Index: llvm/trunk/include/llvm/IR/PassManager.h
===================================================================
--- llvm/trunk/include/llvm/IR/PassManager.h
+++ llvm/trunk/include/llvm/IR/PassManager.h
@@ -987,6 +987,34 @@
   }
 };
 
+/// 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
Index: llvm/trunk/lib/Passes/PassBuilder.cpp
===================================================================
--- llvm/trunk/lib/Passes/PassBuilder.cpp
+++ llvm/trunk/lib/Passes/PassBuilder.cpp
@@ -274,6 +274,15 @@
   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 @@
   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 @@
   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 @@
   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 @@
   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 @@
       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 @@
           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 @@
       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::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 @@
       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;
   }
Index: llvm/trunk/test/Other/new-pass-manager.ll
===================================================================
--- llvm/trunk/test/Other/new-pass-manager.ll
+++ llvm/trunk/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
 }