14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26
27 #include "gc/shared/memset_with_concurrent_readers.hpp"
28 #include "runtime/prefetch.inline.hpp"
29 #include "utilities/align.hpp"
30 #include "utilities/debug.hpp"
31 #include "utilities/globalDefinitions.hpp"
32 #include "utilities/macros.hpp"
33
34 #if INCLUDE_ALL_GCS
35
36 // An implementation of memset, for use when there may be concurrent
37 // readers of the region being stored into.
38 //
39 // We can't use the standard library memset if it is implemented using
40 // block initializing stores. Doing so can result in concurrent readers
41 // seeing spurious zeros.
42 //
43 // We can't use the obvious C/C++ for-loop, because the compiler may
44 // recognize the idiomatic loop and optimize it into a call to the
45 // standard library memset; we've seen exactly this happen with, for
46 // example, Solaris Studio 12.3. Hence the use of inline assembly
47 // code, hiding loops from the compiler's optimizer.
48 //
49 // We don't attempt to use the standard library memset when it is safe
50 // to do so. We could conservatively do so by detecting the presence
51 // of block initializing stores (VM_Version::has_blk_init()), but the
52 // implementation provided here should be sufficient.
53
54 inline void fill_subword(void* start, void* end, int value) {
55 STATIC_ASSERT(BytesPerWord == 8);
139 // DISPATCH: no direct reference, but without it the store block may be elided.
140 "3:\n\t"
141 " stx %[xvalue], [%[aend]-56]\n\t" // aligned_end[-7] = xvalue
142 " stx %[xvalue], [%[aend]-48]\n\t"
143 " stx %[xvalue], [%[aend]-40]\n\t"
144 " stx %[xvalue], [%[aend]-32]\n\t"
145 " stx %[xvalue], [%[aend]-24]\n\t"
146 " stx %[xvalue], [%[aend]-16]\n\t"
147 " stx %[xvalue], [%[aend]-8]\n\t" // aligned_end[-1] = xvalue
148 : /* only temporaries/overwritten outputs */
149 [temp] "=&r" (temp),
150 [ato] "+&r" (aligned_to)
151 : [aend] "r" (aligned_end),
152 [xvalue] "r" (xvalue)
153 : "cc", "memory");
154 to = aligned_end; // setup for suffix
155 }
156 // Fill any partial word suffix. Also the prefix if size < BytesPerWord.
157 fill_subword(to, end, value);
158 }
159
160 #endif // INCLUDE_ALL_GCS
|
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26
27 #include "gc/shared/memset_with_concurrent_readers.hpp"
28 #include "runtime/prefetch.inline.hpp"
29 #include "utilities/align.hpp"
30 #include "utilities/debug.hpp"
31 #include "utilities/globalDefinitions.hpp"
32 #include "utilities/macros.hpp"
33
34 // An implementation of memset, for use when there may be concurrent
35 // readers of the region being stored into.
36 //
37 // We can't use the standard library memset if it is implemented using
38 // block initializing stores. Doing so can result in concurrent readers
39 // seeing spurious zeros.
40 //
41 // We can't use the obvious C/C++ for-loop, because the compiler may
42 // recognize the idiomatic loop and optimize it into a call to the
43 // standard library memset; we've seen exactly this happen with, for
44 // example, Solaris Studio 12.3. Hence the use of inline assembly
45 // code, hiding loops from the compiler's optimizer.
46 //
47 // We don't attempt to use the standard library memset when it is safe
48 // to do so. We could conservatively do so by detecting the presence
49 // of block initializing stores (VM_Version::has_blk_init()), but the
50 // implementation provided here should be sufficient.
51
52 inline void fill_subword(void* start, void* end, int value) {
53 STATIC_ASSERT(BytesPerWord == 8);
137 // DISPATCH: no direct reference, but without it the store block may be elided.
138 "3:\n\t"
139 " stx %[xvalue], [%[aend]-56]\n\t" // aligned_end[-7] = xvalue
140 " stx %[xvalue], [%[aend]-48]\n\t"
141 " stx %[xvalue], [%[aend]-40]\n\t"
142 " stx %[xvalue], [%[aend]-32]\n\t"
143 " stx %[xvalue], [%[aend]-24]\n\t"
144 " stx %[xvalue], [%[aend]-16]\n\t"
145 " stx %[xvalue], [%[aend]-8]\n\t" // aligned_end[-1] = xvalue
146 : /* only temporaries/overwritten outputs */
147 [temp] "=&r" (temp),
148 [ato] "+&r" (aligned_to)
149 : [aend] "r" (aligned_end),
150 [xvalue] "r" (xvalue)
151 : "cc", "memory");
152 to = aligned_end; // setup for suffix
153 }
154 // Fill any partial word suffix. Also the prefix if size < BytesPerWord.
155 fill_subword(to, end, value);
156 }
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