[PM] Add a generic 'repeat N times' pass wrapper to the new pass

manager.

While this has some utility for debugging and testing on its own, it is
primarily intended to demonstrate the technique for adding custom
wrappers that can provide more interesting interation behavior in
a nice, orthogonal, and composable layer.

Being able to write these kinds of very dynamic and customized controls
for running passes was one of the motivating use cases of the new pass
manager design, and this gives a hint at how they might look. The actual
logic is tiny here, and most of this is just wiring in the pipeline
parsing so that this can be widely used.

I'm adding this now to show the wiring without a lot of business logic.
This is a precursor patch for showing how a "iterate up to N times as
long as we devirtualize a call" utility can be added as a separable and
composable component along side the CGSCC pass management.

Differential Revision: https://reviews.llvm.org/D22405

llvm-svn: 277581

llvm/include/llvm/IR/PassManager.h

@@ -987,6 +987,34 @@ struct InvalidateAllAnalysesPass : PassInfoMixin<InvalidateAllAnalysesPass> {
   }
 };
 
+/// A utility pass template that simply runs another pass multiple times.
+///
+/// This can be useful when debugging or testing passes. It also serves as an
+/// example of how to extend the pass manager in ways beyond composition.
+template <typename PassT>
+class RepeatingPassWrapper : public PassInfoMixin<RepeatingPassWrapper<PassT>> {
+public:
+  RepeatingPassWrapper(int Count, PassT P) : Count(Count), P(std::move(P)) {}
+
+  template <typename IRUnitT, typename... Ts>
+  PreservedAnalyses run(IRUnitT &Arg, AnalysisManager<IRUnitT> &AM,
+                        Ts... Args) {
+    auto PA = PreservedAnalyses::all();
+    for (int i = 0; i < Count; ++i)
+      PA.intersect(P.run(Arg, AM, Args...));
+    return PA;
+  }
+
+private:
+  const int Count;
+  PassT P;
+};
+
+template <typename PassT>
+RepeatingPassWrapper<PassT> createRepeatingPassWrapper(int Count, PassT P) {
+  return RepeatingPassWrapper<PassT>(Count, std::move(P));
+}
+
 }
 
 #endif

llvm/lib/Passes/PassBuilder.cpp

@@ -274,6 +274,15 @@ void PassBuilder::addLTODefaultPipeline(ModulePassManager &MPM,
   MPM.addPass(createModuleToFunctionPassAdaptor(std::move(LateFPM)));
 }
 
+static Optional<int> parseRepeatPassName(StringRef Name) {
+  if (!Name.consume_front("repeat<") || !Name.consume_back(">"))
+    return None;
+  int Count;
+  if (Name.getAsInteger(0, Count) || Count <= 0)
+    return None;
+  return Count;
+}
+
 static bool isModulePassName(StringRef Name) {
   // Manually handle aliases for pre-configured pipeline fragments.
   if (Name.startswith("default") || Name.startswith("lto"))
@@ -287,6 +296,10 @@ static bool isModulePassName(StringRef Name) {
   if (Name == "function")
     return true;
 
+  // Explicitly handle custom-parsed pass names.
+  if (parseRepeatPassName(Name))
+    return true;
+
 #define MODULE_PASS(NAME, CREATE_PASS)                                         \
   if (Name == NAME)                                                            \
     return true;
@@ -305,6 +318,10 @@ static bool isCGSCCPassName(StringRef Name) {
   if (Name == "function")
     return true;
 
+  // Explicitly handle custom-parsed pass names.
+  if (parseRepeatPassName(Name))
+    return true;
+
 #define CGSCC_PASS(NAME, CREATE_PASS)                                          \
   if (Name == NAME)                                                            \
     return true;
@@ -323,6 +340,10 @@ static bool isFunctionPassName(StringRef Name) {
   if (Name == "loop")
     return true;
 
+  // Explicitly handle custom-parsed pass names.
+  if (parseRepeatPassName(Name))
+    return true;
+
 #define FUNCTION_PASS(NAME, CREATE_PASS)                                       \
   if (Name == NAME)                                                            \
     return true;
@@ -339,6 +360,10 @@ static bool isLoopPassName(StringRef Name) {
   if (Name == "loop")
     return true;
 
