New OptimizationRemarkEmitter pass for MIR

This allows MIR passes to emit optimization remarks with the same level of functionality that is available to IR passes. It also hooks up the greedy register allocator to report spills. This allows for interesting use cases like increasing interleaving on a loop until spilling of registers is observed. I still need to experiment whether reporting every spill scales but this demonstrates for now that the functionality works from llc using -pass-remarks*=<pass>. Differential Revision: https://reviews.llvm.org/D29004 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@293110 91177308-0d34-0410-b5e6-96231b3b80d8
2024-11-23 11:49:50 +00:00 · 2017-01-25 23:20:33 +00:00 · 2017-01-25 23:20:33 +00:00 · 19925fc03b
commit 19925fc03b
parent 2355a8bd5e
13 changed files with 527 additions and 48 deletions
--- a/include/llvm/Analysis/OptimizationDiagnosticInfo.h
+++ b/include/llvm/Analysis/OptimizationDiagnosticInfo.h
@ -282,5 +282,11 @@ public:
  /// \brief Run the analysis pass over a function and produce BFI.
  Result run(Function &F, FunctionAnalysisManager &AM);
 };
+
+namespace yaml {
+template <> struct MappingTraits<DiagnosticInfoOptimizationBase *> {
+  static void mapping(IO &io, DiagnosticInfoOptimizationBase *&OptDiag);
+};
+}
 }
 #endif // LLVM_IR_OPTIMIZATIONDIAGNOSTICINFO_H
--- a/include/llvm/CodeGen/MachineLoopInfo.h
+++ b/include/llvm/CodeGen/MachineLoopInfo.h
@ -60,6 +60,13 @@ public:
  /// multiple exiting blocks are present.
  MachineBasicBlock *findLoopControlBlock();

+  /// Return the debug location of the start of this loop.
+  /// This looks for a BB terminating instruction with a known debug
+  /// location by looking at the preheader and header blocks. If it
+  /// cannot find a terminating instruction with location information,
+  /// it returns an unknown location.
+  DebugLoc getStartLoc() const;
+
  void dump() const;

