cpu: clean up architectural register classification

Move from a poorly documented scheme where the mapping
of unified architectural register indices to register
classes is hardcoded all over to one where there's an
enum for the register classes and a function that
encapsulates the mapping.

1 files changed, 92 insertions, 0 deletions

diff --git a/src/cpu/reg_class.hh b/src/cpu/reg_class.hh
new file mode 100644
index 000000000..e96c94cbb
--- /dev/null
+++ b/src/cpu/reg_class.hh
@@ -0,0 +1,92 @@
+/*
+ * Copyright (c) 2013 Advanced Micro Devices, Inc.
+ * 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: Steve Reinhardt
+ */
+
+#ifndef __CPU__REG_CLASS_HH__
+#define __CPU__REG_CLASS_HH__
+
+#include <cassert>
+#include <cstddef>
+
+#include "arch/registers.hh"
+#include "config/the_isa.hh"
+
+/// Enumerate the classes of registers.
+enum RegClass {
+    IntRegClass,        ///< Integer register
+    FloatRegClass,      ///< Floating-point register
+    MiscRegClass        ///< Control (misc) register
+};
+
+/// Number of register classes.  This value is not part of the enum,
+/// because putting it there makes the compiler complain about
+/// unhandled cases in some switch statements.
+const int NumRegClasses = MiscRegClass + 1;
+
+/**
+ * Map a 'unified' architectural register index to its register class.
+ * The unified architectural register index space is used to represent
+ * all architectural register identifiers in a single contiguous
+ * index space.  See http://gem5.org/Register_Indexing.
+ *
+ * @param reg_idx Unified-space register index
+ * @param rel_reg_idx Optional output param pointer; if non-NULL, location
+ *        will be written with the relative register index for reg_idx
+ *
+ * @return Register class of reg_idx
+ */
+inline
+RegClass regIdxToClass(TheISA::RegIndex reg_idx,
+                       TheISA::RegIndex *rel_reg_idx = NULL)
+{
+    assert(reg_idx < TheISA::Max_DepTag);
+    RegClass cl;
+    int offset;
+
+    if (reg_idx < TheISA::FP_Base_DepTag) {
+        cl = IntRegClass;
+        offset = 0;
+    } else if (reg_idx < TheISA::Ctrl_Base_DepTag) {
+        cl = FloatRegClass;
+        offset = TheISA::FP_Base_DepTag;
+    } else {
+        cl = MiscRegClass;
+        offset = TheISA::Ctrl_Base_DepTag;
+    }
+
+    if (rel_reg_idx)
+        *rel_reg_idx = reg_idx - offset;
+    return cl;
+}
+
+/// Map enum values to strings for debugging
+extern const char *RegClassStrings[];
+
+
+#endif // __CPU__REG_CLASS_HH__