// Copyright (c) 2015-2016 The Khronos Group 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.

#include "source/text.h"

#include <algorithm>

#include <cassert>

#include <cctype>

#include <cstdio>

#include <cstdlib>

#include <cstring>

#include <memory>

#include <set>

#include <sstream>

#include <string>

#include <unordered_map>

#include <utility>

#include <vector>

#include "source/assembly_grammar.h"

#include "source/binary.h"

#include "source/diagnostic.h"

#include "source/ext_inst.h"

#include "source/instruction.h"

#include "source/opcode.h"

#include "source/operand.h"

#include "source/spirv_constant.h"

#include "source/spirv_target_env.h"

#include "source/table.h"

#include "source/text_handler.h"

#include "source/util/bitutils.h"

#include "source/util/parse_number.h"

#include "spirv-tools/libspirv.h"

bool spvIsValidIDCharacter(const char value) {

  return value == '_' || 0 != ::isalnum(value);

}

// Returns true if the given string represents a valid ID name.

bool spvIsValidID(const char* textValue) {

  const char* c = textValue;

  for (; *c != '\0'; ++c) {

    if (!spvIsValidIDCharacter(*c)) {

      return false;

    }

  }

  // If the string was empty, then the ID also is not valid.

  return c != textValue;

}

// Text API

spv_result_t spvTextToLiteral(const char* textValue, spv_literal_t* pLiteral) {

  bool isSigned = false;

  int numPeriods = 0;

  bool isString = false;

  const size_t len = strlen(textValue);

  if (len == 0) return SPV_FAILED_MATCH;

  for (uint64_t index = 0; index < len; ++index) {

    switch (textValue[index]) {

      case '0':

      case '1':

      case '2':

      case '3':

      case '4':

      case '5':

      case '6':

      case '7':

      case '8':

      case '9':

        break;

      case '.':

        numPeriods++;

        break;

      case '-':

        if (index == 0) {

          isSigned = true;

        } else {

          isString = true;

        }

        break;

      default:

        isString = true;

        index = len;  // break out of the loop too.

        break;

    }

  }

  pLiteral->type = spv_literal_type_t(99);

  if (isString || numPeriods > 1 || (isSigned && len == 1)) {

    if (len < 2 || textValue[0] != '"' || textValue[len - 1] != '"')

      return SPV_FAILED_MATCH;

    bool escaping = false;

    for (const char* val = textValue + 1; val != textValue + len - 1; ++val) {

      if ((*val == '\\') && (!escaping)) {

        escaping = true;

      } else {

        // Have to save space for the null-terminator

        if (pLiteral->str.size() >= SPV_LIMIT_LITERAL_STRING_BYTES_MAX)

          return SPV_ERROR_OUT_OF_MEMORY;

        pLiteral->str.push_back(*val);

        escaping = false;

      }

    }

    pLiteral->type = SPV_LITERAL_TYPE_STRING;

  } else if (numPeriods == 1) {

    double d = std::strtod(textValue, nullptr);

    float f = (float)d;

    if (d == (double)f) {

      pLiteral->type = SPV_LITERAL_TYPE_FLOAT_32;

      pLiteral->value.f = f;

    } else {

      pLiteral->type = SPV_LITERAL_TYPE_FLOAT_64;

      pLiteral->value.d = d;

    }

  } else if (isSigned) {

    int64_t i64 = strtoll(textValue, nullptr, 10);

    int32_t i32 = (int32_t)i64;

    if (i64 == (int64_t)i32) {

      pLiteral->type = SPV_LITERAL_TYPE_INT_32;

      pLiteral->value.i32 = i32;

    } else {

      pLiteral->type = SPV_LITERAL_TYPE_INT_64;

      pLiteral->value.i64 = i64;

    }

  } else {

    uint64_t u64 = strtoull(textValue, nullptr, 10);

    uint32_t u32 = (uint32_t)u64;

    if (u64 == (uint64_t)u32) {

      pLiteral->type = SPV_LITERAL_TYPE_UINT_32;

      pLiteral->value.u32 = u32;

    } else {

      pLiteral->type = SPV_LITERAL_TYPE_UINT_64;

      pLiteral->value.u64 = u64;

    }

  }

  return SPV_SUCCESS;

