//
// Copyright 2015 The ANGLE Project Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
//
// VaryingPacking:
//   Class which describes a mapping from varyings to registers, according
//   to the spec, or using custom packing algorithms. We also keep a register
//   allocation list for the D3D renderer.
//

#include "libANGLE/VaryingPacking.h"

#include "common/utilities.h"
#include "libANGLE/Program.h"

namespace gl
{

// Implementation of VaryingPacking
VaryingPacking::VaryingPacking(GLuint maxVaryingVectors, PackMode packMode)
    : mRegisterMap(maxVaryingVectors), mPackMode(packMode)
{
}

// Packs varyings into generic varying registers, using the algorithm from
// See [OpenGL ES Shading Language 1.00 rev. 17] appendix A section 7 page 111
// Also [OpenGL ES Shading Language 3.00 rev. 4] Section 11 page 119
// Returns false if unsuccessful.
bool VaryingPacking::packVarying(const PackedVarying &packedVarying)
{
    const auto &varying = *packedVarying.varying;

    // "Non - square matrices of type matCxR consume the same space as a square matrix of type matN
    // where N is the greater of C and R."
    // Here we are a bit more conservative and allow packing non-square matrices more tightly.
    // Make sure we use transposed matrix types to count registers correctly.
    ASSERT(!varying.isStruct());
    GLenum transposedType       = gl::TransposeMatrixType(varying.type);
    unsigned int varyingRows    = gl::VariableRowCount(transposedType);
    unsigned int varyingColumns = gl::VariableColumnCount(transposedType);

    // "Variables of type mat2 occupies 2 complete rows."
    // For non-WebGL contexts, we allow mat2 to occupy only two columns per row.
    if (mPackMode == PackMode::WEBGL_STRICT && varying.type == GL_FLOAT_MAT2)
    {
        varyingColumns = 4;
    }

    // "Arrays of size N are assumed to take N times the size of the base type"
    varyingRows *= varying.elementCount();

    unsigned int maxVaryingVectors = static_cast<unsigned int>(mRegisterMap.size());

    // Fail if we are packing a single over-large varying.
    if (varyingRows > maxVaryingVectors)
    {
        return false;
    }

    // "For 2, 3 and 4 component variables packing is started using the 1st column of the 1st row.
    // Variables are then allocated to successive rows, aligning them to the 1st column."
    if (varyingColumns >= 2 && varyingColumns <= 4)
    {
        for (unsigned int row = 0; row <= maxVaryingVectors - varyingRows; ++row)
        {
            if (isFree(row, 0, varyingRows, varyingColumns))
            {
                insert(row, 0, packedVarying);
                return true;
            }
        }

        // "For 2 component variables, when there are no spare rows, the strategy is switched to
        // using the highest numbered row and the lowest numbered column where the variable will
        // fit."
        if (varyingColumns == 2)
        {
            for (unsigned int r = maxVaryingVectors - varyingRows + 1; r-- >= 1;)
            {
                if (isFree(r, 2, varyingRows, 2))
                {
                    insert(r, 2, packedVarying);
                    return true;
                }
            }
        }

        return false;
    }

    // "1 component variables have their own packing rule. They are packed in order of size, largest
    // first. Each variable is placed in the column that leaves the least amount of space in the
    // column and aligned to the lowest available rows within that column."
    ASSERT(varyingColumns == 1);
    unsigned int contiguousSpace[4]     = {0};
    unsigned int bestContiguousSpace[4] = {0};
    unsigned int totalSpace[4]          = {0};

    for (unsigned int row = 0; row < maxVaryingVectors; ++row)
    {
        for (unsigned int column = 0; column < 4; ++column)
        {
            if (mRegisterMap[row][column])
            {
                contiguousSpace[column] = 0;
            }
            else
            {
                contiguousSpace[column]++;
                totalSpace[column]++;

                if (contiguousSpace[column] > bestContiguousSpace[column])
                {
                    bestContiguousSpace[column] = contiguousSpace[column];
                }
            }
        }
    }

    unsigned int bestColumn = 0;
    for (unsigned int column = 1; column < 4; ++column)
    {
        if (bestContiguousSpace[column] >= varyingRows &&
            (bestContiguousSpace[bestColumn] < varyingRows ||
             totalSpace[column] < totalSpace[bestColumn]))
        {
            bestColumn = column;
        }
    }

    if (bestContiguousSpace[bestColumn] >= varyingRows)
    {
        for (unsigned int row = 0; row < maxVaryingVectors; row++)
        {
            if (isFree(row, bestColumn, varyingRows, 1))
            {
                for (unsigned int arrayIndex = 0; arrayIndex < varyingRows; ++arrayIndex)
                {
                    // If varyingRows > 1, it must be an array.
                    PackedVaryingRegister registerInfo;
                    registerInfo.packedVarying     = &packedVarying;
                    registerInfo.registerRow       = row + arrayIndex;
                    registerInfo.registerColumn    = bestColumn;
                    registerInfo.varyingArrayIndex = arrayIndex;
                    registerInfo.varyingRowIndex   = 0;
                    // Do not record register info for builtins.
                    // TODO(jmadill): Clean this up.
                    if (!packedVarying.varying->isBuiltIn())
                    {
                        mRegisterList.push_back(registerInfo);
                    }
                    mRegisterMap[row + arrayIndex][bestColumn] = true;
                }
                break;
            }
        }
        return true;
    }

