From 3b4af6672067c16425e21a49ba1660798605b3c5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=9C=D0=B8=D1=85=D0=B0=D0=B8=D0=BB=20=D0=9A=D0=BE=D1=87?=
 =?UTF-8?q?=D0=B0=D1=80=D0=BC=D0=B8=D0=BD?= <mkocharmin@yandex.ru>
Date: Tue, 30 Jan 2024 19:40:14 +0300
Subject: [PATCH] dead code removing: unreachable code

---
 .../Sapfor_2017/_src/CFGraph/CFGraph.cpp      | 16 ++++++
 .../Sapfor_2017/_src/CFGraph/CFGraph.h        |  3 ++
 .../_src/Transformations/dead_code.cpp        | 53 ++++++++++++++++++-
 3 files changed, 71 insertions(+), 1 deletion(-)

diff --git a/sapfor/experts/Sapfor_2017/_src/CFGraph/CFGraph.cpp b/sapfor/experts/Sapfor_2017/_src/CFGraph/CFGraph.cpp
index d98dc14..b00a2b1 100644
--- a/sapfor/experts/Sapfor_2017/_src/CFGraph/CFGraph.cpp
+++ b/sapfor/experts/Sapfor_2017/_src/CFGraph/CFGraph.cpp
@@ -56,6 +56,22 @@ void BBlock::addInstruction(IR_Block* item)
     item->setBasicBlock(this);
 }
 
+int BBlock::removePrev(BBlock* removed)
+{
+    auto it = std::remove(prev.begin(), prev.end(), removed);
+    auto r = prev.end() - it;
+    prev.erase(it, prev.end());
+    return r;
+}
+
+int BBlock::removeNext(BBlock* removed)
+{
+    auto it = std::remove(next.begin(), next.end(), removed);
+    auto r = next.end() - it;
+    next.erase(it, next.end());
+    return r;
+}
+
 BBlock::~BasicBlock()
 {
     for (auto& instr : instructions)
diff --git a/sapfor/experts/Sapfor_2017/_src/CFGraph/CFGraph.h b/sapfor/experts/Sapfor_2017/_src/CFGraph/CFGraph.h
index e47447c..319b420 100644
--- a/sapfor/experts/Sapfor_2017/_src/CFGraph/CFGraph.h
+++ b/sapfor/experts/Sapfor_2017/_src/CFGraph/CFGraph.h
@@ -42,6 +42,9 @@ namespace SAPFOR
         void addInstruction(IR_Block* item);
         void addPrev(BasicBlock* prev_) { prev.push_back(prev_); }
         void addNext(BasicBlock* next_) { next.push_back(next_); }
+
+        int removePrev(BasicBlock* removed);
+        int removeNext(BasicBlock* removed);
         
         void replacePrevNext(const std::map<BasicBlock*, BasicBlock*>& oldToNew)
         {
diff --git a/sapfor/experts/Sapfor_2017/_src/Transformations/dead_code.cpp b/sapfor/experts/Sapfor_2017/_src/Transformations/dead_code.cpp
index 0590d4e..4df0ca5 100644
--- a/sapfor/experts/Sapfor_2017/_src/Transformations/dead_code.cpp
+++ b/sapfor/experts/Sapfor_2017/_src/Transformations/dead_code.cpp
@@ -4,12 +4,15 @@
 #include <string>
 #include <vector>
 #include <set>
+#include <algorithm>
 
 using std::map;
 using std::string;
 using std::vector;
 using std::set;
 
+using std::remove_if;
+
 #define PRINT_USELESS_STATEMENTS 0
 
 static void updateUseDefForInstruction(SAPFOR::BasicBlock* block, SAPFOR::Instruction* instr,
@@ -325,7 +328,51 @@ void removeDeadCode(SgStatement* func,
     if(cfg.size() != 1)
         printInternalError(convertFileName(__FILE__).c_str(), __LINE__);
 
-    const auto& cfg_pair = *(cfg.begin());
+    auto& cfg_pair = *(cfg.begin());
+
+    // delete unreachable blocks
+
+    set<SAPFOR::BasicBlock*> reachable;
+
+    for (auto b : cfg_pair.second)
+        if(b->getInstructions().front()->isHeader())
+            reachable.insert(b);
+
+    set<SAPFOR::BasicBlock*> worklist = reachable;
+    while (worklist.size() != 0)
+    {
+        set<SAPFOR::BasicBlock*> to_insert;
+
+        for(auto b : worklist)
+            for(auto next: b->getNext())
+                if(reachable.insert(next).second)
+                    to_insert.insert(next);
+
+        worklist = to_insert;
+    }
+
+    auto remove_unreachable_it = remove_if(cfg_pair.second.begin(), cfg_pair.second.end(), 
+        [&reachable](SAPFOR::BasicBlock* b)
+        {
+            if (reachable.find(b) == reachable.end())
+            {
+                for(auto next: b->getNext())
+                    if(reachable.find(next) != reachable.end())
+                        next->removePrev(b);
+
+                delete b;
+                return true;
+            }
+
+            return false;
+        }
+    );
+
+    reachable.clear();
+
+    cfg_pair.second.erase(remove_unreachable_it, cfg_pair.second.end());
+
+    // detect useless code
 
     vector<SAPFOR::Argument*> func_parameters(cfg_pair.first->funcParams.countOfPars, NULL);
 
@@ -334,6 +381,8 @@ void removeDeadCode(SgStatement* func,
     analysis_object.fit(cfg_pair.second);
     analysis_object.analyze();
 
+    // detect dead statements
+
     set<SgStatement*> useful;
 
     for (DeadCodeAnalysisNode* byNode : analysis_object.getNodes())
@@ -358,6 +407,8 @@ void removeDeadCode(SgStatement* func,
         }
     }
 
+    // remove dead statements
+
     SgStatement* end = func->lastNodeOfStmt(), *st = func;
     
     set<int> removable =