}

namespace {

/// Parses an immediate integer from text, guarding against overflow.  If

/// successful, adds the parsed value to pInst, advances the context past it,

/// and returns SPV_SUCCESS.  Otherwise, leaves pInst alone, emits diagnostics,

/// and returns SPV_ERROR_INVALID_TEXT.

spv_result_t encodeImmediate(spvtools::AssemblyContext* context,

                             const char* text, spv_instruction_t* pInst) {

  assert(*text == '!');

  uint32_t parse_result;

  if (!spvtools::utils::ParseNumber(text + 1, &parse_result)) {

    return context->diagnostic(SPV_ERROR_INVALID_TEXT)

           << "Invalid immediate integer: !" << text + 1;

  }

  context->binaryEncodeU32(parse_result, pInst);

  context->seekForward(static_cast<uint32_t>(strlen(text)));

  return SPV_SUCCESS;

}

}  // anonymous namespace

/// @brief Translate an Opcode operand to binary form

///

/// @param[in] grammar the grammar to use for compilation

/// @param[in, out] context the dynamic compilation info

/// @param[in] type of the operand

/// @param[in] textValue word of text to be parsed

/// @param[out] pInst return binary Opcode

/// @param[in,out] pExpectedOperands the operand types expected

///

/// @return result code

spv_result_t spvTextEncodeOperand(const spvtools::AssemblyGrammar& grammar,

                                  spvtools::AssemblyContext* context,

                                  const spv_operand_type_t type,

                                  const char* textValue,

                                  spv_instruction_t* pInst,

                                  spv_operand_pattern_t* pExpectedOperands) {

  // NOTE: Handle immediate int in the stream

  if ('!' == textValue[0]) {

    if (auto error = encodeImmediate(context, textValue, pInst)) {

      return error;

    }

    *pExpectedOperands =

        spvAlternatePatternFollowingImmediate(*pExpectedOperands);

    return SPV_SUCCESS;

  }

  // Optional literal operands can fail to parse. In that case use

  // SPV_FAILED_MATCH to avoid emitting a diagnostic.  Use the following

  // for those situations.

  spv_result_t error_code_for_literals =

      spvOperandIsOptional(type) ? SPV_FAILED_MATCH : SPV_ERROR_INVALID_TEXT;

  switch (type) {

    case SPV_OPERAND_TYPE_ID:

    case SPV_OPERAND_TYPE_TYPE_ID:

    case SPV_OPERAND_TYPE_RESULT_ID:

    case SPV_OPERAND_TYPE_MEMORY_SEMANTICS_ID:

    case SPV_OPERAND_TYPE_SCOPE_ID:

    case SPV_OPERAND_TYPE_OPTIONAL_ID: {

      if ('%' == textValue[0]) {

        textValue++;

      } else {

        return context->diagnostic() << "Expected id to start with %.";

      }

      if (!spvIsValidID(textValue)) {

        return context->diagnostic() << "Invalid ID " << textValue;

      }

      const uint32_t id = context->spvNamedIdAssignOrGet(textValue);

      if (type == SPV_OPERAND_TYPE_TYPE_ID) pInst->resultTypeId = id;

      spvInstructionAddWord(pInst, id);

      // Set the extended instruction type.

      // The import set id is the 3rd operand of OpExtInst.

      if (spvIsExtendedInstruction(pInst->opcode) && pInst->words.size() == 4) {

        auto ext_inst_type = context->getExtInstTypeForId(pInst->words[3]);

        if (ext_inst_type == SPV_EXT_INST_TYPE_NONE) {

          return context->diagnostic()

                 << "Invalid extended instruction import Id "

                 << pInst->words[2];

        }

        pInst->extInstType = ext_inst_type;

      }

    } break;

    case SPV_OPERAND_TYPE_EXTENSION_INSTRUCTION_NUMBER: {

      // The assembler accepts the symbolic name for an extended instruction,

      // and emits its corresponding number.

      spv_ext_inst_desc extInst;

      if (grammar.lookupExtInst(pInst->extInstType, textValue, &extInst) ==

          SPV_SUCCESS) {

        // if we know about this extended instruction, push the numeric value

        spvInstructionAddWord(pInst, extInst->ext_inst);

        // Prepare to parse the operands for the extended instructions.

