// Copyright (c) 2017 Google Inc.

//

// Licensed under the Apache License, Version 2.0 (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

//

//     http://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.

// Validates literal numbers.

#include <cassert>

#include "source/val/instruction.h"

#include "source/val/validate.h"

#include "source/val/validation_state.h"

namespace spvtools {

namespace val {

namespace {

// Returns true if the operand holds a literal number

bool IsLiteralNumber(const spv_parsed_operand_t& operand) {

  switch (operand.number_kind) {

    case SPV_NUMBER_SIGNED_INT:

    case SPV_NUMBER_UNSIGNED_INT:

    case SPV_NUMBER_FLOATING:

      return true;

    default:

      return false;

  }

}

// Verifies that the upper bits of the given upper |word| with given

// lower |width| are zero- or sign-extended when |signed_int| is true

bool VerifyUpperBits(uint32_t word, uint32_t width, bool signed_int) {

  assert(width < 32);

  assert(0 < width);

  const uint32_t upper_mask = 0xFFFFFFFFu << width;

  const uint32_t upper_bits = word & upper_mask;

  bool result = false;

  if (signed_int) {

    const uint32_t sign_bit = word & (1u << (width - 1));

    if (sign_bit) {

      result = upper_bits == upper_mask;

    } else {

      result = upper_bits == 0;

    }

  } else {

    result = upper_bits == 0;

  }

  return result;

}

}  // namespace

// Validates that literal numbers are represented according to the spec

spv_result_t LiteralsPass(ValidationState_t& _, const Instruction* inst) {

  // For every operand that is a literal number

  for (size_t i = 0; i < inst->operands().size(); i++) {

    const spv_parsed_operand_t& operand = inst->operand(i);

    if (!IsLiteralNumber(operand)) continue;

    // The upper bits are always in the last word (little-endian)

    int last_index = operand.offset + operand.num_words - 1;

    const uint32_t upper_word = inst->word(last_index);

    // TODO(jcaraban): is the |word size| defined in some header?

    const uint32_t word_size = 32;

    uint32_t bit_width = operand.number_bit_width;

    // Bit widths that are a multiple of the word size have no upper bits

    const auto remaining_value_bits = bit_width % word_size;

    if (remaining_value_bits == 0) continue;

    const bool signedness = operand.number_kind == SPV_NUMBER_SIGNED_INT;

    if (!VerifyUpperBits(upper_word, remaining_value_bits, signedness)) {

      return _.diag(SPV_ERROR_INVALID_VALUE, inst)

             << "The high-order bits of a literal number in instruction <id> "

             << inst->id() << " must be 0 for a floating-point type, "

             << "or 0 for an integer type with Signedness of 0, "

             << "or sign extended when Signedness is 1";

    }

  }

  return SPV_SUCCESS;

}

}  // namespace val

}  // namespace spvtools