 private:
--- a/include/llvm/CodeGen/MachineOptimizationRemarkEmitter.h
+++ b/include/llvm/CodeGen/MachineOptimizationRemarkEmitter.h
@ -0,0 +1,188 @@
+///===- MachineOptimizationRemarkEmitter.h - Opt Diagnostics -*- C++ -*----===//
+///
+///                     The LLVM Compiler Infrastructure
+///
+/// This file is distributed under the University of Illinois Open Source
+/// License. See LICENSE.TXT for details.
+///
+///===---------------------------------------------------------------------===//
+/// \file
+/// Optimization diagnostic interfaces for machine passes.  It's packaged as an
+/// analysis pass so that by using this service passes become dependent on MBFI
+/// as well.  MBFI is used to compute the "hotness" of the diagnostic message.
+///
+///===---------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_MACHINEOPTIMIZATIONREMARKEMITTER_H
+#define LLVM_CODEGEN_MACHINEOPTIMIZATIONREMARKEMITTER_H
+
+#include "llvm/Analysis/OptimizationDiagnosticInfo.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+
+namespace llvm {
+class MachineBasicBlock;
+class MachineBlockFrequencyInfo;
+
+/// \brief Common features for diagnostics dealing with optimization remarks
+/// that are used by machine passes.
+class DiagnosticInfoMIROptimization : public DiagnosticInfoOptimizationBase {
+public:
+  DiagnosticInfoMIROptimization(enum DiagnosticKind Kind, const char *PassName,
+                                StringRef RemarkName, const DebugLoc &DLoc,
+                                MachineBasicBlock *MBB)
+      : DiagnosticInfoOptimizationBase(Kind, DS_Remark, PassName, RemarkName,
+                                       *MBB->getParent()->getFunction(), DLoc),
+        MBB(MBB) {}
+
+  static bool classof(const DiagnosticInfo *DI) {
+    return DI->getKind() >= DK_FirstMachineRemark &&
+           DI->getKind() <= DK_LastMachineRemark;
+  }
+
+  const MachineBasicBlock *getBlock() const { return MBB; }
+
+private:
+  MachineBasicBlock *MBB;
+};
+
+/// Diagnostic information for applied optimization remarks.
+class MachineOptimizationRemark : public DiagnosticInfoMIROptimization {
+public:
+  /// \p PassName is the name of the pass emitting this diagnostic. If this name
+  /// matches the regular expression given in -Rpass=, then the diagnostic will
+  /// be emitted.  \p RemarkName is a textual identifier for the remark.  \p
+  /// DLoc is the debug location and \p MBB is the block that the optimization
+  /// operates in.
+  MachineOptimizationRemark(const char *PassName, StringRef RemarkName,
+                            const DebugLoc &DLoc, MachineBasicBlock *MBB)
+      : DiagnosticInfoMIROptimization(DK_MachineOptimizationRemark, PassName,
+                                      RemarkName, DLoc, MBB) {}
+
+  static bool classof(const DiagnosticInfo *DI) {
+    return DI->getKind() == DK_MachineOptimizationRemark;
+  }
+
+  /// \see DiagnosticInfoOptimizationBase::isEnabled.
+  bool isEnabled() const override {
+    return OptimizationRemark::isEnabled(getPassName());
+  }
+};
+
+/// Diagnostic information for missed-optimization remarks.
+class MachineOptimizationRemarkMissed : public DiagnosticInfoMIROptimization {
+public:
+  /// \p PassName is the name of the pass emitting this diagnostic. If this name
+  /// matches the regular expression given in -Rpass-missed=, then the
+  /// diagnostic will be emitted.  \p RemarkName is a textual identifier for the
+  /// remark.  \p DLoc is the debug location and \p MBB is the block that the
+  /// optimization operates in.
+  MachineOptimizationRemarkMissed(const char *PassName, StringRef RemarkName,
+                                  const DebugLoc &DLoc, MachineBasicBlock *MBB)
+      : DiagnosticInfoMIROptimization(DK_MachineOptimizationRemarkMissed,
+                                      PassName, RemarkName, DLoc, MBB) {}
+
+  static bool classof(const DiagnosticInfo *DI) {
+    return DI->getKind() == DK_MachineOptimizationRemarkMissed;
+  }
+
+  /// \see DiagnosticInfoOptimizationBase::isEnabled.
+  bool isEnabled() const override {
+    return OptimizationRemarkMissed::isEnabled(getPassName());
+  }
+};
+
+/// Diagnostic information for optimization analysis remarks.
+class MachineOptimizationRemarkAnalysis : public DiagnosticInfoMIROptimization {
+public:
+  /// \p PassName is the name of the pass emitting this diagnostic. If this name
+  /// matches the regular expression given in -Rpass-analysis=, then the
+  /// diagnostic will be emitted.  \p RemarkName is a textual identifier for the
+  /// remark.  \p DLoc is the debug location and \p MBB is the block that the
+  /// optimization operates in.
+  MachineOptimizationRemarkAnalysis(const char *PassName, StringRef RemarkName,
+                                    const DebugLoc &DLoc,
+                                    MachineBasicBlock *MBB)
+      : DiagnosticInfoMIROptimization(DK_MachineOptimizationRemarkAnalysis,
+                                      PassName, RemarkName, DLoc, MBB) {}
+
+  static bool classof(const DiagnosticInfo *DI) {
+    return DI->getKind() == DK_MachineOptimizationRemarkAnalysis;
+  }
+
+  /// \see DiagnosticInfoOptimizationBase::isEnabled.
+  bool isEnabled() const override {
+    return OptimizationRemarkAnalysis::isEnabled(getPassName());
+  }
+};
+
+/// The optimization diagnostic interface.
+///
+/// It allows reporting when optimizations are performed and when they are not
+/// along with the reasons for it.  Hotness information of the corresponding
+/// code region can be included in the remark if DiagnosticHotnessRequested is
+/// enabled in the LLVM context.
+class MachineOptimizationRemarkEmitter {
+public:
+  MachineOptimizationRemarkEmitter(MachineFunction &MF,
+                                   MachineBlockFrequencyInfo *MBFI)
+      : MF(MF), MBFI(MBFI) {}
+
+  /// Emit an optimization remark.
+  void emit(DiagnosticInfoOptimizationBase &OptDiag);
+
+  /// \brief Whether we allow for extra compile-time budget to perform more
+  /// analysis to be more informative.
+  ///
+  /// This is useful to enable additional missed optimizations to be reported
+  /// that are normally too noisy.  In this mode, we can use the extra analysis
+  /// (1) to filter trivial false positives or (2) to provide more context so
+  /// that non-trivial false positives can be quickly detected by the user.
+  bool allowExtraAnalysis() const {
+    // For now, only allow this with -fsave-optimization-record since the -Rpass
+    // options are handled in the front-end.
+    return MF.getFunction()->getContext().getDiagnosticsOutputFile();
+  }
+
+private:
+  MachineFunction &MF;
+
+  /// MBFI is only set if hotness is requested.
+  MachineBlockFrequencyInfo *MBFI;
+
+  /// Compute hotness from IR value (currently assumed to be a block) if PGO is
+  /// available.
+  Optional<uint64_t> computeHotness(const MachineBasicBlock &MBB);
+
+  /// Similar but use value from \p OptDiag and update hotness there.
+  void computeHotness(DiagnosticInfoMIROptimization &Remark);
+
+  /// \brief Only allow verbose messages if we know we're filtering by hotness
+  /// (BFI is only set in this case).
+  bool shouldEmitVerbose() { return MBFI != nullptr; }
+};
+
+/// The analysis pass
+///
+/// Note that this pass shouldn't generally be marked as preserved by other
+/// passes.  It's holding onto BFI, so if the pass does not preserve BFI, BFI
+/// could be freed.
+class MachineOptimizationRemarkEmitterPass : public MachineFunctionPass {
+  std::unique_ptr<MachineOptimizationRemarkEmitter> ORE;
+
+public:
+  MachineOptimizationRemarkEmitterPass();
+
+  bool runOnMachineFunction(MachineFunction &MF) override;
+
+  void getAnalysisUsage(AnalysisUsage &AU) const override;
+
+  MachineOptimizationRemarkEmitter &getORE() {
+    assert(ORE && "pass not run yet");
+    return *ORE;
+  }
+
+  static char ID;
+};
+}
+
+#endif
--- a/include/llvm/IR/DiagnosticInfo.h
+++ b/include/llvm/IR/DiagnosticInfo.h
@ -69,6 +69,11 @@ enum DiagnosticKind {
  DK_OptimizationFailure,
  DK_FirstRemark = DK_OptimizationRemark,
  DK_LastRemark = DK_OptimizationFailure,
+  DK_MachineOptimizationRemark,
+  DK_MachineOptimizationRemarkMissed,
+  DK_MachineOptimizationRemarkAnalysis,
+  DK_FirstMachineRemark = DK_MachineOptimizationRemark,
+  DK_LastMachineRemark = DK_MachineOptimizationRemarkAnalysis,
  DK_MIRParser,
  DK_PGOProfile,
  DK_Unsupported,
@ -440,8 +445,10 @@ public:
  bool isVerbose() const { return IsVerbose; }

