1 //===- AlwaysInliner.cpp - Code to inline always_inline functions ----------===//
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 // This file implements a custom inliner that handles only functions that
10 // are marked as "always inline".
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "llvm/Transforms/IPO/AlwaysInliner.h"
15 #include "llvm/ADT/SetVector.h"
16 #include "llvm/Analysis/AliasAnalysis.h"
17 #include "llvm/Analysis/AssumptionCache.h"
18 #include "llvm/Analysis/InlineCost.h"
19 #include "llvm/Analysis/OptimizationRemarkEmitter.h"
20 #include "llvm/Analysis/ProfileSummaryInfo.h"
21 #include "llvm/IR/Module.h"
22 #include "llvm/InitializePasses.h"
23 #include "llvm/Transforms/IPO/Inliner.h"
24 #include "llvm/Transforms/Utils/Cloning.h"
25 #include "llvm/Transforms/Utils/ModuleUtils.h"
26 
27 using namespace llvm;
28 
29 #define DEBUG_TYPE "inline"
30 
31 namespace {
32 
33 bool AlwaysInlineImpl(
34     Module &M, bool InsertLifetime, ProfileSummaryInfo &PSI,
35     function_ref<AssumptionCache &(Function &)> GetAssumptionCache,
36     function_ref<AAResults &(Function &)> GetAAR,
37     function_ref<BlockFrequencyInfo &(Function &)> GetBFI) {
38   SmallSetVector<CallBase *, 16> Calls;
39   bool Changed = false;
40   SmallVector<Function *, 16> InlinedFunctions;
41   for (Function &F : M) {
42     // When callee coroutine function is inlined into caller coroutine function
43     // before coro-split pass,
44     // coro-early pass can not handle this quiet well.
45     // So we won't inline the coroutine function if it have not been unsplited
46     if (F.isPresplitCoroutine())
47       continue;
48 
49     if (!F.isDeclaration() && isInlineViable(F).isSuccess()) {
50       Calls.clear();
51 
52       for (User *U : F.users())
53         if (auto *CB = dyn_cast<CallBase>(U))
54           if (CB->getCalledFunction() == &F &&
55                 CB->hasFnAttr(Attribute::AlwaysInline) &&
56                 !CB->getAttributes().hasFnAttr(Attribute::NoInline))
57               Calls.insert(CB);
58 
59       for (CallBase *CB : Calls) {
60         Function *Caller = CB->getCaller();
61         OptimizationRemarkEmitter ORE(Caller);
62         DebugLoc DLoc = CB->getDebugLoc();
63         BasicBlock *Block = CB->getParent();
64 
65         InlineFunctionInfo IFI(GetAssumptionCache, &PSI,
66                                GetBFI ? &GetBFI(*Caller) : nullptr,
67                                GetBFI ? &GetBFI(F) : nullptr);
68 
69         InlineResult Res = InlineFunction(*CB, IFI, /*MergeAttributes=*/true,
70                                           &GetAAR(F), InsertLifetime);
71         if (!Res.isSuccess()) {
72           ORE.emit([&]() {
73             return OptimizationRemarkMissed(DEBUG_TYPE, "NotInlined", DLoc,
74                                             Block)
75                    << "'" << ore::NV("Callee", &F) << "' is not inlined into '"
76                    << ore::NV("Caller", Caller)
77                    << "': " << ore::NV("Reason", Res.getFailureReason());
78           });
79           continue;
80         }
81 
82         emitInlinedIntoBasedOnCost(
83             ORE, DLoc, Block, F, *Caller,
84             InlineCost::getAlways("always inline attribute"),
85             /*ForProfileContext=*/false, DEBUG_TYPE);
86 
87         Changed = true;
88       }
89 
90       if (F.hasFnAttribute(Attribute::AlwaysInline)) {
91         // Remember to try and delete this function afterward. This both avoids
92         // re-walking the rest of the module and avoids dealing with any
93         // iterator invalidation issues while deleting functions.
94         InlinedFunctions.push_back(&F);
95       }
96     }
97   }
98 
99   // Remove any live functions.
100   erase_if(InlinedFunctions, [&](Function *F) {
101     F->removeDeadConstantUsers();
102     return !F->isDefTriviallyDead();
103   });
104 
105   // Delete the non-comdat ones from the module and also from our vector.
