1 files changed, 145 insertions, 0 deletions
diff --git a/llvm/lib/Transforms/Scalar/InstSimplifyPass.cpp b/llvm/lib/Transforms/Scalar/InstSimplifyPass.cpp
new file mode 100644
index 000000000000..ec28f790f252
--- /dev/null
+++ b/llvm/lib/Transforms/Scalar/InstSimplifyPass.cpp
@@ -0,0 +1,145 @@
+//===- InstSimplifyPass.cpp -----------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Scalar/InstSimplifyPass.h"
+#include "llvm/ADT/DepthFirstIterator.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Analysis/AssumptionCache.h"
+#include "llvm/Analysis/InstructionSimplify.h"
+#include "llvm/Analysis/OptimizationRemarkEmitter.h"
+#include "llvm/Analysis/TargetLibraryInfo.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/Dominators.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Type.h"
+#include "llvm/Pass.h"
+#include "llvm/Transforms/Utils.h"
+#include "llvm/Transforms/Utils/Local.h"
+using namespace llvm;
+
+#define DEBUG_TYPE "instsimplify"
+
+STATISTIC(NumSimplified, "Number of redundant instructions removed");
+
+static bool runImpl(Function &F, const SimplifyQuery &SQ,
+                    OptimizationRemarkEmitter *ORE) {
+  SmallPtrSet<const Instruction *, 8> S1, S2, *ToSimplify = &S1, *Next = &S2;
+  bool Changed = false;
+
+  do {
+    for (BasicBlock &BB : F) {
+      // Unreachable code can take on strange forms that we are not prepared to
+      // handle. For example, an instruction may have itself as an operand.
+      if (!SQ.DT->isReachableFromEntry(&BB))
+        continue;
+
+      SmallVector<Instruction *, 8> DeadInstsInBB;
+      for (Instruction &I : BB) {
+        // The first time through the loop, ToSimplify is empty and we try to
+        // simplify all instructions. On later iterations, ToSimplify is not
+        // empty and we only bother simplifying instructions that are in it.
+        if (!ToSimplify->empty() && !ToSimplify->count(&I))
+          continue;
+
+        // Don't waste time simplifying dead/unused instructions.
+        if (isInstructionTriviallyDead(&I)) {
+          DeadInstsInBB.push_back(&I);
+          Changed = true;
+        } else if (!I.use_empty()) {
+          if (Value *V = SimplifyInstruction(&I, SQ, ORE)) {
+            // Mark all uses for resimplification next time round the loop.
+            for (User *U : I.users())
+              Next->insert(cast<Instruction>(U));
+            I.replaceAllUsesWith(V);
+            ++NumSimplified;
+            Changed = true;
+            // A call can get simplified, but it may not be trivially dead.
+            if (isInstructionTriviallyDead(&I))
+              DeadInstsInBB.push_back(&I);
+          }
+        }
+      }
+      RecursivelyDeleteTriviallyDeadInstructions(DeadInstsInBB, SQ.TLI);
+    }
+
+    // Place the list of instructions to simplify on the next loop iteration
+    // into ToSimplify.
+    std::swap(ToSimplify, Next);
+    Next->clear();
+  } while (!ToSimplify->empty());
+
+  return Changed;
+}
+
+namespace {
+struct InstSimplifyLegacyPass : public FunctionPass {
+  static char ID; // Pass identification, replacement for typeid
+  InstSimplifyLegacyPass() : FunctionPass(ID) {
+    initializeInstSimplifyLegacyPassPass(*PassRegistry::getPassRegistry());
+  }
+
+  void getAnalysisUsage(AnalysisUsage &AU) const override {
+    AU.setPreservesCFG();
+    AU.addRequired<DominatorTreeWrapperPass>();
+    AU.addRequired<AssumptionCacheTracker>();
+    AU.addRequired<TargetLibraryInfoWrapperPass>();
+    AU.addRequired<OptimizationRemarkEmitterWrapperPass>();
+  }
+
+  /// Remove instructions that simplify.
+  bool runOnFunction(Function &F) override {
+    if (skipFunction(F))
+      return false;
+
+    const DominatorTree *DT =
+        &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
+    const TargetLibraryInfo *TLI =
+        &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(F);
+    AssumptionCache *AC =
+        &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
+    OptimizationRemarkEmitter *ORE =
+        &getAnalysis<OptimizationRemarkEmitterWrapperPass>().getORE();
+    const DataLayout &DL = F.getParent()->getDataLayout();
+    const SimplifyQuery SQ(DL, TLI, DT, AC);
+    return runImpl(F, SQ, ORE);
+  }
+};
+} // namespace
+
+char InstSimplifyLegacyPass::ID = 0;
+INITIALIZE_PASS_BEGIN(InstSimplifyLegacyPass, "instsimplify",
+                      "Remove redundant instructions", false, false)
+INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
+INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
+INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
+INITIALIZE_PASS_DEPENDENCY(OptimizationRemarkEmitterWrapperPass)
+INITIALIZE_PASS_END(InstSimplifyLegacyPass, "instsimplify",
+                    "Remove redundant instructions", false, false)
+
+// Public interface to the simplify instructions pass.
+FunctionPass *llvm::createInstSimplifyLegacyPass() {
+  return new InstSimplifyLegacyPass();
+}
+
+PreservedAnalyses InstSimplifyPass::run(Function &F,
+                                        FunctionAnalysisManager &AM) {
+  auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
+  auto &TLI = AM.getResult<TargetLibraryAnalysis>(F);
+  auto &AC = AM.getResult<AssumptionAnalysis>(F);
+  auto &ORE = AM.getResult<OptimizationRemarkEmitterAnalysis>(F);
+  const DataLayout &DL = F.getParent()->getDataLayout();
+  const SimplifyQuery SQ(DL, &TLI, &DT, &AC);
+  bool Changed = runImpl(F, SQ, &ORE);
+  if (!Changed)
+    return PreservedAnalyses::all();
+
+  PreservedAnalyses PA;
+  PA.preserveSet<CFGAnalyses>();
+  return PA;
+}