  static bool classof(const DiagnosticInfo *DI) {
-    return DI->getKind() >= DK_FirstRemark &&
-           DI->getKind() <= DK_LastRemark;
+    return (DI->getKind() >= DK_FirstRemark &&
+            DI->getKind() <= DK_LastRemark) ||
+           (DI->getKind() >= DK_FirstMachineRemark &&
+            DI->getKind() <= DK_LastMachineRemark);
  }

 protected:
@ -529,6 +536,10 @@ public:

  Value *getCodeRegion() const { return CodeRegion; }

+  static bool classof(const DiagnosticInfo *DI) {
+    return DI->getKind() >= DK_FirstRemark && DI->getKind() <= DK_LastRemark;
+  }
+
 private:
  /// The IR value (currently basic block) that the optimization operates on.
  /// This is currently used to provide run-time hotness information with PGO.
@ -569,8 +580,10 @@ public:
    return DI->getKind() == DK_OptimizationRemark;
  }

+  static bool isEnabled(StringRef PassName);
+
  /// \see DiagnosticInfoOptimizationBase::isEnabled.
-  bool isEnabled() const override;
+  bool isEnabled() const override { return isEnabled(getPassName()); }
 };

 /// Diagnostic information for missed-optimization remarks.
@ -607,8 +620,10 @@ public:
    return DI->getKind() == DK_OptimizationRemarkMissed;
  }

+  static bool isEnabled(StringRef PassName);
+
  /// \see DiagnosticInfoOptimizationBase::isEnabled.
-  bool isEnabled() const override;
+  bool isEnabled() const override { return isEnabled(getPassName()); }
 };

 /// Diagnostic information for optimization analysis remarks.
@ -656,8 +671,12 @@ public:
    return DI->getKind() == DK_OptimizationRemarkAnalysis;
  }

+  static bool isEnabled(StringRef PassName);
+
  /// \see DiagnosticInfoOptimizationBase::isEnabled.
-  bool isEnabled() const override;
+  bool isEnabled() const override {
+    return shouldAlwaysPrint() || isEnabled(getPassName());
+  }

  static const char *AlwaysPrint;

--- a/include/llvm/InitializePasses.h
+++ b/include/llvm/InitializePasses.h
@ -232,6 +232,7 @@ void initializeMachineFunctionPrinterPassPass(PassRegistry&);
 void initializeMachineLICMPass(PassRegistry&);
 void initializeMachineLoopInfoPass(PassRegistry&);
 void initializeMachineModuleInfoPass(PassRegistry&);
+void initializeMachineOptimizationRemarkEmitterPassPass(PassRegistry&);
 void initializeMachinePipelinerPass(PassRegistry&);
 void initializeMachinePostDominatorTreePass(PassRegistry&);
 void initializeMachineRegionInfoPassPass(PassRegistry&);
--- a/lib/Analysis/OptimizationDiagnosticInfo.cpp
+++ b/lib/Analysis/OptimizationDiagnosticInfo.cpp
@ -67,44 +67,43 @@ Optional<uint64_t> OptimizationRemarkEmitter::computeHotness(const Value *V) {
 namespace llvm {
 namespace yaml {

-template <> struct MappingTraits<DiagnosticInfoOptimizationBase *> {
-  static void mapping(IO &io, DiagnosticInfoOptimizationBase *&OptDiag) {
-    assert(io.outputting() && "input not yet implemented");
+void MappingTraits<DiagnosticInfoOptimizationBase *>::mapping(
+    IO &io, DiagnosticInfoOptimizationBase *&OptDiag) {
+  assert(io.outputting() && "input not yet implemented");