106   auto NonComdatBegin = partition(
107       InlinedFunctions, [&](Function *F) { return F->hasComdat(); });
108   for (Function *F : make_range(NonComdatBegin, InlinedFunctions.end())) {
109     M.getFunctionList().erase(F);
110     Changed = true;
111   }
112   InlinedFunctions.erase(NonComdatBegin, InlinedFunctions.end());
113 
114   if (!InlinedFunctions.empty()) {
115     // Now we just have the comdat functions. Filter out the ones whose comdats
116     // are not actually dead.
117     filterDeadComdatFunctions(InlinedFunctions);
118     // The remaining functions are actually dead.
119     for (Function *F : InlinedFunctions) {
120       M.getFunctionList().erase(F);
121       Changed = true;
122     }
123   }
124 
125   return Changed;
126 }
127 
128 struct AlwaysInlinerLegacyPass : public ModulePass {
129   bool InsertLifetime;
130 
131   AlwaysInlinerLegacyPass()
132       : AlwaysInlinerLegacyPass(/*InsertLifetime*/ true) {}
133 
134   AlwaysInlinerLegacyPass(bool InsertLifetime)
135       : ModulePass(ID), InsertLifetime(InsertLifetime) {
136     initializeAlwaysInlinerLegacyPassPass(*PassRegistry::getPassRegistry());
137   }
138 
139   /// Main run interface method.  We override here to avoid calling skipSCC().
140   bool runOnModule(Module &M) override {
141 
142     auto &PSI = getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI();
143     auto GetAAR = [&](Function &F) -> AAResults & {
144       return getAnalysis<AAResultsWrapperPass>(F).getAAResults();
145     };
146     auto GetAssumptionCache = [&](Function &F) -> AssumptionCache & {
147       return getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
148     };
149 
150     return AlwaysInlineImpl(M, InsertLifetime, PSI, GetAssumptionCache, GetAAR,
151                             /*GetBFI*/ nullptr);
152   }
153 
154   static char ID; // Pass identification, replacement for typeid
155 
156   void getAnalysisUsage(AnalysisUsage &AU) const override {
157     AU.addRequired<AssumptionCacheTracker>();
158     AU.addRequired<AAResultsWrapperPass>();
159     AU.addRequired<ProfileSummaryInfoWrapperPass>();
160   }
161 };
162 
163 } // namespace
164 
165 char AlwaysInlinerLegacyPass::ID = 0;
166 INITIALIZE_PASS_BEGIN(AlwaysInlinerLegacyPass, "always-inline",
167                       "Inliner for always_inline functions", false, false)
168 INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
169 INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
170 INITIALIZE_PASS_DEPENDENCY(ProfileSummaryInfoWrapperPass)
171 INITIALIZE_PASS_END(AlwaysInlinerLegacyPass, "always-inline",
172                     "Inliner for always_inline functions", false, false)
173 
174 Pass *llvm::createAlwaysInlinerLegacyPass(bool InsertLifetime) {
175   return new AlwaysInlinerLegacyPass(InsertLifetime);
176 }
177 
178 PreservedAnalyses AlwaysInlinerPass::run(Module &M,
179                                          ModuleAnalysisManager &MAM) {
180   FunctionAnalysisManager &FAM =
181       MAM.getResult<FunctionAnalysisManagerModuleProxy>(M).getManager();
182   auto GetAssumptionCache = [&](Function &F) -> AssumptionCache & {
183     return FAM.getResult<AssumptionAnalysis>(F);
184   };
185   auto GetBFI = [&](Function &F) -> BlockFrequencyInfo & {
186     return FAM.getResult<BlockFrequencyAnalysis>(F);
187   };
188   auto GetAAR = [&](Function &F) -> AAResults & {
189     return FAM.getResult<AAManager>(F);
190   };
191   auto &PSI = MAM.getResult<ProfileSummaryAnalysis>(M);
192 
193   bool Changed = AlwaysInlineImpl(M, InsertLifetime, PSI, GetAssumptionCache,
194                                   GetAAR, GetBFI);
195 
196   return Changed ? PreservedAnalyses::none() : PreservedAnalyses::all();
197 }
198