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Diffstat (limited to 'src/cpu/o3/btb.hh')
-rw-r--r-- | src/cpu/o3/btb.hh | 129 |
1 files changed, 129 insertions, 0 deletions
diff --git a/src/cpu/o3/btb.hh b/src/cpu/o3/btb.hh new file mode 100644 index 000000000..3c4899e89 --- /dev/null +++ b/src/cpu/o3/btb.hh @@ -0,0 +1,129 @@ +/* + * 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. + * + * Authors: Kevin Lim + */ + +#ifndef __CPU_O3_BTB_HH__ +#define __CPU_O3_BTB_HH__ + +#include "base/misc.hh" +#include "sim/host.hh" + +class DefaultBTB +{ + private: + struct BTBEntry + { + BTBEntry() + : tag(0), target(0), valid(false) + { + } + + /** The entry's tag. */ + Addr tag; + + /** The entry's target. */ + Addr target; + + /** The entry's thread id. */ + unsigned 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); + + 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. + */ + Addr lookup(const Addr &inst_PC, unsigned 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(const Addr &inst_PC, unsigned 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(const Addr &inst_PC, const Addr &target_PC, + unsigned 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(const Addr &inst_PC); + + /** Returns the tag bits of a given address. + * @param inst_PC The branch's address. + * @return Returns the tag bits. + */ + inline Addr getTag(const Addr &inst_PC); + + /** 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; +}; + +#endif // __CPU_O3_BTB_HH__ |