Add NoOpLoopNestPass and LOOPNEST_PASS macro

[Whitney]

Summary

Having a NoOpLoopNestPass can ensure that only outermost loop is invoked for a LoopNestPass with a lit test.

There are some existing passes that are implemented as LoopNestPass, but they are still using LOOP_PASS macro.
It would be easier to identify LoopNestPasses with a LOOPNEST_PASS macro.

[etiotto]

LGTM

[Whitney]

clang-format

[eopXD]

LGTM too.

llvm/lib/Passes/PassBuilder.cpp

class NoOpFunctionAnalysis : public AnalysisInfoMixin<NoOpFunctionAnalysis> {
   static AnalysisKey Key;
 
 public:
   struct Result {};
   Result run(Function &, FunctionAnalysisManager &) { return Result(); }
   static StringRef name() { return "NoOpFunctionAnalysis"; }
 };
 
+/// No-op loop nest pass which does nothing.
+struct NoOpLoopNestPass : PassInfoMixin<NoOpLoopNestPass> {
+  PreservedAnalyses run(LoopNest &L, LoopAnalysisManager &,
+                        LoopStandardAnalysisResults &, LPMUpdater &) {
+    return PreservedAnalyses::all();
+  }
+  static StringRef name() { return "NoOpLoopNestPass"; }
+};
+
 /// No-op loop pass which does nothing.
 struct NoOpLoopPass : PassInfoMixin<NoOpLoopPass> {
   PreservedAnalyses run(Loop &L, LoopAnalysisManager &,
                         LoopStandardAnalysisResults &, LPMUpdater &) {
     return PreservedAnalyses::all();
   }
   static StringRef name() { return "NoOpLoopPass"; }
 };

 #define MODULE_ANALYSIS(NAME, CREATE_PASS)                                     \
   PIC->addClassToPassName(decltype(CREATE_PASS)::name(), NAME);
 #define FUNCTION_PASS(NAME, CREATE_PASS)                                       \
   PIC->addClassToPassName(decltype(CREATE_PASS)::name(), NAME);
 #define FUNCTION_PASS_WITH_PARAMS(NAME, CLASS, CREATE_PASS, PARSER, PARAMS)    \
   PIC->addClassToPassName(CLASS, NAME);
 #define FUNCTION_ANALYSIS(NAME, CREATE_PASS)                                   \
   PIC->addClassToPassName(decltype(CREATE_PASS)::name(), NAME);
+#define LOOPNEST_PASS(NAME, CREATE_PASS)                                       \
+  PIC->addClassToPassName(decltype(CREATE_PASS)::name(), NAME);
 #define LOOP_PASS(NAME, CREATE_PASS)                                           \
   PIC->addClassToPassName(decltype(CREATE_PASS)::name(), NAME);
 #define LOOP_PASS_WITH_PARAMS(NAME, CLASS, CREATE_PASS, PARSER, PARAMS)        \
   PIC->addClassToPassName(CLASS, NAME);
 #define LOOP_ANALYSIS(NAME, CREATE_PASS)                                       \
   PIC->addClassToPassName(decltype(CREATE_PASS)::name(), NAME);
 #define CGSCC_PASS(NAME, CREATE_PASS)                                          \
   PIC->addClassToPassName(decltype(CREATE_PASS)::name(), NAME);
#define FUNCTION_ANALYSIS(NAME, CREATE_PASS)                                   \
   if (Name == "require<" NAME ">" || Name == "invalidate<" NAME ">")           \
     return true;
 #include "PassRegistry.def"
 
   return callbacksAcceptPassName<FunctionPassManager>(Name, Callbacks);
 }
 
 template <typename CallbacksT>
+static bool isLoopNestPassName(StringRef Name, CallbacksT &Callbacks,
+                               bool &UseMemorySSA) {
+  UseMemorySSA = false;
+
+  // Explicitly handle custom-parsed pass names.
+  if (parseRepeatPassName(Name))
+    return true;
+
+  if (Name == "lnicm") {
+    UseMemorySSA = true;
+    return true;
+  }
+
+#define LOOPNEST_PASS(NAME, CREATE_PASS)                                       \
+  if (Name == NAME)                                                            \
+    return true;
+#include "PassRegistry.def"
+
+  return callbacksAcceptPassName<LoopPassManager>(Name, Callbacks);
+}
+
+template <typename CallbacksT>
 static bool isLoopPassName(StringRef Name, CallbacksT &Callbacks,
                            bool &UseMemorySSA) {
   UseMemorySSA = false;
 
   // Explicitly handle custom-parsed pass names.
   if (parseRepeatPassName(Name))
     return true;
 

