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     if (LHS.CallsiteCount != RHS.CallsiteCount)
45       return LHS.CallsiteCount < RHS.CallsiteCount;
46 
47     if (LHS.SizeCost != RHS.SizeCost)
48       return LHS.SizeCost > RHS.SizeCost;
49 
50     // Tie breaker using GUID so we have stable/deterministic inlining order
51     assert(LHS.CalleeSamples && RHS.CalleeSamples &&
52            "Expect non-null FunctionSamples");
53     return LHS.CalleeSamples->getGUID(LHS.CalleeSamples->getName()) <
54            RHS.CalleeSamples->getGUID(RHS.CalleeSamples->getName());
55   }
56 };
57 
58 using ProfiledCandidateQueue =
59     PriorityQueue<ProfiledInlineCandidate, std::vector<ProfiledInlineCandidate>,
60                   ProfiledCandidateComparer>;
61 
62 // Pre-compilation inliner based on context-sensitive profile.
63 // The PreInliner estimates inline decision using hotness from profile
64 // and cost estimation from machine code size. It helps merges context
65 // profile globally and achieves better post-inine profile quality, which
66 // otherwise won't be possible for ThinLTO. It also reduce context profile
67 // size by only keep context that is estimated to be inlined.
68 class CSPreInliner {
69 public:
70   CSPreInliner(SampleContextTracker &Tracker, ProfiledBinary &Binary,
71                ProfileSummary *Summary);
72   void run();
73 
74 private:
75   bool getInlineCandidates(ProfiledCandidateQueue &CQueue,
76                            const FunctionSamples *FCallerContextSamples);
77   std::vector<StringRef> buildTopDownOrder();
78   void processFunction(StringRef Name);
79   bool shouldInline(ProfiledInlineCandidate &Candidate);
80   uint32_t getFuncSize(const ContextTrieNode *ContextNode);
81   bool UseContextCost;
82   SampleContextTracker &ContextTracker;
83   ProfiledBinary &Binary;
84   ProfileSummary *Summary;
85 };
86 
87 } // end namespace sampleprof
88 } // end namespace llvm
89 
90 #endif
91