+  // Explicitly handle custom-parsed pass names.
+  if (parseRepeatPassName(Name))
+    return true;
+
 #define LOOP_PASS(NAME, CREATE_PASS)                                           \
   if (Name == NAME)                                                            \
     return true;
@@ -440,6 +465,14 @@ bool PassBuilder::parseModulePass(ModulePassManager &MPM,
       MPM.addPass(createModuleToFunctionPassAdaptor(std::move(FPM)));
       return true;
     }
+    if (auto Count = parseRepeatPassName(Name)) {
+      ModulePassManager NestedMPM(DebugLogging);
+      if (!parseModulePassPipeline(NestedMPM, InnerPipeline, VerifyEachPass,
+                                   DebugLogging))
+        return false;
+      MPM.addPass(createRepeatingPassWrapper(*Count, std::move(NestedMPM)));
+      return true;
+    }
     // Normal passes can't have pipelines.
     return false;
   }
@@ -519,6 +552,14 @@ bool PassBuilder::parseCGSCCPass(CGSCCPassManager &CGPM,
           createCGSCCToFunctionPassAdaptor(std::move(FPM), DebugLogging));
       return true;
     }
+    if (auto Count = parseRepeatPassName(Name)) {
+      CGSCCPassManager NestedCGPM(DebugLogging);
+      if (!parseCGSCCPassPipeline(NestedCGPM, InnerPipeline, VerifyEachPass,
+                                  DebugLogging))
+        return false;
+      CGPM.addPass(createRepeatingPassWrapper(*Count, std::move(NestedCGPM)));
+      return true;
+    }
     // Normal passes can't have pipelines.
     return false;
   }
@@ -571,6 +612,14 @@ bool PassBuilder::parseFunctionPass(FunctionPassManager &FPM,
       FPM.addPass(createFunctionToLoopPassAdaptor(std::move(LPM)));
       return true;
     }
+    if (auto Count = parseRepeatPassName(Name)) {
+      FunctionPassManager NestedFPM(DebugLogging);
+      if (!parseFunctionPassPipeline(NestedFPM, InnerPipeline, VerifyEachPass,
+                                     DebugLogging))
+        return false;
+      FPM.addPass(createRepeatingPassWrapper(*Count, std::move(NestedFPM)));
+      return true;
+    }
     // Normal passes can't have pipelines.
     return false;
   }
@@ -599,7 +648,7 @@ bool PassBuilder::parseFunctionPass(FunctionPassManager &FPM,
 
 bool PassBuilder::parseLoopPass(LoopPassManager &FPM, const PipelineElement &E,
                                 bool VerifyEachPass, bool DebugLogging) {
-  auto &Name = E.Name;
+  StringRef Name = E.Name;
   auto &InnerPipeline = E.InnerPipeline;
 
   // First handle complex passes like the pass managers which carry pipelines.
@@ -613,6 +662,14 @@ bool PassBuilder::parseLoopPass(LoopPassManager &FPM, const PipelineElement &E,
       FPM.addPass(std::move(NestedLPM));
       return true;
     }
+    if (auto Count = parseRepeatPassName(Name)) {
+      LoopPassManager NestedLPM(DebugLogging);
+      if (!parseLoopPassPipeline(NestedLPM, InnerPipeline, VerifyEachPass,
+                                 DebugLogging))
+        return false;
+      FPM.addPass(createRepeatingPassWrapper(*Count, std::move(NestedLPM)));
+      return true;
+    }
     // Normal passes can't have pipelines.
     return false;
   }

llvm/test/Other/new-pass-manager.ll

@@ -48,7 +48,7 @@
 ; CHECK-MODULE-PRINT: Running pass: VerifierPass
 ; CHECK-MODULE-PRINT: Running pass: PrintModulePass
 ; CHECK-MODULE-PRINT: ModuleID
-; CHECK-MODULE-PRINT: define void @foo()
+; CHECK-MODULE-PRINT: define void @foo(i1 %x)
 ; CHECK-MODULE-PRINT: Running pass: VerifierPass
 ; CHECK-MODULE-PRINT: Finished llvm::Module pass manager run
 
