cpu: remove local/globalHistoryBits params from branch pred

having separate params for the local/globalHistoryBits and the
local/globalPredictorSize can lead to inconsistencies if they
are not carefully set. this patch dervies the number of bits
necessary to index into the local/global predictors based on
their size.

the value of the localHistoryTableSize for the ARM O3 CPU has been
increased to 1024 from 64, which is more accurate for an A15 based
on some correlation against A15 hardware.

1 files changed, 14 insertions, 7 deletions

diff --git a/src/cpu/pred/tournament.cc b/src/cpu/pred/tournament.cc
index 52a05960f..e471d08f5 100644
--- a/src/cpu/pred/tournament.cc
+++ b/src/cpu/pred/tournament.cc
@@ -46,17 +46,28 @@
 
 TournamentBP::TournamentBP(const Params *params)
     : BPredUnit(params),
+      localPredictorSize(params->localPredictorSize),
       localCtrBits(params->localCtrBits),
       localHistoryTableSize(params->localHistoryTableSize),
-      localHistoryBits(params->localHistoryBits),
+      localHistoryBits(ceilLog2(params->localPredictorSize)),
       globalPredictorSize(params->globalPredictorSize),
       globalCtrBits(params->globalCtrBits),
-      globalHistoryBits(params->globalHistoryBits),
+      globalHistoryBits(
+          ceilLog2(params->globalPredictorSize) >
+          ceilLog2(params->choicePredictorSize) ?
+          ceilLog2(params->globalPredictorSize) :
+          ceilLog2(params->choicePredictorSize)),
       choicePredictorSize(params->choicePredictorSize),
       choiceCtrBits(params->choiceCtrBits),
       instShiftAmt(params->instShiftAmt)
 {
-    localPredictorSize = ULL(1) << localHistoryBits;
+    if (!isPowerOf2(localPredictorSize)) {
+        fatal("Invalid local predictor size!\n");
+    }
+
+    if (!isPowerOf2(globalPredictorSize)) {
+        fatal("Invalid global predictor size!\n");
+    }
 
     //Set up the array of counters for the local predictor
     localCtrs.resize(localPredictorSize);
@@ -76,10 +87,6 @@ TournamentBP::TournamentBP(const Params *params)
     for (int i = 0; i < localHistoryTableSize; ++i)
         localHistoryTable[i] = 0;
 
-    if (!isPowerOf2(globalPredictorSize)) {
-        fatal("Invalid global predictor size!\n");
-    }
-
     //Setup the array of counters for the global predictor
     globalCtrs.resize(globalPredictorSize);