[DCE] Port -redundant-dbg-inst-elim to NPM

[aeubanks]

Summary

This is used to test RemoveRedundantDbgInstrs(), which is used by other
passes.

[ychen]

LGTM

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

 
 namespace llvm {
 
 /// Basic Dead Code Elimination pass.
 class DCEPass : public PassInfoMixin<DCEPass> {
 public:
   PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
 };
+
+class RedundantDbgInstEliminationPass
+    : public PassInfoMixin<RedundantDbgInstEliminationPass> {
+public:
+  PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
+};
 }
 
 #endif // LLVM_TRANSFORMS_SCALAR_DCE_H

llvm/lib/Passes/PassRegistry.def

 FUNCTION_PASS("print<regions>", RegionInfoPrinterPass(dbgs()))
 FUNCTION_PASS("print<scalar-evolution>", ScalarEvolutionPrinterPass(dbgs()))
 FUNCTION_PASS("print<stack-safety-local>", StackSafetyPrinterPass(dbgs()))
 // TODO: rename to print<foo> after NPM switch
 FUNCTION_PASS("print-alias-sets", AliasSetsPrinterPass(dbgs()))
 FUNCTION_PASS("print-predicateinfo", PredicateInfoPrinterPass(dbgs()))
 FUNCTION_PASS("print-mustexecute", MustExecutePrinterPass(dbgs()))
 FUNCTION_PASS("reassociate", ReassociatePass())
+FUNCTION_PASS("redundant-dbg-inst-elim", RedundantDbgInstEliminationPass())
 FUNCTION_PASS("reg2mem", RegToMemPass())
 FUNCTION_PASS("scalarizer", ScalarizerPass())
 FUNCTION_PASS("separate-const-offset-from-gep", SeparateConstOffsetFromGEPPass())
 FUNCTION_PASS("sccp", SCCPPass())
 FUNCTION_PASS("simplifycfg", SimplifyCFGPass())
 FUNCTION_PASS("sink", SinkingPass())
 FUNCTION_PASS("slp-vectorizer", SLPVectorizerPass())
 FUNCTION_PASS("slsr", StraightLineStrengthReducePass())

llvm/lib/Transforms/Scalar/DCE.cpp

 char RedundantDbgInstElimination::ID = 0;
 INITIALIZE_PASS(RedundantDbgInstElimination, "redundant-dbg-inst-elim",
                 "Redundant Dbg Instruction Elimination", false, false)
 
 Pass *llvm::createRedundantDbgInstEliminationPass() {
   return new RedundantDbgInstElimination();
 }
 
+PreservedAnalyses
+RedundantDbgInstEliminationPass::run(Function &F, FunctionAnalysisManager &AM) {
+  bool Changed = false;
+  for (auto &BB : F)
+    Changed |= RemoveRedundantDbgInstrs(&BB);
+  if (!Changed)
+    return PreservedAnalyses::all();
+  PreservedAnalyses PA;
+  PA.preserveSet<CFGAnalyses>();
+  return PA;
+}
+
 //===--------------------------------------------------------------------===//
 // DeadCodeElimination pass implementation
 //
 
 static bool DCEInstruction(Instruction *I,
                            SmallSetVector<Instruction *, 16> &WorkList,
                            const TargetLibraryInfo *TLI) {
   if (isInstructionTriviallyDead(I, TLI)) {

llvm/test/Transforms/DCE/dbg-value-removal.ll

 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; RUN: opt < %s -S -redundant-dbg-inst-elim | FileCheck %s
+; RUN: opt < %s -S -passes=redundant-dbg-inst-elim | FileCheck %s
 
 ; All dbg.value with location "!dbg !19" are redundant in the input.
 ; FIXME: We do not handle non-overlapping/overlapping fragments perfectly yet.
 
 define dso_local i16 @main(i16 %a1, i16 %a2) local_unnamed_addr #0 !dbg !7 {
 ; CHECK-LABEL: @main(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    br label [[BB0:%.*]]