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153 lines
2.8 KiB
NASM
153 lines
2.8 KiB
NASM
dnl AMD64 mpn_lshsub_n. R = 2^k(U - V).
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dnl Copyright 2006 Free Software Foundation, Inc.
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dnl This file is part of the GNU MP Library.
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dnl The GNU MP Library is free software; you can redistribute it and/or modify
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dnl it under the terms of the GNU Lesser General Public License as published
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dnl by the Free Software Foundation; either version 3 of the License, or (at
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dnl your option) any later version.
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dnl The GNU MP Library is distributed in the hope that it will be useful, but
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dnl WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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dnl or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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dnl License for more details.
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dnl You should have received a copy of the GNU Lesser General Public License
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dnl along with the GNU MP Library. If not, see http://www.gnu.org/licenses/.
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include(`../config.m4')
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C cycles/limb
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C K8,K9: 3.15 (mpn_sub_n + mpn_lshift costs about 4 c/l)
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C K10: 3.15 (mpn_sub_n + mpn_lshift costs about 4 c/l)
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C P4: 16.5
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C P6-15: 4.35
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C This was written quickly and not optimized at all, but it runs very well on
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C K8. But perhaps one could get under 3 c/l. Ideas:
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C 1) Use indexing to save the 3 LEA
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C 2) Write reasonable feed-in code
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C 3) Be more clever about register usage
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C 4) Unroll more, handling CL negation, carry save/restore cost much now
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C 5) Reschedule
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C INPUT PARAMETERS
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define(`rp', `%rdi')
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define(`up', `%rsi')
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define(`vp', `%rdx')
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define(`n', `%rcx')
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define(`cnt', `%r8')
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ASM_START()
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TEXT
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ALIGN(16)
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PROLOGUE(mpn_lshsub_n)
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push %r12
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push %r13
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push %r14
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push %r15
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push %rbx
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mov n, %rax
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xor %ebx, %ebx C clear carry save register
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mov %r8d, %ecx C shift count
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xor %r15d, %r15d C limb carry
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mov %eax, %r11d
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and $3, %r11d
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je L(4)
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sub $1, %r11d
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L(oopette):
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add %ebx, %ebx C restore carry flag
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mov 0(up), %r8
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lea 8(up), up
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sbb 0(vp), %r8
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mov %r8, %r12
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sbb %ebx, %ebx C save carry flag
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shl %cl, %r8
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or %r15, %r8
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mov %r12, %r15
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lea 8(vp), vp
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neg %cl
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shr %cl, %r15
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neg %cl
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mov %r8, 0(rp)
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lea 8(rp), rp
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sub $1, %r11d
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jnc L(oopette)
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L(4):
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sub $4, %rax
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jc L(end)
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ALIGN(16)
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L(oop):
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add %ebx, %ebx C restore carry flag
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mov 0(up), %r8
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mov 8(up), %r9
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mov 16(up), %r10
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mov 24(up), %r11
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lea 32(up), up
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sbb 0(vp), %r8
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mov %r8, %r12
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sbb 8(vp), %r9
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mov %r9, %r13
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sbb 16(vp), %r10
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mov %r10, %r14
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sbb 24(vp), %r11
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sbb %ebx, %ebx C save carry flag
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shl %cl, %r8
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shl %cl, %r9
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shl %cl, %r10
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or %r15, %r8
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mov %r11, %r15
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shl %cl, %r11
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lea 32(vp), vp
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neg %cl
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shr %cl, %r12
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shr %cl, %r13
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shr %cl, %r14
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shr %cl, %r15 C used next loop
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or %r12, %r9
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or %r13, %r10
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or %r14, %r11
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neg %cl
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mov %r8, 0(rp)
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mov %r9, 8(rp)
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mov %r10, 16(rp)
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mov %r11, 24(rp)
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lea 32(rp), rp
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sub $4, %rax
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jnc L(oop)
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L(end):
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neg %ebx
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shl %cl, %rbx
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adc %r15, %rbx
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mov %rbx, %rax
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pop %rbx
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pop %r15
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pop %r14
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pop %r13
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pop %r12
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ret
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EPILOGUE()
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