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#define DEBUG_TYPE "inline" 16#include "llvm/Transforms/IPO.h" 17#include "llvm/ADT/SmallPtrSet.h" 18#include "llvm/Analysis/CallGraph.h" 19#include "llvm/Analysis/InlineCost.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/Support/CallSite.h" 27#include "llvm/Transforms/IPO/InlinerPass.h" 28 29using namespace llvm; 30 31namespace { 32 33/// \brief Inliner pass which only handles "always inline" functions. 34class AlwaysInliner : public Inliner { 35 InlineCostAnalysis *ICA; 36 37public: 38 // Use extremely low threshold. 39 AlwaysInliner() : Inliner(ID, -2000000000, /*InsertLifetime*/ true), ICA(0) { 40 initializeAlwaysInlinerPass(*PassRegistry::getPassRegistry()); 41 } 42 43 AlwaysInliner(bool InsertLifetime) 44 : Inliner(ID, -2000000000, InsertLifetime), ICA(0) { 45 initializeAlwaysInlinerPass(*PassRegistry::getPassRegistry()); 46 } 47 48 static char ID; // Pass identification, replacement for typeid 49 50 virtual InlineCost getInlineCost(CallSite CS); 51 52 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 53 virtual bool runOnSCC(CallGraphSCC &SCC); 54 55 using llvm::Pass::doFinalization; 56 virtual bool doFinalization(CallGraph &CG) { 57 return removeDeadFunctions(CG, /*AlwaysInlineOnly=*/ true); 58 } 59}; 60 61} 62 63char AlwaysInliner::ID = 0; 64INITIALIZE_PASS_BEGIN(AlwaysInliner, "always-inline", 65 "Inliner for always_inline functions", false, false) 66INITIALIZE_AG_DEPENDENCY(CallGraph) 67INITIALIZE_PASS_DEPENDENCY(InlineCostAnalysis) 68INITIALIZE_PASS_END(AlwaysInliner, "always-inline", 69 "Inliner for always_inline functions", false, false) 70 71Pass *llvm::createAlwaysInlinerPass() { return new AlwaysInliner(); } 72 73Pass *llvm::createAlwaysInlinerPass(bool InsertLifetime) { 74 return new AlwaysInliner(InsertLifetime); 75} 76 77/// \brief Get the inline cost for the always-inliner. 78/// 79/// The always inliner *only* handles functions which are marked with the 80/// attribute to force inlining. As such, it is dramatically simpler and avoids 81/// using the powerful (but expensive) inline cost analysis. Instead it uses 82/// a very simple and boring direct walk of the instructions looking for 83/// impossible-to-inline constructs. 84/// 85/// Note, it would be possible to go to some lengths to cache the information 86/// computed here, but as we only expect to do this for relatively few and 87/// small functions which have the explicit attribute to force inlining, it is 88/// likely not worth it in practice. 89InlineCost AlwaysInliner::getInlineCost(CallSite CS) { 90 Function *Callee = CS.getCalledFunction(); 91 92 // Only inline direct calls to functions with always-inline attributes 93 // that are viable for inlining. FIXME: We shouldn't even get here for 94 // declarations. 95 if (Callee && !Callee->isDeclaration() && 96 Callee->getAttributes().hasAttribute(AttributeSet::FunctionIndex, 97 Attribute::AlwaysInline) && 98 ICA->isInlineViable(*Callee)) 99 return InlineCost::getAlways(); 100 101 return InlineCost::getNever(); 102} 103 104bool AlwaysInliner::runOnSCC(CallGraphSCC &SCC) { 105 ICA = &getAnalysis<InlineCostAnalysis>(); 106 return Inliner::runOnSCC(SCC); 107} 108 109void AlwaysInliner::getAnalysisUsage(AnalysisUsage &AU) const { 110 AU.addRequired<InlineCostAnalysis>(); 111 Inliner::getAnalysisUsage(AU); 112} 113