decode_cache.cc revision 9022 
1/*
2 * Copyright (c) 2011-2012 Google
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are
7 * met: redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer;
9 * redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution;
12 * neither the name of the copyright holders nor the names of its
13 * contributors may be used to endorse or promote products derived from
14 * this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
17 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
18 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
19 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
20 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
21 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
22 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
26 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 *
28 * Authors: Gabe Black
29 */
30
31#include "arch/decoder.hh"
32#include "arch/isa_traits.hh"
33#include "arch/types.hh"
34#include "base/hashmap.hh"
35#include "config/the_isa.hh"
36#include "cpu/static_inst.hh"
37
38void
39DecodeCache::DecodePages::update(PageIt recentest)
40{
41    recent[1] = recent[0];
42    recent[0] = recentest;
43}
44
45void
46DecodeCache::DecodePages::addPage(Addr addr, DecodePage *page)
47{
48    Addr page_addr = addr & ~(TheISA::PageBytes - 1);
49    typename PageMap::value_type to_insert(page_addr, page);
50    update(pageMap.insert(to_insert).first);
51}
52
53DecodeCache::DecodePages::DecodePages()
54{
55    recent[0] = recent[1] = pageMap.end();
56}
57
58DecodeCache::DecodePage *
59DecodeCache::DecodePages::getPage(Addr addr)
60{
61    Addr page_addr = addr & ~(TheISA::PageBytes - 1);
62
63    // Check against recent lookups.
64    if (recent[0] != pageMap.end()) {
65        if (recent[0]->first == page_addr)
66            return recent[0]->second;
67        if (recent[1] != pageMap.end() &&
68                recent[1]->first == page_addr) {
69            update(recent[1]);
70            // recent[1] has just become recent[0].
71            return recent[0]->second;
72        }
73    }
74
75    // Actually look in the has_map.
76    PageIt it = pageMap.find(page_addr);
77    if (it != pageMap.end()) {
78        update(it);
79        return it->second;
80    }
81
82    // Didn't find an existing page, so add a new one.
83    DecodePage *newPage = new DecodePage;
84    addPage(page_addr, newPage);
85    return newPage;
86}
87
88StaticInstPtr
89DecodeCache::decode(TheISA::Decoder *decoder,
90        ExtMachInst mach_inst, Addr addr)
91{
92    // Try to find a matching address based table of instructions.
93    DecodePage *page = decodePages.getPage(addr);
94
95    // Use the table to decode the instruction. It will fall back to other
96    // mechanisms if it needs to.
97    Addr offset = addr & (TheISA::PageBytes - 1);
98    StaticInstPtr si = page->insts[offset];
99    if (si && (si->machInst == mach_inst))
100        return si;
101
102    InstMap::iterator iter = instMap.find(mach_inst);
103    if (iter != instMap.end()) {
104        si = iter->second;
105        page->insts[offset] = si;
106        return si;
107    }
108
109    si = decoder->decodeInst(mach_inst);
110    instMap[mach_inst] = si;
111    page->insts[offset] = si;
112    return si;
113}
114