1 /*
2   (C) Copyright 2008
3   International Business Machines Corporation,
4   All rights reserved.
5 
6   Redistribution and use in source and binary forms, with or without
7   modification, are permitted provided that the following conditions are met:
8 
9     * Redistributions of source code must retain the above copyright notice,
10   this list of conditions and the following disclaimer.
11     * Redistributions in binary form must reproduce the above copyright
12   notice, this list of conditions and the following disclaimer in the
13   documentation and/or other materials provided with the distribution.
14     * Neither the names of the copyright holders nor the names of their
15   contributors may be used to endorse or promote products derived from
16   this software without specific prior written permission.
17 
18   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
19   IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
20   TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
21   PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
22   OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
23   EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
24   PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
25   PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
26   LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
27   NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
28   SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 */
30 
31 #include <spu_intrinsics.h>
32 #include "vec_literal.h"
33 #include <string.h>
34 
35 /*
36  * Supply an inline _strncpy for strcpy/cat and strncpy/cat. Relies on
37  * checklen and lastzero code being optimized out when they are constant
38  * zero values.
39  */
_strncpy(char * __restrict__ dest,const char * __restrict__ src,size_t maxlen,int checklen,int lastzero)40 static inline void * _strncpy(char * __restrict__ dest, const char *
41                               __restrict__ src, size_t maxlen, int
42                               checklen, int lastzero)
43 {
44   int adjust, offset, soffset, doffset, shift;
45   vec_uchar16 *vsrc, *vdest;
46   vec_uchar16 sdata1, sdata2, sdata, shuffle;
47   vec_uchar16 mask1, maskzero, cmp0;
48   vec_uint4 nonzeroes, gathered_cmp, vtmp, vtmp2;
49   vec_uint4 curlen; /* assumes size_t is 4 bytes */
50   const vec_uint4 val31 = { 31, 31, 31, 31 };
51   const vec_uint4 val_0123 = { 0x00010203, 0x04050607, 0x08090A0B, 0x0C0D0E0F };
52   const vec_uchar16 all_ones = { 0xff,0xff,0xff,0xff, 0xff,0xff,0xff,0xff,
53                                  0xff,0xff,0xff,0xff, 0xff,0xff,0xff,0xff };
54 
55   vsrc = (vec_uchar16 *) src;
56   vdest = (vec_uchar16 *) dest;
57   soffset = (int) src & 15;
58   doffset = (int) dest & 15;
59 
60   if (checklen) {
61     /*
62      * Set curlen so it is the number of bytes we would copy if starting
63      * from vdest & ~0xf.
64      *
65      * curlen could probably be replaced by comparing vdest plus some
66      * offset to dest + maxlen, that would help mainly in the while loop
67      * but would lose only one instruction (the curlen -= 16).
68      */
69     curlen = spu_splats((unsigned int) (maxlen + doffset));
70   }
71 
72   /*
73    * Setup a shuffle pattern to align the source string with the
74    * alignment of the destination string.
75    */
76   vtmp = spu_cmpgt(spu_promote(doffset, 0), spu_promote(soffset, 0));
77   adjust = spu_extract(vtmp, 0);
78   offset  = soffset - doffset;
79   offset += adjust & 16;
80   shuffle = spu_splats((unsigned char) offset);
81   shuffle = (vec_uchar16) spu_add((vec_uint4) shuffle, val_0123);
82 
83   vsrc += adjust;
84   sdata1 = *vsrc++;
85   sdata2 = *vsrc++;
86   sdata = spu_shuffle(sdata1, sdata2, shuffle);
87 
88   /*
89    * mask out leading bytes
90    */
91   mask1 = spu_rlmaskqwbyte(all_ones, -doffset);
92 
93   cmp0 = spu_and(mask1, spu_cmpeq(sdata, 0));
94   nonzeroes = spu_cntlz(spu_gather(cmp0));
95   /*
96    * First element of nonzeroes - 15 is the number of leading non-zero
97    * bytes plus 1 for the zero byte.
