Remove splitVariables pass as it should be subsumed by the split4GRFVars pass.

Change-Id: Idbb419a9db483307c93b2a1c521bf452e9d56515

Author: weiyu-chen

visa/G4Verifier.cpp

@@ -102,7 +102,6 @@ bool G4Verifier::verifyInst(G4_INST *inst)
         passIndex == Optimizer::PI_renameRegister ||
         passIndex == Optimizer::PI_newLocalDefHoisting ||
         passIndex == Optimizer::PI_newLocalCopyPropagation ||
-        passIndex == Optimizer::PI_splitVariables ||
         passIndex == Optimizer::PI_cselPeepHoleOpt)
     {
         // def-use chain should be valid after these passes

visa/Optimizer.cpp

@@ -579,7 +579,6 @@ void Optimizer::initOptimizations()
     INITIALIZE_PASS(initializePayload,       vISA_InitPayload,             TIMER_NUM_TIMERS);
     INITIALIZE_PASS(cleanupBindless,         vISA_enableCleanupBindless,   TIMER_OPTIMIZER);
     INITIALIZE_PASS(countGRFUsage,           vISA_PrintRegUsage,           TIMER_MISC_OPTS);
-    INITIALIZE_PASS(splitVariables,          vISA_EnableSplitVariables,    TIMER_MISC_OPTS);
     INITIALIZE_PASS(changeMoveType,          vISA_ChangeMoveType,          TIMER_MISC_OPTS);
     INITIALIZE_PASS(reRAPostSchedule,        vISA_ReRAPostSchedule,        TIMER_OPTIMIZER);
     INITIALIZE_PASS(accSubPostSchedule,      vISA_accSubstitution,         TIMER_OPTIMIZER);
@@ -1061,9 +1060,6 @@ int Optimizer::optimization()
     // remove redundant movs
     runPass(PI_newLocalCopyPropagation);
 
-    // split 4GRF variables.
-    runPass(PI_splitVariables);
-
     runPass(PI_mergeScalarInst);
 
     runPass(PI_cselPeepHoleOpt);

visa/Optimizer.h

@@ -342,7 +342,6 @@ class Optimizer
         PI_initializePayload,
         PI_cleanupBindless,
         PI_countGRFUsage,
-        PI_splitVariables,
         PI_changeMoveType,
         PI_reRAPostSchedule,
         PI_accSubPostSchedule,