-    if (io.mapTag("!Passed", OptDiag->getKind() == DK_OptimizationRemark))
-      ;
-    else if (io.mapTag("!Missed",
-                       OptDiag->getKind() == DK_OptimizationRemarkMissed))
-      ;
-    else if (io.mapTag("!Analysis",
-                       OptDiag->getKind() == DK_OptimizationRemarkAnalysis))
-      ;
-    else if (io.mapTag("!AnalysisFPCommute",
-                       OptDiag->getKind() ==
-                           DK_OptimizationRemarkAnalysisFPCommute))
-      ;
-    else if (io.mapTag("!AnalysisAliasing",
-                       OptDiag->getKind() ==
-                           DK_OptimizationRemarkAnalysisAliasing))
-      ;
-    else
-      llvm_unreachable("todo");
+  if (io.mapTag("!Passed", OptDiag->getKind() == DK_OptimizationRemark))
+    ;
+  else if (io.mapTag("!Missed",
+                     OptDiag->getKind() == DK_OptimizationRemarkMissed))
+    ;
+  else if (io.mapTag("!Analysis",
+                     OptDiag->getKind() == DK_OptimizationRemarkAnalysis))
+    ;
+  else if (io.mapTag("!AnalysisFPCommute",
+                     OptDiag->getKind() ==
+                         DK_OptimizationRemarkAnalysisFPCommute))
+    ;
+  else if (io.mapTag("!AnalysisAliasing",
+                     OptDiag->getKind() ==
+                         DK_OptimizationRemarkAnalysisAliasing))
+    ;
+  else
+    llvm_unreachable("todo");

-    // These are read-only for now.
-    DebugLoc DL = OptDiag->getDebugLoc();
-    StringRef FN = GlobalValue::getRealLinkageName(
-        OptDiag->getFunction().getName());
+  // These are read-only for now.
+  DebugLoc DL = OptDiag->getDebugLoc();
+  StringRef FN =
+      GlobalValue::getRealLinkageName(OptDiag->getFunction().getName());

-    StringRef PassName(OptDiag->PassName);
-    io.mapRequired("Pass", PassName);
-    io.mapRequired("Name", OptDiag->RemarkName);
-    if (!io.outputting() || DL)
-      io.mapOptional("DebugLoc", DL);
-    io.mapRequired("Function", FN);
-    io.mapOptional("Hotness", OptDiag->Hotness);
-    io.mapOptional("Args", OptDiag->Args);
-  }
-};
+  StringRef PassName(OptDiag->PassName);
+  io.mapRequired("Pass", PassName);
+  io.mapRequired("Name", OptDiag->RemarkName);
+  if (!io.outputting() || DL)
+    io.mapOptional("DebugLoc", DL);
+  io.mapRequired("Function", FN);
+  io.mapOptional("Hotness", OptDiag->Hotness);
+  io.mapOptional("Args", OptDiag->Args);
+}

 template <> struct MappingTraits<DebugLoc> {
  static void mapping(IO &io, DebugLoc &DL) {
--- a/lib/CodeGen/CMakeLists.txt
+++ b/lib/CodeGen/CMakeLists.txt
@ -71,6 +71,7 @@ add_llvm_library(LLVMCodeGen
  MachineLoopInfo.cpp
  MachineModuleInfo.cpp
  MachineModuleInfoImpls.cpp
+  MachineOptimizationRemarkEmitter.cpp
  MachinePassRegistry.cpp
  MachinePipeliner.cpp
  MachinePostDominators.cpp
--- a/lib/CodeGen/MachineLoopInfo.cpp
+++ b/lib/CodeGen/MachineLoopInfo.cpp
@ -87,6 +87,22 @@ MachineBasicBlock *MachineLoop::findLoopControlBlock() {
  return nullptr;
 }

