ReplaceClipCullDistanceVariable.cpp

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Author : Shahbaz Youssefi
Date : 2021-08-23 11:05:23
Hash : 800e82c6
Message : Translator: Validate precisions When declaring a variable, a struct field, function parameter etc, there's a precision necessarily applied to the entity being declared. AST Validation is added to enforce this. Intermediate nodes derive their precision from these entities automatically. Consistency of intermediate nodes is not validated. This is because AST transformations replace a node with a transformed one, and that may not have the same precision. Take the following code: mediump float x = ...; mediump float y = ...; ... x + y ... and assume is transformed as such: highp float driver_uniform; ... (x * driver_uniform) + y ... The addition was originally done in mediump, but would seemingly need to be done in highp after transformation. There are a number of options here: - Make sure that when nodes are replaced, the precision is unaffected. This can be intrusive, requiring temp variables. - Bubble up the new precision - Accept the discrepancy ANGLE opts for the last option, which actually respects the original shader's intended precision for operations, even if some transformation needs to temporarily evaluate an expression at a higher precision. Bug: angleproject:4889 Bug: angleproject:6132 Change-Id: Ibcde3a230de159157783b1c6d5ef1cd63ceb4d8f Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3114027 Reviewed-by: Tim Van Patten <timvp@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
src/compiler/translator/tree_util/ReplaceClipCullDistanceVariable.cpp
//
// Copyright 2020 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.
//
// ReplaceClipCullDistanceVariable.cpp: Find any references to gl_ClipDistance or gl_CullDistance
// and replace it with ANGLEClipDistance or ANGLECullDistance.
//

#include "compiler/translator/tree_util/ReplaceClipCullDistanceVariable.h"

#include "common/bitset_utils.h"
#include "common/debug.h"
#include "common/utilities.h"
#include "compiler/translator/Compiler.h"
#include "compiler/translator/SymbolTable.h"
#include "compiler/translator/tree_util/BuiltIn.h"
#include "compiler/translator/tree_util/IntermNode_util.h"
#include "compiler/translator/tree_util/IntermTraverse.h"
#include "compiler/translator/tree_util/ReplaceVariable.h"
#include "compiler/translator/tree_util/RunAtTheBeginningOfShader.h"
#include "compiler/translator/tree_util/RunAtTheEndOfShader.h"

namespace sh
{
namespace
{

using ClipCullDistanceIdxSet = angle::BitSet<32>;

typedef TIntermNode *AssignFunc(const unsigned int index,
                                TIntermSymbol *left,
                                TIntermSymbol *right,
                                const TIntermTyped *enableFlags);

template <typename Variable>
const Variable *FindVariable(const std::vector<Variable> &mVars, const ImmutableString &name)
{
    for (const Variable &var : mVars)
    {
        if (name == var.instanceName)
        {
            return &var;
        }
    }

    return nullptr;
}

// Traverse the tree and collect the redeclaration and all constant index references of
// gl_ClipDistance/gl_CullDistance
class GLClipCullDistanceReferenceTraverser : public TIntermTraverser
{
  public:
    GLClipCullDistanceReferenceTraverser(const TIntermSymbol **redeclaredSymOut,
                                         bool *nonConstIdxUsedOut,
                                         unsigned int *maxConstIdxOut,
                                         ClipCullDistanceIdxSet *constIndicesOut,
                                         TQualifier targetQualifier)
        : TIntermTraverser(true, false, false),
          mRedeclaredSym(redeclaredSymOut),
          mUseNonConstClipCullDistanceIndex(nonConstIdxUsedOut),
          mMaxConstClipCullDistanceIndex(maxConstIdxOut),
          mConstClipCullDistanceIndices(constIndicesOut),
          mTargetQualifier(targetQualifier)
    {
        *mRedeclaredSym                    = nullptr;
        *mUseNonConstClipCullDistanceIndex = false;
        *mMaxConstClipCullDistanceIndex    = 0;
        mConstClipCullDistanceIndices->reset();
    }

    bool visitDeclaration(Visit visit, TIntermDeclaration *node) override
    {
        // If gl_ClipDistance/gl_CullDistance is redeclared, we need to collect its information
        const TIntermSequence &sequence = *(node->getSequence());

        if (sequence.size() != 1)
        {
            return true;
        }

        TIntermSymbol *variable = sequence.front()->getAsSymbolNode();
        if (variable == nullptr || variable->getType().getQualifier() != mTargetQualifier)
        {
            return true;
        }

