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