path: root/lib/Transforms/InstCombine/InstCombineCalls.cpp

//===- InstCombineCalls.cpp -----------------------------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the visitCall and visitInvoke functions.
//
//===----------------------------------------------------------------------===//

#include "InstCombine.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/Support/CallSite.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Analysis/MemoryBuiltins.h"
using namespace llvm;

/// getPromotedType - Return the specified type promoted as it would be to pass
/// though a va_arg area.
static const Type *getPromotedType(const Type *Ty) {
  if (const IntegerType* ITy = dyn_cast<IntegerType>(Ty)) {
    if (ITy->getBitWidth() < 32)
      return Type::getInt32Ty(Ty->getContext());
  }
  return Ty;
}

/// EnforceKnownAlignment - If the specified pointer points to an object that
/// we control, modify the object's alignment to PrefAlign. This isn't
/// often possible though. If alignment is important, a more reliable approach
/// is to simply align all global variables and allocation instructions to
/// their preferred alignment from the beginning.
///
static unsigned EnforceKnownAlignment(Value *V,
                                      unsigned Align, unsigned PrefAlign) {

  User *U = dyn_cast<User>(V);
  if (!U) return Align;

  switch (Operator::getOpcode(U)) {
  default: break;
  case Instruction::BitCast:
    return EnforceKnownAlignment(U->getOperand(0), Align, PrefAlign);
  case Instruction::GetElementPtr: {
    // If all indexes are zero, it is just the alignment of the base pointer.
    bool AllZeroOperands = true;
    for (User::op_iterator i = U->op_begin() + 1, e = U->op_end(); i != e; ++i)
      if (!isa<Constant>(*i) ||
          !cast<Constant>(*i)->isNullValue()) {
        AllZeroOperands = false;
        break;
      }

    if (AllZeroOperands) {
      // Treat this like a bitcast.
      return EnforceKnownAlignment(U->getOperand(0), Align, PrefAlign);
    }
    break;
  }
  }

  if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
    // If there is a large requested alignment and we can, bump up the alignment
    // of the global.
    if (!GV->isDeclaration()) {
      if (GV->getAlignment() >= PrefAlign)
        Align = GV->getAlignment();
      else {
        GV->setAlignment(PrefAlign);
        Align = PrefAlign;
      }
    }
  } else if (AllocaInst *AI = dyn_cast<AllocaInst>(V)) {
    // If there is a requested alignment and if this is an alloca, round up.
    if (AI->getAlignment() >= PrefAlign)
      Align = AI->getAlignment();
    else {
      AI->setAlignment(PrefAlign);
      Align = PrefAlign;
    }