[IPO/GlobalDCE] Port to the new PM.

[davide]

Summary

In preparation for porting GlobalDCE to the new PM.

[davide]

Update after Justin's feedback.

[mehdi_amini]

include/llvm/Transforms/IPO/GlobalDCE.h

44 ↗

(On Diff #55842)

Can we split what is the "pass" and what is the actual utility?

[davide]

I think it's possible, but maybe overkill? Probably people with more experience porting passes can tell what they think.

[mehdi_amini]

I think this should be the standard layout, it should be the exception to merge together the utility logic and the pass logic.

[mehdi_amini]

include/llvm/Transforms/IPO/GlobalDCE.h

31 ↗

(On Diff #55842)

why?

[davide]

Anything else that needs to be changed before this goes in?

[mcrosier]

lib/LTO/LTOCodeGenerator.cpp

107 ↗

(On Diff #55842)

GlobalDCELegacyPassPass?

[davide]

lib/LTO/LTOCodeGenerator.cpp

107 ↗

(On Diff #55842)

Just followed what was already there. See, for example InstructionCombining or GlobalOPT.

llvm/trunk/include/llvm/InitializePasses.h

 void initializeScalarizerPass(PassRegistry&);
 void initializeEarlyCSELegacyPassPass(PassRegistry &);
 void initializeEliminateAvailableExternallyPass(PassRegistry&);
 void initializeExpandISelPseudosPass(PassRegistry&);
 void initializeForceFunctionAttrsLegacyPassPass(PassRegistry&);
 void initializeGCMachineCodeAnalysisPass(PassRegistry&);
 void initializeGCModuleInfoPass(PassRegistry&);
 void initializeGVNLegacyPassPass(PassRegistry&);
-void initializeGlobalDCEPass(PassRegistry&);
+void initializeGlobalDCELegacyPassPass(PassRegistry&);
 void initializeGlobalOptLegacyPassPass(PassRegistry&);
 void initializeGlobalsAAWrapperPassPass(PassRegistry&);
 void initializeIPCPPass(PassRegistry&);
 void initializeIPSCCPPass(PassRegistry&);
 void initializeIVUsersPass(PassRegistry&);
 void initializeIfConverterPass(PassRegistry&);
 void initializeInductiveRangeCheckEliminationPass(PassRegistry&);
 void initializeIndVarSimplifyPass(PassRegistry&);

llvm/trunk/include/llvm/Transforms/IPO/GlobalDCE.h

+//===-- GlobalDCE.h - DCE unreachable internal functions ------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This transform is designed to eliminate unreachable internal globals from the
+// program.  It uses an aggressive algorithm, searching out globals that are
+// known to be alive.  After it finds all of the globals which are needed, it
+// deletes whatever is left over.  This allows it to delete recursive chunks of
+// the program which are unreachable.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TRANSFORMS_IPO_GLOBALDCE_H
+#define LLVM_TRANSFORMS_IPO_GLOBALDCE_H
+
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include <unordered_map>
+
+namespace llvm {
+
+/// Pass to remove unused function declarations.
+class GlobalDCEPass : public PassInfoMixin<GlobalDCEPass> {
+public:
+  PreservedAnalyses run(Module &M);
+
+private:
+  SmallPtrSet<GlobalValue*, 32> AliveGlobals;
+  SmallPtrSet<Constant *, 8> SeenConstants;
+  std::unordered_multimap<Comdat *, GlobalValue *> ComdatMembers;
+
+  /// Mark the specific global value as needed, and
+  /// recursively mark anything that it uses as also needed.
+  void GlobalIsNeeded(GlobalValue *GV);
+  void MarkUsedGlobalsAsNeeded(Constant *C);
+  bool RemoveUnusedGlobalValue(GlobalValue &GV);
+};
+
+}
+
+#endif // LLVM_TRANSFORMS_IPO_GLOBALDCE_H

llvm/trunk/lib/LTO/LTOCodeGenerator.cpp

void LTOCodeGenerator::initializeLTOPasses() {
   initializeInternalizeLegacyPassPass(R);
   initializeIPSCCPPass(R);
   initializeGlobalOptLegacyPassPass(R);
   initializeConstantMergePass(R);
   initializeDAHPass(R);
   initializeInstructionCombiningPassPass(R);
   initializeSimpleInlinerPass(R);
   initializePruneEHPass(R);
-  initializeGlobalDCEPass(R);
+  initializeGlobalDCELegacyPassPass(R);
   initializeArgPromotionPass(R);
   initializeJumpThreadingPass(R);
   initializeSROALegacyPassPass(R);
   initializeSROA_DTPass(R);
   initializeSROA_SSAUpPass(R);
   initializePostOrderFunctionAttrsLegacyPassPass(R);
   initializeReversePostOrderFunctionAttrsPass(R);
   initializeGlobalsAAWrapperPassPass(R);

