diff options
author | Thomas Voss <mail@thomasvoss.com> | 2024-06-21 23:36:36 +0200 |
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committer | Thomas Voss <mail@thomasvoss.com> | 2024-06-21 23:42:26 +0200 |
commit | a89a14ef5da44684a16b204e7a70460cc8c4922a (patch) | |
tree | b23b4c6b155977909ef508fdae2f48d33d802813 /vendor/gmp-6.3.0/mpn/x86/k6/divrem_1.asm | |
parent | 1db63fcedab0b288820d66e100b1877b1a5a8851 (diff) |
Basic constant folding implementation
Diffstat (limited to 'vendor/gmp-6.3.0/mpn/x86/k6/divrem_1.asm')
-rw-r--r-- | vendor/gmp-6.3.0/mpn/x86/k6/divrem_1.asm | 203 |
1 files changed, 203 insertions, 0 deletions
diff --git a/vendor/gmp-6.3.0/mpn/x86/k6/divrem_1.asm b/vendor/gmp-6.3.0/mpn/x86/k6/divrem_1.asm new file mode 100644 index 0000000..b4cea4f --- /dev/null +++ b/vendor/gmp-6.3.0/mpn/x86/k6/divrem_1.asm @@ -0,0 +1,203 @@ +dnl AMD K6 mpn_divrem_1 -- mpn by limb division. + +dnl Copyright 1999-2003, 2007 Free Software Foundation, Inc. + +dnl This file is part of the GNU MP Library. +dnl +dnl The GNU MP Library is free software; you can redistribute it and/or modify +dnl it under the terms of either: +dnl +dnl * the GNU Lesser General Public License as published by the Free +dnl Software Foundation; either version 3 of the License, or (at your +dnl option) any later version. +dnl +dnl or +dnl +dnl * the GNU General Public License as published by the Free Software +dnl Foundation; either version 2 of the License, or (at your option) any +dnl later version. +dnl +dnl or both in parallel, as here. +dnl +dnl The GNU MP Library is distributed in the hope that it will be useful, but +dnl WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY +dnl or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License +dnl for more details. +dnl +dnl You should have received copies of the GNU General Public License and the +dnl GNU Lesser General Public License along with the GNU MP Library. If not, +dnl see https://www.gnu.org/licenses/. + +include(`../config.m4') + + +C K6: 20 cycles/limb + + +C mp_limb_t mpn_divrem_1 (mp_ptr dst, mp_size_t xsize, +C mp_srcptr src, mp_size_t size, mp_limb_t divisor); +C mp_limb_t mpn_divrem_1c (mp_ptr dst, mp_size_t xsize, +C mp_srcptr src, mp_size_t size, mp_limb_t divisor, +C mp_limb_t carry); +C +C The code here is basically the same as mpn/x86/divrem_1.asm, but uses loop +C instead of decl+jnz, since it comes out 2 cycles/limb faster. +C +C A test is done to see if the high limb is less than the divisor, and if so +C one less div is done. A div is 20 cycles, so assuming high<divisor about +C half the time, then this test saves half that amount. The branch +C misprediction penalty is less than that. +C +C Back-to-back div instructions run at 20 cycles, the same as the loop here, +C so it seems there's nothing to gain by rearranging the loop. Pairing the +C mov and loop instructions was found to gain nothing. +C +C Enhancements: +C +C The low-latency K6 multiply might be thought to suit a mul-by-inverse, but +C that algorithm has been found to suffer from the relatively poor carry +C handling on K6 and too many auxiliary instructions. The fractional part +C however could be done at about 13 c/l, if it mattered enough. + +defframe(PARAM_CARRY, 24) +defframe(PARAM_DIVISOR,20) +defframe(PARAM_SIZE, 16) +defframe(PARAM_SRC, 12) +defframe(PARAM_XSIZE, 8) +defframe(PARAM_DST, 4) + + TEXT + + ALIGN(32) +PROLOGUE(mpn_divrem_1c) +deflit(`FRAME',0) + + movl PARAM_SIZE, %ecx + pushl %edi FRAME_pushl() + + movl PARAM_SRC, %edi + pushl %esi FRAME_pushl() + + movl PARAM_DIVISOR, %esi + pushl %ebx FRAME_pushl() + + movl PARAM_DST, %ebx + pushl %ebp FRAME_pushl() + + movl PARAM_XSIZE, %ebp + orl %ecx, %ecx C size + + movl PARAM_CARRY, %edx + jz L(fraction) C if size==0 + + leal -4(%ebx,%ebp,4), %ebx C dst one limb below integer part + jmp L(integer_top) + +EPILOGUE() + + + ALIGN(16) +PROLOGUE(mpn_divrem_1) +deflit(`FRAME',0) + + movl PARAM_SIZE, %ecx + pushl %edi FRAME_pushl() + + movl PARAM_SRC, %edi + pushl %esi FRAME_pushl() + + movl PARAM_DIVISOR, %esi + orl %ecx,%ecx C size + + jz L(size_zero) + pushl %ebx FRAME_pushl() + + movl -4(%edi,%ecx,4), %eax C src high limb + xorl %edx, %edx + + movl PARAM_DST, %ebx + pushl %ebp FRAME_pushl() + + movl PARAM_XSIZE, %ebp + cmpl %esi, %eax + + leal -4(%ebx,%ebp,4), %ebx C dst one limb below integer part + jae L(integer_entry) + + + C high<divisor, so high of dst is zero, and avoid one div + + movl %edx, (%ebx,%ecx,4) + decl %ecx + + movl %eax, %edx + jz L(fraction) + + +L(integer_top): + C eax scratch (quotient) + C ebx dst+4*xsize-4 + C ecx counter + C edx scratch (remainder) + C esi divisor + C edi src + C ebp xsize + + movl -4(%edi,%ecx,4), %eax +L(integer_entry): + + divl %esi + + movl %eax, (%ebx,%ecx,4) + loop L(integer_top) + + +L(fraction): + orl %ebp, %ecx + jz L(done) + + movl PARAM_DST, %ebx + + +L(fraction_top): + C eax scratch (quotient) + C ebx dst + C ecx counter + C edx scratch (remainder) + C esi divisor + C edi + C ebp + + xorl %eax, %eax + + divl %esi + + movl %eax, -4(%ebx,%ecx,4) + loop L(fraction_top) + + +L(done): + popl %ebp + movl %edx, %eax + popl %ebx + popl %esi + popl %edi + ret + + +L(size_zero): +deflit(`FRAME',8) + movl PARAM_XSIZE, %ecx + xorl %eax, %eax + + movl PARAM_DST, %edi + + cld C better safe than sorry, see mpn/x86/README + + rep + stosl + + popl %esi + popl %edi + ret +EPILOGUE() |