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1.1 maekawa 1: dnl AMD K6-2 mpn_rshift -- mpn right shift.
2: dnl
3: dnl K6-2: 1.75 cycles/limb
4:
5:
6: dnl Copyright (C) 1999, 2000 Free Software Foundation, Inc.
7: dnl
8: dnl This file is part of the GNU MP Library.
9: dnl
10: dnl The GNU MP Library is free software; you can redistribute it and/or
11: dnl modify it under the terms of the GNU Lesser General Public License as
12: dnl published by the Free Software Foundation; either version 2.1 of the
13: dnl License, or (at your option) any later version.
14: dnl
15: dnl The GNU MP Library is distributed in the hope that it will be useful,
16: dnl but WITHOUT ANY WARRANTY; without even the implied warranty of
17: dnl MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
18: dnl Lesser General Public License for more details.
19: dnl
20: dnl You should have received a copy of the GNU Lesser General Public
21: dnl License along with the GNU MP Library; see the file COPYING.LIB. If
22: dnl not, write to the Free Software Foundation, Inc., 59 Temple Place -
23: dnl Suite 330, Boston, MA 02111-1307, USA.
24:
25:
26: include(`../config.m4')
27:
28:
29: C mp_limb_t mpn_rshift (mp_ptr dst, mp_srcptr src, mp_size_t size,
30: C unsigned shift);
31: C
32:
33: defframe(PARAM_SHIFT,16)
34: defframe(PARAM_SIZE, 12)
35: defframe(PARAM_SRC, 8)
36: defframe(PARAM_DST, 4)
37: deflit(`FRAME',0)
38:
39: dnl Minimum 9, because the unrolled loop can't handle less.
40: dnl
41: deflit(UNROLL_THRESHOLD, 9)
42:
43: .text
44: ALIGN(32)
45:
46: PROLOGUE(mpn_rshift)
47: deflit(`FRAME',0)
48:
49: C The 1 limb case can be done without the push %ebx, but it's then
50: C still the same speed. The push is left as a free helping hand for
51: C the two_or_more code.
52:
53: movl PARAM_SIZE, %eax
54: pushl %ebx FRAME_pushl()
55:
56: movl PARAM_SRC, %ebx
57: decl %eax
58:
59: movl PARAM_SHIFT, %ecx
60: jnz L(two_or_more)
61:
62: movl (%ebx), %edx C src limb
63: movl PARAM_DST, %ebx
64:
65: shrdl( %cl, %edx, %eax) C return value
66:
67: shrl %cl, %edx
68:
69: movl %edx, (%ebx) C dst limb
70: popl %ebx
71:
72: ret
73:
74:
75: C -----------------------------------------------------------------------------
76: ALIGN(16) C avoid offset 0x1f
77: L(two_or_more):
78: C eax size-1
79: C ebx src
80: C ecx shift
81: C edx
82:
83: movl (%ebx), %edx C src low limb
84: negl %ecx
85:
86: addl $32, %ecx
87: movd PARAM_SHIFT, %mm6
88:
89: shll %cl, %edx
90: cmpl $UNROLL_THRESHOLD-1, %eax
91:
92: jae L(unroll)
93:
94:
95: C eax size-1
96: C ebx src
97: C ecx 32-shift
98: C edx retval
99: C
100: C mm6 shift
101:
102: movl PARAM_DST, %ecx
103: leal (%ebx,%eax,4), %ebx
104:
105: leal -4(%ecx,%eax,4), %ecx
106: negl %eax
107:
108: C This loop runs at about 3 cycles/limb, which is the amount of
109: C decoding, and this is despite every second access being unaligned.
