Reapply [IR] Lazily initialize the class to pass name mapping (NFC) (#96321) (#96462)

On MSVC the `this` uses inside `decltype` require a lambda capture. On
clang they result in an unused capture warning instead. Add the capture
and suppress the warning with `(void)this`.

-----

Initializing this map is somewhat expensive (especially for O0), so we
currently only do it if certain flags are used. I would like to make use
of it for crash dumps (#96078), where we don't know in advance whether
it will be needed or not.

This patch changes the initialization to a lazy approach, where a
callback is registered that does the actual initialization. The
callbacks will be run the first time the pass name is requested.

This way there is no compile-time impact if the mapping is not used.

Author: nikic

llvm/include/llvm/IR/PassInstrumentation.h

@@ -149,6 +149,11 @@ class PassInstrumentationCallbacks {
     AnalysesClearedCallbacks.emplace_back(std::move(C));
   }
 
+  template <typename CallableT>
+  void registerClassToPassNameCallback(CallableT C) {
+    ClassToPassNameCallbacks.emplace_back(std::move(C));
+  }
+
   /// Add a class name to pass name mapping for use by pass instrumentation.
   void addClassToPassName(StringRef ClassName, StringRef PassName);
   /// Get the pass name for a given pass class name.
@@ -185,6 +190,7 @@ class PassInstrumentationCallbacks {
   SmallVector<llvm::unique_function<AnalysesClearedFunc>, 4>
       AnalysesClearedCallbacks;
 
+  SmallVector<llvm::unique_function<void ()>, 4> ClassToPassNameCallbacks;
   DenseMap<StringRef, std::string> ClassToPassName;
 };
 

llvm/include/llvm/Passes/TargetPassRegistry.inc

@@ -21,9 +21,12 @@
 #error "must provide <Target>PassRegistry.def"
 #endif
 
-if (PopulateClassToPassNames) {
-  auto *PIC = PB.getPassInstrumentationCallbacks();
-
+auto *PIC = PB.getPassInstrumentationCallbacks();
+if (PIC) {
+  PIC->registerClassToPassNameCallback([this, PIC]() {
+    // MSVC requires this to be captured if it's used inside decltype.
+    // Other compilers consider it an unused lambda capture.
+    (void)this;
 #define ADD_CLASS_PASS_TO_PASS_NAME(NAME, CREATE_PASS)                         \
   PIC->addClassToPassName(decltype(CREATE_PASS)::name(), NAME);
 #define ADD_CLASS_PASS_TO_PASS_NAME_WITH_PARAMS(NAME, CLASS)                   \
@@ -69,6 +72,7 @@ if (PopulateClassToPassNames) {
 #undef MACHINE_FUNCTION_PASS_WITH_PARAMS
 #undef ADD_CLASS_PASS_TO_PASS_NAME
 #undef ADD_CLASS_PASS_TO_PASS_NAME_WITH_PARAMS
+  });
 }
 
 #define ADD_PASS(NAME, CREATE_PASS)                                            \

llvm/include/llvm/Target/TargetMachine.h

@@ -369,8 +369,7 @@ class TargetMachine {
 
   /// Allow the target to modify the pass pipeline.
   // TODO: Populate all pass names by using <Target>PassRegistry.def.
-  virtual void registerPassBuilderCallbacks(PassBuilder &,
-                                            bool PopulateClassToPassNames) {}
+  virtual void registerPassBuilderCallbacks(PassBuilder &) {}
 
   /// Allow the target to register alias analyses with the AAManager for use
   /// with the new pass manager. Only affects the "default" AAManager.

llvm/lib/IR/PassInstrumentation.cpp

@@ -24,6 +24,11 @@ void PassInstrumentationCallbacks::addClassToPassName(StringRef ClassName,
 
 StringRef
 PassInstrumentationCallbacks::getPassNameForClassName(StringRef ClassName) {
+  if (!ClassToPassNameCallbacks.empty()) {
+    for (auto &Fn : ClassToPassNameCallbacks)
+      Fn();
+    ClassToPassNameCallbacks.clear();
+  }
   return ClassToPassName[ClassName];
 }
 

llvm/lib/Passes/PassBuilder.cpp

@@ -325,18 +325,6 @@ AnalysisKey NoOpLoopAnalysis::Key;
 