@@ -57,7 +57,7 @@
 ; CHECK-MODULE-VERIFY: Starting llvm::Module pass manager run
 ; CHECK-MODULE-VERIFY: Running pass: PrintModulePass
 ; CHECK-MODULE-VERIFY: ModuleID
-; CHECK-MODULE-VERIFY: define void @foo()
+; CHECK-MODULE-VERIFY: define void @foo(i1 %x)
 ; CHECK-MODULE-VERIFY: Running pass: VerifierPass
 ; CHECK-MODULE-VERIFY: Finished llvm::Module pass manager run
 
@@ -70,7 +70,7 @@
 ; CHECK-FUNCTION-PRINT: Starting llvm::Function pass manager run
 ; CHECK-FUNCTION-PRINT: Running pass: PrintFunctionPass
 ; CHECK-FUNCTION-PRINT-NOT: ModuleID
-; CHECK-FUNCTION-PRINT: define void @foo()
+; CHECK-FUNCTION-PRINT: define void @foo(i1 %x)
 ; CHECK-FUNCTION-PRINT: Finished llvm::Function pass manager run
 ; CHECK-FUNCTION-PRINT: Running pass: VerifierPass
 ; CHECK-FUNCTION-PRINT: Finished llvm::Module pass manager run
@@ -81,14 +81,19 @@
 ; CHECK-FUNCTION-VERIFY: Starting llvm::Function pass manager run
 ; CHECK-FUNCTION-VERIFY: Running pass: PrintFunctionPass
 ; CHECK-FUNCTION-VERIFY-NOT: ModuleID
-; CHECK-FUNCTION-VERIFY: define void @foo()
+; CHECK-FUNCTION-VERIFY: define void @foo(i1 %x)
 ; CHECK-FUNCTION-VERIFY: Running pass: VerifierPass
 ; CHECK-FUNCTION-VERIFY: Finished llvm::Function pass manager run
 ; CHECK-FUNCTION-VERIFY: Finished llvm::Module pass manager run
 
 ; RUN: opt -S -o - -passes='no-op-module,no-op-module' %s \
 ; RUN:     | FileCheck %s --check-prefix=CHECK-NOOP
-; CHECK-NOOP: define void @foo() {
+; CHECK-NOOP: define void @foo(i1 %x) {
+; CHECK-NOOP: entry:
+; CHECK-NOOP:   br i1 %x, label %loop, label %exit
+; CHECK-NOOP: loop:
+; CHECK-NOOP:   br label %loop
+; CHECK-NOOP: exit:
 ; CHECK-NOOP:   ret void
 ; CHECK-NOOP: }
 
@@ -363,7 +368,98 @@
 ; CHECK-LTO-O2: Running pass: InstCombinePass
 ; CHECK-LTO-O2: Running pass: SimplifyCFGPass
 