+DebugLoc MachineLoop::getStartLoc() const {
+  // Try the pre-header first.
+  if (MachineBasicBlock *PHeadMBB = getLoopPreheader())
+    if (const BasicBlock *PHeadBB = PHeadMBB->getBasicBlock())
+      if (DebugLoc DL = PHeadBB->getTerminator()->getDebugLoc())
+        return DL;
+
+  // If we have no pre-header or there are no instructions with debug
+  // info in it, try the header.
+  if (MachineBasicBlock *HeadMBB = getHeader())
+    if (const BasicBlock *HeadBB = HeadMBB->getBasicBlock())
+      return HeadBB->getTerminator()->getDebugLoc();
+
+  return DebugLoc();
+}
+
 MachineBasicBlock *
 MachineLoopInfo::findLoopPreheader(MachineLoop *L,
                                   bool SpeculativePreheader) const {
--- a/lib/CodeGen/MachineOptimizationRemarkEmitter.cpp
+++ b/lib/CodeGen/MachineOptimizationRemarkEmitter.cpp
@ -0,0 +1,90 @@
+///===- MachineOptimizationRemarkEmitter.cpp - Opt Diagnostic -*- C++ -*---===//
+///
+///                     The LLVM Compiler Infrastructure
+///
+/// This file is distributed under the University of Illinois Open Source
+/// License. See LICENSE.TXT for details.
+///
+///===---------------------------------------------------------------------===//
+/// \file
+/// Optimization diagnostic interfaces for machine passes.  It's packaged as an
+/// analysis pass so that by using this service passes become dependent on MBFI
+/// as well.  MBFI is used to compute the "hotness" of the diagnostic message.
+///
+///===---------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/MachineOptimizationRemarkEmitter.h"
+#include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
+#include "llvm/IR/DebugInfo.h"
+#include "llvm/IR/DiagnosticInfo.h"
+#include "llvm/IR/LLVMContext.h"
+
+using namespace llvm;
+
+Optional<uint64_t>
+MachineOptimizationRemarkEmitter::computeHotness(const MachineBasicBlock &MBB) {
+  if (!MBFI)
+    return None;
+
+  return MBFI->getBlockProfileCount(&MBB);
+}
+
+void MachineOptimizationRemarkEmitter::computeHotness(
+    DiagnosticInfoMIROptimization &Remark) {
+  const MachineBasicBlock *MBB = Remark.getBlock();
+  if (MBB)
+    Remark.setHotness(computeHotness(*MBB));
+}
+
+void MachineOptimizationRemarkEmitter::emit(
+    DiagnosticInfoOptimizationBase &OptDiagCommon) {
+  auto &OptDiag = cast<DiagnosticInfoMIROptimization>(OptDiagCommon);
+  computeHotness(OptDiag);
+
+  LLVMContext &Ctx = MF.getFunction()->getContext();
+  yaml::Output *Out = Ctx.getDiagnosticsOutputFile();
+  if (Out) {
+    auto *P = &const_cast<DiagnosticInfoOptimizationBase &>(OptDiagCommon);
+    *Out << P;
+  }
+  // FIXME: now that IsVerbose is part of DI, filtering for this will be moved
+  // from here to clang.
+  if (!OptDiag.isVerbose() || shouldEmitVerbose())
+    Ctx.diagnose(OptDiag);
+}
+
+MachineOptimizationRemarkEmitterPass::MachineOptimizationRemarkEmitterPass()
+    : MachineFunctionPass(ID) {
+  initializeMachineOptimizationRemarkEmitterPassPass(
+      *PassRegistry::getPassRegistry());
+}
+
+bool MachineOptimizationRemarkEmitterPass::runOnMachineFunction(
+    MachineFunction &MF) {
+  MachineBlockFrequencyInfo *MBFI;
+
+  if (MF.getFunction()->getContext().getDiagnosticHotnessRequested())
+    MBFI = &getAnalysis<MachineBlockFrequencyInfo>();
+  else
+    MBFI = nullptr;
+
+  ORE = llvm::make_unique<MachineOptimizationRemarkEmitter>(MF, MBFI);
+  return false;
+}
+
+void MachineOptimizationRemarkEmitterPass::getAnalysisUsage(
+    AnalysisUsage &AU) const {
+  AU.addRequired<MachineBlockFrequencyInfo>();
+  AU.setPreservesAll();
+  MachineFunctionPass::getAnalysisUsage(AU);
+}
+
+char MachineOptimizationRemarkEmitterPass::ID = 0;
+static const char ore_name[] = "Machine Optimization Remark Emitter";
+#define ORE_NAME "machine-opt-remark-emitter"
+
+INITIALIZE_PASS_BEGIN(MachineOptimizationRemarkEmitterPass, ORE_NAME, ore_name,
+                      false, true)
+INITIALIZE_PASS_DEPENDENCY(MachineBlockFrequencyInfo)
+INITIALIZE_PASS_END(MachineOptimizationRemarkEmitterPass, ORE_NAME, ore_name,
+                    false, true)
--- a/lib/CodeGen/RegAllocGreedy.cpp
+++ b/lib/CodeGen/RegAllocGreedy.cpp
@ -29,8 +29,10 @@
 #include "llvm/CodeGen/LiveStackAnalysis.h"
 #include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
 #include "llvm/CodeGen/MachineDominators.h"
+#include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
 #include "llvm/CodeGen/MachineLoopInfo.h"
+#include "llvm/CodeGen/MachineOptimizationRemarkEmitter.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/CodeGen/Passes.h"
 #include "llvm/CodeGen/RegAllocRegistry.h"
@ -125,6 +127,7 @@ class RAGreedy : public MachineFunctionPass,
  MachineBlockFrequencyInfo *MBFI;
  MachineDominatorTree *DomTree;
  MachineLoopInfo *Loops;
+  MachineOptimizationRemarkEmitter *ORE;
  EdgeBundles *Bundles;
  SpillPlacement *SpillPlacer;
  LiveDebugVariables *DebugVars;
@ -419,6 +422,20 @@ private:
  void collectHintInfo(unsigned, HintsInfo &);

