power: Add support for power models

This patch adds some basic support for power models in gem5.

The power interface is defined so it can interact with thermal
models as well. It implements a simple power evaluator that
can be used for simple power models that express power in the
form of a math expression. These expressions can use stats
within the same SimObject (or down its hierarchy) and some
magic variables such as "temp" for temperature.
In future patches we will extend this functionality to allow
slightly more complex expressions.

The model allows it to be extended to use other kinds of models.

Finally, the thermal model is updated to use the power usage as input.

1 files changed, 127 insertions, 0 deletions

diff --git a/src/sim/mathexpr.hh b/src/sim/mathexpr.hh
new file mode 100644
index 000000000..8f16cc851
--- /dev/null
+++ b/src/sim/mathexpr.hh
@@ -0,0 +1,127 @@
+/*
+ * Copyright (c) 2015 ARM Limited
+ * All rights reserved
+ *
+ * The license below extends only to copyright in the software and shall
+ * not be construed as granting a license to any other intellectual
+ * property including but not limited to intellectual property relating
+ * to a hardware implementation of the functionality of the software
+ * licensed hereunder.  You may use the software subject to the license
+ * terms below provided that you ensure that this notice is replicated
+ * unmodified and in its entirety in all distributions of the software,
+ * modified or unmodified, in source code or in binary form.
+ *
+ * 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: David Guillen Fandos
+ */
+
+#ifndef __SIM_MATHEXPR_HH__
+#define __SIM_MATHEXPR_HH__
+
+#include <algorithm>
+#include <functional>
+#include <string>
+
+class MathExpr {
+  public:
+
+    MathExpr(std::string expr);
+
+    typedef std::function<double(std::string)> EvalCallback;
+
+    /**
+     * Prints an ASCII representation of the expression tree
+     *
+     * @return A string containing the ASCII representation of the expression
+     */
+    std::string toStr() const { return toStr(root, ""); }
+
+    /**
+     * Evaluates the expression
+     *
+     * @param fn A callback funcion to evaluate variables
+     *
+     * @return The value for this expression
+     */
+    double eval(EvalCallback fn) const { return eval(root, fn); }
+
+  private:
+    enum Operator {
+        bAdd, bSub, bMul, bDiv, bPow, uNeg, sValue, sVariable, nInvalid
+    };
+
+    // Match operators
+    const int MAX_PRIO = 4;
+    typedef double (*binOp)(double, double);
+    struct OpSearch {
+        bool binary;
+        Operator op;
+        int priority;
+        char c;
+        binOp fn;
+    };
+
+    /** Operator list */
+    std::array<OpSearch, uNeg + 1> ops;
+
+    class Node {
+      public:
+        Node() : op(nInvalid), l(0), r(0), value(0) {}
+        std::string toStr() const {
+            const char opStr[] = {'+', '-', '*', '/', '^', '-'};
+            switch (op) {
+              case nInvalid:
+                return "INVALID";
+              case sVariable:
+                return variable;
+              case sValue:
+                return std::to_string(value);
+              default:
+                return std::string(1, opStr[op]);
+            };
+        }
+
+        Operator op;
+        Node *l, *r;
+        double value;
+        std::string variable;
+    };
+
+    /** Root node */
+    Node * root;
+
+    /** Parse and create nodes from string */
+    Node *parse(std::string expr);
+
+    /** Print tree as string */
+    std::string toStr(Node *n, std::string prefix) const;
+
+    /** Eval a node */
+    double eval(const Node *n, EvalCallback fn) const;
+};
+
+#endif
+
+