        *mRedeclaredSym = variable->getAsSymbolNode();

        return true;
    }

    bool visitBinary(Visit visit, TIntermBinary *node) override
    {
        TOperator op = node->getOp();
        if (op != EOpIndexDirect && op != EOpIndexIndirect)
        {
            return true;
        }

        // gl_ClipDistance / gl_CullDistance
        TIntermTyped *left = node->getLeft()->getAsTyped();
        if (!left)
        {
            return true;
        }

        ASSERT(op == EOpIndexDirect || op == EOpIndexIndirect);

        TIntermSymbol *clipCullDistance = left->getAsSymbolNode();
        if (!clipCullDistance)
        {
            return true;
        }
        if (clipCullDistance->getType().getQualifier() != mTargetQualifier)
        {
            return true;
        }

        const TConstantUnion *constIdx = node->getRight()->getConstantValue();
        if (!constIdx)
        {
            *mUseNonConstClipCullDistanceIndex = true;
        }
        else
        {
            unsigned int idx = 0;
            switch (constIdx->getType())
            {
                case EbtInt:
                    idx = constIdx->getIConst();
                    break;
                case EbtUInt:
                    idx = constIdx->getUConst();
                    break;
                case EbtFloat:
                    idx = static_cast<unsigned int>(constIdx->getFConst());
                    break;
                case EbtBool:
                    idx = constIdx->getBConst() ? 1 : 0;
                    break;
                default:
                    UNREACHABLE();
                    break;
            }
            ASSERT(idx < mConstClipCullDistanceIndices->size());
            mConstClipCullDistanceIndices->set(idx);

            *mMaxConstClipCullDistanceIndex = std::max(*mMaxConstClipCullDistanceIndex, idx);
        }

        return true;
    }

  private:
    const TIntermSymbol **mRedeclaredSym;
    // Flag indicating whether there is at least one reference of gl_ClipDistance with non-constant
    // index
    bool *mUseNonConstClipCullDistanceIndex;
    // Max constant index that is used to reference gl_ClipDistance
    unsigned int *mMaxConstClipCullDistanceIndex;
    // List of constant index reference of gl_ClipDistance
    ClipCullDistanceIdxSet *mConstClipCullDistanceIndices;
    // Qualifier for gl_ClipDistance/gl_CullDistance
    const TQualifier mTargetQualifier;
};

// Replace all symbolic occurrences of given variables except one symbol.
class ReplaceVariableExceptOneTraverser : public TIntermTraverser
{
  public:
    ReplaceVariableExceptOneTraverser(const TVariable *toBeReplaced,
                                      const TIntermTyped *replacement,
                                      const TIntermSymbol *exception)
        : TIntermTraverser(true, false, false),
          mToBeReplaced(toBeReplaced),
          mException(exception),
          mReplacement(replacement)
    {}

    void visitSymbol(TIntermSymbol *node) override
    {
        if (&node->variable() == mToBeReplaced && node != mException)
        {
            queueReplacement(mReplacement->deepCopy(), OriginalNode::IS_DROPPED);
        }
    }

  private:
    const TVariable *const mToBeReplaced;
    const TIntermSymbol *const mException;
    const TIntermTyped *const mReplacement;
};

TIntermNode *simpleAssignFunc(const unsigned int index,
                              TIntermSymbol *leftSymbol,
                              TIntermSymbol *rightSymbol,
                              const TIntermTyped * /*enableFlags*/)
{
    // leftSymbol[index] = rightSymbol[index]
    // E.g., ANGLEClipDistance[index] = gl_ClipDistance[index]
    TIntermBinary *left =
        new TIntermBinary(EOpIndexDirect, leftSymbol->deepCopy(), CreateIndexNode(index));
    TIntermBinary *right =
        new TIntermBinary(EOpIndexDirect, rightSymbol->deepCopy(), CreateIndexNode(index));

