diff options
Diffstat (limited to 'grub-core/lib/libgcrypt/mpi/pentium4/sse2/mpih-mul3.S')
| -rw-r--r-- | grub-core/lib/libgcrypt/mpi/pentium4/sse2/mpih-mul3.S | 127 |
1 files changed, 127 insertions, 0 deletions
diff --git a/grub-core/lib/libgcrypt/mpi/pentium4/sse2/mpih-mul3.S b/grub-core/lib/libgcrypt/mpi/pentium4/sse2/mpih-mul3.S new file mode 100644 index 0000000..ebcd2a6 --- /dev/null +++ b/grub-core/lib/libgcrypt/mpi/pentium4/sse2/mpih-mul3.S @@ -0,0 +1,127 @@ +/* Intel Pentium-4 mpn_submul_1 -- Multiply a limb vector with a limb and + * subtract the result from a second limb vector. + * + * Copyright 2001, 2002 Free Software Foundation, Inc. + * + * This file is part of Libgcrypt. + * + * Libgcrypt 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 2.1 of + * the License, or (at your option) any later version. + * + * Libgcrypt 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 this program; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA + * + * Note: This code is heavily based on the GNU MP Library. + * Actually it's the same code with only minor changes in the + * way the data is stored; this is to support the abstraction + * of an optional secure memory allocation which may be used + * to avoid revealing of sensitive data due to paging etc. + */ + + +#include "sysdep.h" +#include "asm-syntax.h" + + +/******************* + * mpi_limb_t + * _gcry_mpih_submul_1( mpi_ptr_t res_ptr, (sp + 4) + * mpi_ptr_t s1_ptr, (sp + 8) + * mpi_size_t s1_size, (sp + 12) + * mpi_limb_t s2_limb) (sp + 16) + * + * P4: 7 cycles/limb, unstable timing, at least on early Pentium4 silicon + * (stepping 10). + * + * This code is not particularly good at 7 c/l. The dependent chain is only + * 4 c/l and there's only 4 MMX unit instructions, so it's not clear why that + * speed isn't achieved. + * + * The arrangements made here to get a two instruction dependent chain are + * slightly subtle. In the loop the carry (or borrow rather) is a negative + * so that a paddq can be used to give a low limb ready to store, and a high + * limb ready to become the new carry after a psrlq. + * + * If the carry was a simple twos complement negative then the psrlq shift + * would need to bring in 0 bits or 1 bits according to whether the high was + * zero or non-zero, since a non-zero value would represent a negative + * needing sign extension. That wouldn't be particularly easy to arrange and + * certainly would add an instruction to the dependent chain, so instead an + * offset is applied so that the high limb will be 0xFFFFFFFF+c. With c in + * the range -0xFFFFFFFF to 0, the value 0xFFFFFFFF+c is in the range 0 to + * 0xFFFFFFFF and is therefore always positive and can always have 0 bits + * shifted in, which is what psrlq does. + * + * The extra 0xFFFFFFFF must be subtracted before c is used, but that can be + * done off the dependent chain. The total adjustment then is to add + * 0xFFFFFFFF00000000 to offset the new carry, and subtract + * 0x00000000FFFFFFFF to remove the offset from the current carry, for a net + * add of 0xFFFFFFFE00000001. In the code this is applied to the destination + * limb when fetched. + * + * It's also possible to view the 0xFFFFFFFF adjustment as a ones-complement + * negative, which is how it's undone for the return value, but that doesn't + * seem as clear. +*/ + + TEXT + ALIGN (4) + GLOBL C_SYMBOL_NAME(_gcry_mpih_submul_1) +C_SYMBOL_NAME(_gcry_mpih_submul_1:) + + pxor %mm1, %mm1 + +.Lstart_1c: + movl 8(%esp), %eax + pcmpeqd %mm0, %mm0 + + movd 16(%esp), %mm7 + pcmpeqd %mm6, %mm6 + + movl 4(%esp), %edx + psrlq $32, %mm0 + + movl 12(%esp), %ecx + psllq $32, %mm6 + + psubq %mm0, %mm6 + + psubq %mm1, %mm0 + +/* + C eax src, incrementing + C ebx + C ecx loop counter, decrementing + C edx dst, incrementing + C + C mm0 0xFFFFFFFF - borrow + C mm6 0xFFFFFFFE00000001 + C mm7 multiplier +*/ + +.Lloop: + movd (%eax), %mm1 + leal 4(%eax), %eax + movd (%edx), %mm2 + paddq %mm6, %mm2 + pmuludq %mm7, %mm1 + psubq %mm1, %mm2 + paddq %mm2, %mm0 + subl $1, %ecx + movd %mm0, (%edx) + psrlq $32, %mm0 + leal 4(%edx), %edx + jnz .Lloop + + movd %mm0, %eax + notl %eax + emms + ret |