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/CallGraph.h"
18 #include "llvm/Analysis/InlineCost.h"
19 #include "llvm/IR/CallSite.h"
20 #include "llvm/IR/CallingConv.h"
21 #include "llvm/IR/DataLayout.h"
22 #include "llvm/IR/Instructions.h"
23 #include "llvm/IR/IntrinsicInst.h"
24 #include "llvm/IR/Module.h"
25 #include "llvm/IR/Type.h"
26 #include "llvm/Transforms/IPO/InlinerPass.h"
30 #define DEBUG_TYPE "inline"
34 /// \brief Inliner pass which only handles "always inline" functions.
35 class AlwaysInliner : public Inliner {
36 InlineCostAnalysis *ICA;
39 // Use extremely low threshold.
40 AlwaysInliner() : Inliner(ID, -2000000000, /*InsertLifetime*/ true),
42 initializeAlwaysInlinerPass(*PassRegistry::getPassRegistry());
45 AlwaysInliner(bool InsertLifetime)
46 : Inliner(ID, -2000000000, InsertLifetime), ICA(nullptr) {
47 initializeAlwaysInlinerPass(*PassRegistry::getPassRegistry());
50 static char ID; // Pass identification, replacement for typeid
52 InlineCost getInlineCost(CallSite CS) override;
54 void getAnalysisUsage(AnalysisUsage &AU) const override;
55 bool runOnSCC(CallGraphSCC &SCC) override;
57 using llvm::Pass::doFinalization;
58 bool doFinalization(CallGraph &CG) override {
59 return removeDeadFunctions(CG, /*AlwaysInlineOnly=*/ true);
65 char AlwaysInliner::ID = 0;
66 INITIALIZE_PASS_BEGIN(AlwaysInliner, "always-inline",
67 "Inliner for always_inline functions", false, false)
68 INITIALIZE_PASS_DEPENDENCY(CallGraphWrapperPass)
69 INITIALIZE_PASS_DEPENDENCY(InlineCostAnalysis)
70 INITIALIZE_PASS_END(AlwaysInliner, "always-inline",
71 "Inliner for always_inline functions", false, false)
73 Pass *llvm::createAlwaysInlinerPass() { return new AlwaysInliner(); }
75 Pass *llvm::createAlwaysInlinerPass(bool InsertLifetime) {
76 return new AlwaysInliner(InsertLifetime);
79 /// \brief Get the inline cost for the always-inliner.
81 /// The always inliner *only* handles functions which are marked with the
82 /// attribute to force inlining. As such, it is dramatically simpler and avoids
83 /// using the powerful (but expensive) inline cost analysis. Instead it uses
84 /// a very simple and boring direct walk of the instructions looking for
85 /// impossible-to-inline constructs.
87 /// Note, it would be possible to go to some lengths to cache the information
88 /// computed here, but as we only expect to do this for relatively few and
89 /// small functions which have the explicit attribute to force inlining, it is
90 /// likely not worth it in practice.
91 InlineCost AlwaysInliner::getInlineCost(CallSite CS) {
92 Function *Callee = CS.getCalledFunction();
94 // Only inline direct calls to functions with always-inline attributes
95 // that are viable for inlining. FIXME: We shouldn't even get here for
97 if (Callee && !Callee->isDeclaration() &&
98 CS.hasFnAttr(Attribute::AlwaysInline) &&
99 ICA->isInlineViable(*Callee))
100 return InlineCost::getAlways();
102 return InlineCost::getNever();
105 bool AlwaysInliner::runOnSCC(CallGraphSCC &SCC) {
106 ICA = &getAnalysis<InlineCostAnalysis>();
107 return Inliner::runOnSCC(SCC);
110 void AlwaysInliner::getAnalysisUsage(AnalysisUsage &AU) const {
111 AU.addRequired<InlineCostAnalysis>();
112 Inliner::getAnalysisUsage(AU);