 #define FUNCTION_PASS_WITH_PARAMS(NAME, CLASS, CREATE_PASS, PARSER, PARAMS)    \
   if (checkParametrizedPassName(Name, NAME)) {                                 \
     auto Params = parsePassParameters(PARSER, Name, NAME);                     \
     if (!Params)                                                               \
       return Params.takeError();                                               \
     MPM.addPass(createModuleToFunctionPassAdaptor(CREATE_PASS(Params.get()))); \
     return Error::success();                                                   \
   }
+#define LOOPNEST_PASS(NAME, CREATE_PASS)                                       \
+  if (Name == NAME) {                                                          \
+    MPM.addPass(createModuleToFunctionPassAdaptor(                             \
+        createFunctionToLoopPassAdaptor(CREATE_PASS, false, false)));          \
+    return Error::success();                                                   \
+  }
 #define LOOP_PASS(NAME, CREATE_PASS)                                           \
   if (Name == NAME) {                                                          \
     MPM.addPass(createModuleToFunctionPassAdaptor(                             \
         createFunctionToLoopPassAdaptor(CREATE_PASS, false, false)));          \
     return Error::success();                                                   \
   }
 #define LOOP_PASS_WITH_PARAMS(NAME, CLASS, CREATE_PASS, PARSER, PARAMS)        \
   if (checkParametrizedPassName(Name, NAME)) {                                 \

 #define FUNCTION_PASS_WITH_PARAMS(NAME, CLASS, CREATE_PASS, PARSER, PARAMS)    \
   if (checkParametrizedPassName(Name, NAME)) {                                 \
     auto Params = parsePassParameters(PARSER, Name, NAME);                     \
     if (!Params)                                                               \
       return Params.takeError();                                               \
     CGPM.addPass(createCGSCCToFunctionPassAdaptor(CREATE_PASS(Params.get()))); \
     return Error::success();                                                   \
   }
+#define LOOPNEST_PASS(NAME, CREATE_PASS)                                       \
+  if (Name == NAME) {                                                          \
+    CGPM.addPass(createCGSCCToFunctionPassAdaptor(                             \
+        createFunctionToLoopPassAdaptor(CREATE_PASS, false, false)));          \
+    return Error::success();                                                   \
+  }
 #define LOOP_PASS(NAME, CREATE_PASS)                                           \
   if (Name == NAME) {                                                          \
     CGPM.addPass(createCGSCCToFunctionPassAdaptor(                             \
         createFunctionToLoopPassAdaptor(CREATE_PASS, false, false)));          \
     return Error::success();                                                   \
   }
 #define LOOP_PASS_WITH_PARAMS(NAME, CLASS, CREATE_PASS, PARSER, PARAMS)        \
   if (checkParametrizedPassName(Name, NAME)) {                                 \
if (Name == "invalidate<" NAME ">") {                                        \
     FPM.addPass(InvalidateAnalysisPass<                                        \
                 std::remove_reference<decltype(CREATE_PASS)>::type>());        \
     return Error::success();                                                   \
   }
 // FIXME: UseMemorySSA is set to false. Maybe we could do things like:
 //        bool UseMemorySSA = !("canon-freeze" || "loop-predication" ||
 //                              "guard-widening");
 //        The risk is that it may become obsolete if we're not careful.
+#define LOOPNEST_PASS(NAME, CREATE_PASS)                                       \
+  if (Name == NAME) {                                                          \
+    FPM.addPass(createFunctionToLoopPassAdaptor(CREATE_PASS, false, false));   \
+    return Error::success();                                                   \
+  }
 #define LOOP_PASS(NAME, CREATE_PASS)                                           \
   if (Name == NAME) {                                                          \
     FPM.addPass(createFunctionToLoopPassAdaptor(CREATE_PASS, false, false));   \
     return Error::success();                                                   \
   }
 #define LOOP_PASS_WITH_PARAMS(NAME, CLASS, CREATE_PASS, PARSER, PARAMS)        \
   if (checkParametrizedPassName(Name, NAME)) {                                 \
     auto Params = parsePassParameters(PARSER, Name, NAME);                     \
if (!InnerPipeline.empty()) {
 
     // Normal passes can't have pipelines.
     return make_error<StringError>(
         formatv("invalid use of '{0}' pass as loop pipeline", Name).str(),
         inconvertibleErrorCode());
   }
 