        spvPushOperandTypes(extInst->operandTypes, pExpectedOperands);

      } else {

        // if we don't know this extended instruction and the set isn't

        // non-semantic, we cannot process further

        if (!spvExtInstIsNonSemantic(pInst->extInstType)) {

          return context->diagnostic()

                 << "Invalid extended instruction name '" << textValue << "'.";

        } else {

          // for non-semantic instruction sets, as long as the text name is an

          // integer value we can encode it since we know the form of all such

          // extended instructions

          spv_literal_t extInstValue;

          if (spvTextToLiteral(textValue, &extInstValue) ||

              extInstValue.type != SPV_LITERAL_TYPE_UINT_32) {

            return context->diagnostic()

                   << "Couldn't translate unknown extended instruction name '"

                   << textValue << "' to unsigned integer.";

          }

          spvInstructionAddWord(pInst, extInstValue.value.u32);

          // opcode contains an unknown number of IDs.

          pExpectedOperands->push_back(SPV_OPERAND_TYPE_VARIABLE_ID);

        }

      }

    } break;

    case SPV_OPERAND_TYPE_SPEC_CONSTANT_OP_NUMBER: {

      // The assembler accepts the symbolic name for the opcode, but without

      // the "Op" prefix.  For example, "IAdd" is accepted.  The number

      // of the opcode is emitted.

      spv::Op opcode;

      if (grammar.lookupSpecConstantOpcode(textValue, &opcode)) {

        return context->diagnostic() << "Invalid " << spvOperandTypeStr(type)

                                     << " '" << textValue << "'.";

      }

      spv_opcode_desc opcodeEntry = nullptr;

      if (grammar.lookupOpcode(opcode, &opcodeEntry)) {

        return context->diagnostic(SPV_ERROR_INTERNAL)

               << "OpSpecConstant opcode table out of sync";

      }

      spvInstructionAddWord(pInst, uint32_t(opcodeEntry->opcode));

      // Prepare to parse the operands for the opcode.  Except skip the

      // type Id and result Id, since they've already been processed.

      assert(opcodeEntry->hasType);

      assert(opcodeEntry->hasResult);

      assert(opcodeEntry->numTypes >= 2);

      spvPushOperandTypes(opcodeEntry->operandTypes + 2, pExpectedOperands);

    } break;

    case SPV_OPERAND_TYPE_LITERAL_INTEGER:

    case SPV_OPERAND_TYPE_OPTIONAL_LITERAL_INTEGER: {

      // The current operand is an *unsigned* 32-bit integer.

      // That's just how the grammar works.

      spvtools::IdType expected_type = {

          32, false, spvtools::IdTypeClass::kScalarIntegerType};

      if (auto error = context->binaryEncodeNumericLiteral(

              textValue, error_code_for_literals, expected_type, pInst)) {

        return error;

      }

    } break;

    case SPV_OPERAND_TYPE_LITERAL_FLOAT: {

      // The current operand is a 32-bit float.

      // That's just how the grammar works.

      spvtools::IdType expected_type = {

          32, false, spvtools::IdTypeClass::kScalarFloatType};

      if (auto error = context->binaryEncodeNumericLiteral(

              textValue, error_code_for_literals, expected_type, pInst)) {

        return error;

      }

    } break;

    case SPV_OPERAND_TYPE_OPTIONAL_LITERAL_NUMBER:

      // This is a context-independent literal number which can be a 32-bit

      // number of floating point value.

      if (auto error = context->binaryEncodeNumericLiteral(

              textValue, error_code_for_literals, spvtools::kUnknownType,

              pInst)) {

        return error;

      }

      break;

    case SPV_OPERAND_TYPE_OPTIONAL_TYPED_LITERAL_INTEGER:

    case SPV_OPERAND_TYPE_TYPED_LITERAL_NUMBER: {

      spvtools::IdType expected_type = spvtools::kUnknownType;

      // The encoding for OpConstant, OpSpecConstant and OpSwitch all

      // depend on either their own result-id or the result-id of

      // one of their parameters.

      if (spv::Op::OpConstant == pInst->opcode ||

          spv::Op::OpSpecConstant == pInst->opcode) {

        // The type of the literal is determined by the type Id of the

        // instruction.