98    */
99   if (checklen) {
100     vtmp = spu_add(curlen, 15);
101     vtmp2 = spu_cmpgt(nonzeroes, vtmp);
102     nonzeroes = spu_sel(nonzeroes, vtmp, vtmp2);
103   }
104 
105   vtmp = spu_cmpgt(nonzeroes, val31);
106   /*
107    * Note: using immediate (constant 31) vs a vector value (val31) does
108    * not give different results, and we have to have a vector val31 for
109    * the spu_sel below, so use val31 everywhere.
110    */
111   vtmp = spu_sel(nonzeroes, val31, vtmp);
112   /*
113    * So vtmp is now min(nonzeroes, 31), the number of bytes + 16 that we
114    * want to copy from the first 16 bytes of the source.
115    */
116   if (checklen) {
117     curlen = spu_sub(vtmp, curlen);
118     curlen = spu_sub(15, curlen);
119   }
120 
121   /*
122    * We want a right shift 0xff with fill by ones of (vtmp - 15) bytes, but
123    * that doesn't exist so use spu_slqwbyte and vtmp all ones left by
124    * (31 - vtmp). Note: this can also use spu_rlqwbytebc with spu_rlqw.
125    */
126   shift = spu_extract(spu_sub(val31, vtmp), 0);
127   maskzero = spu_slqwbyte(all_ones, shift);
128   maskzero = spu_and(mask1, maskzero);
129   *vdest = spu_sel(*vdest, sdata, maskzero);
130 
131   vtmp = spu_cmpgt(nonzeroes, val31);
132   if (checklen) {
133     vtmp2 = spu_cmpgt(curlen, 0);
134     vtmp = spu_and(vtmp, vtmp2);
135   }
136   if (spu_extract(vtmp, 0)) {
137     sdata1 = sdata2;
138     sdata2 = *vsrc++;
139     sdata = spu_shuffle(sdata1, sdata2, shuffle);
140     cmp0 = spu_cmpeq(sdata, 0);
141     gathered_cmp = spu_gather(cmp0);
142     /*
143      * Copy 16 bytes at a time.
144      */
145     while ((spu_extract(gathered_cmp, 0) == 0) &&
146            (!checklen || (spu_extract(curlen, 0) > 15))) {
147       if (checklen)
148         curlen = spu_add(curlen, -16);
149       *++vdest = sdata;
150       sdata1 = sdata2;
151       sdata2 = *vsrc++;
152       sdata = spu_shuffle(sdata1, sdata2, shuffle);
153       cmp0 = spu_cmpeq(sdata, 0);
154       gathered_cmp = spu_gather(cmp0);
155     }
156     /*
157      * Copy 0 to 15 trailing bytes, either up to the smaller of curlen or
158      * the number of non-zero bytes.
159      */
160     nonzeroes = spu_cntlz(gathered_cmp);
161     if (checklen) {
162       vtmp = spu_add(curlen, 15);
163       vtmp2 = spu_cmpgt(nonzeroes, vtmp);
164       nonzeroes = spu_sel(nonzeroes, vtmp, vtmp2);
165       curlen = spu_sub(nonzeroes, curlen);
166       curlen = spu_sub(15, curlen);
167     }
168     shift = spu_extract(spu_sub(val31, nonzeroes), 0);
169     maskzero = spu_slqwbyte(all_ones, shift);
170     ++vdest;
171     *vdest = spu_sel(*vdest, sdata, maskzero);
172   }
173 
174   if (checklen && lastzero) {
175     /*
176      * For strncat.
177      */
178     dest[maxlen - spu_extract(curlen, 0)] = '\0';
179   }
180 
181   /* Pad null bytes if the length of the "src" is less than "n" (strncpy).  */
182   if (checklen && !lastzero && spu_extract(curlen, 0))
183     memset(dest + maxlen - spu_extract(curlen, 0), 0, spu_extract(curlen, 0));
184   return (dest);
185 }
186