  bool isUnusedCalleeSavedReg(unsigned PhysReg) const;
+
+  /// Compute and report the number of spills and reloads for a loop.
+  void reportNumberOfSplillsReloads(MachineLoop *L, unsigned &Reloads,
+                                    unsigned &FoldedReloads, unsigned &Spills,
+                                    unsigned &FoldedSpills);
+
+  /// Report the number of spills and reloads for each loop.
+  void reportNumberOfSplillsReloads() {
+    for (MachineLoop *L : *Loops) {
+      unsigned Reloads, FoldedReloads, Spills, FoldedSpills;
+      reportNumberOfSplillsReloads(L, Reloads, FoldedReloads, Spills,
+                                   FoldedSpills);
+    }
+  }
 };
 } // end anonymous namespace

@ -439,6 +456,7 @@ INITIALIZE_PASS_DEPENDENCY(VirtRegMap)
 INITIALIZE_PASS_DEPENDENCY(LiveRegMatrix)
 INITIALIZE_PASS_DEPENDENCY(EdgeBundles)
 INITIALIZE_PASS_DEPENDENCY(SpillPlacement)
+INITIALIZE_PASS_DEPENDENCY(MachineOptimizationRemarkEmitterPass)
 INITIALIZE_PASS_END(RAGreedy, "greedy",
                "Greedy Register Allocator", false, false)

@ -490,6 +508,7 @@ void RAGreedy::getAnalysisUsage(AnalysisUsage &AU) const {
  AU.addPreserved<LiveRegMatrix>();
  AU.addRequired<EdgeBundles>();
  AU.addRequired<SpillPlacement>();
+  AU.addRequired<MachineOptimizationRemarkEmitterPass>();
  MachineFunctionPass::getAnalysisUsage(AU);
 }

@ -2611,6 +2630,69 @@ unsigned RAGreedy::selectOrSplitImpl(LiveInterval &VirtReg,
  return 0;
 }

+void RAGreedy::reportNumberOfSplillsReloads(MachineLoop *L, unsigned &Reloads,
+                                            unsigned &FoldedReloads,
+                                            unsigned &Spills,
+                                            unsigned &FoldedSpills) {
+  Reloads = 0;
+  FoldedReloads = 0;
+  Spills = 0;
+  FoldedSpills = 0;
+
+  // Sum up the spill and reloads in subloops.
+  for (MachineLoop *SubLoop : *L) {
+    unsigned SubReloads;
+    unsigned SubFoldedReloads;
+    unsigned SubSpills;
+    unsigned SubFoldedSpills;
+
+    reportNumberOfSplillsReloads(SubLoop, SubReloads, SubFoldedReloads,
+                                 SubSpills, SubFoldedSpills);
+    Reloads += SubReloads;
+    FoldedReloads += SubFoldedReloads;
+    Spills += SubSpills;
+    FoldedSpills += SubFoldedSpills;
+  }
+
+  const MachineFrameInfo &MFI = MF->getFrameInfo();
+  const TargetInstrInfo *TII = MF->getSubtarget().getInstrInfo();
+  int FI;
+
+  for (MachineBasicBlock *MBB : L->getBlocks())
+    // Handle blocks that were not included in subloops.
+    if (Loops->getLoopFor(MBB) == L)
+      for (MachineInstr &MI : *MBB) {
+        const MachineMemOperand *MMO;
+
+        if (TII->isLoadFromStackSlot(MI, FI) && MFI.isSpillSlotObjectIndex(FI))
+          ++Reloads;
+        else if (TII->hasLoadFromStackSlot(MI, MMO, FI) &&
+                 MFI.isSpillSlotObjectIndex(FI))
+          ++FoldedReloads;
+        else if (TII->isStoreToStackSlot(MI, FI) &&
+                 MFI.isSpillSlotObjectIndex(FI))
+          ++Spills;
+        else if (TII->hasStoreToStackSlot(MI, MMO, FI) &&
+                 MFI.isSpillSlotObjectIndex(FI))
+          ++FoldedSpills;
+      }
+
+  if (Reloads || FoldedReloads || Spills || FoldedSpills) {
+    using namespace ore;
+    MachineOptimizationRemarkMissed R(DEBUG_TYPE, "LoopSpillReload",
+                                      L->getStartLoc(), L->getHeader());
+    if (Spills)
+      R << NV("NumSpills", Spills) << " spills ";
+    if (FoldedSpills)
+      R << NV("NumFoldedSpills", FoldedSpills) << " folded spills ";
+    if (Reloads)
+      R << NV("NumReloads", Reloads) << " reloads ";
+    if (FoldedReloads)
+      R << NV("NumFoldedReloads", FoldedReloads) << " folded reloads ";
+    ORE->emit(R << "generated in loop");
+  }
+}
+
 bool RAGreedy::runOnMachineFunction(MachineFunction &mf) {
  DEBUG(dbgs() << "********** GREEDY REGISTER ALLOCATION **********\n"
               << "********** Function: " << mf.getName() << '\n');
@ -2633,6 +2715,7 @@ bool RAGreedy::runOnMachineFunction(MachineFunction &mf) {
  Indexes = &getAnalysis<SlotIndexes>();
  MBFI = &getAnalysis<MachineBlockFrequencyInfo>();
  DomTree = &getAnalysis<MachineDominatorTree>();
+  ORE = &getAnalysis<MachineOptimizationRemarkEmitterPass>().getORE();
  SpillerInstance.reset(createInlineSpiller(*this, *MF, *VRM));
  Loops = &getAnalysis<MachineLoopInfo>();
  Bundles = &getAnalysis<EdgeBundles>();
@ -2658,6 +2741,7 @@ bool RAGreedy::runOnMachineFunction(MachineFunction &mf) {
  allocatePhysRegs();
  tryHintsRecoloring();
  postOptimization();
+  reportNumberOfSplillsReloads();