        expected_type =

            context->getTypeOfTypeGeneratingValue(pInst->resultTypeId);

        if (!spvtools::isScalarFloating(expected_type) &&

            !spvtools::isScalarIntegral(expected_type)) {

          spv_opcode_desc d;

          const char* opcode_name = "opcode";

          if (SPV_SUCCESS == grammar.lookupOpcode(pInst->opcode, &d)) {

            opcode_name = d->name;

          }

          return context->diagnostic()

                 << "Type for " << opcode_name

                 << " must be a scalar floating point or integer type";

        }

      } else if (pInst->opcode == spv::Op::OpSwitch) {

        // The type of the literal is the same as the type of the selector.

        expected_type = context->getTypeOfValueInstruction(pInst->words[1]);

        if (!spvtools::isScalarIntegral(expected_type)) {

          return context->diagnostic()

                 << "The selector operand for OpSwitch must be the result"

                    " of an instruction that generates an integer scalar";

        }

      }

      if (auto error = context->binaryEncodeNumericLiteral(

              textValue, error_code_for_literals, expected_type, pInst)) {

        return error;

      }

    } break;

    case SPV_OPERAND_TYPE_LITERAL_STRING:

    case SPV_OPERAND_TYPE_OPTIONAL_LITERAL_STRING: {

      spv_literal_t literal = {};

      spv_result_t error = spvTextToLiteral(textValue, &literal);

      if (error != SPV_SUCCESS) {

        if (error == SPV_ERROR_OUT_OF_MEMORY) return error;

        return context->diagnostic(error_code_for_literals)

               << "Invalid literal string '" << textValue << "'.";

      }

      if (literal.type != SPV_LITERAL_TYPE_STRING) {

        return context->diagnostic()

               << "Expected literal string, found literal number '" << textValue

               << "'.";

      }

      // NOTE: Special case for extended instruction library import

      if (spv::Op::OpExtInstImport == pInst->opcode) {

        const spv_ext_inst_type_t ext_inst_type =

            spvExtInstImportTypeGet(literal.str.c_str());

        if (SPV_EXT_INST_TYPE_NONE == ext_inst_type) {

          return context->diagnostic()

                 << "Invalid extended instruction import '" << literal.str

                 << "'";

        }

        if ((error = context->recordIdAsExtInstImport(pInst->words[1],

                                                      ext_inst_type)))

          return error;

      }

      if (context->binaryEncodeString(literal.str.c_str(), pInst))

        return SPV_ERROR_INVALID_TEXT;

    } break;

    // Masks.

    case SPV_OPERAND_TYPE_FP_FAST_MATH_MODE:

    case SPV_OPERAND_TYPE_FUNCTION_CONTROL:

    case SPV_OPERAND_TYPE_LOOP_CONTROL:

    case SPV_OPERAND_TYPE_IMAGE:

    case SPV_OPERAND_TYPE_OPTIONAL_IMAGE:

    case SPV_OPERAND_TYPE_OPTIONAL_MEMORY_ACCESS:

    case SPV_OPERAND_TYPE_OPTIONAL_RAW_ACCESS_CHAIN_OPERANDS:

    case SPV_OPERAND_TYPE_SELECTION_CONTROL:

    case SPV_OPERAND_TYPE_DEBUG_INFO_FLAGS:

    case SPV_OPERAND_TYPE_CLDEBUG100_DEBUG_INFO_FLAGS:

    case SPV_OPERAND_TYPE_OPTIONAL_COOPERATIVE_MATRIX_OPERANDS:

    case SPV_OPERAND_TYPE_TENSOR_ADDRESSING_OPERANDS:

    case SPV_OPERAND_TYPE_COOPERATIVE_MATRIX_REDUCE:

    case SPV_OPERAND_TYPE_OPTIONAL_MATRIX_MULTIPLY_ACCUMULATE_OPERANDS: {

      uint32_t value;

      if (auto error = grammar.parseMaskOperand(type, textValue, &value)) {

        return context->diagnostic(error)

               << "Invalid " << spvOperandTypeStr(type) << " operand '"

               << textValue << "'.";

      }

      if (auto error = context->binaryEncodeU32(value, pInst)) return error;

      // Prepare to parse the operands for this logical operand.

      grammar.pushOperandTypesForMask(type, value, pExpectedOperands);

