| /* |
| * Copyright (c) 2004-2005 The Regents of The University of Michigan |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions are |
| * met: redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer; |
| * redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution; |
| * neither the name of the copyright holders nor the names of its |
| * contributors may be used to endorse or promote products derived from |
| * this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| |
| #ifndef __CPU_PRED_BTB_HH__ |
| #define __CPU_PRED_BTB_HH__ |
| |
| #include "arch/types.hh" |
| #include "base/logging.hh" |
| #include "base/types.hh" |
| #include "config/the_isa.hh" |
| |
| class DefaultBTB |
| { |
| private: |
| struct BTBEntry |
| { |
| BTBEntry() |
| : tag(0), target(0), valid(false) |
| {} |
| |
| /** The entry's tag. */ |
| Addr tag; |
| |
| /** The entry's target. */ |
| TheISA::PCState target; |
| |
| /** The entry's thread id. */ |
| ThreadID tid; |
| |
| /** Whether or not the entry is valid. */ |
| bool valid; |
| }; |
| |
| public: |
| /** Creates a BTB with the given number of entries, number of bits per |
| * tag, and instruction offset amount. |
| * @param numEntries Number of entries for the BTB. |
| * @param tagBits Number of bits for each tag in the BTB. |
| * @param instShiftAmt Offset amount for instructions to ignore alignment. |
| */ |
| DefaultBTB(unsigned numEntries, unsigned tagBits, |
| unsigned instShiftAmt, unsigned numThreads); |
| |
| void reset(); |
| |
| /** Looks up an address in the BTB. Must call valid() first on the address. |
| * @param inst_PC The address of the branch to look up. |
| * @param tid The thread id. |
| * @return Returns the target of the branch. |
| */ |
| TheISA::PCState lookup(Addr instPC, ThreadID tid); |
| |
| /** Checks if a branch is in the BTB. |
| * @param inst_PC The address of the branch to look up. |
| * @param tid The thread id. |
| * @return Whether or not the branch exists in the BTB. |
| */ |
| bool valid(Addr instPC, ThreadID tid); |
| |
| /** Updates the BTB with the target of a branch. |
| * @param inst_PC The address of the branch being updated. |
| * @param target_PC The target address of the branch. |
| * @param tid The thread id. |
| */ |
| void update(Addr instPC, const TheISA::PCState &targetPC, |
| ThreadID tid); |
| |
| private: |
| /** Returns the index into the BTB, based on the branch's PC. |
| * @param inst_PC The branch to look up. |
| * @return Returns the index into the BTB. |
| */ |
| inline unsigned getIndex(Addr instPC, ThreadID tid); |
| |
| /** Returns the tag bits of a given address. |
| * @param inst_PC The branch's address. |
| * @return Returns the tag bits. |
| */ |
| inline Addr getTag(Addr instPC); |
| |
| /** The actual BTB. */ |
| std::vector<BTBEntry> btb; |
| |
| /** The number of entries in the BTB. */ |
| unsigned numEntries; |
| |
| /** The index mask. */ |
| unsigned idxMask; |
| |
| /** The number of tag bits per entry. */ |
| unsigned tagBits; |
| |
| /** The tag mask. */ |
| unsigned tagMask; |
| |
| /** Number of bits to shift PC when calculating index. */ |
| unsigned instShiftAmt; |
| |
| /** Number of bits to shift PC when calculating tag. */ |
| unsigned tagShiftAmt; |
| |
| /** Log2 NumThreads used for hashing threadid */ |
| unsigned log2NumThreads; |
| }; |
| |
| #endif // __CPU_PRED_BTB_HH__ |