Remove unused code from rematerialization pass.

Change-Id: I5bc8498088f48a38ca5ecd48a56c68bb1b1d6bd1

Author: pratikashar

visa/FlowGraph.h

@@ -246,10 +246,6 @@ class G4_BB
     //
     unsigned traversal;
     //
-    // its immediate dominator
-    //
-    G4_BB* idom;
-    //
     // if the current BB is the return block after a CALL subroutine, then beforeCall points
     // to the BB before the subroutine call.
     //
@@ -377,7 +373,7 @@ class G4_BB
 
     G4_BB(INST_LIST_NODE_ALLOCATOR& alloc, unsigned i, FlowGraph* fg) :
         id(i), preId(0), rpostId(0),
-        traversal(0), idom(NULL), beforeCall(NULL),
+        traversal(0), beforeCall(NULL),
         afterCall(NULL), calleeInfo(NULL), BBType(G4_BB_NONE_TYPE),
         inNaturalLoop(false), hasSendInBB(false), loopNestLevel(0), scopeID(0),
         inSimdFlow(false), divergent(false), physicalPred(NULL), physicalSucc(NULL),
@@ -407,8 +403,6 @@ class G4_BB
     void     removePredEdge(G4_BB* pred);
     void     writeBBId(std::ostream& cout)    {cout << "BB" << id;}
     G4_BB*   fallThroughBB();
-    G4_BB*   getIDom()                        {return idom;}
-    void     setIDom(G4_BB* dom)              {idom = dom;}
     G4_BB*   BBBeforeCall()                   {return beforeCall;}
     G4_BB*   BBAfterCall()                    {return afterCall;}
     void     setBBBeforeCall(G4_BB* before)   {beforeCall = before;}

visa/Rematerialization.cpp

@@ -500,15 +500,6 @@ namespace vISA
         if (!inSameSubroutine(bb, uniqueDefBB))
             return false;
 
-#if 0
-        // idom currently not computed
-
-        // Def must be in a dominating BB
-        auto defDomsUse = doms.dominates(uniqueDefBB, bb);
-        if (!defDomsUse)
-            return false;
-#endif
-
         // If uniqueDefBB is not under SIMD CF, current BB is under SIMD CF
         // then we can remat only if def has NoMask option set.
         if (!uniqueDefBB->isInSimdFlow() &&
@@ -1181,46 +1172,4 @@ namespace vISA
 
         //unsigned int after = getNumSamplers(kernel);
     }
-
-    void Dominators::computeDominators()
-    {
-        // Compute all doms for given bb.
-        // Flowgraph already has idoms for each bb.
-        for (auto&& bb : fg)
-        {
-            std::pair<G4_BB*, std::set<G4_BB*>> domBB;
-            domBB.first = bb;
-            auto idom = bb->getIDom();
-            while (idom)
-            {
-                domBB.second.insert(bb->getIDom());
-                idom = idom->getIDom();
-            }
-        }
-    }
-    bool Dominators::dominates(G4_BB* def, G4_BB* use)
-    {
-        auto dIt = dom.find(use);
-        if (dIt == dom.end())
-            return false;
-
-        auto bbIt = dIt->second.find(def);
-        if (bbIt == dIt->second.end())
-            return false;
-
-        return true;
-    }
-
-    void Dominators::dump()
-    {
-        for (auto&& bb : dom)
-        {
-            printf("BB%d:", bb.first->getId());
-            for (auto&& d : bb.second)
-            {
-                printf("BB%d, ", d->getId());
-            }
-            printf("\n\n");
-        }
-    }
 }

visa/Rematerialization.h

@@ -70,34 +70,13 @@ namespace vISA
         std::unordered_set<unsigned int> rowsUsed;
     };
 
-    class Dominators
-    {
-    private:
-        std::map<G4_BB*, std::set<G4_BB*>> dom;
-
-        FlowGraph& fg;
-
-    public:
-        Dominators(FlowGraph& f) : fg(f)
-        {
-            computeDominators();
-        }
-
-        // Store dominator information in data structure above for easy querying.
-        // Flow graph stores immediate doms of each BB.s
-        void computeDominators();
-        bool dominates(G4_BB*, G4_BB*);
-        void dump();
-    };
-
     class Rematerialization
     {
     private:
         G4_Kernel& kernel;
         LivenessAnalysis& liveness;
         GraphColor& coloring;
         GlobalRA& gra;
-        Dominators doms;
         G4_Declare* samplerHeader = nullptr;
         unsigned int numRematsInLoop = 0;
         bool IRChanged = false;
@@ -223,7 +202,7 @@ namespace vISA
 
     public:
         Rematerialization(G4_Kernel& k, LivenessAnalysis& l, GraphColor& c, RPE& r, GlobalRA& g) :
-            kernel(k), liveness(l), coloring(c), gra(g), doms(k.fg), rpe(r)
+            kernel(k), liveness(l), coloring(c), gra(g), rpe(r)
         {
             unsigned numGRFs = k.getNumRegTotal();
             auto scale = [=](unsigned threshold) -> unsigned {