    return new TIntermBinary(EOpAssign, left, right);
}

// This is only used for gl_ClipDistance
TIntermNode *assignFuncWithEnableFlags(const unsigned int index,
                                       TIntermSymbol *leftSymbol,
                                       TIntermSymbol *rightSymbol,
                                       const TIntermTyped *enableFlags)
{
    //  if (ANGLEUniforms.clipDistancesEnabled & (0x1 << index))
    //      gl_ClipDistance[index] = ANGLEClipDistance[index];
    //  else
    //      gl_ClipDistance[index] = 0;
    TIntermConstantUnion *bitMask = CreateUIntNode(0x1 << index);
    TIntermBinary *bitwiseAnd = new TIntermBinary(EOpBitwiseAnd, enableFlags->deepCopy(), bitMask);
    TIntermBinary *nonZero    = new TIntermBinary(EOpNotEqual, bitwiseAnd, CreateUIntNode(0));

    TIntermBinary *left =
        new TIntermBinary(EOpIndexDirect, leftSymbol->deepCopy(), CreateIndexNode(index));
    TIntermBinary *right =
        new TIntermBinary(EOpIndexDirect, rightSymbol->deepCopy(), CreateIndexNode(index));
    TIntermBinary *assignment = new TIntermBinary(EOpAssign, left, right);
    TIntermBlock *trueBlock   = new TIntermBlock();
    trueBlock->appendStatement(assignment);

    TIntermBinary *zeroAssignment =
        new TIntermBinary(EOpAssign, left->deepCopy(), CreateFloatNode(0, EbpMedium));
    TIntermBlock *falseBlock = new TIntermBlock();
    falseBlock->appendStatement(zeroAssignment);

    return new TIntermIfElse(nonZero, trueBlock, falseBlock);
}

class ReplaceClipCullDistanceAssignments : angle::NonCopyable
{
  public:
    ReplaceClipCullDistanceAssignments(TCompiler *compiler,
                                       TIntermBlock *root,
                                       TSymbolTable *symbolTable,
                                       const TVariable *glClipCullDistanceVar,
                                       const TIntermSymbol *redeclaredGlClipDistance,
                                       const ImmutableString &angleVarName)
        : mCompiler(compiler),
          mRoot(root),
          mSymbolTable(symbolTable),
          mGlVar(glClipCullDistanceVar),
          mRedeclaredGLVar(redeclaredGlClipDistance),
          mANGLEVarName(angleVarName)
    {
        mEnabledDistances = 0;
    }

    unsigned int getEnabledClipCullDistance(const bool useNonConstIndex,
                                            const unsigned int maxConstIndex);
    const TVariable *declareANGLEVariable(const TVariable *originalVariable);
    bool assignOriginalValueToANGLEVariable(const GLenum shaderType);
    bool assignANGLEValueToOriginalVariable(const GLenum shaderType,
                                            const bool isRedeclared,
                                            const TIntermTyped *enableFlags,
                                            const ClipCullDistanceIdxSet *constIndices);

  private:
    bool assignOriginalValueToANGLEVariableImpl();
    bool assignANGLEValueToOriginalVariableImpl(const bool isRedeclared,
                                                const TIntermTyped *enableFlags,
                                                const ClipCullDistanceIdxSet *constIndices,
                                                AssignFunc assignFunc);

    // Common variables for replacing gl_Clip/CullDistances with ANGLEClip/CullDistances
    TCompiler *mCompiler;
    TIntermBlock *mRoot;
    TSymbolTable *mSymbolTable;

    const TVariable *mGlVar;
    const TIntermSymbol *mRedeclaredGLVar;
    const ImmutableString mANGLEVarName;

    unsigned int mEnabledDistances;
    const TVariable *mANGLEVar;
};

unsigned int ReplaceClipCullDistanceAssignments::getEnabledClipCullDistance(
    const bool useNonConstIndex,
    const unsigned int maxConstIndex)
{
    if (mRedeclaredGLVar)
    {
        // If array is redeclared by user, use that redeclared size.
        mEnabledDistances = mRedeclaredGLVar->getType().getOutermostArraySize();
    }
    else if (!useNonConstIndex)
    {
        ASSERT(maxConstIndex < mGlVar->getType().getOutermostArraySize());
        // Only use constant index, then use max array index used.
        mEnabledDistances = maxConstIndex + 1;
    }

    return mEnabledDistances;
}

const TVariable *ReplaceClipCullDistanceAssignments::declareANGLEVariable(
    const TVariable *originalVariable)
{
    ASSERT(mEnabledDistances > 0);

