cpu: Physical register structural + flat indexing

Mimic the changes done on the architectural register indexes on the
physical register indexes. This is specific to the O3 model. The
structure, called PhysRegId, contains a register class, a register
index and a flat register index. The flat register index is kept
because it is useful in some cases where the type of register is not
important (dependency graph and scoreboard for example). Instead
of directly using the structure, most of the code is working with
a const PhysRegId* (typedef to PhysRegIdPtr). The actual PhysRegId
objects are stored in the regFile.

Change-Id: Ic879a3cc608aa2f34e2168280faac1846de77667
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/2701
Reviewed-by: Anthony Gutierrez <anthony.gutierrez@amd.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

1 files changed, 24 insertions, 51 deletions

diff --git a/src/cpu/o3/scoreboard.hh b/src/cpu/o3/scoreboard.hh
index ec84becdf..44e449944 100644
--- a/src/cpu/o3/scoreboard.hh
+++ b/src/cpu/o3/scoreboard.hh
@@ -46,12 +46,8 @@
 /**
  * Implements a simple scoreboard to track which registers are
  * ready. This class operates on the unified physical register space,
- * so integer and floating-point registers are not distinguished.  For
- * convenience, it also accepts operations on the physical-space
- * mapping of misc registers, which are numbered starting after the
- * end of the actual physical register file.  However, there is no
- * actual scoreboard for misc registers, and they are always
- * considered ready.
+ * because the different classes of registers do not need to be distinguished.
+ * Registers being part of a fixed mapping are always considered ready.
  */
 class Scoreboard
 {
@@ -67,38 +63,13 @@ class Scoreboard
     /** The number of actual physical registers */
     unsigned numPhysRegs;
 
-    /**
-     * The total number of registers which can be indexed, including
-     * the misc registers that come after the physical registers and
-     * which are hardwired to be always considered ready.
-     */
-    unsigned M5_CLASS_VAR_USED numTotalRegs;
-
-    /** The index of the zero register. */
-    PhysRegIndex zeroRegIdx;
-
-    /** The index of the FP zero register. */
-    PhysRegIndex fpZeroRegIdx;
-
-    bool isZeroReg(PhysRegIndex idx) const
-    {
-        return (idx == zeroRegIdx ||
-                (THE_ISA == ALPHA_ISA && idx == fpZeroRegIdx));
-    }
-
   public:
     /** Constructs a scoreboard.
      *  @param _numPhysicalRegs Number of physical registers.
      *  @param _numMiscRegs Number of miscellaneous registers.
-     *  @param _zeroRegIdx Index of the zero register.
-     *  @param _fpZeroRegIdx Index of the FP zero register (if any, currently
-     *                       used only for Alpha).
      */
     Scoreboard(const std::string &_my_name,
-               unsigned _numPhysicalRegs,
-               unsigned _numMiscRegs,
-               PhysRegIndex _zeroRegIdx,
-               PhysRegIndex _fpZeroRegIdx);
+               unsigned _numPhysicalRegs);
 
     /** Destructor. */
     ~Scoreboard() {}
@@ -107,54 +78,56 @@ class Scoreboard
     std::string name() const { return _name; };
 
     /** Checks if the register is ready. */
-    bool getReg(PhysRegIndex reg_idx) const
+    bool getReg(PhysRegIdPtr phys_reg) const
     {
-        assert(reg_idx < numTotalRegs);
+        assert(phys_reg->flatIdx < numPhysRegs);
 
-        if (reg_idx >= numPhysRegs) {
-            // misc regs are always ready
+        if (phys_reg->isFixedMapping()) {
+            // Fixed mapping regs are always ready
             return true;
         }
 
-        bool ready = regScoreBoard[reg_idx];
+        bool ready = regScoreBoard[phys_reg->flatIdx];
 
-        if (isZeroReg(reg_idx))
+        if (phys_reg->isZeroReg())
             assert(ready);
 
         return ready;
     }
 
     /** Sets the register as ready. */
-    void setReg(PhysRegIndex reg_idx)
+    void setReg(PhysRegIdPtr phys_reg)
     {
-        assert(reg_idx < numTotalRegs);
+        assert(phys_reg->flatIdx < numPhysRegs);
 
-        if (reg_idx >= numPhysRegs) {
-            // misc regs are always ready, ignore attempts to change that
+        if (phys_reg->isFixedMapping()) {
+            // Fixed mapping regs are always ready, ignore attempts to change
+            // that
             return;
         }
 
-        DPRINTF(Scoreboard, "Setting reg %i as ready\n", reg_idx);
+        DPRINTF(Scoreboard, "Setting reg %i (%s) as ready\n", phys_reg->regIdx,
+                RegClassStrings[phys_reg->regClass]);
 
-        assert(reg_idx < numTotalRegs);
-        regScoreBoard[reg_idx] = true;
+        regScoreBoard[phys_reg->flatIdx] = true;
     }
 
     /** Sets the register as not ready. */
-    void unsetReg(PhysRegIndex reg_idx)
+    void unsetReg(PhysRegIdPtr phys_reg)
     {
-        assert(reg_idx < numTotalRegs);
+        assert(phys_reg->flatIdx < numPhysRegs);
 
-        if (reg_idx >= numPhysRegs) {
-            // misc regs are always ready, ignore attempts to change that
+        if (phys_reg->isFixedMapping()) {
+            // Fixed mapping regs are always ready, ignore attempts to
+            // change that
             return;
         }
 
         // zero reg should never be marked unready
-        if (isZeroReg(reg_idx))
+        if (phys_reg->isZeroReg())
             return;
 
-        regScoreBoard[reg_idx] = false;
+        regScoreBoard[phys_reg->flatIdx] = false;
     }
 
 };