path: root/lib/Transforms/Scalar/SimplifyLibCalls.cpp

//===- SimplifyLibCalls.cpp - Optimize specific well-known library calls --===//
//
//                     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 simple pass that applies a variety of small
// optimizations for calls to specific well-known function calls (e.g. runtime
// library functions).   Any optimization that takes the very simple form
// "replace call to library function with simpler code that provides the same
// result" belongs in this file.
//
//===----------------------------------------------------------------------===//

#define DEBUG_TYPE "simplify-libcalls"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/BuildLibCalls.h"
#include "llvm/IRBuilder.h"
#include "llvm/LLVMContext.h"
#include "llvm/Module.h"
#include "llvm/Pass.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/DataLayout.h"
#include "llvm/Target/TargetLibraryInfo.h"
#include "llvm/Config/config.h"            // FIXME: Shouldn't depend on host!
using namespace llvm;

STATISTIC(NumSimplified, "Number of library calls simplified");
STATISTIC(NumAnnotated, "Number of attributes added to library functions");

//===----------------------------------------------------------------------===//
// Optimizer Base Class
//===----------------------------------------------------------------------===//

/// This class is the abstract base class for the set of optimizations that
/// corresponds to one library call.
namespace {
class LibCallOptimization {
protected:
  Function *Caller;
  const DataLayout *TD;
  const TargetLibraryInfo *TLI;
  LLVMContext* Context;
public:
  LibCallOptimization() { }
  virtual ~LibCallOptimization() {}

  /// CallOptimizer - This pure virtual method is implemented by base classes to
  /// do various optimizations.  If this returns null then no transformation was
  /// performed.  If it returns CI, then it transformed the call and CI is to be
  /// deleted.  If it returns something else, replace CI with the new value and
  /// delete CI.
  virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B)
    =0;

  Value *OptimizeCall(CallInst *CI, const DataLayout *TD,
                      const TargetLibraryInfo *TLI, IRBuilder<> &B) {
    Caller = CI->getParent()->getParent();
    this->TD = TD;
    this->TLI = TLI;
    if (CI->getCalledFunction())
      Context = &CI->getCalledFunction()->getContext();

    // We never change the calling convention.
    if (CI->getCallingConv() != llvm::CallingConv::C)
      return NULL;

    return CallOptimizer(CI->getCalledFunction(), CI, B);
  }
};
} // End anonymous namespace.


//===----------------------------------------------------------------------===//
// Helper Functions
//===----------------------------------------------------------------------===//

static bool CallHasFloatingPointArgument(const CallInst *CI) {
  for (CallInst::const_op_iterator it = CI->op_begin(), e = CI->op_end();
       it != e; ++it) {
    if ((*it)->getType()->isFloatingPointTy())
      return true;
  }
  return false;
}

namespace {
//===----------------------------------------------------------------------===//
// Formatting and IO Optimizations
//===----------------------------------------------------------------------===//

//===---------------------------------------===//
// 'fwrite' Optimizations

struct FWriteOpt : public LibCallOptimization {
  virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
    // Require a pointer, an integer, an integer, a pointer, returning integer.
    FunctionType *FT = Callee->getFunctionType();
    if (FT->getNumParams() != 4 || !FT->getParamType(0)->isPointerTy() ||
        !FT->getParamType(1)->isIntegerTy()