    return false;
}

bool VaryingPacking::isFree(unsigned int registerRow,
                            unsigned int registerColumn,
                            unsigned int varyingRows,
                            unsigned int varyingColumns) const
{
    for (unsigned int row = 0; row < varyingRows; ++row)
    {
        ASSERT(registerRow + row < mRegisterMap.size());
        for (unsigned int column = 0; column < varyingColumns; ++column)
        {
            ASSERT(registerColumn + column < 4);
            if (mRegisterMap[registerRow + row][registerColumn + column])
            {
                return false;
            }
        }
    }

    return true;
}

void VaryingPacking::insert(unsigned int registerRow,
                            unsigned int registerColumn,
                            const PackedVarying &packedVarying)
{
    unsigned int varyingRows    = 0;
    unsigned int varyingColumns = 0;

    const auto &varying = *packedVarying.varying;
    ASSERT(!varying.isStruct());
    GLenum transposedType = gl::TransposeMatrixType(varying.type);
    varyingRows           = gl::VariableRowCount(transposedType);
    varyingColumns        = gl::VariableColumnCount(transposedType);

    PackedVaryingRegister registerInfo;
    registerInfo.packedVarying  = &packedVarying;
    registerInfo.registerColumn = registerColumn;

    for (unsigned int arrayElement = 0; arrayElement < varying.elementCount(); ++arrayElement)
    {
        for (unsigned int varyingRow = 0; varyingRow < varyingRows; ++varyingRow)
        {
            registerInfo.registerRow     = registerRow + (arrayElement * varyingRows) + varyingRow;
            registerInfo.varyingRowIndex = varyingRow;
            registerInfo.varyingArrayIndex = arrayElement;
            // Do not record register info for builtins.
            // TODO(jmadill): Clean this up.
            if (!packedVarying.varying->isBuiltIn())
            {
                mRegisterList.push_back(registerInfo);
            }

            for (unsigned int columnIndex = 0; columnIndex < varyingColumns; ++columnIndex)
            {
                mRegisterMap[registerInfo.registerRow][registerColumn + columnIndex] = true;
            }
        }
    }
}

// See comment on packVarying.
bool VaryingPacking::packUserVaryings(gl::InfoLog &infoLog,
                                      const std::vector<PackedVarying> &packedVaryings,
                                      const std::vector<std::string> &transformFeedbackVaryings)
{
    std::set<std::string> uniqueVaryingNames;

    // "Variables are packed into the registers one at a time so that they each occupy a contiguous
    // subrectangle. No splitting of variables is permitted."
    for (const PackedVarying &packedVarying : packedVaryings)
    {
        const auto &varying = *packedVarying.varying;

        // Do not assign registers to built-in or unreferenced varyings
        if (!varying.staticUse && !packedVarying.isStructField())
        {
            continue;
        }

        ASSERT(!varying.isStruct());
        ASSERT(uniqueVaryingNames.count(varying.name) == 0);

        if (packVarying(packedVarying))
        {
            uniqueVaryingNames.insert(varying.name);
        }
        else
        {
            infoLog << "Could not pack varying " << varying.name;
            return false;
        }
    }

    for (const std::string &transformFeedbackVaryingName : transformFeedbackVaryings)
    {
        if (transformFeedbackVaryingName.compare(0, 3, "gl_") == 0)
        {
            // do not pack builtin XFB varyings
            continue;
        }

        bool found = false;
        for (const PackedVarying &packedVarying : packedVaryings)
        {
            const auto &varying = *packedVarying.varying;

            // Make sure transform feedback varyings aren't optimized out.
            if (uniqueVaryingNames.count(transformFeedbackVaryingName) > 0)
            {
                found = true;
                break;
            }

            if (transformFeedbackVaryingName == varying.name)
            {
                if (!packVarying(packedVarying))
                {
                    infoLog << "Could not pack varying " << varying.name;
                    return false;
                }

                found = true;
                break;
            }
        }

        if (!found)
        {
            infoLog << "Transform feedback varying " << transformFeedbackVaryingName
                    << " does not exist in the vertex shader.";
            return false;
        }
    }

    // Sort the packed register list
    std::sort(mRegisterList.begin(), mRegisterList.end());

    // Assign semantic indices
    for (unsigned int semanticIndex = 0;
         semanticIndex < static_cast<unsigned int>(mRegisterList.size()); ++semanticIndex)
    {
        mRegisterList[semanticIndex].semanticIndex = semanticIndex;
    }

    return true;
}

unsigned int VaryingPacking::getRegisterCount() const
{
    unsigned int count = 0;

    for (const Register &reg : mRegisterMap)
    {
        if (reg.data[0] || reg.data[1] || reg.data[2] || reg.data[3])
        {
            ++count;
        }
    }

    return count;
}

}  // namespace rx
