Add some different parameters. The main change is that the writeback count is now limited so that it doesn't overflow the buffer.

src/cpu/o3/alpha_cpu_builder.cc:
src/cpu/o3/alpha_params.hh:
    Add in dispatchWidth, wbWidth, wbDepth parameters.  wbDepth is the number of cycles of wbWidth instructions that can be buffered.
src/cpu/o3/iew.hh:
    Include separate parameter for dispatch width.
    Also limit the number of outstanding writebacks so the writeback buffer isn't overflowed.  The IQ must make sure with the IEW stage that it can issue instructions prior to issuing.
src/cpu/o3/iew_impl.hh:
    Include separate parameter for dispatch width.
    Also limit the number of outstanding writebacks so the writeback buffer isn't overflowed.
src/cpu/o3/inst_queue_impl.hh:
    IQ needs to check with the IEW to make sure it can issue instructions, and increments the IEW wb counter each time there is an outstanding instruction that will writeback.
src/cpu/o3/lsq_unit_impl.hh:
    Be sure to decrement the writeback counter if there's a squashed load that returned.
src/python/m5/objects/AlphaO3CPU.py:
    Change the parameters to include dispatch width, writeback width, and writeback depth.

--HG--
extra : convert_revision : 31c8cc495273e3c481b79055562fc40f71291fc4

1 files changed, 52 insertions, 5 deletions

diff --git a/src/cpu/o3/iew.hh b/src/cpu/o3/iew.hh
index 2af68d8fc..9627609c2 100644
--- a/src/cpu/o3/iew.hh
+++ b/src/cpu/o3/iew.hh
@@ -204,6 +204,45 @@ class DefaultIEW
     /** Returns if the LSQ has any stores to writeback. */
     bool hasStoresToWB() { return ldstQueue.hasStoresToWB(); }
 
+    void incrWb(InstSeqNum &sn)
+    {
+        if (++wbOutstanding == wbMax)
+            ableToIssue = false;
+        DPRINTF(IEW, "wbOutstanding: %i\n", wbOutstanding);
+#if DEBUG
+        wbList.insert(sn);
+#endif
+    }
+
+    void decrWb(InstSeqNum &sn)
+    {
+        if (wbOutstanding-- == wbMax)
+            ableToIssue = true;
+        DPRINTF(IEW, "wbOutstanding: %i\n", wbOutstanding);
+#if DEBUG
+        assert(wbList.find(sn) != wbList.end());
+        wbList.erase(sn);
+#endif
+    }
+
+#if DEBUG
+    std::set<InstSeqNum> wbList;
+
+    void dumpWb()
+    {
+        std::set<InstSeqNum>::iterator wb_it = wbList.begin();
+        while (wb_it != wbList.end()) {
+            cprintf("[sn:%lli]\n",
+                    (*wb_it));
+            wb_it++;
+        }
+    }
+#endif
+
+    bool canIssue() { return ableToIssue; }
+
+    bool ableToIssue;
+
   private:
     /** Sends commit proper information for a squash due to a branch
      * mispredict.
@@ -384,11 +423,8 @@ class DefaultIEW
      */
     unsigned issueToExecuteDelay;
 
-    /** Width of issue's read path, in instructions.  The read path is both
-     *  the skid buffer and the rename instruction queue.
-     *  Note to self: is this really different than issueWidth?
-     */
-    unsigned issueReadWidth;
+    /** Width of dispatch, in instructions. */
+    unsigned dispatchWidth;
 
     /** Width of issue, in instructions. */
     unsigned issueWidth;
@@ -403,6 +439,17 @@ class DefaultIEW
      */
     unsigned wbCycle;
 
+    /** Number of instructions in flight that will writeback. */
+    unsigned wbOutstanding;
+
+    /** Writeback width. */
+    unsigned wbWidth;
+
+    /** Writeback width * writeback depth, where writeback depth is
+     * the number of cycles of writing back instructions that can be
+     * buffered. */
+    unsigned wbMax;
+
     /** Number of active threads. */
     unsigned numThreads;