llvm-project/llvm/lib/Transforms/IPO/InlineSimple.cpp

//===- InlineSimple.cpp - Code to perform simple function inlining --------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements bottom-up inlining of functions into callees.
//
//===----------------------------------------------------------------------===//

#define DEBUG_TYPE "inline"
#include "llvm/CallingConv.h"
#include "llvm/Instructions.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/Module.h"
#include "llvm/Type.h"
#include "llvm/Analysis/CallGraph.h"
#include "llvm/Support/CallSite.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Transforms/IPO.h"
#include "llvm/Transforms/IPO/InlinerPass.h"
#include "llvm/Transforms/Utils/InlineCost.h"
#include "llvm/ADT/SmallPtrSet.h"

using namespace llvm;

namespace {

  class VISIBILITY_HIDDEN SimpleInliner : public Inliner {
    // Functions that are never inlined
    SmallPtrSet<const Function*, 16> NeverInline; 
    InlineCostAnalyzer CA;
  public:
    SimpleInliner() : Inliner(&ID) {}
    static char ID; // Pass identification, replacement for typeid
    int getInlineCost(CallSite CS) {
      return CA.getInlineCost(CS, NeverInline);
    }
    virtual bool doInitialization(CallGraph &CG);
  };
  char SimpleInliner::ID = 0;
  RegisterPass<SimpleInliner> X("inline", "Function Integration/Inlining");
}

Pass *llvm::createFunctionInliningPass() { return new SimpleInliner(); }

// doInitialization - Initializes the vector of functions that have been
// annotated with the noinline attribute.
bool SimpleInliner::doInitialization(CallGraph &CG) {
  
  Module &M = CG.getModule();
  
  // Get llvm.noinline
  GlobalVariable *GV = M.getNamedGlobal("llvm.noinline");
  
  if (GV == 0)
    return false;

  const ConstantArray *InitList = dyn_cast<ConstantArray>(GV->getInitializer());
  
  if (InitList == 0)
    return false;

  // Iterate over each element and add to the NeverInline set
  for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i) {
        
    // Get Source
    const Constant *Elt = InitList->getOperand(i);
        
    if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(Elt))
      if (CE->getOpcode() == Instruction::BitCast) 
        Elt = CE->getOperand(0);
    
    // Insert into set of functions to never inline
    if (const Function *F = dyn_cast<Function>(Elt))
      NeverInline.insert(F);
  }
  
  return false;
}