1 //===- InlineAlways.cpp - Code to inline always_inline functions ----------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file implements a custom inliner that handles only functions that 11 // are marked as "always inline". 12 // 13 //===----------------------------------------------------------------------===// 14 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" 27 28 using namespace llvm; 29 30 #define DEBUG_TYPE "inline" 31 32 namespace { 33 34 /// \brief Inliner pass which only handles "always inline" functions. 35 class AlwaysInliner : public Inliner { 36 InlineCostAnalysis *ICA; 37 38 public: 39 // Use extremely low threshold. 40 AlwaysInliner() : Inliner(ID, -2000000000, /*InsertLifetime*/ true), 41 ICA(nullptr) { 42 initializeAlwaysInlinerPass(*PassRegistry::getPassRegistry()); 43 } 44 45 AlwaysInliner(bool InsertLifetime) 46 : Inliner(ID, -2000000000, InsertLifetime), ICA(nullptr) { 47 initializeAlwaysInlinerPass(*PassRegistry::getPassRegistry()); 48 } 49 50 static char ID; // Pass identification, replacement for typeid 51 52 InlineCost getInlineCost(CallSite CS) override; 53 54 void getAnalysisUsage(AnalysisUsage &AU) const override; 55 bool runOnSCC(CallGraphSCC &SCC) override; 56 57 using llvm::Pass::doFinalization; 58 bool doFinalization(CallGraph &CG) override { 59 return removeDeadFunctions(CG, /*AlwaysInlineOnly=*/ true); 60 } 61 }; 62 63 } 64 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) 72 73 Pass *llvm::createAlwaysInlinerPass() { return new AlwaysInliner(); } 74 75 Pass *llvm::createAlwaysInlinerPass(bool InsertLifetime) { 76 return new AlwaysInliner(InsertLifetime); 77 } 78 79 /// \brief Get the inline cost for the always-inliner. 80 /// 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. 86 /// 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(); 93 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 96 // declarations. 97 if (Callee && !Callee->isDeclaration() && 98 CS.hasFnAttr(Attribute::AlwaysInline) && 99 ICA->isInlineViable(*Callee)) 100 return InlineCost::getAlways(); 101 102 return InlineCost::getNever(); 103 } 104 105 bool AlwaysInliner::runOnSCC(CallGraphSCC &SCC) { 106 ICA = &getAnalysis<InlineCostAnalysis>(); 107 return Inliner::runOnSCC(SCC); 108 } 109 110 void AlwaysInliner::getAnalysisUsage(AnalysisUsage &AU) const { 111 AU.addRequired<InlineCostAnalysis>(); 112 Inliner::getAnalysisUsage(AU); 113 } 114