    } break;

    case SPV_OPERAND_TYPE_OPTIONAL_CIV: {

      auto error = spvTextEncodeOperand(

          grammar, context, SPV_OPERAND_TYPE_OPTIONAL_LITERAL_NUMBER, textValue,

          pInst, pExpectedOperands);

      if (error == SPV_FAILED_MATCH) {

        // It's not a literal number -- is it a literal string?

        error = spvTextEncodeOperand(grammar, context,

                                     SPV_OPERAND_TYPE_OPTIONAL_LITERAL_STRING,

                                     textValue, pInst, pExpectedOperands);

      }

      if (error == SPV_FAILED_MATCH) {

        // It's not a literal -- is it an ID?

        error =

            spvTextEncodeOperand(grammar, context, SPV_OPERAND_TYPE_OPTIONAL_ID,

                                 textValue, pInst, pExpectedOperands);

      }

      if (error) {

        return context->diagnostic(error)

               << "Invalid word following !<integer>: " << textValue;

      }

      if (pExpectedOperands->empty()) {

        pExpectedOperands->push_back(SPV_OPERAND_TYPE_OPTIONAL_CIV);

      }

    } break;

    default: {

      // NOTE: All non literal operands are handled here using the operand

      // table.

      spv_operand_desc entry;

      if (grammar.lookupOperand(type, textValue, strlen(textValue), &entry)) {

        return context->diagnostic() << "Invalid " << spvOperandTypeStr(type)

                                     << " '" << textValue << "'.";

      }

      if (context->binaryEncodeU32(entry->value, pInst)) {

        return context->diagnostic() << "Invalid " << spvOperandTypeStr(type)

                                     << " '" << textValue << "'.";

      }

      // Prepare to parse the operands for this logical operand.

      spvPushOperandTypes(entry->operandTypes, pExpectedOperands);

    } break;

  }

  return SPV_SUCCESS;

}

namespace {

/// Encodes an instruction started by !<integer> at the given position in text.

///

/// Puts the encoded words into *pInst.  If successful, moves position past the

/// instruction and returns SPV_SUCCESS.  Otherwise, returns an error code and

/// leaves position pointing to the error in text.

spv_result_t encodeInstructionStartingWithImmediate(

    const spvtools::AssemblyGrammar& grammar,

    spvtools::AssemblyContext* context, spv_instruction_t* pInst) {

  std::string firstWord;

  spv_position_t nextPosition = {};

  auto error = context->getWord(&firstWord, &nextPosition);

  if (error) return context->diagnostic(error) << "Internal Error";

  if ((error = encodeImmediate(context, firstWord.c_str(), pInst))) {

    return error;

  }

  while (context->advance() != SPV_END_OF_STREAM) {

    // A beginning of a new instruction means we're done.

    if (context->isStartOfNewInst()) return SPV_SUCCESS;

    // Otherwise, there must be an operand that's either a literal, an ID, or

    // an immediate.

    std::string operandValue;

    if ((error = context->getWord(&operandValue, &nextPosition)))

      return context->diagnostic(error) << "Internal Error";

    if (operandValue == "=")

      return context->diagnostic() << firstWord << " not allowed before =.";

    // Needed to pass to spvTextEncodeOpcode(), but it shouldn't ever be

    // expanded.

    spv_operand_pattern_t dummyExpectedOperands;

    error = spvTextEncodeOperand(

        grammar, context, SPV_OPERAND_TYPE_OPTIONAL_CIV, operandValue.c_str(),

        pInst, &dummyExpectedOperands);

    if (error) return error;

    context->setPosition(nextPosition);

  }

  return SPV_SUCCESS;

}

/// @brief Translate an instruction started by OpUnknown and the following

/// operands to binary form

///

/// @param[in] grammar the grammar to use for compilation

/// @param[in, out] context the dynamic compilation info

/// @param[out] pInst returned binary Opcode

///

/// @return result code

spv_result_t encodeInstructionStartingWithOpUnknown(

    const spvtools::AssemblyGrammar& grammar,

    spvtools::AssemblyContext* context, spv_instruction_t* pInst) {

  spv_position_t nextPosition = {};

  uint16_t opcode;

  uint16_t wordCount;

  // The '(' character.

