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diff --git a/llvm/lib/Transforms/AggressiveInstCombine/AggressiveInstCombine.cpp b/llvm/lib/Transforms/AggressiveInstCombine/AggressiveInstCombine.cpp
new file mode 100644
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+++ b/llvm/lib/Transforms/AggressiveInstCombine/AggressiveInstCombine.cpp
@@ -0,0 +1,110 @@
+//===- AggressiveInstCombine.cpp ------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the aggressive expression pattern combiner classes.
+// Currently, it handles expression patterns for:
+//  * Truncate instruction
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/AggressiveInstCombine/AggressiveInstCombine.h"
+#include "AggressiveInstCombineInternal.h"
+#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/Analysis/BasicAliasAnalysis.h"
+#include "llvm/Analysis/GlobalsModRef.h"
+#include "llvm/Analysis/TargetLibraryInfo.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/Pass.h"
+#include "llvm/Transforms/Scalar.h"
+using namespace llvm;
+
+#define DEBUG_TYPE "aggressive-instcombine"
+
+namespace {
+/// Contains expression pattern combiner logic.
+/// This class provides both the logic to combine expression patterns and
+/// combine them. It differs from InstCombiner class in that each pattern
+/// combiner runs only once as opposed to InstCombine's multi-iteration,
+/// which allows pattern combiner to have higher complexity than the O(1)
+/// required by the instruction combiner.
+class AggressiveInstCombinerLegacyPass : public FunctionPass {
+public:
+  static char ID; // Pass identification, replacement for typeid
+
+  AggressiveInstCombinerLegacyPass() : FunctionPass(ID) {
+    initializeAggressiveInstCombinerLegacyPassPass(
+        *PassRegistry::getPassRegistry());
+  }
+
+  void getAnalysisUsage(AnalysisUsage &AU) const override;
+
+  /// Run all expression pattern optimizations on the given /p F function.
+  ///
+  /// \param F function to optimize.
+  /// \returns true if the IR is changed.
+  bool runOnFunction(Function &F) override;
+};
+} // namespace
+
+void AggressiveInstCombinerLegacyPass::getAnalysisUsage(
+    AnalysisUsage &AU) const {
+  AU.setPreservesCFG();
+  AU.addRequired<TargetLibraryInfoWrapperPass>();
+  AU.addPreserved<AAResultsWrapperPass>();
+  AU.addPreserved<BasicAAWrapperPass>();
+  AU.addPreserved<GlobalsAAWrapperPass>();
+}
+
+bool AggressiveInstCombinerLegacyPass::runOnFunction(Function &F) {
+  auto &TLI = getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
+  auto &DL = F.getParent()->getDataLayout();
+
+  bool MadeIRChange = false;
+
+  // Handle TruncInst patterns
+  TruncInstCombine TIC(TLI, DL);
+  MadeIRChange |= TIC.run(F);
+
+  // TODO: add more patterns to handle...
+
+  return MadeIRChange;
+}
+
+PreservedAnalyses AggressiveInstCombinePass::run(Function &F,
+                                                 FunctionAnalysisManager &AM) {
+  auto &TLI = AM.getResult<TargetLibraryAnalysis>(F);
+  auto &DL = F.getParent()->getDataLayout();
+  bool MadeIRChange = false;
+
+  // Handle TruncInst patterns
+  TruncInstCombine TIC(TLI, DL);
+  MadeIRChange |= TIC.run(F);
+  if (!MadeIRChange)
+    // No changes, all analyses are preserved.
+    return PreservedAnalyses::all();
+
+  // Mark all the analyses that instcombine updates as preserved.
+  PreservedAnalyses PA;
+  PA.preserveSet<CFGAnalyses>();
+  PA.preserve<AAManager>();
+  PA.preserve<GlobalsAA>();
+  return PA;
+}
+
+char AggressiveInstCombinerLegacyPass::ID = 0;
+INITIALIZE_PASS_BEGIN(AggressiveInstCombinerLegacyPass,
+                      "aggressive-instcombine",
+                      "Combine pattern based expressions", false, false)
+INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
+INITIALIZE_PASS_END(AggressiveInstCombinerLegacyPass, "aggressive-instcombine",
+                    "Combine pattern based expressions", false, false)
+
+FunctionPass *llvm::createAggressiveInstCombinerPass() {
+  return new AggressiveInstCombinerLegacyPass();
+}