New OptimizationRemarkEmitter pass for MIR

[anemet]

Summary

This allows MIR passes to emit optimization remarks with the same level
of functionality that is available to IR passes.

We need a MIR-specific analysis pass because this pass uses MachineBFI while ORE uses BFI.

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>.

[MatzeB]

I am a bit confused by the isEnabled() code. Is this meant as a common tool for frontends to configure filtering? I couldn't find any user in llvm before this patch, maybe I missed something? Shouldn't opt and clang have similar lines like the 3 lines you added to llc.cpp?

include/llvm/CodeGen/MachineOptimizationRemarkEmitter.h

10–12

Use /// \file ...

27

by machine passes.

31

Side remarks that we should not fix in this commit (because it's the same for other classes):

• The base class is specifically designed to use an int for the diagnostic kind to stay extensible for plugins and then all the subclasses just go back to enum DiagnosticKind.
• DebugLoc is basically a pointer with special semantics so it is simpler and more efficient to pass it by value instead of const DebugLoc&.

43

Could be const

127–128

Use reference for MF and MBFI if they cannot be nullptr.

131

/// Emits an optimization remark ?

142–143

Wouldn't a user of -Rpass not want false positives eliminated as well? I keep wondering why not just using isEnabled() to decide whether to do extra work or not.

169

Wouldn't you expect the big majority of uses to be as an analysis pass? So maybe this could be merged with MachineOptimizationRemarkEmitter to keep things simpler? (We can always revert this decision when we find cases where we want a non-pass emitter).

179

Can be const

lib/CodeGen/InlineSpiller.cpp

181

Why not `pass.getAnalysis<MachineOptimizationRemarkEmitter>() instead of passing around the instance?

lib/CodeGen/RegAllocGreedy.cpp

2639–2640

I assume we do not need to create a new spiller instance each time when you change the spiller to do the getAnalysis<> (see above).

[MatzeB]

Thinking some more about what is reported here: Reporting every single spill will produce a lot of data and most probably force optviewer to summarize/aggregate the information anyway to be any useful. My expectation would be that anything finer grained than per-loop is probably unnecessary, so:

Maybe a better approach would be to look whether reporting is enabled and if so walk the machine loops after greedy is finished. And then count the spill/reload instructions for each loop and only report that as a remark. A technique as used in AsmPrinter.cpp:emitComments() should be good enough to identify an instruction as performing a spill/reload.

[anemet]

In D29004#653623, @MatzeB wrote:

I am a bit confused by the isEnabled() code. Is this meant as a common tool for frontends to configure filtering? I couldn't find any user in llvm before this patch, maybe I missed something? Shouldn't opt and clang have similar lines like the 3 lines you added to llc.cpp?

So backend users can use the default diagnostic handler (like opt) or define their own (like llc and clang). The default handler is in LLVMContext::diagnose which has similar code via isDiagnosticEnabled.

include/llvm/CodeGen/MachineOptimizationRemarkEmitter.h

142–143

I think that the comments are misleading. The idea of this flag is not to reduce the number of false positives but to be able to report cases where the false positive rate is expected to be high without some further analysis.

In other words if this flag is off (i.e. -Rpass) we won't report these cases at all.

Let me fix the comment in a separate commit.

169

The other reason why this got split for LLVM-IR ORE was the new pass manager where you have now "two" passes (legacy, new) producing ORE.

I think I would prefer to keep this separation.

lib/CodeGen/InlineSpiller.cpp

181

Because the InlineSpiller is used from other allocators as well. I'll add a comment that explains this.

[MatzeB]

include/llvm/CodeGen/MachineOptimizationRemarkEmitter.h

142–143

Ah that makes sense. I guess even the term "false positive" feels a bit out of place for information like where/how much was spilled. As those aren't immediately actionable things but rather extra information / statistics (at least when viewed in isolation without having something to compare against).

169

Ah I didn't think about the new pass manager, makes sense.

lib/CodeGen/InlineSpiller.cpp

181

Sure it's used by multiple allocators, but I don't see why this would prohibit the use of getAnalysis<> here.

[anemet]

The main change is that we now report spills & reloads per loop as suggested
by Matthias.

