dead code: fix for variables from loop headers

sapfor/experts/Sapfor_2017/_src/Transformations/dead_code.cpp

@@ -14,6 +14,40 @@ using std::set;
 using std::remove_if;
 
 #define PRINT_USELESS_STATEMENTS 1
+#define DEBUG_IR 0
+
+// detect wich registers are used at more than one block
+// such registers should participate in live analysis to spread information about useful instructions
+// such registers appears at loops
+static void fillSharedRegs(const map<FuncInfo*, vector<SAPFOR::BasicBlock*>>& cfg, set<SAPFOR::Argument*>& shared_regs)
+{
+    map<SAPFOR::Argument*, SAPFOR::BasicBlock*> used_at;
+
+    for (const auto& byFunc : cfg)
+    {
+        for (const auto& byBlock : byFunc.second)
+        {
+            for (const auto& byIrBlock : byBlock->getInstructions())
+            {
+                auto instr = byIrBlock->getInstruction();
+
+                set<SAPFOR::Argument*> used = { instr->getResult(), instr->getArg1(), instr->getArg2() };
+                for (auto arg : used)
+                {
+                    if(arg && arg->getType() == SAPFOR::CFG_ARG_TYPE::REG)
+                    {
+                        auto it = used_at.find(arg);
+
+                        if (it == used_at.end())
+                            used_at[arg] = byBlock;
+                        else if(it->second != byBlock)
+                            shared_regs.insert(arg);
+                    }
+                }
+            }
+        }
+    }
+}
 
 static void updateUseDefForInstruction(SAPFOR::BasicBlock* block, SAPFOR::Instruction* instr,
                                        set<SAPFOR::Argument*>& use, set<SAPFOR::Argument*>& def,
@@ -91,7 +125,7 @@ static void updateUseDefForInstruction(SAPFOR::BasicBlock* block, SAPFOR::Instru
             def.erase(e);
         }
         
-        insertIfVar(args.begin(), args.end(), usedByThisBlock);
+        usedByThisBlock.insert(args.begin(), args.end());
     }
 
     if ((instr->getOperation() == SAPFOR::CFG_OP::F_CALL || instr->getOperation() == SAPFOR::CFG_OP::PARAM) && fName == "")
@@ -130,8 +164,8 @@ static void buildUseDef(SAPFOR::BasicBlock* block, set<SAPFOR::Argument*>& use,
         useful[i] = u;
     }
 
-    insertIfVar(use_with_regs.begin(), use_with_regs.end(), use);
+    use.insert(use_with_regs.begin(), use_with_regs.end());
-    insertIfVar(def_with_regs.begin(), def_with_regs.end(), def);
+    def.insert(def_with_regs.begin(), def_with_regs.end());
 }
 
 
@@ -145,6 +179,7 @@ private:
 
     vector<SAPFOR::Argument*>& formal_parameters;
     const map<string, FuncInfo*>& funcByName;
+    const set<SAPFOR::Argument*>& shared_regs;
 public:
     bool updateJumpStatus()
     {
@@ -248,6 +283,9 @@ public:
         auto in = bb->getLiveIn(), out = bb->getLiveOut();
 
         for (SAPFOR::Argument* arg : use)
+        {
+            if(arg && (arg->getType() == SAPFOR::CFG_ARG_TYPE::VAR ||
+              (arg->getType() == SAPFOR::CFG_ARG_TYPE::REG && shared_regs.find(arg) != shared_regs.end())))
             {
                 bool this_block = usedByThisBlock.find(arg) != usedByThisBlock.end();
 
@@ -275,6 +313,7 @@ public:
                         inserted |= bb->addLiveIn({ { arg, { bb } } });
                 }
             }
+        }
 
         if(!useful_block)
         {
@@ -305,10 +344,12 @@ public:
 
     DeadCodeAnalysisNode(SAPFOR::BasicBlock* block,
                          vector<SAPFOR::Argument*>& formal_parameters,
-                         const map<string, FuncInfo*>& funcByName)
+                         const map<string, FuncInfo*>& funcByName,
+                         const set<SAPFOR::Argument*>& shared_regs)
     :
         formal_parameters(formal_parameters),
-        funcByName(funcByName)
+        funcByName(funcByName),
+        shared_regs(shared_regs)
     {
         setBlock(block);
         useful.resize(block->getInstructions().size(), false);
@@ -322,16 +363,20 @@ class DeadCodeAnalysis : public BackwardDataFlowAnalysis<DeadCodeAnalysisNode>
 protected:
     vector<SAPFOR::Argument*>& formal_parameters;
     const map<string, FuncInfo*>& funcByName;
+    const set<SAPFOR::Argument*>& shared_regs;
 
     DeadCodeAnalysisNode* createNode(SAPFOR::BasicBlock* block) override
     {
-        return new DeadCodeAnalysisNode(block, formal_parameters, funcByName);
+        return new DeadCodeAnalysisNode(block, formal_parameters, funcByName, shared_regs);
     }
 public:
-    DeadCodeAnalysis(vector<SAPFOR::Argument*>& formal_parameters, const map<string, FuncInfo*>& funcByName)
+    DeadCodeAnalysis(vector<SAPFOR::Argument*>& formal_parameters, 
+                     const map<string, FuncInfo*>& funcByName,
+                     const set<SAPFOR::Argument*>& shared_regs)
     :
         formal_parameters(formal_parameters),
-        funcByName(funcByName)
+        funcByName(funcByName),
+        shared_regs(shared_regs)
     { }
 };
 
@@ -403,8 +448,10 @@ void removeDeadCode(SgStatement* func,
 
     cfg_pair.second.erase(remove_unreachable_it, cfg_pair.second.end());
 
+#if DEBUG_IR
+    dumpCFG({ cfg_pair }, false);
+#endif
     // detect useless code
-
     vector<SAPFOR::Argument*> func_parameters(cfg_pair.first->funcParams.countOfPars, NULL);
 
     map<string, FuncInfo*> funcByName;
@@ -413,7 +460,10 @@ void removeDeadCode(SgStatement* func,
         for (auto byFunc : byFile.second)
             funcByName[byFunc->funcName] = byFunc;
     
-    DeadCodeAnalysis analysis_object(func_parameters, funcByName);
+    set<SAPFOR::Argument*> shared_regs;
+    fillSharedRegs({ cfg_pair }, shared_regs);
+
+    DeadCodeAnalysis analysis_object(func_parameters, funcByName, shared_regs);
 
     analysis_object.fit(cfg_pair.second);
     analysis_object.analyze();