1 //===- InlineAlways.cpp - Code to inline always_inline functions ----------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements a custom inliner that handles only functions that
11 // are marked as "always inline".
13 //===----------------------------------------------------------------------===//
15 #include "llvm/Transforms/IPO.h"
16 #include "llvm/ADT/SmallPtrSet.h"
17 #include "llvm/Analysis/AliasAnalysis.h"
18 #include "llvm/Analysis/CallGraph.h"
19 #include "llvm/Analysis/InlineCost.h"
20 #include "llvm/IR/CallSite.h"
21 #include "llvm/IR/CallingConv.h"
22 #include "llvm/IR/DataLayout.h"
23 #include "llvm/IR/Instructions.h"
24 #include "llvm/IR/IntrinsicInst.h"
25 #include "llvm/IR/Module.h"
26 #include "llvm/IR/Type.h"
27 #include "llvm/Transforms/IPO/InlinerPass.h"
31 #define DEBUG_TYPE "inline"
35 /// \brief Inliner pass which only handles "always inline" functions.
36 class AlwaysInliner : public Inliner {
37 InlineCostAnalysis *ICA;
40 // Use extremely low threshold.
41 AlwaysInliner() : Inliner(ID, -2000000000, /*InsertLifetime*/ true),
43 initializeAlwaysInlinerPass(*PassRegistry::getPassRegistry());
46 AlwaysInliner(bool InsertLifetime)
47 : Inliner(ID, -2000000000, InsertLifetime), ICA(nullptr) {
48 initializeAlwaysInlinerPass(*PassRegistry::getPassRegistry());
51 static char ID; // Pass identification, replacement for typeid
53 InlineCost getInlineCost(CallSite CS) override;
55 void getAnalysisUsage(AnalysisUsage &AU) const override;
56 bool runOnSCC(CallGraphSCC &SCC) override;
58 using llvm::Pass::doFinalization;
59 bool doFinalization(CallGraph &CG) override {
60 return removeDeadFunctions(CG, /*AlwaysInlineOnly=*/ true);
66 char AlwaysInliner::ID = 0;
67 INITIALIZE_PASS_BEGIN(AlwaysInliner, "always-inline",
68 "Inliner for always_inline functions", false, false)
69 INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
70 INITIALIZE_PASS_DEPENDENCY(CallGraphWrapperPass)
71 INITIALIZE_PASS_DEPENDENCY(InlineCostAnalysis)
72 INITIALIZE_PASS_END(AlwaysInliner, "always-inline",
73 "Inliner for always_inline functions", false, false)
75 Pass *llvm::createAlwaysInlinerPass() { return new AlwaysInliner(); }
77 Pass *llvm::createAlwaysInlinerPass(bool InsertLifetime) {
78 return new AlwaysInliner(InsertLifetime);
81 /// \brief Get the inline cost for the always-inliner.
83 /// The always inliner *only* handles functions which are marked with the
84 /// attribute to force inlining. As such, it is dramatically simpler and avoids
85 /// using the powerful (but expensive) inline cost analysis. Instead it uses
86 /// a very simple and boring direct walk of the instructions looking for
87 /// impossible-to-inline constructs.
89 /// Note, it would be possible to go to some lengths to cache the information
90 /// computed here, but as we only expect to do this for relatively few and
91 /// small functions which have the explicit attribute to force inlining, it is
92 /// likely not worth it in practice.
93 InlineCost AlwaysInliner::getInlineCost(CallSite CS) {
94 Function *Callee = CS.getCalledFunction();
96 // Only inline direct calls to functions with always-inline attributes
97 // that are viable for inlining. FIXME: We shouldn't even get here for
99 if (Callee && !Callee->isDeclaration() &&
100 CS.hasFnAttr(Attribute::AlwaysInline) &&
101 ICA->isInlineViable(*Callee))
102 return InlineCost::getAlways();
104 return InlineCost::getNever();
107 bool AlwaysInliner::runOnSCC(CallGraphSCC &SCC) {
108 ICA = &getAnalysis<InlineCostAnalysis>();
109 return Inliner::runOnSCC(SCC);
112 void AlwaysInliner::getAnalysisUsage(AnalysisUsage &AU) const {
113 AU.addRequired<InlineCostAnalysis>();
114 Inliner::getAnalysisUsage(AU);