-define void @foo() {
+; RUN: opt -disable-output -disable-verify -debug-pass-manager \
+; RUN:     -passes='repeat<3>(no-op-module)' %s 2>&1 \
+; RUN:     | FileCheck %s --check-prefix=CHECK-REPEAT-MODULE-PASS
+; CHECK-REPEAT-MODULE-PASS: Starting llvm::Module pass manager run
+; CHECK-REPEAT-MODULE-PASS-NEXT: Running pass: RepeatingPassWrapper
+; CHECK-REPEAT-MODULE-PASS-NEXT: Starting llvm::Module pass manager run
+; CHECK-REPEAT-MODULE-PASS-NEXT: Running pass: NoOpModulePass
+; CHECK-REPEAT-MODULE-PASS-NEXT: Finished llvm::Module pass manager run
+; CHECK-REPEAT-MODULE-PASS-NEXT: Starting llvm::Module pass manager run
+; CHECK-REPEAT-MODULE-PASS-NEXT: Running pass: NoOpModulePass
+; CHECK-REPEAT-MODULE-PASS-NEXT: Finished llvm::Module pass manager run
+; CHECK-REPEAT-MODULE-PASS-NEXT: Starting llvm::Module pass manager run
+; CHECK-REPEAT-MODULE-PASS-NEXT: Running pass: NoOpModulePass
+; CHECK-REPEAT-MODULE-PASS-NEXT: Finished llvm::Module pass manager run
+; CHECK-REPEAT-MODULE-PASS-NEXT: Finished llvm::Module pass manager run
+
+; RUN: opt -disable-output -disable-verify -debug-pass-manager \
+; RUN:     -passes='cgscc(repeat<3>(no-op-cgscc))' %s 2>&1 \
+; RUN:     | FileCheck %s --check-prefix=CHECK-REPEAT-CGSCC-PASS
+; CHECK-REPEAT-CGSCC-PASS: Starting llvm::Module pass manager run
+; CHECK-REPEAT-CGSCC-PASS-NEXT: Running pass: ModuleToPostOrderCGSCCPassAdaptor
+; CHECK-REPEAT-CGSCC-PASS-NEXT: Running analysis: InnerAnalysisManagerProxy<{{.*}}>
+; CHECK-REPEAT-CGSCC-PASS-NEXT: Running analysis: LazyCallGraphAnalysis
+; CHECK-REPEAT-CGSCC-PASS-NEXT: Running an SCC pass across the RefSCC: [(foo)]
+; CHECK-REPEAT-CGSCC-PASS-NEXT: Starting llvm::LazyCallGraph::SCC pass manager run
+; CHECK-REPEAT-CGSCC-PASS-NEXT: Running pass: RepeatingPassWrapper
+; CHECK-REPEAT-CGSCC-PASS-NEXT: Starting llvm::LazyCallGraph::SCC pass manager run
+; CHECK-REPEAT-CGSCC-PASS-NEXT: Running pass: NoOpCGSCCPass
+; CHECK-REPEAT-CGSCC-PASS-NEXT: Finished llvm::LazyCallGraph::SCC pass manager run
+; CHECK-REPEAT-CGSCC-PASS-NEXT: Starting llvm::LazyCallGraph::SCC pass manager run
+; CHECK-REPEAT-CGSCC-PASS-NEXT: Running pass: NoOpCGSCCPass
+; CHECK-REPEAT-CGSCC-PASS-NEXT: Finished llvm::LazyCallGraph::SCC pass manager run
+; CHECK-REPEAT-CGSCC-PASS-NEXT: Starting llvm::LazyCallGraph::SCC pass manager run
+; CHECK-REPEAT-CGSCC-PASS-NEXT: Running pass: NoOpCGSCCPass
+; CHECK-REPEAT-CGSCC-PASS-NEXT: Finished llvm::LazyCallGraph::SCC pass manager run
+; CHECK-REPEAT-CGSCC-PASS-NEXT: Finished llvm::LazyCallGraph::SCC pass manager run
+; CHECK-REPEAT-CGSCC-PASS-NEXT: Finished llvm::Module pass manager run
+
+; RUN: opt -disable-output -disable-verify -debug-pass-manager \
+; RUN:     -passes='function(repeat<3>(no-op-function))' %s 2>&1 \
+; RUN:     | FileCheck %s --check-prefix=CHECK-REPEAT-FUNCTION-PASS
+; CHECK-REPEAT-FUNCTION-PASS: Starting llvm::Module pass manager run
