O3: Fix issue w/wbOutstading being decremented multiple times on blocked cache.

If a split load fails on a blocked cache wbOutstanding can be decremented
twice if the first part of the split load succeeds and the second part fails.
Condition the decrementing on not having completed the first part of the load.

3 files changed, 10 insertions, 3 deletions

diff --git a/src/cpu/o3/iew.hh b/src/cpu/o3/iew.hh
index 8ebbfb2e6..113d0756e 100644
--- a/src/cpu/o3/iew.hh
+++ b/src/cpu/o3/iew.hh
@@ -228,7 +228,7 @@ class DefaultIEW
     {
         if (++wbOutstanding == wbMax)
             ableToIssue = false;
-        DPRINTF(IEW, "wbOutstanding: %i\n", wbOutstanding);
+        DPRINTF(IEW, "wbOutstanding: %i [sn:%lli]\n", wbOutstanding, sn);
         assert(wbOutstanding <= wbMax);
 #ifdef DEBUG
         wbList.insert(sn);
diff --git a/src/cpu/o3/iew_impl.hh b/src/cpu/o3/iew_impl.hh
index 3bdf1f28d..00a7ef0d9 100644
--- a/src/cpu/o3/iew_impl.hh
+++ b/src/cpu/o3/iew_impl.hh
@@ -1221,7 +1221,9 @@ DefaultIEW<Impl>::executeInsts()
 
         // Check if the instruction is squashed; if so then skip it
         if (inst->isSquashed()) {
-            DPRINTF(IEW, "Execute: Instruction was squashed.\n");
+            DPRINTF(IEW, "Execute: Instruction was squashed. PC: %s, [tid:%i]"
+                         " [sn:%i]\n", inst->pcState(), inst->threadNumber,
+                         inst->seqNum);
 
             // Consider this instruction executed so that commit can go
             // ahead and retire the instruction.
diff --git a/src/cpu/o3/lsq_unit.hh b/src/cpu/o3/lsq_unit.hh
index be9c91a23..8e311d275 100644
--- a/src/cpu/o3/lsq_unit.hh
+++ b/src/cpu/o3/lsq_unit.hh
@@ -804,7 +804,12 @@ LSQUnit<Impl>::read(Request *req, Request *sreqLow, Request *sreqHigh,
 
         ++lsqCacheBlocked;
 
-        iewStage->decrWb(load_inst->seqNum);
+        // If the first part of a split access succeeds, then let the LSQ
+        // handle the decrWb when completeDataAccess is called upon return
+        // of the requested first part of data
+        if (!completedFirst)
+            iewStage->decrWb(load_inst->seqNum);
+
         // There's an older load that's already going to squash.
         if (isLoadBlocked && blockedLoadSeqNum < load_inst->seqNum)
             return NoFault;