For this I had to somehow find the source line info for a MachineLoop (see
MachineLoop::getStartLoc()). This is a dumbed-down version of the LLVM IR
variant which uses LoopID. We can explore later if we can somehow find our
way back to the IR LoopID.

[anemet]

include/llvm/CodeGen/MachineOptimizationRemarkEmitter.h

127–128

MF is done. MBFI can be null.

179

No, we need to call emit through this reference.

[MatzeB]

LGTM, the issues mentioned can be fixed without further review.

include/llvm/CodeGen/MachineOptimizationRemarkEmitter.h

10

Needs three slashes.

155

Use a reference for MBB parameter as it cannot be nullptr.

179

getORE() const should still be possible (const MachineOptimizationRemarkEmitter& is not possible of course)

lib/CodeGen/MachineOptimizationRemarkEmitter.cpp

10

/// \file ...

35–36

Could move the declaration into the if

lib/CodeGen/RegAllocGreedy.cpp

428

Would it make sense to add a if (!OptimizationRemark::isEnabled(DEBUG_TYPE)) return; here?

436

Shouldn't this do Reloads = 0; FoldedReloads = 0; ... in each loop iteration as we shouldn't add the values of an earlier loop to a later loop (we just want it from inner loops to outer loops I assume).

[anemet]

lib/CodeGen/MachineOptimizationRemarkEmitter.cpp

35–36

No, they control-dependent :)

lib/CodeGen/RegAllocGreedy.cpp

428

No, -fsave-optimization-record should get this regardless of Enabled. Filtering is on the consumer side.

436

What?! You can't count for a single loop and for all contained loops in the same variable?! Thanks for noticing!

Also extended the test to cover for this.

include/llvm/Analysis/OptimizationDiagnosticInfo.h

 
 public:
   /// \brief Provide the result typedef for this analysis pass.
   typedef OptimizationRemarkEmitter Result;
 
   /// \brief Run the analysis pass over a function and produce BFI.
   Result run(Function &F, FunctionAnalysisManager &AM);
 };
+
+namespace yaml {
+template <> struct MappingTraits<DiagnosticInfoOptimizationCommonBase *> {
+  static void mapping(IO &io, DiagnosticInfoOptimizationCommonBase *&OptDiag);
+};
+}
 }
 #endif // LLVM_IR_OPTIMIZATIONDIAGNOSTICINFO_H

include/llvm/CodeGen/MachineOptimizationRemarkEmitter.h

+//===- 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.
+//
+//===----------------------------------------------------------------------===//
+//
+// 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 IR passes.
+class MachineOptimizationRemarkBase
+    : public DiagnosticInfoOptimizationCommonBase {
+public:
+  MachineOptimizationRemarkBase(enum DiagnosticKind Kind, const char *PassName,
+                                StringRef RemarkName, const DebugLoc &DLoc,
+                                MachineBasicBlock *MBB)
+      : DiagnosticInfoOptimizationCommonBase(
+            Kind, DS_Remark, PassName, RemarkName,
+            *MBB->getParent()->getFunction(), DLoc),
+        MBB(MBB) {}
+
+  static bool classof(const DiagnosticInfo *DI) {
+    return DI->getKind() == DK_MachineOptimizationRemark;
+  }
+
+  MachineBasicBlock *getBlock() { return MBB; }
+
+private:
+  MachineBasicBlock *MBB;
+};
+
+/// Diagnostic information for applied optimization remarks.
+class MachineOptimizationRemark : public MachineOptimizationRemarkBase {
+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)
+      : MachineOptimizationRemarkBase(DK_MachineOptimizationRemark, PassName,
+                                      RemarkName, DLoc, MBB) {}
+
+  static bool classof(const DiagnosticInfo *DI) {
+    return DI->getKind() == DK_MachineOptimizationRemark;
+  }
+
+  /// \see DiagnosticInfoOptimizationCommonBase::isEnabled.
+  bool isEnabled() const override {
+    return OptimizationRemark::isEnabled(getPassName());
+  }
+};
+
+/// Diagnostic information for missed-optimization remarks.
+class MachineOptimizationRemarkMissed : public MachineOptimizationRemarkBase {
+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)
+      : MachineOptimizationRemarkBase(DK_MachineOptimizationRemarkMissed,
+                                      PassName, RemarkName, DLoc, MBB) {}
+
+  static bool classof(const DiagnosticInfo *DI) {
+    return DI->getKind() == DK_MachineOptimizationRemarkMissed;
+  }
+
+  /// \see DiagnosticInfoOptimizationCommonBase::isEnabled.
+  bool isEnabled() const override {
+    return OptimizationRemarkMissed::isEnabled(getPassName());
+  }
+};
+
+/// Diagnostic information for optimization analysis remarks.
+class MachineOptimizationRemarkAnalysis : public MachineOptimizationRemarkBase {
+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)
+      : MachineOptimizationRemarkBase(DK_MachineOptimizationRemarkAnalysis,
+                                      PassName, RemarkName, DLoc, MBB) {}
+
+  static bool classof(const DiagnosticInfo *DI) {
+    return DI->getKind() == DK_MachineOptimizationRemarkAnalysis;
+  }
+
+  /// \see DiagnosticInfoOptimizationCommonBase::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) {}
+
+  /// The new interface to emit remarks.
+  void emit(DiagnosticInfoOptimizationCommonBase &OptDiag);
+
+  /// \brief Whether we allow for extra compile-time budget to perform more
+  /// analysis to produce fewer false positives.
+  ///
+  /// This is useful when reporting missed optimizations.  In this case 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;
+
+  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(MachineOptimizationRemarkBase &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