llvm/trunk/lib/Passes/PassBuilder.cpp

 #include "llvm/IR/IRPrintingPasses.h"
 #include "llvm/IR/PassManager.h"
 #include "llvm/IR/Verifier.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/Regex.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Transforms/IPO/ForceFunctionAttrs.h"
 #include "llvm/Transforms/IPO/FunctionAttrs.h"
+#include "llvm/Transforms/IPO/GlobalDCE.h"
 #include "llvm/Transforms/IPO/GlobalOpt.h"
 #include "llvm/Transforms/IPO/InferFunctionAttrs.h"
 #include "llvm/Transforms/IPO/Internalize.h"
 #include "llvm/Transforms/IPO/StripDeadPrototypes.h"
 #include "llvm/Transforms/InstCombine/InstCombine.h"
 #include "llvm/Transforms/InstrProfiling.h"
 #include "llvm/Transforms/Scalar/ADCE.h"
 #include "llvm/Transforms/Scalar/DCE.h"

llvm/trunk/lib/Passes/PassRegistry.def

 MODULE_ALIAS_ANALYSIS("globals-aa", GlobalsAA())
 #undef MODULE_ALIAS_ANALYSIS
 #undef MODULE_ANALYSIS
 
 #ifndef MODULE_PASS
 #define MODULE_PASS(NAME, CREATE_PASS)
 #endif
 MODULE_PASS("forceattrs", ForceFunctionAttrsPass())
+MODULE_PASS("globaldce", GlobalDCEPass())
 MODULE_PASS("globalopt", GlobalOptPass())
 MODULE_PASS("inferattrs", InferFunctionAttrsPass())
 MODULE_PASS("internalize", InternalizePass())
 MODULE_PASS("instrprof", InstrProfiling())
 MODULE_PASS("invalidate<all>", InvalidateAllAnalysesPass())
 MODULE_PASS("no-op-module", NoOpModulePass())
 MODULE_PASS("print", PrintModulePass(dbgs()))
 MODULE_PASS("print-callgraph", CallGraphPrinterPass(dbgs()))

llvm/trunk/lib/Transforms/IPO/GlobalDCE.cpp

 // This transform is designed to eliminate unreachable internal globals from the
 // program.  It uses an aggressive algorithm, searching out globals that are
 // known to be alive.  After it finds all of the globals which are needed, it
 // deletes whatever is left over.  This allows it to delete recursive chunks of
 // the program which are unreachable.
 //
 //===----------------------------------------------------------------------===//
 
+#include "llvm/Transforms/IPO/GlobalDCE.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/Module.h"
 #include "llvm/Pass.h"
 #include "llvm/Transforms/IPO.h"
 #include "llvm/Transforms/Utils/CtorUtils.h"
 #include "llvm/Transforms/Utils/GlobalStatus.h"
 #include <unordered_map>
 using namespace llvm;
 
 #define DEBUG_TYPE "globaldce"
 
 STATISTIC(NumAliases  , "Number of global aliases removed");
 STATISTIC(NumFunctions, "Number of functions removed");
 STATISTIC(NumVariables, "Number of global variables removed");
 
 namespace {
-  struct GlobalDCE : public ModulePass {
+  class GlobalDCELegacyPass : public ModulePass {
+  public:
     static char ID; // Pass identification, replacement for typeid
-    GlobalDCE() : ModulePass(ID) {
-      initializeGlobalDCEPass(*PassRegistry::getPassRegistry());
+    GlobalDCELegacyPass() : ModulePass(ID) {
+      initializeGlobalDCELegacyPassPass(*PassRegistry::getPassRegistry());
     }
 
     // run - Do the GlobalDCE pass on the specified module, optionally updating
     // the specified callgraph to reflect the changes.
     //
-    bool runOnModule(Module &M) override;
+    bool runOnModule(Module &M) override {
+      if (skipModule(M))
+        return false;
+
+      auto PA = Impl.run(M);
+      return !PA.areAllPreserved();
+    }
 
   private:
-    SmallPtrSet<GlobalValue*, 32> AliveGlobals;
-    SmallPtrSet<Constant *, 8> SeenConstants;
-    std::unordered_multimap<Comdat *, GlobalValue *> ComdatMembers;
+    GlobalDCEPass Impl;
+  };
+}
 
-    /// GlobalIsNeeded - mark the specific global value as needed, and
-    /// recursively mark anything that it uses as also needed.
-    void GlobalIsNeeded(GlobalValue *GV);
-    void MarkUsedGlobalsAsNeeded(Constant *C);
+char GlobalDCELegacyPass::ID = 0;
+INITIALIZE_PASS(GlobalDCELegacyPass, "globaldce",
+                "Dead Global Elimination", false, false)
 
-    bool RemoveUnusedGlobalValue(GlobalValue &GV);
-  };
+// Public interface to the GlobalDCEPass.
+ModulePass *llvm::createGlobalDCEPass() {
+  return new GlobalDCELegacyPass();
 }
 
