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+/*
+ * 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_O3_BTB_HH__
+#define __CPU_O3_BTB_HH__
+
+// For Addr type.
+#include "arch/isa_traits.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__