decode_cache.hh revision 9021
1/* 2 * Copyright (c) 2011 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#ifndef __CPU_DECODE_CACHE_HH__ 32#define __CPU_DECODE_CACHE_HH__ 33 34#include "arch/isa_traits.hh" 35#include "arch/types.hh" 36#include "base/hashmap.hh" 37#include "config/the_isa.hh" 38#include "cpu/static_inst.hh" 39 40typedef StaticInstPtr (*DecodeInstFunc)(TheISA::ExtMachInst); 41 42template <DecodeInstFunc decodeInstFunc> 43class DecodeCache 44{ 45 private: 46 typedef TheISA::ExtMachInst ExtMachInst; 47 48 /// Hash of decoded instructions. 49 typedef m5::hash_map<ExtMachInst, StaticInstPtr> InstMap; 50 InstMap instMap; 51 struct DecodePage { 52 StaticInstPtr insts[TheISA::PageBytes]; 53 }; 54 55 /// A store of DecodePages. Basically a slightly smarter hash_map. 56 class DecodePages 57 { 58 protected: 59 typedef typename m5::hash_map<Addr, DecodePage *> PageMap; 60 typedef typename PageMap::iterator PageIt; 61 PageIt recent[2]; 62 PageMap pageMap; 63 64 /// Update the small cache of recent lookups. 65 /// @param recentest The most recent result; 66 void 67 update(PageIt recentest) 68 { 69 recent[1] = recent[0]; 70 recent[0] = recentest; 71 } 72 73 void 74 addPage(Addr addr, DecodePage *page) 75 { 76 Addr page_addr = addr & ~(TheISA::PageBytes - 1); 77 typename PageMap::value_type to_insert(page_addr, page); 78 update(pageMap.insert(to_insert).first); 79 } 80 81 public: 82 /// Constructor 83 DecodePages() 84 { 85 recent[0] = recent[1] = pageMap.end(); 86 } 87 88 /// Attempt to find the DecodePage which goes with a particular 89 /// address. First check the small cache of recent results, then 90 /// actually look in the hash_map. 91 /// @param addr The address to look up. 92 DecodePage * 93 getPage(Addr addr) 94 { 95 Addr page_addr = addr & ~(TheISA::PageBytes - 1); 96 97 // Check against recent lookups. 98 if (recent[0] != pageMap.end()) { 99 if (recent[0]->first == page_addr) 100 return recent[0]->second; 101 if (recent[1] != pageMap.end() && 102 recent[1]->first == page_addr) { 103 update(recent[1]); 104 // recent[1] has just become recent[0]. 105 return recent[0]->second; 106 } 107 } 108 109 // Actually look in the has_map. 110 PageIt it = pageMap.find(page_addr); 111 if (it != pageMap.end()) { 112 update(it); 113 return it->second; 114 } 115 116 // Didn't find an existing page, so add a new one. 117 DecodePage *newPage = new DecodePage; 118 addPage(page_addr, newPage); 119 return newPage; 120 } 121 } decodePages; 122 123 public: 124 /// Decode a machine instruction. 125 /// @param mach_inst The binary instruction to decode. 126 /// @retval A pointer to the corresponding StaticInst object. 127 StaticInstPtr 128 decode(ExtMachInst mach_inst, Addr addr) 129 { 130 // Try to find a matching address based table of instructions. 131 DecodePage *page = decodePages.getPage(addr); 132 133 // Use the table to decode the instruction. It will fall back to other 134 // mechanisms if it needs to. 135 Addr offset = addr & (TheISA::PageBytes - 1); 136 StaticInstPtr si = page->insts[offset]; 137 if (si && (si->machInst == mach_inst)) 138 return si; 139 140 InstMap::iterator iter = instMap.find(mach_inst); 141 if (iter != instMap.end()) { 142 si = iter->second; 143 page->insts[offset] = si; 144 return si; 145 } 146 147 si = decodeInstFunc(mach_inst); 148 instMap[mach_inst] = si; 149 page->insts[offset] = si; 150 return si; 151 } 152}; 153 154#endif // __CPU_DECODE_CACHE_HH__ 155