  if (context->advance())

    return context->diagnostic() << "Expected '(', found end of stream.";

  if ('(' != context->peek()) {

    return context->diagnostic() << "'(' expected after OpUnknown but found '"

                                 << context->peek() << "'.";

  }

  context->seekForward(1);

  // The opcode enumerant.

  if (context->advance())

    return context->diagnostic()

           << "Expected opcode enumerant, found end of stream.";

  std::string opcodeString;

  spv_result_t error = context->getWord(&opcodeString, &nextPosition);

  if (error) return context->diagnostic(error) << "Internal Error";

  if (!spvtools::utils::ParseNumber(opcodeString.c_str(), &opcode)) {

    return context->diagnostic()

           << "Invalid opcode enumerant: \"" << opcodeString << "\".";

  }

  context->setPosition(nextPosition);

  // The ',' character.

  if (context->advance())

    return context->diagnostic() << "Expected ',', found end of stream.";

  if (',' != context->peek()) {

    return context->diagnostic()

           << "',' expected after opcode enumerant but found '"

           << context->peek() << "'.";

  }

  context->seekForward(1);

  // The number of words.

  if (context->advance())

    return context->diagnostic()

           << "Expected number of words, found end of stream.";

  std::string wordCountString;

  error = context->getWord(&wordCountString, &nextPosition);

  if (error) return context->diagnostic(error) << "Internal Error";

  if (!spvtools::utils::ParseNumber(wordCountString.c_str(), &wordCount)) {

    return context->diagnostic()

           << "Invalid number of words: \"" << wordCountString << "\".";

  }

  if (wordCount == 0) {

    return context->diagnostic() << "Number of words (which includes the "

                                    "opcode) must be greater than zero.";

  }

  context->setPosition(nextPosition);

  // The ')' character.

  if (context->advance())

    return context->diagnostic() << "Expected ')', found end of stream.";

  if (')' != context->peek()) {

    return context->diagnostic()

           << "')' expected after number of words but found '"

           << context->peek() << "'.";

  }

  context->seekForward(1);

  pInst->opcode = static_cast<spv::Op>(opcode);

  context->binaryEncodeU32(spvOpcodeMake(wordCount, pInst->opcode), pInst);

  wordCount--;  // Subtract the opcode from the number of words left to read.

  while (wordCount-- > 0) {

    if (context->advance() == SPV_END_OF_STREAM) {

      return context->diagnostic() << "Expected " << wordCount + 1

                                   << " more operands, found end of stream.";

    }

    if (context->isStartOfNewInst()) {

      std::string invalid;

      context->getWord(&invalid, &nextPosition);

      return context->diagnostic()

             << "Unexpected start of new instruction: \"" << invalid

             << "\". Expected " << wordCount + 1 << " more operands";

    }

    std::string operandValue;

    if ((error = context->getWord(&operandValue, &nextPosition)))

      return context->diagnostic(error) << "Internal Error";

    if (operandValue == "=")

      return context->diagnostic() << "OpUnknown not allowed before =.";

    // Needed to pass to spvTextEncodeOpcode(), but it shouldn't ever be

    // expanded.

    spv_operand_pattern_t dummyExpectedOperands;

    error = spvTextEncodeOperand(

        grammar, context, SPV_OPERAND_TYPE_OPTIONAL_CIV, operandValue.c_str(),

        pInst, &dummyExpectedOperands);

    if (error) return error;

    context->setPosition(nextPosition);

  }

  return SPV_SUCCESS;

}

/// @brief Translate single Opcode and operands to binary form

///

/// @param[in] grammar the grammar to use for compilation

/// @param[in, out] context the dynamic compilation info

/// @param[in] text stream to translate

/// @param[out] pInst returned binary Opcode

/// @param[in,out] pPosition in the text stream

///

/// @return result code

spv_result_t spvTextEncodeOpcode(const spvtools::AssemblyGrammar& grammar,

                                 spvtools::AssemblyContext* context,

                                 spv_instruction_t* pInst) {

  // Check for !<integer> first.

  if ('!' == context->peek()) {

    return encodeInstructionStartingWithImmediate(grammar, context, pInst);