110:
111: L(simple):
112: C eax counter, -(size-1) to -1
113: C ebx &src[size-1]
114: C ecx &dst[size-1]
115: C edx retval
116: C
117: C mm0 scratch
118: C mm6 shift
119:
120: Zdisp( movq, 0,(%ebx,%eax,4), %mm0)
121: incl %eax
122:
123: psrlq %mm6, %mm0
124:
125: Zdisp( movd, %mm0, 0,(%ecx,%eax,4))
126: jnz L(simple)
127:
128:
129: movq %mm0, (%ecx)
130: movl %edx, %eax
131:
132: popl %ebx
133:
134: femms
135: ret
136:
137:
138: C -----------------------------------------------------------------------------
139: ALIGN(16)
140: L(unroll):
141: C eax size-1
142: C ebx src
143: C ecx 32-shift
144: C edx retval
145: C
146: C mm6 shift
147:
148: addl $32, %ecx
149: subl $7, %eax C size-8
150:
151: movd %ecx, %mm7
152: movl PARAM_DST, %ecx
153:
154: movq (%ebx), %mm2 C src low qword
155: leal (%ebx,%eax,4), %ebx C src end - 32
156:
157: testb $4, %cl
158: leal (%ecx,%eax,4), %ecx C dst end - 32
159:
160: notl %eax C -(size-7)
161: jz L(dst_aligned)
162:
163: psrlq %mm6, %mm2
164: incl %eax
165:
166: Zdisp( movd, %mm2, 0,(%ecx,%eax,4)) C dst low limb
167: movq 4(%ebx,%eax,4), %mm2 C new src low qword
168: L(dst_aligned):
169:
170: movq 12(%ebx,%eax,4), %mm0 C src second lowest qword
171: nop C avoid bad cache line crossing
172:
173:
174: C This loop is the important bit, the rest is just support for it.
175: C Four src limbs are held at the start, and four more will be read.
176: C Four dst limbs will be written. This schedule seems necessary for
177: C full speed.
178: C
179: C The use of -(size-7) lets the loop stop when %eax becomes >= 0 and
180: C and leaves 0 to 3 which can be tested with test $1 and $2.
181:
182: L(top):
183: C eax counter, -(size-7) step by +4 until >=0
184: C ebx src end - 32
185: C ecx dst end - 32
186: C edx retval
187: C
188: C mm0 src next qword
189: C mm1 scratch
190: C mm2 src prev qword
191: C mm6 shift
192: C mm7 64-shift
193:
194: psrlq %mm6, %mm2
195: addl $4, %eax
196:
197: movq %mm0, %mm1
198: psllq %mm7, %mm0
199:
200: por %mm0, %mm2
201: movq 4(%ebx,%eax,4), %mm0
202:
203: psrlq %mm6, %mm1
204: movq %mm2, -12(%ecx,%eax,4)
205:
206: movq %mm0, %mm2
207: psllq %mm7, %mm0
208:
209: por %mm0, %mm1
210: movq 12(%ebx,%eax,4), %mm0
211:
212: movq %mm1, -4(%ecx,%eax,4)
213: ja L(top) C jump if no carry and not zero
214:
215:
216:
217: C Now have the four limbs in mm2 (low) and mm0 (high), and %eax is 0
218: C to 3 representing respectively 3 to 0 further limbs.
219:
220: testl $2, %eax C testl to avoid bad cache line crossings
221: jnz L(finish_nottwo)
222:
223: C Two or three extra limbs: rshift mm2, OR it with lshifted mm0, mm0
224: C becomes new mm2 and a new mm0 is loaded.
225:
226: psrlq %mm6, %mm2
227: movq %mm0, %mm1
228:
229: psllq %mm7, %mm0
230: addl $2, %eax
231:
232: por %mm0, %mm2
233: movq 12(%ebx,%eax,4), %mm0
234:
235: movq %mm2, -4(%ecx,%eax,4)
236: movq %mm1, %mm2
237: L(finish_nottwo):
238:
239:
240: testb $1, %al
241: psrlq %mm6, %mm2
242:
243: movq %mm0, %mm1
244: psllq %mm7, %mm0
245:
246: por %mm0, %mm2
247: psrlq %mm6, %mm1
248:
249: movq %mm2, 4(%ecx,%eax,4)
250: jnz L(finish_even)
251:
252:
253: C one further extra limb to process
254:
255: movd 32-4(%ebx), %mm0 C src[size-1], most significant limb
256: popl %ebx
257:
258: movq %mm0, %mm2
259: psllq %mm7, %mm0
260:
261: por %mm0, %mm1
262: psrlq %mm6, %mm2
263:
264: movq %mm1, 32-12(%ecx) C dst[size-3,size-2]
265: movd %mm2, 32-4(%ecx) C dst[size-1]
266:
267: movl %edx, %eax C retval
268:
269: femms
270: ret
271:
272:
273: nop C avoid bad cache line crossing
274: L(finish_even):
275: C no further extra limbs
276:
277: movq %mm1, 32-8(%ecx) C dst[size-2,size-1]
278: movl %edx, %eax C retval
279:
280: popl %ebx
281:
282: femms
283: ret
284:
285: EPILOGUE()