misc: Add a generic cache library

Add a generic cache library modeled after AssociativeSet that can be used for
constructing internal caching structures.

Change-Id: I1767309ed01f52672b32810636a09142ff23242f

src/base/cache/cache_entry.hh

@@ -0,0 +1,136 @@
+/**
+ * Copyright (c) 2024 - Pranith Kumar
+ * Copyright (c) 2020 Inria
+ * 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 __BASE_CACHE_CACHE_ENTRY_HH__
+#define __BASE_CACHE_CACHE_ENTRY_HH__
+
+#include <cassert>
+
+#include "base/cprintf.hh"
+#include "base/types.hh"
+#include "mem/cache/replacement_policies/replaceable_entry.hh"
+
+namespace gem5
+{
+
+/**
+ * A CacheEntry is an entry containing a tag. A tagged entry's contents
+ * are only relevant if it is marked as valid.
+ */
+class CacheEntry : public ReplaceableEntry
+{
+  public:
+    CacheEntry() = default;
+    ~CacheEntry() = default;
+
+    /**
+     * Checks if the entry is valid.
+     *
+     * @return True if the entry is valid.
+     */
+    virtual bool isValid() const { return valid; }
+
+    /**
+     * Get tag associated to this block.
+     *
+     * @return The tag value.
+     */
+    virtual Addr getTag() const { return tag; }
+
+    /**
+     * Checks if the given tag information corresponds to this entry's.
+     *
+     * @param tag The tag value to compare to.
+     * @return True if the tag information match this entry's.
+     */
+    virtual bool
+    matchTag(const Addr tag) const
+    {
+        return isValid() && (getTag() == tag);
+    }
+
+    /**
+     * Insert the block by assigning it a tag and marking it valid. Touches
+     * block if it hadn't been touched previously.
+     *
+     * @param tag The tag value.
+     */
+    virtual void
+    insert(const Addr tag)
+    {
+        setValid();
+        setTag(tag);
+    }
+
+    /** Invalidate the block. Its contents are no longer valid. */
+    virtual void
+    invalidate()
+    {
+        valid = false;
+        setTag(MaxAddr);
+    }
+
+    std::string
+    print() const override
+    {
+        return csprintf("tag: %#x valid: %d | %s", getTag(),
+                        isValid(), ReplaceableEntry::print());
+    }
+
+  protected:
+    /**
+     * Set tag associated to this block.
+     *
+     * @param tag The tag value.
+     */
+    virtual void setTag(Addr _tag) { tag = _tag; }
+
+    /** Set valid bit. The block must be invalid beforehand. */
+    virtual void
+    setValid()
+    {
+        assert(!isValid());
+        valid = true;
+    }
+
+  private:
+    /**
+     * Valid bit. The contents of this entry are only valid if this bit is set.
+     * @sa invalidate()
+     * @sa insert()
+     */
+    bool valid{false};
+
+    /** The entry's tag. */
+    Addr tag{MaxAddr};
+};
+
+} // namespace gem5
+
+#endif //__CACHE_ENTRY_HH__