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1da177e4 LT |
1 | /* |
2 | * | |
3 | * Optimized version of the standard memcpy() function | |
4 | * | |
5 | * Inputs: | |
6 | * in0: destination address | |
7 | * in1: source address | |
8 | * in2: number of bytes to copy | |
9 | * Output: | |
10 | * no return value | |
11 | * | |
12 | * Copyright (C) 2000-2001 Hewlett-Packard Co | |
13 | * Stephane Eranian <eranian@hpl.hp.com> | |
14 | * David Mosberger-Tang <davidm@hpl.hp.com> | |
15 | */ | |
16 | #include <asm/asmmacro.h> | |
e007c533 | 17 | #include <asm/export.h> |
1da177e4 LT |
18 | |
19 | GLOBAL_ENTRY(memcpy) | |
20 | ||
21 | # define MEM_LAT 21 /* latency to memory */ | |
22 | ||
23 | # define dst r2 | |
24 | # define src r3 | |
25 | # define retval r8 | |
26 | # define saved_pfs r9 | |
27 | # define saved_lc r10 | |
28 | # define saved_pr r11 | |
29 | # define cnt r16 | |
30 | # define src2 r17 | |
31 | # define t0 r18 | |
32 | # define t1 r19 | |
33 | # define t2 r20 | |
34 | # define t3 r21 | |
35 | # define t4 r22 | |
36 | # define src_end r23 | |
37 | ||
38 | # define N (MEM_LAT + 4) | |
39 | # define Nrot ((N + 7) & ~7) | |
40 | ||
41 | /* | |
42 | * First, check if everything (src, dst, len) is a multiple of eight. If | |
43 | * so, we handle everything with no taken branches (other than the loop | |
44 | * itself) and a small icache footprint. Otherwise, we jump off to | |
45 | * the more general copy routine handling arbitrary | |
46 | * sizes/alignment etc. | |
47 | */ | |
48 | .prologue | |
49 | .save ar.pfs, saved_pfs | |
50 | alloc saved_pfs=ar.pfs,3,Nrot,0,Nrot | |
51 | .save ar.lc, saved_lc | |
52 | mov saved_lc=ar.lc | |
53 | or t0=in0,in1 | |
54 | ;; | |
55 | ||
56 | or t0=t0,in2 | |
57 | .save pr, saved_pr | |
58 | mov saved_pr=pr | |
59 | ||
60 | .body | |
61 | ||
62 | cmp.eq p6,p0=in2,r0 // zero length? | |
63 | mov retval=in0 // return dst | |
64 | (p6) br.ret.spnt.many rp // zero length, return immediately | |
65 | ;; | |
66 | ||
67 | mov dst=in0 // copy because of rotation | |
68 | shr.u cnt=in2,3 // number of 8-byte words to copy | |
69 | mov pr.rot=1<<16 | |
70 | ;; | |
71 | ||
72 | adds cnt=-1,cnt // br.ctop is repeat/until | |
73 | cmp.gtu p7,p0=16,in2 // copying less than 16 bytes? | |
74 | mov ar.ec=N | |
75 | ;; | |
76 | ||
77 | and t0=0x7,t0 | |
78 | mov ar.lc=cnt | |
79 | ;; | |
80 | cmp.ne p6,p0=t0,r0 | |
81 | ||
82 | mov src=in1 // copy because of rotation | |
83 | (p7) br.cond.spnt.few .memcpy_short | |
84 | (p6) br.cond.spnt.few .memcpy_long | |
85 | ;; | |
86 | nop.m 0 | |
87 | ;; | |
88 | nop.m 0 | |
89 | nop.i 0 | |
90 | ;; | |
91 | nop.m 0 | |
92 | ;; | |
93 | .rotr val[N] | |
94 | .rotp p[N] | |
95 | .align 32 | |
96 | 1: { .mib | |
97 | (p[0]) ld8 val[0]=[src],8 | |
98 | nop.i 0 | |
99 | brp.loop.imp 1b, 2f | |
100 | } | |
101 | 2: { .mfb | |
102 | (p[N-1])st8 [dst]=val[N-1],8 | |
103 | nop.f 0 | |
104 | br.ctop.dptk.few 1b | |
105 | } | |
106 | ;; | |
107 | mov ar.lc=saved_lc | |
108 | mov pr=saved_pr,-1 | |
109 | mov ar.pfs=saved_pfs | |
110 | br.ret.sptk.many rp | |
111 | ||
112 | /* | |
113 | * Small (<16 bytes) unaligned copying is done via a simple byte-at-the-time | |
