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/AssumptionCache.h" 18 #include "llvm/Analysis/CallGraph.h" 19 #include "llvm/Analysis/InlineCost.h" 20 #include "llvm/Analysis/ProfileSummaryInfo.h" 21 #include "llvm/Analysis/TargetLibraryInfo.h" 22 #include "llvm/IR/CallSite.h" 23 #include "llvm/IR/CallingConv.h" 24 #include "llvm/IR/DataLayout.h" 25 #include "llvm/IR/Instructions.h" 26 #include "llvm/IR/IntrinsicInst.h" 27 #include "llvm/IR/Module.h" 28 #include "llvm/IR/Type.h" 29 #include "llvm/Transforms/IPO/InlinerPass.h" 30 31 using namespace llvm; 32 33 #define DEBUG_TYPE "inline" 34 35 namespace { 36 37 /// \brief Inliner pass which only handles "always inline" functions. 38 class AlwaysInliner : public Inliner { 39 40 public: 41 AlwaysInliner() : Inliner(ID, /*InsertLifetime*/ true) { 42 initializeAlwaysInlinerPass(*PassRegistry::getPassRegistry()); 43 } 44 45 AlwaysInliner(bool InsertLifetime) : Inliner(ID, InsertLifetime) { 46 initializeAlwaysInlinerPass(*PassRegistry::getPassRegistry()); 47 } 48 49 /// Main run interface method. We override here to avoid calling skipSCC(). 50 bool runOnSCC(CallGraphSCC &SCC) override { return inlineCalls(SCC); } 51 52 static char ID; // Pass identification, replacement for typeid 53 54 InlineCost getInlineCost(CallSite CS) override; 55 56 using llvm::Pass::doFinalization; 57 bool doFinalization(CallGraph &CG) override { 58 return removeDeadFunctions(CG, /*AlwaysInlineOnly=*/ true); 59 } 60 }; 61 62 } 63 64 char AlwaysInliner::ID = 0; 65 INITIALIZE_PASS_BEGIN(AlwaysInliner, "always-inline", 66 "Inliner for always_inline functions", false, false) 67 INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker) 68 INITIALIZE_PASS_DEPENDENCY(CallGraphWrapperPass) 69 INITIALIZE_PASS_DEPENDENCY(ProfileSummaryInfoWrapperPass) 70 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass) 71 INITIALIZE_PASS_END(AlwaysInliner, "always-inline", 72 "Inliner for always_inline functions", false, false) 73 74 Pass *llvm::createAlwaysInlinerPass() { return new AlwaysInliner(); } 75 76 Pass *llvm::createAlwaysInlinerPass(bool InsertLifetime) { 77 return new AlwaysInliner(InsertLifetime); 78 } 79 80 /// \brief Get the inline cost for the always-inliner. 81 /// 82 /// The always inliner *only* handles functions which are marked with the 83 /// attribute to force inlining. As such, it is dramatically simpler and avoids 84 /// using the powerful (but expensive) inline cost analysis. Instead it uses 85 /// a very simple and boring direct walk of the instructions looking for 86 /// impossible-to-inline constructs. 87 /// 88 /// Note, it would be possible to go to some lengths to cache the information 89 /// computed here, but as we only expect to do this for relatively few and 90 /// small functions which have the explicit attribute to force inlining, it is 91 /// likely not worth it in practice. 92 InlineCost AlwaysInliner::getInlineCost(CallSite CS) { 93 Function *Callee = CS.getCalledFunction(); 94 95 // Only inline direct calls to functions with always-inline attributes 96 // that are viable for inlining. FIXME: We shouldn't even get here for 97 // declarations. 98 if (Callee && !Callee->isDeclaration() && 99 CS.hasFnAttr(Attribute::AlwaysInline) && isInlineViable(*Callee)) 100 return InlineCost::getAlways(); 101 102 return InlineCost::getNever(); 103 } 104
