From 9bc4fa246cc5d2c9e4736e05196266e72b662e17 Mon Sep 17 00:00:00 2001
From: Mikhail Kocharmin <xnpster@yandex.ru>
Date: Sun, 7 Apr 2024 17:40:30 +0300
Subject: [PATCH] dead code: improve perfomance by removing unnecessary checks

---
 .../_src/Transformations/dead_code.cpp        | 57 +++----------------
 1 file changed, 7 insertions(+), 50 deletions(-)

diff --git a/sapfor/experts/Sapfor_2017/_src/Transformations/dead_code.cpp b/sapfor/experts/Sapfor_2017/_src/Transformations/dead_code.cpp
index 0db25af..5befc48 100644
--- a/sapfor/experts/Sapfor_2017/_src/Transformations/dead_code.cpp
+++ b/sapfor/experts/Sapfor_2017/_src/Transformations/dead_code.cpp
@@ -16,39 +16,6 @@ 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,
                                        vector<SAPFOR::Argument*>& formal_parameters,
@@ -179,7 +146,6 @@ private:
 
     vector<SAPFOR::Argument*>& formal_parameters;
     const map<string, FuncInfo*>& funcByName;
-    const set<SAPFOR::Argument*>& shared_regs;
 public:
     bool updateJumpStatus()
     {
@@ -284,8 +250,7 @@ public:
 
         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())))
+            if(arg && (arg->getType() == SAPFOR::CFG_ARG_TYPE::VAR || arg->getType() == SAPFOR::CFG_ARG_TYPE::REG))
             {
                 bool this_block = usedByThisBlock.find(arg) != usedByThisBlock.end();
 
@@ -344,12 +309,10 @@ public:
 
     DeadCodeAnalysisNode(SAPFOR::BasicBlock* block,
                          vector<SAPFOR::Argument*>& formal_parameters,
-                         const map<string, FuncInfo*>& funcByName,
-                         const set<SAPFOR::Argument*>& shared_regs)
+                         const map<string, FuncInfo*>& funcByName)
     :
         formal_parameters(formal_parameters),
-        funcByName(funcByName),
-        shared_regs(shared_regs)
+        funcByName(funcByName)
     {
         setBlock(block);
         useful.resize(block->getInstructions().size(), false);
@@ -363,20 +326,17 @@ 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, shared_regs);
+        return new DeadCodeAnalysisNode(block, formal_parameters, funcByName);
     }
 public:
     DeadCodeAnalysis(vector<SAPFOR::Argument*>& formal_parameters, 
-                     const map<string, FuncInfo*>& funcByName,
-                     const set<SAPFOR::Argument*>& shared_regs)
+                     const map<string, FuncInfo*>& funcByName)
     :
         formal_parameters(formal_parameters),
-        funcByName(funcByName),
-        shared_regs(shared_regs)
+        funcByName(funcByName)
     { }
 };
 
@@ -459,11 +419,8 @@ void removeDeadCode(SgStatement* func,
     for (auto& byFile : allFuncs)
         for (auto byFunc : byFile.second)
             funcByName[byFunc->funcName] = byFunc;
-    
-    set<SAPFOR::Argument*> shared_regs;
-    fillSharedRegs({ cfg_pair }, shared_regs);
 
-    DeadCodeAnalysis analysis_object(func_parameters, funcByName, shared_regs);
+    DeadCodeAnalysis analysis_object(func_parameters, funcByName);
 
     analysis_object.fit(cfg_pair.second);
     analysis_object.analyze();