  }

  std::string firstWord;

  spv_position_t nextPosition = {};

  spv_result_t error = context->getWord(&firstWord, &nextPosition);

  if (error) return context->diagnostic() << "Internal Error";

  std::string opcodeName;

  std::string result_id;

  spv_position_t result_id_position = {};

  if (context->startsWithOp()) {

    opcodeName = firstWord;

  } else {

    result_id = firstWord;

    if ('%' != result_id.front()) {

      return context->diagnostic()

             << "Expected <opcode> or <result-id> at the beginning "

                "of an instruction, found '"

             << result_id << "'.";

    }

    result_id_position = context->position();

    // The '=' sign.

    context->setPosition(nextPosition);

    if (context->advance())

      return context->diagnostic() << "Expected '=', found end of stream.";

    std::string equal_sign;

    error = context->getWord(&equal_sign, &nextPosition);

    if ("=" != equal_sign)

      return context->diagnostic() << "'=' expected after result id but found '"

                                   << equal_sign << "'.";

    // The <opcode> after the '=' sign.

    context->setPosition(nextPosition);

    if (context->advance())

      return context->diagnostic() << "Expected opcode, found end of stream.";

    error = context->getWord(&opcodeName, &nextPosition);

    if (error) return context->diagnostic(error) << "Internal Error";

    if (!context->startsWithOp()) {

      return context->diagnostic()

             << "Invalid Opcode prefix '" << opcodeName << "'.";

    }

  }

  if (opcodeName == "OpUnknown") {

    if (!result_id.empty()) {

      return context->diagnostic()

             << "OpUnknown not allowed in assignment. Use an explicit result "

                "id operand instead.";

    }

    context->setPosition(nextPosition);

    return encodeInstructionStartingWithOpUnknown(grammar, context, pInst);

  }

  // NOTE: The table contains Opcode names without the "Op" prefix.

  const char* pInstName = opcodeName.data() + 2;

  spv_opcode_desc opcodeEntry;

  error = grammar.lookupOpcode(pInstName, &opcodeEntry);

  if (error) {

    return context->diagnostic(error)

           << "Invalid Opcode name '" << opcodeName << "'";

  }

  if (opcodeEntry->hasResult && result_id.empty()) {

    return context->diagnostic()

           << "Expected <result-id> at the beginning of an instruction, found '"

           << firstWord << "'.";

  }

  if (!opcodeEntry->hasResult && !result_id.empty()) {

    return context->diagnostic()

           << "Cannot set ID " << result_id << " because " << opcodeName

           << " does not produce a result ID.";

  }

  pInst->opcode = opcodeEntry->opcode;

  context->setPosition(nextPosition);

  // Reserve the first word for the instruction.

  spvInstructionAddWord(pInst, 0);

  // Maintains the ordered list of expected operand types.

  // For many instructions we only need the {numTypes, operandTypes}

  // entries in opcodeEntry.  However, sometimes we need to modify

  // the list as we parse the operands. This occurs when an operand

  // has its own logical operands (such as the LocalSize operand for

  // ExecutionMode), or for extended instructions that may have their

  // own operands depending on the selected extended instruction.

  spv_operand_pattern_t expectedOperands;

  expectedOperands.reserve(opcodeEntry->numTypes);

  for (auto i = 0; i < opcodeEntry->numTypes; i++)

    expectedOperands.push_back(

        opcodeEntry->operandTypes[opcodeEntry->numTypes - i - 1]);

  while (!expectedOperands.empty()) {

    const spv_operand_type_t type = expectedOperands.back();

    expectedOperands.pop_back();

    // Expand optional tuples lazily.

    if (spvExpandOperandSequenceOnce(type, &expectedOperands)) continue;

    if (type == SPV_OPERAND_TYPE_RESULT_ID && !result_id.empty()) {

      // Handle the <result-id> for value generating instructions.