    TType *clipCullDistanceType = new TType(originalVariable->getType());
    clipCullDistanceType->setQualifier(EvqGlobal);
    clipCullDistanceType->toArrayBaseType();
    clipCullDistanceType->makeArray(mEnabledDistances);

    mANGLEVar =
        new TVariable(mSymbolTable, mANGLEVarName, clipCullDistanceType, SymbolType::AngleInternal);

    TIntermSymbol *clipCullDistanceDeclarator = new TIntermSymbol(mANGLEVar);
    TIntermDeclaration *clipCullDistanceDecl  = new TIntermDeclaration;
    clipCullDistanceDecl->appendDeclarator(clipCullDistanceDeclarator);

    // Must declare ANGLEClipdistance/ANGLECullDistance before any function, since
    // gl_ClipDistance/gl_CullDistance might be accessed within a function declared before main.
    mRoot->insertStatement(0, clipCullDistanceDecl);

    return mANGLEVar;
}

bool ReplaceClipCullDistanceAssignments::assignOriginalValueToANGLEVariableImpl()
{
    ASSERT(mEnabledDistances > 0);

    TIntermBlock *readBlock                 = new TIntermBlock;
    TIntermSymbol *glClipCullDistanceSymbol = new TIntermSymbol(mGlVar);
    TIntermSymbol *clipCullDistanceSymbol   = new TIntermSymbol(mANGLEVar);

    for (unsigned int i = 0; i < mEnabledDistances; i++)
    {
        readBlock->appendStatement(
            simpleAssignFunc(i, clipCullDistanceSymbol, glClipCullDistanceSymbol, nullptr));
    }

    return RunAtTheBeginningOfShader(mCompiler, mRoot, readBlock);
}

bool ReplaceClipCullDistanceAssignments::assignANGLEValueToOriginalVariableImpl(
    const bool isRedeclared,
    const TIntermTyped *enableFlags,
    const ClipCullDistanceIdxSet *constIndices,
    AssignFunc assignFunc)
{
    ASSERT(mEnabledDistances > 0);

    TIntermBlock *assignBlock               = new TIntermBlock;
    TIntermSymbol *glClipCullDistanceSymbol = new TIntermSymbol(mGlVar);
    TIntermSymbol *clipCullDistanceSymbol   = new TIntermSymbol(mANGLEVar);

    // The array size is decided by either redeclaring the variable or accessing the variable with a
    // integral constant index. And this size is the count of the enabled value. So, if the index
    // which is greater than the array size, is used to access the variable, this access will be
    // ignored.
    if (isRedeclared || !constIndices)
    {
        for (unsigned int i = 0; i < mEnabledDistances; ++i)
        {
            assignBlock->appendStatement(
                assignFunc(i, glClipCullDistanceSymbol, clipCullDistanceSymbol, enableFlags));
        }
    }
    else
    {
        // Assign ANGLEClip/CullDistance[i]'s value to gl_Clip/CullDistance[i] if i is in the
        // constant indices list. Those elements whose index is not in the constant index list will
        // be zeroise for initialization.
        for (unsigned int i = 0; i < mEnabledDistances; ++i)
        {
            if (constIndices->test(i))
            {
                assignBlock->appendStatement(
                    assignFunc(i, glClipCullDistanceSymbol, clipCullDistanceSymbol, enableFlags));
            }
            else
            {
                // gl_Clip/CullDistance[i] = 0;
                TIntermBinary *left = new TIntermBinary(
                    EOpIndexDirect, glClipCullDistanceSymbol->deepCopy(), CreateIndexNode(i));
                TIntermBinary *zeroAssignment =
                    new TIntermBinary(EOpAssign, left, CreateFloatNode(0, EbpMedium));
                assignBlock->appendStatement(zeroAssignment);
            }
        }
    }

    return RunAtTheEndOfShader(mCompiler, mRoot, assignBlock, mSymbolTable);
}

ANGLE_NO_DISCARD bool ReplaceClipCullDistanceAssignments::assignOriginalValueToANGLEVariable(
    const GLenum shaderType)
{
    switch (shaderType)
    {
        case GL_VERTEX_SHADER:
            // Vertex shader can use gl_Clip/CullDistance as a output only
            break;
        case GL_FRAGMENT_SHADER:
        {
            // These shader types can use gl_Clip/CullDistance as input
            if (!assignOriginalValueToANGLEVariableImpl())
            {
                return false;
            }
            break;
        }
        default:
        {
            UNREACHABLE();
            return false;
        }
    }