include/llvm/IR/DiagnosticInfo.h

enum DiagnosticKind {
   DK_OptimizationRemark,
   DK_OptimizationRemarkMissed,
   DK_OptimizationRemarkAnalysis,
   DK_OptimizationRemarkAnalysisFPCommute,
   DK_OptimizationRemarkAnalysisAliasing,
   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,
   DK_FirstPluginKind
 };
 
 /// \brief Get the next available kind ID for a plugin diagnostic.
 /// Each time this function is called, it returns a different number.
public:
   StringRef getPassName() const { return PassName; }
   std::string getMsg() const;
   Optional<uint64_t> getHotness() const { return Hotness; }
   void setHotness(Optional<uint64_t> H) { Hotness = H; }
 
   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:
   /// Name of the pass that triggers this report. If this matches the
   /// regular expression given in -Rpass=regexp, then the remark will
   /// be emitted.
   const char *PassName;
 
DiagnosticInfoOptimizationBase(enum DiagnosticKind Kind,
       : DiagnosticInfoOptimizationCommonBase(Kind, Severity, PassName, "", Fn,
                                              DLoc) {
     setHotness(Hotness);
     *this << Msg.str();
   }
 
   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.
   Value *CodeRegion;
 };
 
 /// Diagnostic information for applied optimization remarks.
 class OptimizationRemark : public DiagnosticInfoOptimizationBase {
public:
   /// Instr.
   OptimizationRemark(const char *PassName, StringRef RemarkName,
                      Instruction *Inst);
 
   static bool classof(const DiagnosticInfo *DI) {
     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.
 class OptimizationRemarkMissed : public DiagnosticInfoOptimizationBase {
 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 Fn is the function where the diagnostic
public:
   /// location.
   OptimizationRemarkMissed(const char *PassName, StringRef RemarkName,
                            Instruction *Inst);
 
   static bool classof(const DiagnosticInfo *DI) {
     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.
 class OptimizationRemarkAnalysis : public DiagnosticInfoOptimizationBase {
 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 Fn is the function where the diagnostic
public:
   /// location.
   OptimizationRemarkAnalysis(const char *PassName, StringRef RemarkName,
                              Instruction *Inst);
 
   static bool classof(const DiagnosticInfo *DI) {
     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;
 
   bool shouldAlwaysPrint() const { return getPassName() == AlwaysPrint; }
 
 protected:
   OptimizationRemarkAnalysis(enum DiagnosticKind Kind, const char *PassName,
                              const Function &Fn, const DebugLoc &DLoc,

