PM: Port DCE to the new pass manager

Also add a very basic test, since apparently there aren't any tests
for DCE whatsoever to add the new pass version to.

llvm-svn: 267196

llvm/include/llvm/InitializePasses.h

@@ -104,7 +104,7 @@ void initializeCorrelatedValuePropagationPass(PassRegistry&);
 void initializeCrossDSOCFIPass(PassRegistry&);
 void initializeDAEPass(PassRegistry&);
 void initializeDAHPass(PassRegistry&);
-void initializeDCEPass(PassRegistry&);
+void initializeDCELegacyPassPass(PassRegistry&);
 void initializeDSEPass(PassRegistry&);
 void initializeDeadInstEliminationPass(PassRegistry&);
 void initializeDeadMachineInstructionElimPass(PassRegistry&);

llvm/include/llvm/Transforms/Scalar/DCE.h

@@ -0,0 +1,29 @@
+//===- DCE.h - Dead code elimination ----------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file provides the interface for the Dead Code Elimination pass.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TRANSFORMS_SCALAR_DCE_H
+#define LLVM_TRANSFORMS_SCALAR_DCE_H
+
+#include "llvm/IR/Function.h"
+#include "llvm/IR/PassManager.h"
+
+namespace llvm {
+
+/// Basic Dead Code Elimination pass.
+class DCEPass : public PassInfoMixin<DCEPass> {
+public:
+  PreservedAnalyses run(Function &F, AnalysisManager<Function> &AM);
+};
+}
+
+#endif // LLVM_TRANSFORMS_SCALAR_DCE_H

llvm/lib/LTO/LTOCodeGenerator.cpp

@@ -117,7 +117,7 @@ void LTOCodeGenerator::initializeLTOPasses() {
   initializeMergedLoadStoreMotionPass(R);
   initializeGVNLegacyPassPass(R);
   initializeMemCpyOptPass(R);
-  initializeDCEPass(R);
+  initializeDCELegacyPassPass(R);
   initializeCFGSimplifyPassPass(R);
 }
 

llvm/lib/Passes/PassBuilder.cpp

@@ -52,6 +52,7 @@
 #include "llvm/Transforms/InstCombine/InstCombine.h"
 #include "llvm/Transforms/InstrProfiling.h"
 #include "llvm/Transforms/Scalar/ADCE.h"
+#include "llvm/Transforms/Scalar/DCE.h"
 #include "llvm/Transforms/Scalar/EarlyCSE.h"
 #include "llvm/Transforms/Scalar/LowerExpectIntrinsic.h"
 #include "llvm/Transforms/Scalar/GVN.h"

llvm/lib/Passes/PassRegistry.def

@@ -96,6 +96,7 @@ FUNCTION_ALIAS_ANALYSIS("type-based-aa", TypeBasedAA())
 #endif
 FUNCTION_PASS("aa-eval", AAEvaluator())
 FUNCTION_PASS("adce", ADCEPass())
+FUNCTION_PASS("dce", DCEPass())
 FUNCTION_PASS("early-cse", EarlyCSEPass())
 FUNCTION_PASS("instcombine", InstCombinePass())
 FUNCTION_PASS("invalidate<all>", InvalidateAllAnalysesPass())

llvm/lib/Transforms/Scalar/DCE.cpp

@@ -16,13 +16,14 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/Transforms/Scalar.h"
+#include "llvm/Transforms/Scalar/DCE.h"
 #include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/IR/InstIterator.h"
 #include "llvm/IR/Instruction.h"
 #include "llvm/Pass.h"
 #include "llvm/Analysis/TargetLibraryInfo.h"
+#include "llvm/Transforms/Scalar.h"
 #include "llvm/Transforms/Utils/Local.h"
 using namespace llvm;
 
@@ -71,28 +72,6 @@ Pass *llvm::createDeadInstEliminationPass() {
   return new DeadInstElimination();
 }
 