+; CHECK-REPEAT-FUNCTION-PASS-NEXT: Running pass: ModuleToFunctionPassAdaptor
+; CHECK-REPEAT-FUNCTION-PASS-NEXT: Running analysis: InnerAnalysisManagerProxy<{{.*}}>
+; CHECK-REPEAT-FUNCTION-PASS-NEXT: Starting llvm::Function pass manager run
+; CHECK-REPEAT-FUNCTION-PASS-NEXT: Running pass: RepeatingPassWrapper
+; CHECK-REPEAT-FUNCTION-PASS-NEXT: Starting llvm::Function pass manager run
+; CHECK-REPEAT-FUNCTION-PASS-NEXT: Running pass: NoOpFunctionPass
+; CHECK-REPEAT-FUNCTION-PASS-NEXT: Finished llvm::Function pass manager run
+; CHECK-REPEAT-FUNCTION-PASS-NEXT: Starting llvm::Function pass manager run
+; CHECK-REPEAT-FUNCTION-PASS-NEXT: Running pass: NoOpFunctionPass
+; CHECK-REPEAT-FUNCTION-PASS-NEXT: Finished llvm::Function pass manager run
+; CHECK-REPEAT-FUNCTION-PASS-NEXT: Starting llvm::Function pass manager run
+; CHECK-REPEAT-FUNCTION-PASS-NEXT: Running pass: NoOpFunctionPass
+; CHECK-REPEAT-FUNCTION-PASS-NEXT: Finished llvm::Function pass manager run
+; CHECK-REPEAT-FUNCTION-PASS-NEXT: Finished llvm::Function pass manager run
+; CHECK-REPEAT-FUNCTION-PASS-NEXT: Finished llvm::Module pass manager run
+
+; RUN: opt -disable-output -disable-verify -debug-pass-manager \
+; RUN:     -passes='loop(repeat<3>(no-op-loop))' %s 2>&1 \
+; RUN:     | FileCheck %s --check-prefix=CHECK-REPEAT-LOOP-PASS
+; CHECK-REPEAT-LOOP-PASS: Starting llvm::Module pass manager run
+; CHECK-REPEAT-LOOP-PASS-NEXT: Running pass: ModuleToFunctionPassAdaptor
+; CHECK-REPEAT-LOOP-PASS-NEXT: Running analysis: InnerAnalysisManagerProxy<{{.*}}>
+; CHECK-REPEAT-LOOP-PASS-NEXT: Starting llvm::Function pass manager run
+; CHECK-REPEAT-LOOP-PASS-NEXT: Running pass: FunctionToLoopPassAdaptor
+; CHECK-REPEAT-LOOP-PASS-NEXT: Running analysis: InnerAnalysisManagerProxy<{{.*}}>
+; CHECK-REPEAT-LOOP-PASS-NEXT: Running analysis: LoopAnalysis
+; CHECK-REPEAT-LOOP-PASS-NEXT: Running analysis: DominatorTreeAnalysis
+; CHECK-REPEAT-LOOP-PASS-NEXT: Starting llvm::Loop pass manager run
+; CHECK-REPEAT-LOOP-PASS-NEXT: Running pass: RepeatingPassWrapper
+; CHECK-REPEAT-LOOP-PASS-NEXT: Starting llvm::Loop pass manager run
+; CHECK-REPEAT-LOOP-PASS-NEXT: Running pass: NoOpLoopPass
+; CHECK-REPEAT-LOOP-PASS-NEXT: Finished llvm::Loop pass manager run
+; CHECK-REPEAT-LOOP-PASS-NEXT: Starting llvm::Loop pass manager run
+; CHECK-REPEAT-LOOP-PASS-NEXT: Running pass: NoOpLoopPass
+; CHECK-REPEAT-LOOP-PASS-NEXT: Finished llvm::Loop pass manager run
+; CHECK-REPEAT-LOOP-PASS-NEXT: Starting llvm::Loop pass manager run
+; CHECK-REPEAT-LOOP-PASS-NEXT: Running pass: NoOpLoopPass
+; CHECK-REPEAT-LOOP-PASS-NEXT: Finished llvm::Loop pass manager run
+; CHECK-REPEAT-LOOP-PASS-NEXT: Finished llvm::Loop pass manager run
+; CHECK-REPEAT-LOOP-PASS-NEXT: Finished llvm::Function pass manager run
+; CHECK-REPEAT-LOOP-PASS-NEXT: Finished llvm::Module pass manager run
+
+define void @foo(i1 %x) {
+entry:
+  br i1 %x, label %loop, label %exit
+
+loop:
+  br label %loop
+
+exit:
   ret void
 }