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/InlineAdvisor.h"
19#include "llvm/Analysis/InlineCost.h"
20#include "llvm/Analysis/OptimizationRemarkEmitter.h"
21#include "llvm/Analysis/ProfileSummaryInfo.h"
22#include "llvm/IR/Module.h"
23#include "llvm/InitializePasses.h"
24#include "llvm/Transforms/Utils/Cloning.h"
25#include "llvm/Transforms/Utils/ModuleUtils.h"
26
27using namespace llvm;
28
29#define DEBUG_TYPE "inline"
30
31namespace {
32
33bool AlwaysInlineImpl(
34 Module &M, bool InsertLifetime, ProfileSummaryInfo &PSI,
35 FunctionAnalysisManager *FAM,
36 function_ref<AssumptionCache &(Function &)> GetAssumptionCache,
37 function_ref<AAResults &(Function &)> GetAAR) {
38 SmallSetVector<CallBase *, 16> Calls;
39 bool Changed = false;
40 SmallVector<Function *, 16> InlinedComdatFunctions;
41
42 for (Function &F : make_early_inc_range(Range&: M)) {
43 if (F.isPresplitCoroutine())
44 continue;
45
46 if (F.isDeclaration() || !isInlineViable(Callee&: F).isSuccess())
47 continue;
48
49 Calls.clear();
50
51 for (User *U : F.users())
52 if (auto *CB = dyn_cast<CallBase>(Val: U))
53 if (CB->getCalledFunction() == &F &&
54 CB->hasFnAttr(Kind: Attribute::AlwaysInline) &&
55 !CB->getAttributes().hasFnAttr(Kind: Attribute::NoInline))
56 Calls.insert(X: CB);
57
58 for (CallBase *CB : Calls) {
59 Function *Caller = CB->getCaller();
60 OptimizationRemarkEmitter ORE(Caller);
61 DebugLoc DLoc = CB->getDebugLoc();
62 BasicBlock *Block = CB->getParent();
63
64 InlineFunctionInfo IFI(GetAssumptionCache, &PSI, nullptr, nullptr);
65 InlineResult Res = InlineFunction(CB&: *CB, IFI, /*MergeAttributes=*/true,
66 CalleeAAR: &GetAAR(F), InsertLifetime);
67 if (!Res.isSuccess()) {
68 ORE.emit(RemarkBuilder: [&]() {
69 return OptimizationRemarkMissed(DEBUG_TYPE, "NotInlined", DLoc, Block)
70 << "'" << ore::NV("Callee", &F) << "' is not inlined into '"
71 << ore::NV("Caller", Caller)
72 << "': " << ore::NV("Reason", Res.getFailureReason());
73 });
74 continue;
75 }
76
77 emitInlinedIntoBasedOnCost(
78 ORE, DLoc, Block, Callee: F, Caller: *Caller,
79 IC: InlineCost::getAlways(Reason: "always inline attribute"),
80 /*ForProfileContext=*/false, DEBUG_TYPE);
81
82 Changed = true;
83 if (FAM)
84 FAM->invalidate(IR&: *Caller, PA: PreservedAnalyses::none());
85 }
86
87 F.removeDeadConstantUsers();
88 if (F.hasFnAttribute(Kind: Attribute::AlwaysInline) && F.isDefTriviallyDead()) {
89 // Remember to try and delete this function afterward. This allows to call
90 // filterDeadComdatFunctions() only once.
91 if (F.hasComdat()) {
92 InlinedComdatFunctions.push_back(Elt: &F);
93 } else {
94 if (FAM)
95 FAM->clear(IR&: F, Name: F.getName());
96 M.getFunctionList().erase(IT&: F);
97 Changed = true;
98 }
99 }
100 }
101
102 if (!InlinedComdatFunctions.empty()) {
103 // Now we just have the comdat functions. Filter out the ones whose comdats
104 // are not actually dead.
105 filterDeadComdatFunctions(DeadComdatFunctions&: InlinedComdatFunctions);
106 // The remaining functions are actually dead.
107 for (Function *F : InlinedComdatFunctions) {
108 if (FAM)
109 FAM->clear(IR&: *F, Name: F->getName());
110 M.getFunctionList().erase(IT: F);
111 Changed = true;
112 }
113 }
114
115 return Changed;
116}
117
118struct AlwaysInlinerLegacyPass : public ModulePass {
119 bool InsertLifetime;
120
121 AlwaysInlinerLegacyPass()
122 : AlwaysInlinerLegacyPass(/*InsertLifetime*/ true) {}
123
124 AlwaysInlinerLegacyPass(bool InsertLifetime)
125 : ModulePass(ID), InsertLifetime(InsertLifetime) {}
126
127 /// Main run interface method.
128 bool runOnModule(Module &M) override {
129
130 auto &PSI = getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI();
131 auto GetAAR = [&](Function &F) -> AAResults & {
132 return getAnalysis<AAResultsWrapperPass>(F).getAAResults();
133 };
134 auto GetAssumptionCache = [&](Function &F) -> AssumptionCache & {
135 return getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
136 };
137
138 return AlwaysInlineImpl(M, InsertLifetime, PSI, /*FAM=*/nullptr,
139 GetAssumptionCache, GetAAR);
140 }
141
142 static char ID; // Pass identification, replacement for typeid
143
144 void getAnalysisUsage(AnalysisUsage &AU) const override {
145 AU.addRequired<AssumptionCacheTracker>();
146 AU.addRequired<AAResultsWrapperPass>();
147 AU.addRequired<ProfileSummaryInfoWrapperPass>();
148 }
149};
150
151} // namespace
152
153char AlwaysInlinerLegacyPass::ID = 0;
154INITIALIZE_PASS_BEGIN(AlwaysInlinerLegacyPass, "always-inline",
155 "Inliner for always_inline functions", false, false)
156INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
157INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
158INITIALIZE_PASS_DEPENDENCY(ProfileSummaryInfoWrapperPass)
159INITIALIZE_PASS_END(AlwaysInlinerLegacyPass, "always-inline",
160 "Inliner for always_inline functions", false, false)
161
162Pass *llvm::createAlwaysInlinerLegacyPass(bool InsertLifetime) {
163 return new AlwaysInlinerLegacyPass(InsertLifetime);
164}
165
166PreservedAnalyses AlwaysInlinerPass::run(Module &M,
167 ModuleAnalysisManager &MAM) {
168 FunctionAnalysisManager &FAM =
169 MAM.getResult<FunctionAnalysisManagerModuleProxy>(IR&: M).getManager();
170 auto GetAssumptionCache = [&](Function &F) -> AssumptionCache & {
171 return FAM.getResult<AssumptionAnalysis>(IR&: F);
172 };
173 auto GetAAR = [&](Function &F) -> AAResults & {
174 return FAM.getResult<AAManager>(IR&: F);
175 };
176 auto &PSI = MAM.getResult<ProfileSummaryAnalysis>(IR&: M);
177
178 bool Changed = AlwaysInlineImpl(M, InsertLifetime, PSI, FAM: &FAM,
179 GetAssumptionCache, GetAAR);
180 if (!Changed)
181 return PreservedAnalyses::all();
182
183 PreservedAnalyses PA;
184 // We have already invalidated all analyses on modified functions.
185 PA.preserveSet<AllAnalysesOn<Function>>();
186 return PA;
187}
188