[Autobackout][FuncReg]Revert of change: 7f78aef

Decide emission of pre-fill for spills based on presence of
corresponding pseudo kill or def count of spill.

Author: pratikashar

visa/SpillManagerGMRF.cpp

@@ -2804,103 +2804,9 @@ void SpillManagerGRF::insertSpillRangeCode(
         return;
     }
 
-    auto IsUniqueDef = [this, inst, bb, spillDcl]()
-    {
-        // return true if spilled variable has a single def
-        // and it is not live-in to current bb (eg, loop, sub).
-        if (VarDefs[spillDcl].size() != 1)
-        {
-            // check whether multiple defs exist in program for current
-            // lb, rb
-            auto lb = inst->getDst()->getLeftBound();
-            auto rb = inst->getDst()->getRightBound();
-            unsigned int count = 0;
-            auto& defs = VarDefs[spillDcl];
-            for (auto& def : defs)
-            {
-                if (def.first <= rb &&
-                    def.second >= lb)
-                    ++count;
-            }
-
-            if(count > 1)
-                return false;
-        }
-
-        // check whether variable is live-in to BB
-        if (lvInfo_->isLiveAtEntry(bb, spillDcl->getRegVar()->getId()))
-            return false;
-
-        return true;
-    };
-
-    auto PseudoKillFound = [spilledInstIter, bb, spillDcl]()
-    {
-        // Search upwards from spilledInstIter to find a pseudo kill.
-        // Return true if one is found, false otherwise.
-        // When a pseudo kill is found, it means read-modify-write is
-        // not needed.
-        auto bbBegin = bb->begin();
-        if (spilledInstIter == bbBegin)
-            return false;
-        auto it = spilledInstIter;
-        --it;
-        while (it != bbBegin)
-        {
-            auto inst = *it;
-            // check if adjacent instruction is a pseudo kill
-            if (inst->isPseudoKill())
-            {
-                if (inst->getDst()->getTopDcl() == spillDcl)
-                    return true;
-            }
-            else
-            {
-                auto dst = inst->getDst();
-                if (!dst)
-                    return false;
-
-                // recognize pattern where V10 is spilled:
-                // pseudo_kill V10
-                // op (8) V10(0,0) ...
-                // op (8) V10(2,0) ... <-- Current inst
-                //
-                // becomes:
-                // pseudo_kill V10
-                // op (8) SP_V10(0,0) ... [2]
-                // intrinsic_spill (8) ... SP_V10 ... [1]
-                // op (8) V10(2,0) <-- Current inst
-                if (inst->isSpillIntrinsic() &&
-                    inst->asSpillIntrinsic()->getPayload() &&
-                    inst->asSpillIntrinsic()->getPayload()->getTopDcl()->getRegVar()->isRegVarTransient())
-                {
-                    auto spillBase = ((G4_RegVarTransient*)inst->asSpillIntrinsic()->getPayload()->getTopDcl()->getRegVar())->getAbsBaseRegVar();
-                    if (spillBase->getDeclare()->getRootDeclare() != spillDcl)
-                        return false;
-                    // Fall through for instruction [1] above
-                }
-                else if (dst &&
-                    dst->getTopDcl() &&
-                    dst->getTopDcl()->getRegVar()->isRegVarTransient())
-                {
-                    auto spillBase = ((G4_RegVarTransient*)dst->getTopDcl()->getRegVar())->getAbsBaseRegVar();
-                    if (spillBase->getDeclare()->getRootDeclare() != spillDcl)
-                        return false;
-                    // Fall through for instruction [2] above
-                }
-                else if(inst->getDst()->getTopDcl() != spillDcl)
-                    return false;
-            }
-            --it;
-        }
-        return false;
-    };
-
     //subreg offset for new dst that replaces the spilled dst
     auto newSubregOff = 0;
 
-    auto pseudoKillFound = PseudoKillFound();
-    auto isUniqueDef = IsUniqueDef();
     if (inst->mayExceedTwoGRF())
     {
         // Handle send instructions (special treatment)
@@ -2915,9 +2821,7 @@ void SpillManagerGRF::insertSpillRangeCode(
             createAndInitMHeader (
                 (G4_RegVarTransient *) spillRangeDcl->getRegVar());
 