  releaseMemory();
  return true;
--- a/lib/IR/DiagnosticInfo.cpp
+++ b/lib/IR/DiagnosticInfo.cpp
@ -222,9 +222,9 @@ OptimizationRemark::OptimizationRemark(const char *PassName,
                                   RemarkName, *Inst->getParent()->getParent(),
                                   Inst->getDebugLoc(), Inst->getParent()) {}

-bool OptimizationRemark::isEnabled() const {
+bool OptimizationRemark::isEnabled(StringRef PassName) {
  return PassRemarksOptLoc.Pattern &&
-         PassRemarksOptLoc.Pattern->match(getPassName());
+         PassRemarksOptLoc.Pattern->match(PassName);
 }

 OptimizationRemarkMissed::OptimizationRemarkMissed(const char *PassName,
@ -243,9 +243,9 @@ OptimizationRemarkMissed::OptimizationRemarkMissed(const char *PassName,
                                   *Inst->getParent()->getParent(),
                                   Inst->getDebugLoc(), Inst->getParent()) {}

-bool OptimizationRemarkMissed::isEnabled() const {
+bool OptimizationRemarkMissed::isEnabled(StringRef PassName) {
  return PassRemarksMissedOptLoc.Pattern &&
-         PassRemarksMissedOptLoc.Pattern->match(getPassName());
+         PassRemarksMissedOptLoc.Pattern->match(PassName);
 }

 OptimizationRemarkAnalysis::OptimizationRemarkAnalysis(const char *PassName,
@ -273,10 +273,9 @@ OptimizationRemarkAnalysis::OptimizationRemarkAnalysis(enum DiagnosticKind Kind,
                                   *cast<BasicBlock>(CodeRegion)->getParent(),
                                   DLoc, CodeRegion) {}

-bool OptimizationRemarkAnalysis::isEnabled() const {
-  return shouldAlwaysPrint() ||
-         (PassRemarksAnalysisOptLoc.Pattern &&
-          PassRemarksAnalysisOptLoc.Pattern->match(getPassName()));
+bool OptimizationRemarkAnalysis::isEnabled(StringRef PassName) {
+  return PassRemarksAnalysisOptLoc.Pattern &&
+         PassRemarksAnalysisOptLoc.Pattern->match(PassName);
 }