114 | * copy loop. This performs relatively poorly on Itanium, but it doesn't | |
115 | * get used very often (gcc inlines small copies) and due to atomicity | |
116 | * issues, we want to avoid read-modify-write of entire words. | |
117 | */ | |
118 | .align 32 | |
119 | .memcpy_short: | |
120 | adds cnt=-1,in2 // br.ctop is repeat/until | |
121 | mov ar.ec=MEM_LAT | |
122 | brp.loop.imp 1f, 2f | |
123 | ;; | |
124 | mov ar.lc=cnt | |
125 | ;; | |
126 | nop.m 0 | |
127 | ;; | |
128 | nop.m 0 | |
129 | nop.i 0 | |
130 | ;; | |
131 | nop.m 0 | |
132 | ;; | |
133 | nop.m 0 | |
134 | ;; | |
135 | /* | |
136 | * It is faster to put a stop bit in the loop here because it makes | |
137 | * the pipeline shorter (and latency is what matters on short copies). | |
138 | */ | |
139 | .align 32 | |
140 | 1: { .mib | |
141 | (p[0]) ld1 val[0]=[src],1 | |
142 | nop.i 0 | |
143 | brp.loop.imp 1b, 2f | |
144 | } ;; | |
145 | 2: { .mfb | |
146 | (p[MEM_LAT-1])st1 [dst]=val[MEM_LAT-1],1 | |
147 | nop.f 0 | |
148 | br.ctop.dptk.few 1b | |
149 | } ;; | |
150 | mov ar.lc=saved_lc | |
151 | mov pr=saved_pr,-1 | |
152 | mov ar.pfs=saved_pfs | |
153 | br.ret.sptk.many rp | |
154 | ||
155 | /* | |
156 | * Large (>= 16 bytes) copying is done in a fancy way. Latency isn't | |
157 | * an overriding concern here, but throughput is. We first do | |
158 | * sub-word copying until the destination is aligned, then we check | |
159 | * if the source is also aligned. If so, we do a simple load/store-loop | |
160 | * until there are less than 8 bytes left over and then we do the tail, | |
161 | * by storing the last few bytes using sub-word copying. If the source | |
162 | * is not aligned, we branch off to the non-congruent loop. | |
163 | * | |
164 | * stage: op: | |
165 | * 0 ld | |
166 | * : | |
167 | * MEM_LAT+3 shrp | |
168 | * MEM_LAT+4 st | |
169 | * | |
170 | * On Itanium, the pipeline itself runs without stalls. However, br.ctop | |
171 | * seems to introduce an unavoidable bubble in the pipeline so the overall | |
172 | * latency is 2 cycles/iteration. This gives us a _copy_ throughput | |
173 | * of 4 byte/cycle. Still not bad. | |
174 | */ | |
175 | # undef N | |
176 | # undef Nrot | |
177 | # define N (MEM_LAT + 5) /* number of stages */ | |
178 | # define Nrot ((N+1 + 2 + 7) & ~7) /* number of rotating regs */ | |
179 | ||
180 | #define LOG_LOOP_SIZE 6 | |
181 | ||
182 | .memcpy_long: | |
183 | alloc t3=ar.pfs,3,Nrot,0,Nrot // resize register frame | |
184 | and t0=-8,src // t0 = src & ~7 | |
185 | and t2=7,src // t2 = src & 7 | |
186 | ;; | |
187 | ld8 t0=[t0] // t0 = 1st source word | |
188 | adds src2=7,src // src2 = (src + 7) | |
189 | sub t4=r0,dst // t4 = -dst | |
190 | ;; | |
191 | and src2=-8,src2 // src2 = (src + 7) & ~7 | |
192 | shl t2=t2,3 // t2 = 8*(src & 7) | |
193 | shl t4=t4,3 // t4 = 8*(dst & 7) | |
194 | ;; | |
195 | ld8 t1=[src2] // t1 = 1st source word if src is 8-byte aligned, 2nd otherwise | |
196 | sub t3=64,t2 // t3 = 64-8*(src & 7) | |
197 | shr.u t0=t0,t2 | |
198 | ;; | |
199 | add src_end=src,in2 | |
200 | shl t1=t1,t3 | |
201 | mov pr=t4,0x38 // (p5,p4,p3)=(dst & 7) | |