include/llvm/InitializePasses.h

 void initializeMachineCombinerPass(PassRegistry &);
 void initializeMachineCopyPropagationPass(PassRegistry&);
 void initializeMachineDominanceFrontierPass(PassRegistry&);
 void initializeMachineDominatorTreePass(PassRegistry&);
 void initializeMachineFunctionPrinterPassPass(PassRegistry&);
 void initializeMachineLICMPass(PassRegistry&);
 void initializeMachineLoopInfoPass(PassRegistry&);
 void initializeMachineModuleInfoPass(PassRegistry&);
+void initializeMachineOptimizationRemarkEmitterPassPass(PassRegistry&);
 void initializeMachinePipelinerPass(PassRegistry&);
 void initializeMachinePostDominatorTreePass(PassRegistry&);
 void initializeMachineRegionInfoPassPass(PassRegistry&);
 void initializeMachineSchedulerPass(PassRegistry&);
 void initializeMachineSinkingPass(PassRegistry&);
 void initializeMachineTraceMetricsPass(PassRegistry&);
 void initializeMachineVerifierPassPass(PassRegistry&);
 void initializeMemCpyOptLegacyPassPass(PassRegistry&);

lib/Analysis/OptimizationDiagnosticInfo.cpp

if (!BFI)
     return None;
 
   return BFI->getBlockProfileCount(cast<BasicBlock>(V));
 }
 
 namespace llvm {
 namespace yaml {
 
-template <> struct MappingTraits<DiagnosticInfoOptimizationCommonBase *> {
-  static void mapping(IO &io, DiagnosticInfoOptimizationCommonBase *&OptDiag) {
-    assert(io.outputting() && "input not yet implemented");
+void MappingTraits<DiagnosticInfoOptimizationCommonBase *>::mapping(
+    IO &io, DiagnosticInfoOptimizationCommonBase *&OptDiag) {
 
-    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());
+  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);
-  }
-};
 
 template <> struct MappingTraits<DebugLoc> {
   static void mapping(IO &io, DebugLoc &DL) {
     assert(io.outputting() && "input not yet implemented");
 
     auto *Scope = cast<DIScope>(DL.getScope());
     StringRef File = Scope->getFilename();
     unsigned Line = DL.getLine();

lib/CodeGen/CMakeLists.txt

add_llvm_library(LLVMCodeGen
   MachineFunctionPass.cpp
   MachineFunctionPrinterPass.cpp
   MachineInstrBundle.cpp
   MachineInstr.cpp
   MachineLICM.cpp
   MachineLoopInfo.cpp
   MachineModuleInfo.cpp
   MachineModuleInfoImpls.cpp
+  MachineOptimizationRemarkEmitter.cpp
   MachinePassRegistry.cpp
   MachinePipeliner.cpp
   MachinePostDominators.cpp
   MachineRegionInfo.cpp
   MachineRegisterInfo.cpp
   MachineScheduler.cpp
   MachineSink.cpp
   MachineSSAUpdater.cpp

lib/CodeGen/InlineSpiller.cpp

 #include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
 #include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
 #include "llvm/CodeGen/MachineDominators.h"
 #include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
 #include "llvm/CodeGen/MachineInstrBundle.h"
 #include "llvm/CodeGen/MachineLoopInfo.h"
+#include "llvm/CodeGen/MachineOptimizationRemarkEmitter.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/CodeGen/VirtRegMap.h"
 #include "llvm/IR/DebugInfo.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Target/TargetInstrInfo.h"
 
class InlineSpiller : public Spiller {
   MachineDominatorTree &MDT;
   MachineLoopInfo &Loops;
   VirtRegMap &VRM;
   MachineFrameInfo &MFI;
   MachineRegisterInfo &MRI;
   const TargetInstrInfo &TII;
   const TargetRegisterInfo &TRI;
   const MachineBlockFrequencyInfo &MBFI;
+  MachineOptimizationRemarkEmitter *ORE;
 
   // Variables that are valid during spill(), but used by multiple methods.
   LiveRangeEdit *Edit;
   LiveInterval *StackInt;
   int StackSlot;
   unsigned Original;
 
   // All registers to spill to StackSlot, including the main register.
class InlineSpiller : public Spiller {
   SmallVector<MachineInstr*, 8> DeadDefs;
 
   // Object records spills information and does the hoisting.
   HoistSpillHelper HSpiller;
 