 void DiagnosticInfoMIRParser::print(DiagnosticPrinter &DP) const {
--- a/test/CodeGen/AArch64/arm64-spill-remarks.ll
+++ b/test/CodeGen/AArch64/arm64-spill-remarks.ll
@ -0,0 +1,65 @@
+; RUN: llc < %s -mtriple=arm64-apple-ios7.0 -aarch64-neon-syntax=apple -pass-remarks-missed=regalloc 2>&1 | FileCheck -check-prefix=REMARK %s
+; RUN: llc < %s -mtriple=arm64-apple-ios7.0 -aarch64-neon-syntax=apple 2>&1 | FileCheck -check-prefix=NO_REMARK %s
+
+; This has two nested loops, each with one value that has to be spilled and
+; then reloaded.
+
+; (loop3:)
+; REMARK: remark: /tmp/kk.c:3:20: 1 spills 1 reloads generated in loop
+; (loop2:)
+; REMARK: remark: /tmp/kk.c:2:20: 1 spills 1 reloads generated in loop
+; (loop:)
+; REMARK: remark: /tmp/kk.c:1:20: 2 spills 2 reloads generated in loop
+
+; NO_REMARK-NOT: remark
+
+define void @fpr128(<4 x float>* %p) nounwind ssp {
+entry:
+  br label %loop, !dbg !8
+
+loop:
+  %i = phi i32 [ 0, %entry], [ %i.2, %end2 ]
+  br label %loop2, !dbg !9
+
+loop2:
+  %j = phi i32 [ 0, %loop], [ %j.2, %loop2 ]
+  call void asm sideeffect "; inlineasm", "~{q0},~{q1},~{q2},~{q3},~{q4},~{q5},~{q6},~{q7},~{q8},~{q9},~{q10},~{q11},~{q12},~{q13},~{q14},~{q15},~{q16},~{q17},~{q18},~{q19},~{q20},~{q21},~{q22},~{q23},~{q24},~{q25},~{q26},~{q27},~{q28},~{q29},~{q30},~{q31},~{x0},~{x1},~{x2},~{x3},~{x4},~{x5},~{x6},~{x7},~{x8},~{x9},~{x10},~{x11},~{x12},~{x13},~{x14},~{x15},~{x16},~{x17},~{x18},~{x19},~{x20},~{x21},~{x22},~{x23},~{x24},~{x25},~{x26},~{x27},~{x28},~{fp},~{lr},~{sp},~{memory}"() nounwind
+  %j.2 = add i32 %j, 1
+  %c2 = icmp slt i32 %j.2, 100
+  br i1 %c2, label %loop2, label %end2
+
+end2:
+  call void asm sideeffect "; inlineasm", "~{q0},~{q1},~{q2},~{q3},~{q4},~{q5},~{q6},~{q7},~{q8},~{q9},~{q10},~{q11},~{q12},~{q13},~{q14},~{q15},~{q16},~{q17},~{q18},~{q19},~{q20},~{q21},~{q22},~{q23},~{q24},~{q25},~{q26},~{q27},~{q28},~{q29},~{q30},~{q31},~{x0},~{x1},~{x2},~{x3},~{x4},~{x5},~{x6},~{x7},~{x8},~{x9},~{x10},~{x11},~{x12},~{x13},~{x14},~{x15},~{x16},~{x17},~{x18},~{x19},~{x20},~{x21},~{x22},~{x23},~{x24},~{x25},~{x26},~{x27},~{x28},~{fp},~{lr},~{sp},~{memory}"() nounwind
+  %i.2 = add i32 %i, 1
+  %c = icmp slt i32 %i.2, 100
+  br i1 %c, label %loop, label %end
+
+end:
+  br label %loop3
+
+loop3:
+  %k = phi i32 [ 0, %end], [ %k.2, %loop3 ]
+  call void asm sideeffect "; inlineasm", "~{q0},~{q1},~{q2},~{q3},~{q4},~{q5},~{q6},~{q7},~{q8},~{q9},~{q10},~{q11},~{q12},~{q13},~{q14},~{q15},~{q16},~{q17},~{q18},~{q19},~{q20},~{q21},~{q22},~{q23},~{q24},~{q25},~{q26},~{q27},~{q28},~{q29},~{q30},~{q31},~{x0},~{x1},~{x2},~{x3},~{x4},~{x5},~{x6},~{x7},~{x8},~{x9},~{x10},~{x11},~{x12},~{x13},~{x14},~{x15},~{x16},~{x17},~{x18},~{x19},~{x20},~{x21},~{x22},~{x23},~{x24},~{x25},~{x26},~{x27},~{x28},~{fp},~{lr},~{sp},~{memory}"() nounwind
+  %k.2 = add i32 %k, 1
+  %c3 = icmp slt i32 %k.2, 100
+  br i1 %c3, label %loop3, label %end3, !dbg !10
+
+end3:
+  ret void
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4}
+!llvm.ident = !{!5}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 3.9.0 ", isOptimized: true, runtimeVersion: 0, emissionKind: NoDebug, enums: !2)
+!1 = !DIFile(filename: "/tmp/kk.c", directory: "/tmp")
+!2 = !{}
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!4 = !{i32 1, !"PIC Level", i32 2}
+!5 = !{!"clang version 3.9.0 "}
+!6 = distinct !DISubprogram(name: "success", scope: !1, file: !1, line: 1, type: !7, isLocal: false, isDefinition: true, scopeLine: 1, flags: DIFlagPrototyped, isOptimized: true, unit: !0, variables: !2)
+!7 = !DISubroutineType(types: !2)
+!8 = !DILocation(line: 1, column: 20, scope: !6)
+!9 = !DILocation(line: 2, column: 20, scope: !6)
+!10 = !DILocation(line: 3, column: 20, scope: !6)
--- a/tools/llc/llc.cpp
+++ b/tools/llc/llc.cpp
@ -233,6 +233,10 @@ static void DiagnosticHandler(const DiagnosticInfo &DI, void *Context) {
  if (DI.getSeverity() == DS_Error)
    *HasError = true;

+  if (auto *Remark = dyn_cast<DiagnosticInfoOptimizationBase>(&DI))
+    if (!Remark->isEnabled())
+      return;
+
  DiagnosticPrinterRawOStream DP(errs());
  errs() << LLVMContext::getDiagnosticMessagePrefix(DI.getSeverity()) << ": ";
  DI.print(DP);