-        bool needRMW = !pseudoKillFound &&
-            !isUniqueDef &&
-            inst->isPartialWriteForSpill(!bb->isAllLaneActive());
+        bool needRMW = inst->isPartialWriteForSpill(!bb->isAllLaneActive());
         if (needRMW)
         {
             sendInSpilledRegVarPortions(
@@ -2952,9 +2856,7 @@ void SpillManagerGRF::insertSpillRangeCode(
 
         // Unaligned region specific handling.
         unsigned int spillSendOption = InstOpt_WriteEnable;
-        if (!pseudoKillFound &&
-            !isUniqueDef &&
-            shouldPreloadSpillRange(*spilledInstIter, bb)) {
+        if (shouldPreloadSpillRange(*spilledInstIter, bb)) {
 
             // Preload the segment aligned spill range from memory to use
             // as an overlay
@@ -3036,13 +2938,7 @@ void SpillManagerGRF::insertSpillRangeCode(
             newSubregOff = spilledRegion->getSubRegOff();
             if (!bb->isAllLaneActive())
             {
-                if (!pseudoKillFound &&
-                    !isUniqueDef)
-                {
-                    // If either pseudo kill is found or if the range is a unique def,
-                    // use WriteEnable option in spill.
-                    spillSendOption = (*spilledInstIter)->getMaskOption();
-                }
+                spillSendOption = (*spilledInstIter)->getMaskOption();
             }
         }
 
@@ -3977,33 +3873,6 @@ void SpillManagerGRF::runSpillAnalysis()
     }
 }
 
-void SpillManagerGRF::populateDefsTable()
-{
-    for (auto bb : gra.kernel.fg)
-    {
-        for (auto inst : *bb)
-        {
-            if (inst->isPseudoKill())
-                continue;
-
-            auto dst = inst->getDst();
-
-            if (dst && !dst->isNullReg())
-            {
-                auto topdcl = dst->getTopDcl();
-
-                if (topdcl)
-                {
-                    auto lb = dst->getLeftBound();
-                    auto rb = dst->getRightBound();
-                    VarDefs[topdcl].push_back(std::make_pair(lb, rb));
-                }
-            }
-        }
-    }
-}
-
-
 // Insert spill/fill code for all registers that have not been assigned
 // physical registers in the current iteration of the graph coloring
 // allocator.
@@ -4044,9 +3913,6 @@ bool SpillManagerGRF::insertSpillFillCode (
         return false;
     }
 
-    // Populate def table as it helps us decide whether read-modify-write is needed
-    populateDefsTable();
-
     // Insert spill/fill code for all basic blocks.
 
     FlowGraph& fg = kernel->fg;
@@ -4055,7 +3921,6 @@ bool SpillManagerGRF::insertSpillFillCode (
     {
         bbId_ = (*it)->getId();
         INST_LIST::iterator jt = (*it)->begin();
-        std::list<INST_LIST_ITER> pseudoKills;
 
         while (jt != (*it)->end()) {
             INST_LIST::iterator kt = jt;
@@ -4085,11 +3950,7 @@ bool SpillManagerGRF::insertSpillFillCode (
                     {
                         if (inst->isPseudoKill())
                         {
-                            // This pseudo kill corresponds to a spilled variable, so
-                            // it can be removed. But it is preserved till spill code
-                            // is inserted for the variable as it provides a hint to
-                            // spill insertion that read-modify-write is not needed.
-                            pseudoKills.push_back(jt);
+                            (*it)->erase(jt);
                             jt = kt;
                             continue;
                         }
@@ -4142,11 +4003,6 @@ bool SpillManagerGRF::insertSpillFillCode (
 
             jt = kt;
         }
-
-        for(auto killIt : pseudoKills)
-        {
-            (*it)->erase(killIt);
-        }
     }
 
     bbId_ = UINT_MAX;

visa/SpillManagerGMRF.h

@@ -593,8 +593,6 @@ class SpillManagerGRF
         }
     }
 
-    void populateDefsTable();
-
     // Data
     GlobalRA&                gra;
     IR_Builder *             builder_;
@@ -625,11 +623,6 @@ class SpillManagerGRF
     const Interference *     spillIntf_;
     vISA::Mem_Manager              mem_;
 
-    // Dcl -> vector[<lb, rb>]
-    // this data structure helps check whether a definition or part of it
-    // has multiple definitions in the program.
-    std::unordered_map<G4_Declare*, std::vector<std::pair<unsigned int, unsigned int>>> VarDefs;
-
     // The number of GRF spill.
     unsigned numGRFSpill = 0;