InlineAlways.cpp revision 276479
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 28using namespace llvm; 29 30#define DEBUG_TYPE "inline" 31 32namespace { 33 34/// \brief Inliner pass which only handles "always inline" functions. 35class AlwaysInliner : public Inliner { 36 InlineCostAnalysis *ICA; 37 38public: 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 65char AlwaysInliner::ID = 0; 66INITIALIZE_PASS_BEGIN(AlwaysInliner, "always-inline", 67 "Inliner for always_inline functions", false, false) 68INITIALIZE_PASS_DEPENDENCY(CallGraphWrapperPass) 69INITIALIZE_PASS_DEPENDENCY(InlineCostAnalysis) 70INITIALIZE_PASS_END(AlwaysInliner, "always-inline", 71 "Inliner for always_inline functions", false, false) 72 73Pass *llvm::createAlwaysInlinerPass() { return new AlwaysInliner(); } 74 75Pass *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. 91InlineCost 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 105bool AlwaysInliner::runOnSCC(CallGraphSCC &SCC) { 106 ICA = &getAnalysis<InlineCostAnalysis>(); 107 return Inliner::runOnSCC(SCC); 108} 109 110void AlwaysInliner::getAnalysisUsage(AnalysisUsage &AU) const { 111 AU.addRequired<InlineCostAnalysis>(); 112 Inliner::getAnalysisUsage(AU); 113} 114