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

llvm-svn: 293110

5 files changed, 226 insertions, 5 deletions

diff --git a/llvm/include/llvm/Analysis/OptimizationDiagnosticInfo.h b/llvm/include/llvm/Analysis/OptimizationDiagnosticInfo.h
index fd821a47a41..426fbb548e6 100644
--- a/llvm/include/llvm/Analysis/OptimizationDiagnosticInfo.h
+++ b/llvm/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
diff --git a/llvm/include/llvm/CodeGen/MachineLoopInfo.h b/llvm/include/llvm/CodeGen/MachineLoopInfo.h
index dc72ae1810e..5c814f22f99 100644
--- a/llvm/include/llvm/CodeGen/MachineLoopInfo.h
+++ b/llvm/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:
diff --git a/llvm/include/llvm/CodeGen/MachineOptimizationRemarkEmitter.h b/llvm/include/llvm/CodeGen/MachineOptimizationRemarkEmitter.h
new file mode 100644
index 00000000000..fd48347d51a
--- /dev/null
+++ b/llvm/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
diff --git a/llvm/include/llvm/IR/DiagnosticInfo.h b/llvm/include/llvm/IR/DiagnosticInfo.h
index afa7bba524a..23b37a08a85 100644
--- a/llvm/include/llvm/IR/DiagnosticInfo.h
+++ b/llvm/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;
 
diff --git a/llvm/include/llvm/InitializePasses.h b/llvm/include/llvm/InitializePasses.h
index c59dfee9693..a6cc44d4387 100644
--- a/llvm/include/llvm/InitializePasses.h
+++ b/llvm/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&);