//===-- InstrinsicInst.cpp - Intrinsic Instruction Wrappers ---------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements methods that make it really easy to deal with intrinsic
// functions.
//
// All intrinsic function calls are instances of the call instruction, so these
// are all subclasses of the CallInst class.  Note that none of these classes
// has state or virtual methods, which is an important part of this gross/neat
// hack working.
// 
// In some cases, arguments to intrinsics need to be generic and are defined as
// type pointer to empty struct { }*.  To access the real item of interest the
// cast instruction needs to be stripped away. 
//
//===----------------------------------------------------------------------===//

#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/Metadata.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;

//===----------------------------------------------------------------------===//
/// DbgInfoIntrinsic - This is the common base class for debug info intrinsics
///

static Value *CastOperand(Value *C) {
  if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
    if (CE->isCast())
      return CE->getOperand(0);
  return nullptr;
}

Value *DbgInfoIntrinsic::StripCast(Value *C) {
  if (Value *CO = CastOperand(C)) {
    C = StripCast(CO);
  } else if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) {
    if (GV->hasInitializer())
      if (Value *CO = CastOperand(GV->getInitializer()))
        C = StripCast(CO);
  }
  return dyn_cast<GlobalVariable>(C);
}

Value *DbgInfoIntrinsic::getVariableLocation(bool AllowNullOp) const {
  Value *Op = getArgOperand(0);
  if (AllowNullOp && !Op)
    return nullptr;

  auto *MD = cast<MetadataAsValue>(Op)->getMetadata();
  if (auto *V = dyn_cast<ValueAsMetadata>(MD))
    return V->getValue();

  // When the value goes to null, it gets replaced by an empty MDNode.
  assert(!cast<MDNode>(MD)->getNumOperands() && "Expected an empty MDNode");
  return nullptr;
}

int llvm::Intrinsic::lookupLLVMIntrinsicByName(ArrayRef<const char *> NameTable,
                                               StringRef Name) {
  assert(Name.startswith("llvm."));

  // Do successive binary searches of the dotted name components. For
  // "llvm.gc.experimental.statepoint.p1i8.p1i32", we will find the range of
  // intrinsics starting with "llvm.gc", then "llvm.gc.experimental", then
  // "llvm.gc.experimental.statepoint", and then we will stop as the range is
  // size 1. During the search, we can skip the prefix that we already know is
  // identical. By using strncmp we consider names with differing suffixes to
  // be part of the equal range.
  size_t CmpStart = 0;
  size_t CmpEnd = 4; // Skip the "llvm" component.
  const char *const *Low = NameTable.begin();
  const char *const *High = NameTable.end();
  const char *const *LastLow = Low;
  while (CmpEnd < Name.size() && High - Low > 0) {
    CmpStart = CmpEnd;
    CmpEnd = Name.find('.', CmpStart + 1);
    CmpEnd = CmpEnd == StringRef::npos ? Name.size() : CmpEnd;
    auto Cmp = [CmpStart, CmpEnd](const char *LHS, const char *RHS) {
      return strncmp(LHS + CmpStart, RHS + CmpStart, CmpEnd - CmpStart) < 0;
    };
    LastLow = Low;
    std::tie(Low, High) = std::equal_range(Low, High, Name.data(), Cmp);
  }
  if (High - Low > 0)
    LastLow = Low;

  if (LastLow == NameTable.end())
    return -1;
  StringRef NameFound = *LastLow;
  if (Name == NameFound ||
      (Name.startswith(NameFound) && Name[NameFound.size()] == '.'))
    return LastLow - NameTable.begin();
  return -1;
}