10,r12 ; WB mul_4
- mask.u r10,r10,0xffff ; move the 16 most significant bits...
- addu.ci r10,r10,r0 ; ...to the low half of the word...
- rot r10,r10,16 ; ...and put carry in pos 16.
- addu.co r26,r26,r2 ; add old carry limb
- bcnd.n ne0,r4,Loop
- addu.ci r2,r25,r10 ; compute new carry limb
- st r26,r6[r4]
- ld.d r25,r31,8
- jmp.n r1
- addu r31,r31,16
- ; Fast code for S2_LIMB < 0x10000
- Lsmall:
- ; Enter the loop in the middle
- br.n SL1
- addu r4,r4,1
- SLoop: ld r9,r3[r4] ;
- st r8,r6[r4] ;
- addu r4,r4,1 ;
- SL1: mul r8,r9,r5 ; low word of product
- mask r12,r9,0xffff ; r12 = lo(s1_limb)
- extu r13,r9,16 ; r13 = hi(s1_limb)
- mul r11,r12,r7 ; r11 = prod_0
- mul r12,r13,r7 ; r12 = prod_1b
- addu.cio r8,r8,r2 ; add old carry limb
- extu r10,r11,16 ; r11 = hi(prod_0)
- addu r10,r10,r12 ;
- bcnd.n ne0,r4,SLoop
- extu r2,r10,16 ; r2 = new carry limb
- jmp.n r1
- st r8,r6[r4]