//===- InlineAlways.cpp - Code to inline always_inline functions ----------===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This file implements a custom inliner that handles only functions that // are marked as "always inline". // //===----------------------------------------------------------------------===// #include "llvm/Transforms/IPO.h" #include "llvm/ADT/SmallPtrSet.h" #include "llvm/Analysis/CallGraph.h" #include "llvm/Analysis/InlineCost.h" #include "llvm/IR/CallSite.h" #include "llvm/IR/CallingConv.h" #include "llvm/IR/DataLayout.h" #include "llvm/IR/Instructions.h" #include "llvm/IR/IntrinsicInst.h" #include "llvm/IR/Module.h" #include "llvm/IR/Type.h" #include "llvm/Transforms/IPO/InlinerPass.h" using namespace llvm; #define DEBUG_TYPE "inline" namespace { /// \brief Inliner pass which only handles "always inline" functions. class AlwaysInliner : public Inliner { InlineCostAnalysis *ICA; public: // Use extremely low threshold. AlwaysInliner() : Inliner(ID, -2000000000, /*InsertLifetime*/ true), ICA(nullptr) { initializeAlwaysInlinerPass(*PassRegistry::getPassRegistry()); } AlwaysInliner(bool InsertLifetime) : Inliner(ID, -2000000000, InsertLifetime), ICA(nullptr) { initializeAlwaysInlinerPass(*PassRegistry::getPassRegistry()); } static char ID; // Pass identification, replacement for typeid InlineCost getInlineCost(CallSite CS) override; void getAnalysisUsage(AnalysisUsage &AU) const override; bool runOnSCC(CallGraphSCC &SCC) override; using llvm::Pass::doFinalization; bool doFinalization(CallGraph &CG) override { return removeDeadFunctions(CG, /*AlwaysInlineOnly=*/ true); } }; } char AlwaysInliner::ID = 0; INITIALIZE_PASS_BEGIN(AlwaysInliner, "always-inline", "Inliner for always_inline functions", false, false) INITIALIZE_PASS_DEPENDENCY(CallGraphWrapperPass) INITIALIZE_PASS_DEPENDENCY(InlineCostAnalysis) INITIALIZE_PASS_END(AlwaysInliner, "always-inline", "Inliner for always_inline functions", false, false) Pass *llvm::createAlwaysInlinerPass() { return new AlwaysInliner(); } Pass *llvm::createAlwaysInlinerPass(bool InsertLifetime) { return new AlwaysInliner(InsertLifetime); } /// \brief Get the inline cost for the always-inliner. /// /// The always inliner *only* handles functions which are marked with the /// attribute to force inlining. As such, it is dramatically simpler and avoids /// using the powerful (but expensive) inline cost analysis. Instead it uses /// a very simple and boring direct walk of the instructions looking for /// impossible-to-inline constructs. /// /// Note, it would be possible to go to some lengths to cache the information /// computed here, but as we only expect to do this for relatively few and /// small functions which have the explicit attribute to force inlining, it is /// likely not worth it in practice. InlineCost AlwaysInliner::getInlineCost(CallSite CS) { Function *Callee = CS.getCalledFunction(); // Only inline direct calls to functions with always-inline attributes // that are viable for inlining. FIXME: We shouldn't even get here for // declarations. if (Callee && !Callee->isDeclaration() && CS.hasFnAttr(Attribute::AlwaysInline) && ICA->isInlineViable(*Callee)) return InlineCost::getAlways(); return InlineCost::getNever(); } bool AlwaysInliner::runOnSCC(CallGraphSCC &SCC) { ICA = &getAnalysis<InlineCostAnalysis>(); return Inliner::runOnSCC(SCC); } void AlwaysInliner::getAnalysisUsage(AnalysisUsage &AU) const { AU.addRequired<InlineCostAnalysis>(); Inliner::getAnalysisUsage(AU); }