   ~InlineSpiller() override {}
 
 public:
-  InlineSpiller(MachineFunctionPass &pass, MachineFunction &mf, VirtRegMap &vrm)
+  InlineSpiller(MachineFunctionPass &pass, MachineFunction &mf, VirtRegMap &vrm,
+                MachineOptimizationRemarkEmitter *ORE)
       : MF(mf), LIS(pass.getAnalysis<LiveIntervals>()),
         LSS(pass.getAnalysis<LiveStacks>()),
         AA(&pass.getAnalysis<AAResultsWrapperPass>().getAAResults()),
         MDT(pass.getAnalysis<MachineDominatorTree>()),
         Loops(pass.getAnalysis<MachineLoopInfo>()), VRM(vrm),
         MFI(mf.getFrameInfo()), MRI(mf.getRegInfo()),
         TII(*mf.getSubtarget().getInstrInfo()),
         TRI(*mf.getSubtarget().getRegisterInfo()),
-        MBFI(pass.getAnalysis<MachineBlockFrequencyInfo>()),
+        MBFI(pass.getAnalysis<MachineBlockFrequencyInfo>()), ORE(ORE),
         HSpiller(pass, mf, vrm) {}
 
   void spill(LiveRangeEdit &) override;
   void postOptimization() override;
 
 private:
   bool isSnippet(const LiveInterval &SnipLI);
   void collectRegsToSpill();

 };
 }
 
 namespace llvm {
 
 Spiller::~Spiller() { }
 void Spiller::anchor() { }
 
-Spiller *createInlineSpiller(MachineFunctionPass &pass,
-                             MachineFunction &mf,
-                             VirtRegMap &vrm) {
-  return new InlineSpiller(pass, mf, vrm);
+Spiller *createInlineSpiller(MachineFunctionPass &pass, MachineFunction &mf,
+                             VirtRegMap &vrm,
+                             MachineOptimizationRemarkEmitter *ore) {
+  return new InlineSpiller(pass, mf, vrm, ore);
 }
 
 }
 
 //===----------------------------------------------------------------------===//
 //                                Snippets
 //===----------------------------------------------------------------------===//
 
void InlineSpiller::insertSpill(unsigned NewVReg, bool isKill,
   MachineInstrSpan MIS(MI);
   TII.storeRegToStackSlot(MBB, std::next(MI), NewVReg, isKill, StackSlot,
                           MRI.getRegClass(NewVReg), &TRI);
 
   LIS.InsertMachineInstrRangeInMaps(std::next(MI), MIS.end());
 
   DEBUG(dumpMachineInstrRangeWithSlotIndex(std::next(MI), MIS.end(), LIS,
                                            "spill"));
+  if (ORE)
+    ORE->emit(
+        MachineOptimizationRemark(DEBUG_TYPE, "Spill", MI->getDebugLoc(), &MBB)
+        << "Spilled register");
   ++NumSpills;
   HSpiller.addToMergeableSpills(*std::next(MI), StackSlot, Original);
 }
 
 /// spillAroundUses - insert spill code around each use of Reg.
 void InlineSpiller::spillAroundUses(unsigned Reg) {
   DEBUG(dbgs() << "spillAroundUses " << PrintReg(Reg) << '\n');
   LiveInterval &OldLI = LIS.getInterval(Reg);

lib/CodeGen/MachineOptimizationRemarkEmitter.cpp

+//===- 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.
+//
+//===----------------------------------------------------------------------===//
+//
+// 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(
+    MachineOptimizationRemarkBase &Remark) {
+  MachineBasicBlock *MBB = Remark.getBlock();
+  if (MBB)
+    Remark.setHotness(computeHotness(MBB));
+}
+
+void MachineOptimizationRemarkEmitter::emit(
+    DiagnosticInfoOptimizationCommonBase &OptDiagCommon) {
+  auto *OptDiag = cast<MachineOptimizationRemarkBase>(&OptDiagCommon);
+  computeHotness(*OptDiag);
+
+  LLVMContext &Ctx = MF->getFunction()->getContext();
+  yaml::Output *Out = Ctx.getDiagnosticsOutputFile();
+  if (Out) {
+    auto *P =
+        &const_cast<DiagnosticInfoOptimizationCommonBase &>(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)

