From 706c7da4c837dfb487ede162bf6dbc84a2fd3ed2 Mon Sep 17 00:00:00 2001
From: Francesco Bertolaccini <francesco.bertolaccini@trailofbits.com>
Date: Fri, 26 Aug 2022 11:27:02 +0200
Subject: [PATCH] Remove temporary variables for `load`s

---
 include/rellic/BC/Util.h   |  2 --
 lib/AST/IRToASTVisitor.cpp |  4 ---
 lib/BC/Util.cpp            | 57 --------------------------------------
 lib/Decompiler.cpp         |  1 -
 tools/xref/Xref.cpp        |  1 -
 5 files changed, 65 deletions(-)

diff --git a/include/rellic/BC/Util.h b/include/rellic/BC/Util.h
index 2435395a..a08e5aa2 100644
--- a/include/rellic/BC/Util.h
+++ b/include/rellic/BC/Util.h
@@ -67,6 +67,4 @@ void RemoveInsertValues(llvm::Module &module);
 // Converts by value array arguments and wraps them into a struct, so that
 // semantics are preserved in C
 void ConvertArrayArguments(llvm::Module &module);
-
-void FindRedundantLoads(llvm::Module &module);
 }  // namespace rellic
\ No newline at end of file
diff --git a/lib/AST/IRToASTVisitor.cpp b/lib/AST/IRToASTVisitor.cpp
index 1bc58662..19c872f7 100755
--- a/lib/AST/IRToASTVisitor.cpp
+++ b/lib/AST/IRToASTVisitor.cpp
@@ -1313,11 +1313,7 @@ void IRToASTVisitor::VisitFunctionDecl(llvm::Function &func) {
       fdecl->addDecl(var);
     } else if (inst.hasNUsesOrMore(2) ||
                (inst.hasNUsesOrMore(1) && llvm::isa<llvm::CallInst>(inst)) ||
-               llvm::isa<llvm::LoadInst>(inst) ||
                llvm::isa<llvm::PHINode>(inst)) {
-      if (inst.getMetadata("rellic.notemp")) {
-        continue;
-      }
       if (!inst.getType()->isVoidTy()) {
         auto GetPrefix{[&](llvm::Instruction *inst) {
           if (llvm::isa<llvm::CallInst>(inst)) {
diff --git a/lib/BC/Util.cpp b/lib/BC/Util.cpp
index 76052e4c..63f7dd0f 100644
--- a/lib/BC/Util.cpp
+++ b/lib/BC/Util.cpp
@@ -437,61 +437,4 @@ void ConvertArrayArguments(llvm::Module &m) {
   CHECK(VerifyModule(&m)) << "Transformation broke module correctness";
 }
 
-static void FindRedundantLoads(llvm::Function &func) {
-  auto HasStoreBeforeUse = [&](llvm::Value *ptr, llvm::User *user,
-                               llvm::LoadInst *load) {
-    std::unordered_set<llvm::BasicBlock *> visited_blocks;
-    std::vector<llvm::Instruction *> work_list;
-    auto inst{llvm::cast<llvm::Instruction>(user)};
-    work_list.push_back(inst);
-    while (!work_list.empty()) {
-      inst = work_list.back();
-      work_list.pop_back();
-      auto bb{inst->getParent()};
-      visited_blocks.insert(bb);
-
-      while (inst) {
-        if (auto store = llvm::dyn_cast<llvm::StoreInst>(inst)) {
-          if (store->getPointerOperand() == ptr) {
-            return true;
-          }
-        }
-        if (inst == load) {
-          return false;
-        }
-        inst = inst->getPrevNode();
-      }
-      for (auto pred : llvm::predecessors(bb)) {
-        if (!visited_blocks.count(pred)) {
-          work_list.push_back(pred->getTerminator());
-        }
-      }
-    }
-
-    return false;
-  };
-
-  for (auto &inst : llvm::instructions(func)) {
-    if (auto load = llvm::dyn_cast<llvm::LoadInst>(&inst)) {
-      for (auto &use : load->uses()) {
-        auto ptr{load->getPointerOperand()};
-        if (!llvm::isa<llvm::AllocaInst>(ptr)) {
-          continue;
-        }
-        if (HasStoreBeforeUse(ptr, use.getUser(), load)) {
-          continue;
-        }
-        load->setMetadata("rellic.notemp",
-                          llvm::MDNode::get(func.getContext(), {}));
-      }
-    }
-  }
-}
-
-void FindRedundantLoads(llvm::Module &module) {
-  for (auto &func : module.functions()) {
-    FindRedundantLoads(func);
-  }
-}
-
 }  // namespace rellic
\ No newline at end of file
diff --git a/lib/Decompiler.cpp b/lib/Decompiler.cpp
index 5bae24a0..001d8748 100644
--- a/lib/Decompiler.cpp
+++ b/lib/Decompiler.cpp
@@ -73,7 +73,6 @@ Result<DecompilationResult, DecompilationError> Decompile(
 
     ConvertArrayArguments(*module);
     RemoveInsertValues(*module);
-    FindRedundantLoads(*module);
 
     InitOptPasses();
     rellic::DebugInfoCollector dic;
diff --git a/tools/xref/Xref.cpp b/tools/xref/Xref.cpp
index 315de3ef..c5200006 100644
--- a/tools/xref/Xref.cpp
+++ b/tools/xref/Xref.cpp
@@ -248,7 +248,6 @@ static void LoadModule(const httplib::Request& req, httplib::Response& res) {
     return;
   }
   session.Module = std::unique_ptr<llvm::Module>(mod);
-  rellic::FindRedundantLoads(*session.Module);
   llvm::json::Object msg{{"message", "Ok."}};
   SendJSON(res, msg);
   res.status = 200;