1 files changed, 134 insertions, 0 deletions
diff --git a/src/cpu/pred/btb.cc b/src/cpu/pred/btb.cc
new file mode 100644
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+++ b/src/cpu/pred/btb.cc
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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.
+ *
+ * Authors: Kevin Lim
+ */
+
+#include "base/intmath.hh"
+#include "base/trace.hh"
+#include "cpu/pred/btb.hh"
+
+DefaultBTB::DefaultBTB(unsigned _numEntries,
+                       unsigned _tagBits,
+                       unsigned _instShiftAmt)
+    : numEntries(_numEntries),
+      tagBits(_tagBits),
+      instShiftAmt(_instShiftAmt)
+{
+    DPRINTF(Fetch, "BTB: Creating BTB object.\n");
+
+    if (!isPowerOf2(numEntries)) {
+        fatal("BTB entries is not a power of 2!");
+    }
+
+    btb.resize(numEntries);
+
+    for (int i = 0; i < numEntries; ++i) {
+        btb[i].valid = false;
+    }
+
+    idxMask = numEntries - 1;
+
+    tagMask = (1 << tagBits) - 1;
+
+    tagShiftAmt = instShiftAmt + floorLog2(numEntries);
+}
+
+void
+DefaultBTB::reset()
+{
+    for (int i = 0; i < numEntries; ++i) {
+        btb[i].valid = false;
+    }
+}
+
+inline
+unsigned
+DefaultBTB::getIndex(const Addr &inst_PC)
+{
+    // Need to shift PC over by the word offset.
+    return (inst_PC >> instShiftAmt) & idxMask;
+}
+
+inline
+Addr
+DefaultBTB::getTag(const Addr &inst_PC)
+{
+    return (inst_PC >> tagShiftAmt) & tagMask;
+}
+
+bool
+DefaultBTB::valid(const Addr &inst_PC, ThreadID tid)
+{
+    unsigned btb_idx = getIndex(inst_PC);
+
+    Addr inst_tag = getTag(inst_PC);
+
+    assert(btb_idx < numEntries);
+
+    if (btb[btb_idx].valid
+        && inst_tag == btb[btb_idx].tag
+        && btb[btb_idx].tid == tid) {
+        return true;
+    } else {
+        return false;
+    }
+}
+
+// @todo Create some sort of return struct that has both whether or not the
+// address is valid, and also the address.  For now will just use addr = 0 to
+// represent invalid entry.
+Addr
+DefaultBTB::lookup(const Addr &inst_PC, ThreadID tid)
+{
+    unsigned btb_idx = getIndex(inst_PC);
+
+    Addr inst_tag = getTag(inst_PC);
+
+    assert(btb_idx < numEntries);
+
+    if (btb[btb_idx].valid
+        && inst_tag == btb[btb_idx].tag
+        && btb[btb_idx].tid == tid) {
+        return btb[btb_idx].target;
+    } else {
+        return 0;
+    }
+}
+
+void
+DefaultBTB::update(const Addr &inst_PC, const Addr &target, ThreadID tid)
+{
+    unsigned btb_idx = getIndex(inst_PC);
+
+    assert(btb_idx < numEntries);
+
+    btb[btb_idx].tid = tid;
+    btb[btb_idx].valid = true;
+    btb[btb_idx].target = target;
+    btb[btb_idx].tag = getTag(inst_PC);
+}