202 | ;; | |
203 | or t0=t0,t1 | |
204 | mov cnt=r0 | |
205 | adds src_end=-1,src_end | |
206 | ;; | |
207 | (p3) st1 [dst]=t0,1 | |
208 | (p3) shr.u t0=t0,8 | |
209 | (p3) adds cnt=1,cnt | |
210 | ;; | |
211 | (p4) st2 [dst]=t0,2 | |
212 | (p4) shr.u t0=t0,16 | |
213 | (p4) adds cnt=2,cnt | |
214 | ;; | |
215 | (p5) st4 [dst]=t0,4 | |
216 | (p5) adds cnt=4,cnt | |
217 | and src_end=-8,src_end // src_end = last word of source buffer | |
218 | ;; | |
219 | ||
220 | // At this point, dst is aligned to 8 bytes and there at least 16-7=9 bytes left to copy: | |
221 | ||
222 | 1:{ add src=cnt,src // make src point to remainder of source buffer | |
223 | sub cnt=in2,cnt // cnt = number of bytes left to copy | |
224 | mov t4=ip | |
225 | } ;; | |
226 | and src2=-8,src // align source pointer | |
227 | adds t4=.memcpy_loops-1b,t4 | |
228 | mov ar.ec=N | |
229 | ||
230 | and t0=7,src // t0 = src & 7 | |
231 | shr.u t2=cnt,3 // t2 = number of 8-byte words left to copy | |
232 | shl cnt=cnt,3 // move bits 0-2 to 3-5 | |
233 | ;; | |
234 | ||
235 | .rotr val[N+1], w[2] | |
236 | .rotp p[N] | |
237 | ||
238 | cmp.ne p6,p0=t0,r0 // is src aligned, too? | |
239 | shl t0=t0,LOG_LOOP_SIZE // t0 = 8*(src & 7) | |
240 | adds t2=-1,t2 // br.ctop is repeat/until | |
241 | ;; | |
242 | add t4=t0,t4 | |
243 | mov pr=cnt,0x38 // set (p5,p4,p3) to # of bytes last-word bytes to copy | |
244 | mov ar.lc=t2 | |
245 | ;; | |
246 | nop.m 0 | |
247 | ;; | |
248 | nop.m 0 | |
249 | nop.i 0 | |
250 | ;; | |
251 | nop.m 0 | |
252 | ;; | |
253 | (p6) ld8 val[1]=[src2],8 // prime the pump... | |
254 | mov b6=t4 | |
255 | br.sptk.few b6 | |
256 | ;; | |
257 | ||
258 | .memcpy_tail: | |
259 | // At this point, (p5,p4,p3) are set to the number of bytes left to copy (which is | |
260 | // less than 8) and t0 contains the last few bytes of the src buffer: | |
261 | (p5) st4 [dst]=t0,4 | |
262 | (p5) shr.u t0=t0,32 | |
263 | mov ar.lc=saved_lc | |
264 | ;; | |
265 | (p4) st2 [dst]=t0,2 | |
266 | (p4) shr.u t0=t0,16 | |
267 | mov ar.pfs=saved_pfs | |
268 | ;; | |
269 | (p3) st1 [dst]=t0 | |
270 | mov pr=saved_pr,-1 | |
271 | br.ret.sptk.many rp | |
272 | ||
273 | /////////////////////////////////////////////////////// | |
274 | .align 64 | |
275 | ||
276 | #define COPY(shift,index) \ | |
277 | 1: { .mib \ | |
278 | (p[0]) ld8 val[0]=[src2],8; \ | |
279 | (p[MEM_LAT+3]) shrp w[0]=val[MEM_LAT+3],val[MEM_LAT+4-index],shift; \ | |
280 | brp.loop.imp 1b, 2f \ | |
281 | }; \ | |
282 | 2: { .mfb \ | |
283 | (p[MEM_LAT+4]) st8 [dst]=w[1],8; \ | |
284 | nop.f 0; \ | |
285 | br.ctop.dptk.few 1b; \ | |
286 | }; \ | |
287 | ;; \ | |
288 | ld8 val[N-1]=[src_end]; /* load last word (may be same as val[N]) */ \ | |
289 | ;; \ | |
290 | shrp t0=val[N-1],val[N-index],shift; \ | |
291 | br .memcpy_tail | |
292 | .memcpy_loops: | |
293 | COPY(0, 1) /* no point special casing this---it doesn't go any faster without shrp */ | |
294 | COPY(8, 0) | |
295 | COPY(16, 0) | |
296 | COPY(24, 0) | |
297 | COPY(32, 0) | |
298 | COPY(40, 0) | |
299 | COPY(48, 0) | |
300 | COPY(56, 0) | |
301 | ||
302 | END(memcpy) | |
e007c533 | 303 | EXPORT_SYMBOL(memcpy) |