-
-namespace {
-  //===--------------------------------------------------------------------===//
-  // DeadCodeElimination pass implementation
-  //
-  struct DCE : public FunctionPass {
-    static char ID; // Pass identification, replacement for typeid
-    DCE() : FunctionPass(ID) {
-      initializeDCEPass(*PassRegistry::getPassRegistry());
-    }
-
-    bool runOnFunction(Function &F) override;
-
-    void getAnalysisUsage(AnalysisUsage &AU) const override {
-      AU.setPreservesCFG();
-    }
- };
-}
-
-char DCE::ID = 0;
-INITIALIZE_PASS(DCE, "dce", "Dead Code Elimination", false, false)
-
 static bool DCEInstruction(Instruction *I,
                            SmallSetVector<Instruction *, 16> &WorkList,
                            const TargetLibraryInfo *TLI) {
@@ -121,13 +100,7 @@ static bool DCEInstruction(Instruction *I,
   return false;
 }
 
-bool DCE::runOnFunction(Function &F) {
-  if (skipOptnoneFunction(F))
-    return false;
-
-  auto *TLIP = getAnalysisIfAvailable<TargetLibraryInfoWrapperPass>();
-  TargetLibraryInfo *TLI = TLIP ? &TLIP->getTLI() : nullptr;
-
+bool eliminateDeadCode(Function &F, TargetLibraryInfo *TLI) {
   bool MadeChange = false;
   SmallSetVector<Instruction *, 16> WorkList;
   // Iterate over the original function, only adding insts to the worklist
@@ -150,7 +123,38 @@ bool DCE::runOnFunction(Function &F) {
   return MadeChange;
 }
 
-FunctionPass *llvm::createDeadCodeEliminationPass() {
-  return new DCE();
+PreservedAnalyses DCEPass::run(Function &F, AnalysisManager<Function> &AM) {
+  if (eliminateDeadCode(F, AM.getCachedResult<TargetLibraryAnalysis>(F)))
+    return PreservedAnalyses::none();
+  return PreservedAnalyses::all();
 }
 
+namespace {
+struct DCELegacyPass : public FunctionPass {
+  static char ID; // Pass identification, replacement for typeid
+  DCELegacyPass() : FunctionPass(ID) {
+    initializeDCELegacyPassPass(*PassRegistry::getPassRegistry());
+  }
+
+  bool runOnFunction(Function &F) override {
+    if (skipOptnoneFunction(F))
+      return false;
+
+    auto *TLIP = getAnalysisIfAvailable<TargetLibraryInfoWrapperPass>();
+    TargetLibraryInfo *TLI = TLIP ? &TLIP->getTLI() : nullptr;
+
+    return eliminateDeadCode(F, TLI);
+  }
+
+  void getAnalysisUsage(AnalysisUsage &AU) const override {
+    AU.setPreservesCFG();
+  }
+};
+}
+
+char DCELegacyPass::ID = 0;
+INITIALIZE_PASS(DCELegacyPass, "dce", "Dead Code Elimination", false, false)
+
+FunctionPass *llvm::createDeadCodeEliminationPass() {
+  return new DCELegacyPass();
+}

llvm/lib/Transforms/Scalar/Scalar.cpp

@@ -37,7 +37,7 @@ void llvm::initializeScalarOpts(PassRegistry &Registry) {
   initializeConstantHoistingPass(Registry);
   initializeConstantPropagationPass(Registry);
   initializeCorrelatedValuePropagationPass(Registry);
-  initializeDCEPass(Registry);
+  initializeDCELegacyPassPass(Registry);
   initializeDeadInstEliminationPass(Registry);
   initializeScalarizerPass(Registry);
   initializeDSEPass(Registry);

llvm/test/Transforms/DCE/basic.ll

@@ -0,0 +1,11 @@
+; RUN: opt -dce -S < %s | FileCheck %s
+; RUN: opt -passes=dce -S < %s | FileCheck %s
+
+; CHECK-LABEL: @test
+define void @test() {
+; CHECK-NOT: add
+  %add = add i32 1, 2
+; CHECK-NOT: sub
+  %sub = sub i32 %add, 1
+  ret void
+}