lib/CodeGen/RegAllocGreedy.cpp

 #include "llvm/CodeGen/LiveIntervalAnalysis.h"
 #include "llvm/CodeGen/LiveRangeEdit.h"
 #include "llvm/CodeGen/LiveRegMatrix.h"
 #include "llvm/CodeGen/LiveStackAnalysis.h"
 #include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
 #include "llvm/CodeGen/MachineDominators.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"
 #include "llvm/CodeGen/RegisterClassInfo.h"
 #include "llvm/CodeGen/VirtRegMap.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/PassAnalysisSupport.h"
 #include "llvm/Support/BranchProbability.h"
private:
   void collectHintInfo(unsigned, HintsInfo &);
 
   bool isUnusedCalleeSavedReg(unsigned PhysReg) const;
 };
 } // end anonymous namespace
 
 char RAGreedy::ID = 0;
 char &llvm::RAGreedyID = RAGreedy::ID;
 
 INITIALIZE_PASS_BEGIN(RAGreedy, "greedy",
                 "Greedy Register Allocator", false, false)
 INITIALIZE_PASS_DEPENDENCY(LiveDebugVariables)
 INITIALIZE_PASS_DEPENDENCY(SlotIndexes)
 INITIALIZE_PASS_DEPENDENCY(LiveIntervals)
 INITIALIZE_PASS_DEPENDENCY(RegisterCoalescer)
 INITIALIZE_PASS_DEPENDENCY(MachineScheduler)
 INITIALIZE_PASS_DEPENDENCY(LiveStacks)
 INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
 INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo)
 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)
 
 #ifndef NDEBUG
 const char *const RAGreedy::StageName[] = {
     "RS_New",
     "RS_Assign",
     "RS_Split",
void RAGreedy::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.addRequired<MachineLoopInfo>();
   AU.addPreserved<MachineLoopInfo>();
   AU.addRequired<VirtRegMap>();
   AU.addPreserved<VirtRegMap>();
   AU.addRequired<LiveRegMatrix>();
   AU.addPreserved<LiveRegMatrix>();
   AU.addRequired<EdgeBundles>();
   AU.addRequired<SpillPlacement>();
+  AU.addRequired<MachineOptimizationRemarkEmitterPass>();
   MachineFunctionPass::getAnalysisUsage(AU);
 }
 
 
 //===----------------------------------------------------------------------===//
 //                     LiveRangeEdit delegate methods
 //===----------------------------------------------------------------------===//
 
if (VerifyEnabled)
     MF->verify(this, "Before greedy register allocator");
 
   RegAllocBase::init(getAnalysis<VirtRegMap>(),
                      getAnalysis<LiveIntervals>(),
                      getAnalysis<LiveRegMatrix>());
   Indexes = &getAnalysis<SlotIndexes>();
   MBFI = &getAnalysis<MachineBlockFrequencyInfo>();
   DomTree = &getAnalysis<MachineDominatorTree>();
-  SpillerInstance.reset(createInlineSpiller(*this, *MF, *VRM));
+  auto *ORE = &getAnalysis<MachineOptimizationRemarkEmitterPass>().getORE();
+  SpillerInstance.reset(createInlineSpiller(*this, *MF, *VRM, ORE));
   Loops = &getAnalysis<MachineLoopInfo>();
   Bundles = &getAnalysis<EdgeBundles>();
   SpillPlacer = &getAnalysis<SpillPlacement>();
   DebugVars = &getAnalysis<LiveDebugVariables>();
   AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
 
   initializeCSRCost();
 

lib/CodeGen/Spiller.h

 #ifndef LLVM_LIB_CODEGEN_SPILLER_H
 #define LLVM_LIB_CODEGEN_SPILLER_H
 
 namespace llvm {
 
   class LiveRangeEdit;
   class MachineFunction;
   class MachineFunctionPass;
+  class MachineOptimizationRemarkEmitter;
   class VirtRegMap;
   class LiveIntervals;
 
   /// Spiller interface.
   ///
   /// Implementations are utility classes which insert spill or remat code on
   /// demand.
   class Spiller {
     virtual void anchor();
   public:
     virtual ~Spiller() = 0;
 
