VaryingPacking.cpp

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Author : Jamie Madill
Date : 2016-12-22 15:58:21
Hash : 192745a7
Message : Add varying packing validation for WebGL. This CL moves the varying packing from the D3D layer up to Program. This is necessary for WebGL validation, and gives us consistency for the various back-ends. There may be some additional cleanup work on the VaryingPacking class, because it does some work that is D3D- specific. WebGL requires strict varying packing. Instead of allowing success unconditionally, it's an explicit error to succeed to pack a set of varyings that the sample algorithm would fail to pack. Introduce a new packing mode option to the varying packing class to handle this different packing style, while keeping our old more relaxed packing method for ES code. BUG=angleproject:1675 Change-Id: I674ae685ba573cc2ad7d9dfb7441efa8cb2d55fc Reviewed-on: https://chromium-review.googlesource.com/423254 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Corentin Wallez <cwallez@chromium.org>
src/libANGLE/VaryingPacking.cpp
//
// 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
kc3-lang/angle/src/libANGLE/VaryingPacking.cpp

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kc3-lang/angle /src/libANGLE/VaryingPacking.cpp