 // Now expand the basic registered passes from the .inc file.
+#define LOOPNEST_PASS(NAME, CREATE_PASS)                                       \
+  if (Name == NAME) {                                                          \
+    LPM.addPass(CREATE_PASS);                                                  \
+    return Error::success();                                                   \
+  }
 #define LOOP_PASS(NAME, CREATE_PASS)                                           \
   if (Name == NAME) {                                                          \
     LPM.addPass(CREATE_PASS);                                                  \
     return Error::success();                                                   \
   }
 #define LOOP_PASS_WITH_PARAMS(NAME, CLASS, CREATE_PASS, PARSER, PARAMS)        \
   if (checkParametrizedPassName(Name, NAME)) {                                 \
     auto Params = parsePassParameters(PARSER, Name, NAME);                     \
Error PassBuilder::parsePassPipeline(ModulePassManager &MPM,
 
   if (!isModulePassName(FirstName, ModulePipelineParsingCallbacks)) {
     bool UseMemorySSA;
     if (isCGSCCPassName(FirstName, CGSCCPipelineParsingCallbacks)) {
       Pipeline = {{"cgscc", std::move(*Pipeline)}};
     } else if (isFunctionPassName(FirstName,
                                   FunctionPipelineParsingCallbacks)) {
       Pipeline = {{"function", std::move(*Pipeline)}};
+    } else if (isLoopNestPassName(FirstName, LoopPipelineParsingCallbacks,
+                                  UseMemorySSA)) {
+      Pipeline = {{"function", {{UseMemorySSA ? "loop-mssa" : "loop",
+                                 std::move(*Pipeline)}}}};
     } else if (isLoopPassName(FirstName, LoopPipelineParsingCallbacks,
                               UseMemorySSA)) {
       Pipeline = {{"function", {{UseMemorySSA ? "loop-mssa" : "loop",
                                  std::move(*Pipeline)}}}};
     } else {
       for (auto &C : TopLevelPipelineParsingCallbacks)
         if (C(MPM, *Pipeline))
           return Error::success();
#include "PassRegistry.def"
   OS << "Function analyses:\n";
 #define FUNCTION_ANALYSIS(NAME, CREATE_PASS) printPassName(NAME, OS);
 #include "PassRegistry.def"
 
   OS << "Function alias analyses:\n";
 #define FUNCTION_ALIAS_ANALYSIS(NAME, CREATE_PASS) printPassName(NAME, OS);
 #include "PassRegistry.def"
 
+  OS << "LoopNest passes:\n";
+#define LOOPNEST_PASS(NAME, CREATE_PASS) printPassName(NAME, OS);
+#include "PassRegistry.def"
+
   OS << "Loop passes:\n";
 #define LOOP_PASS(NAME, CREATE_PASS) printPassName(NAME, OS);
 #include "PassRegistry.def"
 
   OS << "Loop passes with params:\n";
 #define LOOP_PASS_WITH_PARAMS(NAME, CLASS, CREATE_PASS, PARSER, PARAMS)        \
   printPassName(NAME, PARAMS, OS);
 #include "PassRegistry.def"

llvm/lib/Passes/PassRegistry.def

FUNCTION_PASS_WITH_PARAMS("print<stack-lifetime>",
                           "StackLifetimePrinterPass",
                            [](StackLifetime::LivenessType Type) {
                              return StackLifetimePrinterPass(dbgs(), Type);
                            },
                           parseStackLifetimeOptions,
                           "may;must")
 #undef FUNCTION_PASS_WITH_PARAMS
 
+#ifndef LOOPNEST_PASS
+#define LOOPNEST_PASS(NAME, CREATE_PASS)
+#endif
+LOOPNEST_PASS("lnicm", LNICMPass())
+LOOPNEST_PASS("loop-flatten", LoopFlattenPass())
+LOOPNEST_PASS("loop-interchange", LoopInterchangePass())
+LOOPNEST_PASS("loop-unroll-and-jam", LoopUnrollAndJamPass())
+LOOPNEST_PASS("no-op-loopnest", NoOpLoopNestPass())
+#undef LOOPNEST_PASS
+
 #ifndef LOOP_ANALYSIS
 #define LOOP_ANALYSIS(NAME, CREATE_PASS)
 #endif
 LOOP_ANALYSIS("no-op-loop", NoOpLoopAnalysis())
 LOOP_ANALYSIS("access-info", LoopAccessAnalysis())
 LOOP_ANALYSIS("ddg", DDGAnalysis())
 LOOP_ANALYSIS("iv-users", IVUsersAnalysis())
 LOOP_ANALYSIS("pass-instrumentation", PassInstrumentationAnalysis(PIC))
 #undef LOOP_ANALYSIS
 
