New Pass Added

Author: lahiri-phdworks

ModifyBuildCFG/ModifyBuildCFG.cpp

@@ -0,0 +1,108 @@
+
+#include "llvm/Analysis/CFG.h"
+#include "llvm/Analysis/DomTreeUpdater.h"
+#include "llvm/Analysis/PostDominators.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/InstIterator.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/Passes/PassBuilder.h"
+#include "llvm/Passes/PassPlugin.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
+
+// only needed for printing
+#include <assert.h>
+#include <iostream>
+using namespace llvm;
+
+namespace {
+
+struct ModifyBuildCFG : public PassInfoMixin<ModifyBuildCFG> {
+
+  PreservedAnalyses run(Function &F, FunctionAnalysisManager &FAM) {
+
+    if (F.getName() != "main")
+      return PreservedAnalyses::all();
+
+    // What we intend do do in the pass starts here.
+    LoopInfo &getLI = FAM.getResult<llvm::LoopAnalysis>(F);
+    DominatorTree &DT = FAM.getResult<DominatorTreeAnalysis>(F);
+    PostDominatorTree &PDT = FAM.getResult<PostDominatorTreeAnalysis>(F);
+
+    /**
+     * @brief Loop Info Analysis
+     */
+    if (getLI.empty())
+      std::cout << "\nNo Loops !\n";
+    else
+      getLI.print(errs());
+
+    /**
+     * @brief Print Dominator Tree to llvm::errs()
+     */
+    DT.print(errs());
+
+    auto DTU = DomTreeUpdater(DT, PDT, DomTreeUpdater::UpdateStrategy::Lazy);
+    int found = 0;
+
+    Instruction *binop = nullptr;
+    for (auto &BB : F) {
+      errs() << "\t\tBasic Block : " << BB.getName().str() << "\n";
+      for (auto &I : BB) {
+        errs() << "\tOperation : " << I.getOpcodeName() << "\n";
+        binop = dyn_cast<BinaryOperator>(&I);
+        if (binop != NULL) {
+          errs() << "\t\t Binary Operation : " << binop->getOpcodeName()
+                 << "\n";
+          found = 1;
+          break;
+          assert(0);
+        }
+      }
+      if (found == 1)
+        break;
+    }
+
+    // Use the operands of a binary operator to
+    // get the operands of Compare Not Equal Instruction.
+    if (binop != NULL) {
+      IRBuilder<> IRModIfElse(binop);
+      Value *v1 = binop->getOperand(0);
+      Value *v2 = binop->getOperand(1);
+      Value *Cmp = IRModIfElse.CreateICmpNE(v1, v2, "dummy_compare_op");
+      Instruction *ThenTerm, *ElseTerm;
+      errs() << Cmp->getValueID() << "\n";
+      SplitBlockAndInsertIfThenElse(Cmp, binop, &ThenTerm, &ElseTerm);
+      errs() << ThenTerm->getOpcodeName() << "\n";
+      errs() << ElseTerm->getOpcodeName() << "\n";
+    }
+
+    for (auto &BB : F) {
+      errs() << "\t\tBasic Block : " << BB.getName().str() << "\n";
+    }
+
+    // Preserve previous analysis in the pass. Like Dominator information.
+    // THe pass we made does not modify that.
+    return PreservedAnalyses::none();
+  }
+};
+} // namespace
+
+// Registering the pass.
+extern "C" ::llvm::PassPluginLibraryInfo LLVM_ATTRIBUTE_WEAK
+llvmGetPassPluginInfo() {
+  return {LLVM_PLUGIN_API_VERSION, "ModifyBuildCFG", "v0.1",
+          [](PassBuilder &PB) {
+            PB.registerPipelineParsingCallback(
+                [](StringRef Name, FunctionPassManager &FPM,
+                   ArrayRef<PassBuilder::PipelineElement>) {
+                  if (Name == "modifyncfg") {
+                    FPM.addPass(ModifyBuildCFG());
+                    return true;
+                  }
+                  return false;
+                });
+          }};
+}

ModifyBuildCFG/cfg_example1.pdf

@@ -0,0 +1,49 @@
+#include <iostream>
+#include <stdio.h>
+#include <time.h>
+
+int retval() { return rand() % 5; }
+
+int main() {
+  int a = 0, b = 7, c = 0, d = 0, z = 0, p = 0, m = 0, n = 0,
+      arr[5] = {0, 0, 0, 0, 0};
+  srand(time(NULL));
+
+  // We add a branch here
+  a = rand() % 10;
+
+  for (int i = 0; i < rand() % 5; i++) {
+    if (i % 5 == 0) {
+      for (int j = 0; j < 5; j++) {
+        if (rand() % 100 == 10) {
+          a = b + 1;
+          std::cout << a << c << d << std::endl;
+        } else {
+          d = c - a;
+          z = b;
+          a = p - 50;
+          std::cout << d << z << a << std::endl;
+          if (c < d) {
+            c = c - 1;
+            a = a + 1;
+            std::cout << c << d << a << std::endl;
+            a = retval();
+            a = m - n;
+          }
+          for (int k = 10; i > 0; i--) {
+            a = a + 1;
+            std::cout << a << std::endl;
+          }
+        }
+        a = retval();
+        std::cout << j << a << b << c << d << std::endl;
+      }
+    }
+  }
+
+  c = a;
+  d = b;
+  std::cout << d << c << std::endl;
+
+  return 0;
+}