src/tint/lang/spirv/writer/common/binary_writer.cc

// Copyright 2020 The Dawn & Tint Authors
//
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// modification, are permitted provided that the following conditions are met:
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#include "src/tint/lang/spirv/writer/common/binary_writer.h"

#include <cstring>
#include <string>

namespace tint::spirv::writer {
namespace {

const uint32_t kGeneratorId = 23u << 16;

}  // namespace

BinaryWriter::BinaryWriter() = default;

BinaryWriter::~BinaryWriter() = default;

void BinaryWriter::WriteModule(const Module& module) {
    out_.reserve(module.TotalSize());
    module.Iterate([this](const Instruction& inst) { this->process_instruction(inst); });
}

void BinaryWriter::WriteInstruction(const Instruction& inst) {
    process_instruction(inst);
}

void BinaryWriter::WriteHeader(uint32_t bound, uint32_t version) {
    out_.push_back(spv::MagicNumber);
    out_.push_back(0x00010300);  // Version 1.3
    out_.push_back(kGeneratorId | version);
    out_.push_back(bound);
    out_.push_back(0);
}

void BinaryWriter::process_instruction(const Instruction& inst) {
    out_.push_back(inst.word_length() << 16 | static_cast<uint32_t>(inst.opcode()));
    for (const auto& op : inst.operands()) {
        process_op(op);
    }
}

void BinaryWriter::process_op(const Operand& op) {
    if (auto* i = std::get_if<uint32_t>(&op)) {
        out_.push_back(*i);
        return;
    }
    if (auto* f = std::get_if<float>(&op)) {
        // Allocate space for the float
        out_.push_back(0);
        uint8_t* ptr = reinterpret_cast<uint8_t*>(out_.data() + (out_.size() - 1));
        memcpy(ptr, f, 4);
        return;
    }
    if (auto* str = std::get_if<std::string>(&op)) {
        auto idx = out_.size();
        out_.resize(out_.size() + OperandLength(op), 0);
        memcpy(out_.data() + idx, str->c_str(), str->size() + 1);
        return;
    }
}

}  // namespace tint::spirv::writer