 #ifndef LOOP_PASS
 #define LOOP_PASS(NAME, CREATE_PASS)
 #endif
 LOOP_PASS("canon-freeze", CanonicalizeFreezeInLoopsPass())
 LOOP_PASS("dot-ddg", DDGDotPrinterPass())
 LOOP_PASS("invalidate<all>", InvalidateAllAnalysesPass())
 LOOP_PASS("licm", LICMPass())
-LOOP_PASS("lnicm", LNICMPass())
-LOOP_PASS("loop-flatten", LoopFlattenPass())
 LOOP_PASS("loop-idiom", LoopIdiomRecognizePass())
 LOOP_PASS("loop-instsimplify", LoopInstSimplifyPass())
-LOOP_PASS("loop-interchange", LoopInterchangePass())
 LOOP_PASS("loop-rotate", LoopRotatePass())
 LOOP_PASS("no-op-loop", NoOpLoopPass())
 LOOP_PASS("print", PrintLoopPass(dbgs()))
 LOOP_PASS("loop-deletion", LoopDeletionPass())
 LOOP_PASS("loop-simplifycfg", LoopSimplifyCFGPass())
 LOOP_PASS("loop-reduce", LoopStrengthReducePass())
 LOOP_PASS("indvars", IndVarSimplifyPass())
-LOOP_PASS("loop-unroll-and-jam", LoopUnrollAndJamPass())
 LOOP_PASS("loop-unroll-full", LoopFullUnrollPass())
 LOOP_PASS("print-access-info", LoopAccessInfoPrinterPass(dbgs()))
 LOOP_PASS("print<ddg>", DDGAnalysisPrinterPass(dbgs()))
 LOOP_PASS("print<iv-users>", IVUsersPrinterPass(dbgs()))
 LOOP_PASS("print<loopnest>", LoopNestPrinterPass(dbgs()))
 LOOP_PASS("print<loop-cache-cost>", LoopCachePrinterPass(dbgs()))
 LOOP_PASS("loop-predication", LoopPredicationPass())
 LOOP_PASS("guard-widening", GuardWideningPass())

llvm/test/Other/loopnest-pass-ordering.ll

+; RUN: opt -disable-output -debug-pass-manager \
+; RUN:     -passes='no-op-loopnest' %s 2>&1 \
+; RUN:     | FileCheck %s
+
+;            @f()
+;           /    \
+;       loop.0   loop.1
+;      /      \        \
+; loop.0.0  loop.0.1  loop.1.0
+;
+; CHECK: Running pass: NoOpLoopNestPass on Loop at depth 1 containing: %loop.0<header><exiting>,%loop.0.0,%loop.0.1,%loop.0.1.preheader,%loop.0.loopexit<latch>,%loop.0.0.preheader
+; CHECK: Running pass: NoOpLoopNestPass on Loop at depth 1 containing: %loop.1<header>,%loop.1.bb1,%loop.1.bb2<exiting>,%loop.1.0,%loop.1.0.preheader,%loop.1.loopexit,%loop.1.backedge<latch>
+; CHECK-NOT: Running pass: NoOpLoopNestPass on Loop at depth 2
+
+define void @f() {
+entry:
+  br label %loop.0
+loop.0:
+  br i1 undef, label %loop.0.0, label %loop.1
+loop.0.0:
+  br i1 undef, label %loop.0.0, label %loop.0.1
+loop.0.1:
+  br i1 undef, label %loop.0.1, label %loop.0
+loop.1:
+  br i1 undef, label %loop.1, label %loop.1.bb1
+loop.1.bb1:
+  br i1 undef, label %loop.1, label %loop.1.bb2
+loop.1.bb2:
+  br i1 undef, label %end, label %loop.1.0
+loop.1.0:
+  br i1 undef, label %loop.1.0, label %loop.1
+end:
+  ret void
+}

llvm/test/Other/print-passes.ll

 ; CHECK: Function passes:
 ; CHECK: no-op-function
 ; CHECK: Function passes with params:
 ; CHECK: loop-unroll<O0;O1;O2;O3;full-unroll-max=N;no-partial;partial;no-peeling;peeling;no-profile-peeling;profile-peeling;no-runtime;runtime;no-upperbound;upperbound>
 ; CHECK: Function analyses:
 ; CHECK: no-op-function
 ; CHECK: Function alias analyses:
 ; CHECK: basic-aa
+; CHECK: LoopNest passes:
+; CHECK: no-op-loopnest
 ; CHECK: Loop passes:
 ; CHECK: no-op-loop
 ; CHECK: Loop passes with params:
 ; CHECK: simple-loop-unswitch<nontrivial;no-nontrivial;trivial;no-trivial>
 ; CHECK: Loop analyses:
 ; CHECK: no-op-loop