 namespace {
 
-/// Whether or not we should populate a PassInstrumentationCallbacks's class to
-/// pass name map.
-///
-/// This is for optimization purposes so we don't populate it if we never use
-/// it. This should be updated if new pass instrumentation wants to use the map.
-/// We currently only use this for --print-before/after.
-bool shouldPopulateClassToPassNames() {
-  return PrintPipelinePasses || !printBeforePasses().empty() ||
-         !printAfterPasses().empty() || !isFilterPassesEmpty() ||
-         TargetPassConfig::hasLimitedCodeGenPipeline();
-}
-
 // A pass for testing -print-on-crash.
 // DO NOT USE THIS EXCEPT FOR TESTING!
 class TriggerCrashPass : public PassInfoMixin<TriggerCrashPass> {
@@ -416,10 +404,13 @@ PassBuilder::PassBuilder(TargetMachine *TM, PipelineTuningOptions PTO,
                          std::optional<PGOOptions> PGOOpt,
                          PassInstrumentationCallbacks *PIC)
     : TM(TM), PTO(PTO), PGOOpt(PGOOpt), PIC(PIC) {
-  bool ShouldPopulateClassToPassNames = PIC && shouldPopulateClassToPassNames();
   if (TM)
-    TM->registerPassBuilderCallbacks(*this, ShouldPopulateClassToPassNames);
-  if (ShouldPopulateClassToPassNames) {
+    TM->registerPassBuilderCallbacks(*this);
+  if (PIC) {
+    PIC->registerClassToPassNameCallback([this, PIC]() {
+      // MSVC requires this to be captured if it's used inside decltype.
+      // Other compilers consider it an unused lambda capture.
+      (void)this;
 #define MODULE_PASS(NAME, CREATE_PASS)                                         \
   PIC->addClassToPassName(decltype(CREATE_PASS)::name(), NAME);
 #define MODULE_PASS_WITH_PARAMS(NAME, CLASS, CREATE_PASS, PARSER, PARAMS)      \
@@ -453,6 +444,7 @@ PassBuilder::PassBuilder(TargetMachine *TM, PipelineTuningOptions PTO,
 #define MACHINE_FUNCTION_PASS(NAME, CREATE_PASS)                               \
   PIC->addClassToPassName(decltype(CREATE_PASS)::name(), NAME);
 #include "llvm/Passes/MachinePassRegistry.def"
+    });
   }
 }
 

llvm/lib/Target/AArch64/AArch64TargetMachine.cpp

@@ -554,8 +554,7 @@ class AArch64PassConfig : public TargetPassConfig {
 
 } // end anonymous namespace
 
-void AArch64TargetMachine::registerPassBuilderCallbacks(
-    PassBuilder &PB, bool PopulateClassToPassNames) {
+void AArch64TargetMachine::registerPassBuilderCallbacks(PassBuilder &PB) {
 
   PB.registerLateLoopOptimizationsEPCallback(
       [=](LoopPassManager &LPM, OptimizationLevel Level) {

llvm/lib/Target/AArch64/AArch64TargetMachine.h

@@ -43,8 +43,7 @@ class AArch64TargetMachine : public LLVMTargetMachine {
   // Pass Pipeline Configuration
   TargetPassConfig *createPassConfig(PassManagerBase &PM) override;
 
-  void registerPassBuilderCallbacks(PassBuilder &PB,
-                                    bool PopulateClassToPassNames) override;
+  void registerPassBuilderCallbacks(PassBuilder &PB) override;
 
   TargetTransformInfo getTargetTransformInfo(const Function &F) const override;
 

llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp

@@ -658,8 +658,7 @@ Error AMDGPUTargetMachine::buildCodeGenPipeline(
   return CGPB.buildPipeline(MPM, Out, DwoOut, FileType);
 }
 
-void AMDGPUTargetMachine::registerPassBuilderCallbacks(
-    PassBuilder &PB, bool PopulateClassToPassNames) {
+void AMDGPUTargetMachine::registerPassBuilderCallbacks(PassBuilder &PB) {
 
 #define GET_PASS_REGISTRY "AMDGPUPassRegistry.def"
 #include "llvm/Passes/TargetPassRegistry.inc"

llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.h

@@ -58,8 +58,7 @@ class AMDGPUTargetMachine : public LLVMTargetMachine {
                              const CGPassBuilderOption &Opts,
                              PassInstrumentationCallbacks *PIC) override;
 
-  void registerPassBuilderCallbacks(PassBuilder &PB,
-                                    bool PopulateClassToPassNames) override;
+  void registerPassBuilderCallbacks(PassBuilder &PB) override;
   void registerDefaultAliasAnalyses(AAManager &) override;
 
   /// Get the integer value of a null pointer in the given address space.

llvm/lib/Target/BPF/BPFTargetMachine.cpp

@@ -113,8 +113,7 @@ static Expected<bool> parseBPFPreserveStaticOffsetOptions(StringRef Params) {
                                             "BPFPreserveStaticOffsetPass");
 }
 
-void BPFTargetMachine::registerPassBuilderCallbacks(
-    PassBuilder &PB, bool PopulateClassToPassNames) {
+void BPFTargetMachine::registerPassBuilderCallbacks(PassBuilder &PB) {
 #define GET_PASS_REGISTRY "BPFPassRegistry.def"
 #include "llvm/Passes/TargetPassRegistry.inc"