 /// Returns true if F contains only a single "ret" instruction.
 static bool isEmptyFunction(Function *F) {
   BasicBlock &Entry = F->getEntryBlock();
   if (Entry.size() != 1 || !isa<ReturnInst>(Entry.front()))
     return false;
   ReturnInst &RI = cast<ReturnInst>(Entry.front());
   return RI.getReturnValue() == nullptr;
 }
 
-char GlobalDCE::ID = 0;
-INITIALIZE_PASS(GlobalDCE, "globaldce",
-                "Dead Global Elimination", false, false)
-
-ModulePass *llvm::createGlobalDCEPass() { return new GlobalDCE(); }
-
-bool GlobalDCE::runOnModule(Module &M) {
-  if (skipModule(M))
-    return false;
-
+PreservedAnalyses GlobalDCEPass::run(Module &M) {
   bool Changed = false;
 
   // Remove empty functions from the global ctors list.
   Changed |= optimizeGlobalCtorsList(M, isEmptyFunction);
 
   // Collect the set of members for each comdat.
   for (Function &F : M)
     if (Comdat *C = F.getComdat())
if (!DeadAliases.empty()) {
     Changed = true;
   }
 
   // Make sure that all memory is released
   AliveGlobals.clear();
   SeenConstants.clear();
   ComdatMembers.clear();
 
-  return Changed;
+  if (Changed)
+    return PreservedAnalyses::none();
+  return PreservedAnalyses::all();
 }
 
 /// GlobalIsNeeded - the specific global value as needed, and
 /// recursively mark anything that it uses as also needed.
-void GlobalDCE::GlobalIsNeeded(GlobalValue *G) {
+void GlobalDCEPass::GlobalIsNeeded(GlobalValue *G) {
   // If the global is already in the set, no need to reprocess it.
   if (!AliveGlobals.insert(G).second)
     return;
 
   if (Comdat *C = G->getComdat()) {
     for (auto &&CM : make_range(ComdatMembers.equal_range(C)))
       GlobalIsNeeded(CM.second);
   }
for (BasicBlock &BB : *F)
         for (Use &U : I.operands())
           if (GlobalValue *GV = dyn_cast<GlobalValue>(U))
             GlobalIsNeeded(GV);
           else if (Constant *C = dyn_cast<Constant>(U))
             MarkUsedGlobalsAsNeeded(C);
   }
 }
 
-void GlobalDCE::MarkUsedGlobalsAsNeeded(Constant *C) {
+void GlobalDCEPass::MarkUsedGlobalsAsNeeded(Constant *C) {
   if (GlobalValue *GV = dyn_cast<GlobalValue>(C))
     return GlobalIsNeeded(GV);
 
   // Loop over all of the operands of the constant, adding any globals they
   // use to the list of needed globals.
   for (Use &U : C->operands()) {
     // If we've already processed this constant there's no need to do it again.
     Constant *Op = dyn_cast<Constant>(U);
     if (Op && SeenConstants.insert(Op).second)
       MarkUsedGlobalsAsNeeded(Op);
   }
 }
 
 // RemoveUnusedGlobalValue - Loop over all of the uses of the specified
 // GlobalValue, looking for the constant pointer ref that may be pointing to it.
 // If found, check to see if the constant pointer ref is safe to destroy, and if
 // so, nuke it.  This will reduce the reference count on the global value, which
 // might make it deader.
 //
-bool GlobalDCE::RemoveUnusedGlobalValue(GlobalValue &GV) {
+bool GlobalDCEPass::RemoveUnusedGlobalValue(GlobalValue &GV) {
   if (GV.use_empty())
     return false;
   GV.removeDeadConstantUsers();
   return GV.use_empty();
 }

llvm/trunk/lib/Transforms/IPO/IPO.cpp

 
 void llvm::initializeIPO(PassRegistry &Registry) {
   initializeArgPromotionPass(Registry);
   initializeConstantMergePass(Registry);
   initializeCrossDSOCFIPass(Registry);
   initializeDAEPass(Registry);
   initializeDAHPass(Registry);
   initializeForceFunctionAttrsLegacyPassPass(Registry);
-  initializeGlobalDCEPass(Registry);
+  initializeGlobalDCELegacyPassPass(Registry);
   initializeGlobalOptLegacyPassPass(Registry);
   initializeIPCPPass(Registry);
   initializeAlwaysInlinerPass(Registry);
   initializeSimpleInlinerPass(Registry);
   initializeInferFunctionAttrsLegacyPassPass(Registry);
   initializeInternalizeLegacyPassPass(Registry);
   initializeLoopExtractorPass(Registry);
   initializeBlockExtractorPassPass(Registry);

llvm/trunk/test/Transforms/GlobalDCE/basicvariabletest.ll

-; RUN: opt < %s -globaldce -S | FileCheck %s
+; RUN: opt < %s -passes=globaldce -S | FileCheck %s
 
 ; CHECK-NOT: global
 @X = external global i32
 @Y = internal global i32 7