      // We've already consumed it from the text stream.  Here

      // we inject its words into the instruction.

      spv_position_t temp_pos = context->position();

      error = spvTextEncodeOperand(grammar, context, SPV_OPERAND_TYPE_RESULT_ID,

                                   result_id.c_str(), pInst, nullptr);

      result_id_position = context->position();

      // Because we are injecting we have to reset the position afterwards.

      context->setPosition(temp_pos);

      if (error) return error;

    } else {

      // Find the next word.

      error = context->advance();

      if (error == SPV_END_OF_STREAM) {

        if (spvOperandIsOptional(type)) {

          // This would have been the last potential operand for the

          // instruction,

          // and we didn't find one.  We're finished parsing this instruction.

          break;

        } else {

          return context->diagnostic()

                 << "Expected operand for " << opcodeName

                 << " instruction, but found the end of the stream.";

        }

      }

      assert(error == SPV_SUCCESS && "Somebody added another way to fail");

      if (context->isStartOfNewInst()) {

        if (spvOperandIsOptional(type)) {

          break;

        } else {

          return context->diagnostic()

                 << "Expected operand for " << opcodeName

                 << " instruction, but found the next instruction instead.";

        }

      }

      std::string operandValue;

      error = context->getWord(&operandValue, &nextPosition);

      if (error) return context->diagnostic(error) << "Internal Error";

      error = spvTextEncodeOperand(grammar, context, type, operandValue.c_str(),

                                   pInst, &expectedOperands);

      if (error == SPV_FAILED_MATCH && spvOperandIsOptional(type))

        return SPV_SUCCESS;

      if (error) return error;

      context->setPosition(nextPosition);

    }

  }

  if (spvOpcodeGeneratesType(pInst->opcode)) {

    if (context->recordTypeDefinition(pInst) != SPV_SUCCESS) {

      return SPV_ERROR_INVALID_TEXT;

    }

  } else if (opcodeEntry->hasType) {

    // SPIR-V dictates that if an instruction has both a return value and a

    // type ID then the type id is first, and the return value is second.

    assert(opcodeEntry->hasResult &&

           "Unknown opcode: has a type but no result.");

    context->recordTypeIdForValue(pInst->words[2], pInst->words[1]);

  }

  if (pInst->words.size() > SPV_LIMIT_INSTRUCTION_WORD_COUNT_MAX) {

    return context->diagnostic()

           << opcodeName << " Instruction too long: " << pInst->words.size()

           << " words, but the limit is "

           << SPV_LIMIT_INSTRUCTION_WORD_COUNT_MAX;

  }

  pInst->words[0] =

      spvOpcodeMake(uint16_t(pInst->words.size()), opcodeEntry->opcode);

  return SPV_SUCCESS;

}

enum { kAssemblerVersion = 0 };

// Populates a binary stream's |header|. The target environment is specified via

// |env| and Id bound is via |bound|.

spv_result_t SetHeader(spv_target_env env, const uint32_t bound,

                       uint32_t* header) {

  if (!header) return SPV_ERROR_INVALID_BINARY;

  header[SPV_INDEX_MAGIC_NUMBER] = spv::MagicNumber;

  header[SPV_INDEX_VERSION_NUMBER] = spvVersionForTargetEnv(env);

  header[SPV_INDEX_GENERATOR_NUMBER] =

      SPV_GENERATOR_WORD(SPV_GENERATOR_KHRONOS_ASSEMBLER, kAssemblerVersion);

  header[SPV_INDEX_BOUND] = bound;

  header[SPV_INDEX_SCHEMA] = 0;  // NOTE: Reserved

  return SPV_SUCCESS;

}

// Collects all numeric ids in the module source into |numeric_ids|.

// This function is essentially a dry-run of spvTextToBinary.

spv_result_t GetNumericIds(const spvtools::AssemblyGrammar& grammar,

                           const spvtools::MessageConsumer& consumer,

                           const spv_text text,

                           std::set<uint32_t>* numeric_ids) {

  spvtools::AssemblyContext context(text, consumer);

  if (!text->str) return context.diagnostic() << "Missing assembly text.";

  if (!grammar.isValid()) {

    return SPV_ERROR_INVALID_TABLE;

  }

  // Skip past whitespace and comments.

  context.advance();

  while (context.hasText()) {

    spv_instruction_t inst;

    // Operand parsing sometimes involves knowing the opcode of the instruction

    // being parsed. A malformed input might feature such an operand *before*

    // the opcode is known. To guard against accessing an uninitialized opcode,

    // the instruction's opcode is initialized to a default value.

    inst.opcode = spv::Op::Max;

    if (spvTextEncodeOpcode(grammar, &context, &inst)) {

      return SPV_ERROR_INVALID_TEXT;

    }

    if (context.advance()) break;

  }