llvm/tools/llvm-profgen/CSPreInliner.h

   1 //===-- CSPreInliner.h - Profile guided preinliner ---------------- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef LLVM_TOOLS_LLVM_PROFGEN_PGOINLINEADVISOR_H
  10 #define LLVM_TOOLS_LLVM_PROFGEN_PGOINLINEADVISOR_H
  11
  12 #include "ProfiledBinary.h"
  13 #include "llvm/ADT/PriorityQueue.h"
  14 #include "llvm/ProfileData/ProfileCommon.h"
  15 #include "llvm/ProfileData/SampleProf.h"
  16 #include "llvm/Transforms/IPO/ProfiledCallGraph.h"
  17 #include "llvm/Transforms/IPO/SampleContextTracker.h"
  18
  19 using namespace llvm;
  20 using namespace sampleprof;
  21
  22 namespace llvm {
  23 namespace sampleprof {
  24
  25 // Inline candidate seen from profile
  26 struct ProfiledInlineCandidate {
  27   ProfiledInlineCandidate(const FunctionSamples *Samples, uint64_t Count,
  28                           uint32_t Size)
  29       : CalleeSamples(Samples), CallsiteCount(Count), SizeCost(Size) {}
  30   // Context-sensitive function profile for inline candidate
  31   const FunctionSamples *CalleeSamples;
  32   // Call site count for an inline candidate
  33   // TODO: make sure entry count for context profile and call site
  34   // target count for corresponding call are consistent.
  35   uint64_t CallsiteCount;
  36   // Size proxy for function under particular call context.
  37   uint64_t SizeCost;
  38 };
  39
  40 // Inline candidate comparer using call site weight
  41 struct ProfiledCandidateComparer {
  42   bool operator()(const ProfiledInlineCandidate &LHS,
  43                   const ProfiledInlineCandidate &RHS) {
  44     // Always prioritize inlining zero-sized functions as they do not affect the
  45     // size budget. This could happen when all of the callee's code is gone and
  46     // only pseudo probes are left.
  47     if ((LHS.SizeCost == 0 || RHS.SizeCost == 0) &&
  48         (LHS.SizeCost != RHS.SizeCost))
  49       return RHS.SizeCost == 0;
  50
  51     if (LHS.CallsiteCount != RHS.CallsiteCount)
  52       return LHS.CallsiteCount < RHS.CallsiteCount;
  53
  54     if (LHS.SizeCost != RHS.SizeCost)
  55       return LHS.SizeCost > RHS.SizeCost;
  56
  57     // Tie breaker using GUID so we have stable/deterministic inlining order
  58     assert(LHS.CalleeSamples && RHS.CalleeSamples &&
  59            "Expect non-null FunctionSamples");
  60     return LHS.CalleeSamples->getGUID() < RHS.CalleeSamples->getGUID();
  61   }
  62 };
  63
  64 using ProfiledCandidateQueue =
  65     PriorityQueue<ProfiledInlineCandidate, std::vector<ProfiledInlineCandidate>,
  66                   ProfiledCandidateComparer>;
  67
  68 // Pre-compilation inliner based on context-sensitive profile.
  69 // The PreInliner estimates inline decision using hotness from profile
  70 // and cost estimation from machine code size. It helps merges context
  71 // profile globally and achieves better post-inine profile quality, which
  72 // otherwise won't be possible for ThinLTO. It also reduce context profile
  73 // size by only keep context that is estimated to be inlined.
  74 class CSPreInliner {
  75 public:
  76   CSPreInliner(SampleContextTracker &Tracker, ProfiledBinary &Binary,
  77                ProfileSummary *Summary);
  78   void run();
  79
  80 private:
  81   bool getInlineCandidates(ProfiledCandidateQueue &CQueue,
  82                            const FunctionSamples *FCallerContextSamples);
  83   std::vector<FunctionId> buildTopDownOrder();
  84   void processFunction(FunctionId Name);
  85   bool shouldInline(ProfiledInlineCandidate &Candidate);
  86   uint32_t getFuncSize(const ContextTrieNode *ContextNode);
  87   bool UseContextCost;
  88   SampleContextTracker &ContextTracker;
  89   ProfiledBinary &Binary;
  90   ProfileSummary *Summary;
  91 };
  92
  93 } // end namespace sampleprof
  94 } // end namespace llvm
  95
  96 #endif