cpu: Add an indirect branch target predictor

This patch adds a configurable indirect branch predictor that can be indexed
by a combination of GHR and path history hashes. Implements the functionality
described in:

"Target prediction for indirect jumps" by Chang, Hao, and Patt
http://dl.acm.org/citation.cfm?id=264209

This is a re-spin of fb9d142 after the revert (bd1c6789).

1 files changed, 97 insertions, 0 deletions

diff --git a/src/cpu/pred/indirect.hh b/src/cpu/pred/indirect.hh
new file mode 100644
index 000000000..89450530e
--- /dev/null
+++ b/src/cpu/pred/indirect.hh
@@ -0,0 +1,97 @@
+/*
+ * Copyright (c) 2014 ARM Limited
+ * 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: Mitch Hayenga
+ */
+
+#ifndef __CPU_PRED_INDIRECT_HH__
+#define __CPU_PRED_INDIRECT_HH__
+
+#include <deque>
+
+#include "arch/isa_traits.hh"
+#include "config/the_isa.hh"
+#include "cpu/inst_seq.hh"
+
+class IndirectPredictor
+{
+  public:
+    IndirectPredictor(bool hash_ghr, bool hash_targets,
+                      unsigned num_sets, unsigned num_ways,
+                      unsigned tag_bits, unsigned path_len,
+                      unsigned inst_shift, unsigned num_threads);
+    bool lookup(Addr br_addr, unsigned ghr, TheISA::PCState& br_target,
+                ThreadID tid);
+    void recordIndirect(Addr br_addr, Addr tgt_addr, InstSeqNum seq_num,
+                        ThreadID tid);
+    void commit(InstSeqNum seq_num, ThreadID tid);
+    void squash(InstSeqNum seq_num, ThreadID tid);
+    void recordTarget(InstSeqNum seq_num, unsigned ghr,
+                      const TheISA::PCState& target, ThreadID tid);
+
+  private:
+    const bool hashGHR;
+    const bool hashTargets;
+    const unsigned numSets;
+    const unsigned numWays;
+    const unsigned tagBits;
+    const unsigned pathLength;
+    const unsigned instShift;
+
+    struct IPredEntry
+    {
+        IPredEntry() : tag(0), target(0) { }
+        Addr tag;
+        TheISA::PCState target;
+    };
+
+    std::vector<std::vector<IPredEntry> > targetCache;
+
+    Addr getSetIndex(Addr br_addr, unsigned ghr, ThreadID tid);
+    Addr getTag(Addr br_addr);
+
+    struct HistoryEntry
+    {
+        HistoryEntry(Addr br_addr, Addr tgt_addr, InstSeqNum seq_num)
+            : pcAddr(br_addr), targetAddr(tgt_addr), seqNum(seq_num) { }
+        Addr pcAddr;
+        Addr targetAddr;
+        InstSeqNum seqNum;
+    };
+
+
+    struct ThreadInfo {
+        ThreadInfo() : headHistEntry(0) { }
+
+        std::deque<HistoryEntry> pathHist;
+        unsigned headHistEntry;
+    };
+
+    std::vector<ThreadInfo> threadInfo;
+};
+
+#endif // __CPU_PRED_INDIRECT_HH__