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+/* alpha rshift
+ * Copyright (C) 1994, 1995, 1998, 1999,
+ * 2000, 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.
+ */
+
+
+
+
+/*******************
+ * mpi_limb_t
+ * _gcry_mpih_rshift( mpi_ptr_t wp, (r16)
+ * mpi_ptr_t up, (r17)
+ * mpi_size_t usize, (r18)
+ * unsigned cnt) (r19)
+ *
+ * This code runs at 4.8 cycles/limb on the 21064. With infinite unrolling,
+ * it would take 4 cycles/limb. It should be possible to get down to 3
+ * cycles/limb since both ldq and stq can be paired with the other used
+ * instructions. But there are many restrictions in the 21064 pipeline that
+ * makes it hard, if not impossible, to get down to 3 cycles/limb:
+ *
+ * 1. ldq has a 3 cycle delay, srl and sll have a 2 cycle delay.
+ * 2. Only aligned instruction pairs can be paired.
+ * 3. The store buffer or silo might not be able to deal with the bandwidth.
+ */
+
+ .set noreorder
+ .set noat
+.text
+ .align 3
+ .globl _gcry_mpih_rshift
+ .ent _gcry_mpih_rshift
+_gcry_mpih_rshift:
+ .frame $30,0,$26,0
+
+ ldq $4,0($17) # load first limb
+ addq $17,8,$17
+ subq $31,$19,$7
+ subq $18,1,$18
+ and $18,4-1,$20 # number of limbs in first loop
+ sll $4,$7,$0 # compute function result
+
+ beq $20,.R0
+ subq $18,$20,$18
+
+ .align 3
+.Roop0:
+ ldq $3,0($17)
+ addq $16,8,$16
+ addq $17,8,$17
+ subq $20,1,$20
+ srl $4,$19,$5
+ sll $3,$7,$6
+ bis $3,$3,$4
+ bis $5,$6,$8
+ stq $8,-8($16)
+ bne $20,.Roop0
+
+.R0: beq $18,.Rend
+
+ .align 3
+.Roop: ldq $3,0($17)
+ addq $16,32,$16
+ subq $18,4,$18
+ srl $4,$19,$5
+ sll $3,$7,$6
+
+ ldq $4,8($17)
+ srl $3,$19,$1
+ bis $5,$6,$8
+ stq $8,-32($16)
+ sll $4,$7,$2
+
+ ldq $3,16($17)
+ srl $4,$19,$5
+ bis $1,$2,$8
+ stq $8,-24($16)
+ sll $3,$7,$6
+
+ ldq $4,24($17)
+ srl $3,$19,$1
+ bis $5,$6,$8
+ stq $8,-16($16)
+ sll $4,$7,$2
+
+ addq $17,32,$17
+ bis $1,$2,$8
+ stq $8,-8($16)
+
+ bgt $18,.Roop
+
+.Rend: srl $4,$19,$8
+ stq $8,0($16)
+ ret $31,($26),1
+ .end _gcry_mpih_rshift
+