     /// spill - Spill the LRE.getParent() live interval.
     virtual void spill(LiveRangeEdit &LRE) = 0;
     virtual void postOptimization(){};
   };
 
   /// Create and return a spiller that will insert spill code directly instead
   /// of deferring though VirtRegMap.
-  Spiller *createInlineSpiller(MachineFunctionPass &pass,
-                               MachineFunction &mf,
-                               VirtRegMap &vrm);
+  Spiller *createInlineSpiller(MachineFunctionPass &pass, MachineFunction &mf,
+                               VirtRegMap &vrm,
+                               MachineOptimizationRemarkEmitter *ORE = nullptr);
 }
 
 #endif

lib/IR/DiagnosticInfo.cpp

 
 OptimizationRemark::OptimizationRemark(const char *PassName,
                                        StringRef RemarkName, Instruction *Inst)
     : DiagnosticInfoOptimizationBase(DK_OptimizationRemark, DS_Remark, 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,
                                                    StringRef RemarkName,
                                                    const DebugLoc &DLoc,
                                                    Value *CodeRegion)
     : DiagnosticInfoOptimizationBase(
           DK_OptimizationRemarkMissed, DS_Remark, PassName, RemarkName,
           *cast<BasicBlock>(CodeRegion)->getParent(), DLoc, CodeRegion) {}
 
 OptimizationRemarkMissed::OptimizationRemarkMissed(const char *PassName,
                                                    StringRef RemarkName,
                                                    Instruction *Inst)
     : DiagnosticInfoOptimizationBase(DK_OptimizationRemarkMissed, DS_Remark,
                                      PassName, RemarkName,
                                      *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,
                                                        StringRef RemarkName,
                                                        const DebugLoc &DLoc,
                                                        Value *CodeRegion)
     : DiagnosticInfoOptimizationBase(
           DK_OptimizationRemarkAnalysis, DS_Remark, PassName, RemarkName,
OptimizationRemarkAnalysis::OptimizationRemarkAnalysis(enum DiagnosticKind Kind,
                                                        const char *PassName,
                                                        StringRef RemarkName,
                                                        const DebugLoc &DLoc,
                                                        Value *CodeRegion)
     : DiagnosticInfoOptimizationBase(Kind, DS_Remark, PassName, RemarkName,
                                      *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 {
   DP << Diagnostic;
 }
 
 void llvm::emitOptimizationRemark(LLVMContext &Ctx, const char *PassName,
                                   const Function &Fn, const DebugLoc &DLoc,

test/CodeGen/AArch64/arm64-spill-remarks.ll

+; RUN: llc < %s -mtriple=arm64-apple-ios7.0 -aarch64-neon-syntax=apple -pass-remarks=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
+
+; REMARK: remark: /tmp/kk.c:2:20: Spilled register
+; NO_REMARK-NOT: remark: /tmp/kk.c:2:20: Spilled register
+
+define void @fpr128(<4 x float>* %p) nounwind ssp {
+entry:
+  %x = load <4 x float>, <4 x float>* %p, align 16, !dbg !8
+  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, !dbg !9
+  store <4 x float> %x, <4 x float>* %p, align 16, !dbg !10
+  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: 2, column: 20, scope: !6)
+!9 = !DILocation(line: 3, column: 20, scope: !6)
+!10 = !DILocation(line: 4, column: 20, scope: !6)

tools/llc/llc.cpp

GetOutputStream(const char *TargetName, Triple::OSType OS,
   return FDOut;
 }
 
 static void DiagnosticHandler(const DiagnosticInfo &DI, void *Context) {
   bool *HasError = static_cast<bool *>(Context);
   if (DI.getSeverity() == DS_Error)
     *HasError = true;
 
+  if (auto *Remark = dyn_cast<DiagnosticInfoOptimizationCommonBase>(&DI))
+    if (!Remark->isEnabled())
+      return;
+
   DiagnosticPrinterRawOStream DP(errs());
   errs() << LLVMContext::getDiagnosticMessagePrefix(DI.getSeverity()) << ": ";
   DI.print(DP);
   errs() << "\n";
 }
 
 // main - Entry point for the llc compiler.
 //