    return true;
}

ANGLE_NO_DISCARD bool ReplaceClipCullDistanceAssignments::assignANGLEValueToOriginalVariable(
    const GLenum shaderType,
    const bool isRedeclared,
    const TIntermTyped *enableFlags,
    const ClipCullDistanceIdxSet *constIndices)
{
    switch (shaderType)
    {
        case GL_VERTEX_SHADER:
        {
            // Vertex shader can use gl_Clip/CullDistance as output.
            // If the enabled gl_Clip/CullDistances are not initialized, results are undefined.
            // EXT_clip_cull_distance spec :
            // The shader must also set all values in gl_ClipDistance that have been enabled via the
            // OpenGL ES API, or results are undefined. Values written into gl_ClipDistance for
            // planes that are not enabled have no effect.
            // ...
            // Shaders writing gl_CullDistance must write all enabled distances, or culling results
            // are undefined.
            if (!assignANGLEValueToOriginalVariableImpl(
                    isRedeclared, enableFlags, constIndices,
                    enableFlags ? assignFuncWithEnableFlags : simpleAssignFunc))
            {
                return false;
            }
            break;
        }
        case GL_FRAGMENT_SHADER:
            // Fragment shader can use gl_Clip/CullDistance as input only
            break;
        default:
        {
            UNREACHABLE();
            return false;
        }
    }

    return true;
}

// Common code to transform gl_ClipDistance and gl_CullDistance.  Comments reference
// gl_ClipDistance, but are also applicable to gl_CullDistance.
ANGLE_NO_DISCARD bool ReplaceClipCullDistanceAssignmentsImpl(
    TCompiler *compiler,
    TIntermBlock *root,
    TSymbolTable *symbolTable,
    const GLenum shaderType,
    const TIntermTyped *clipDistanceEnableFlags,
    const char *builtInName,
    const char *replacementName,
    TQualifier builtInQualifier)
{
    // Collect all constant index references of gl_ClipDistance
    ImmutableString name(builtInName);
    ClipCullDistanceIdxSet constIndices;
    bool useNonConstIndex                  = false;
    const TIntermSymbol *redeclaredBuiltIn = nullptr;
    unsigned int maxConstIndex             = 0;
    GLClipCullDistanceReferenceTraverser indexTraverser(
        &redeclaredBuiltIn, &useNonConstIndex, &maxConstIndex, &constIndices, builtInQualifier);
    root->traverse(&indexTraverser);
    if (!useNonConstIndex && constIndices.none())
    {
        // No references of gl_ClipDistance
        return true;
    }

    // Retrieve gl_ClipDistance variable reference
    // Search user redeclared gl_ClipDistance first
    const TVariable *builtInVar = nullptr;
    if (redeclaredBuiltIn)
    {
        builtInVar = &redeclaredBuiltIn->variable();
    }
    else
    {
        // User defined not found, find in built-in table
        builtInVar = static_cast<const TVariable *>(
            symbolTable->findBuiltIn(name, compiler->getShaderVersion()));
    }
    if (!builtInVar)
    {
        return false;
    }

    ReplaceClipCullDistanceAssignments replacementUtils(compiler, root, symbolTable, builtInVar,
                                                        redeclaredBuiltIn,
                                                        ImmutableString(replacementName));

    // Declare a global variable substituting gl_ClipDistance
    unsigned int enabledClipDistances =
        replacementUtils.getEnabledClipCullDistance(useNonConstIndex, maxConstIndex);
    if (!enabledClipDistances)
    {
        // Spec :
        // The gl_ClipDistance array is predeclared as unsized and must be explicitly sized by the
        // shader either redeclaring it with a size or implicitly sized by indexing it only with
        // integral constant expressions.
        return false;
    }

    const TVariable *replacementVar = replacementUtils.declareANGLEVariable(builtInVar);

    // Replace gl_ClipDistance reference with ANGLEClipDistance, except the declaration
    ReplaceVariableExceptOneTraverser replaceTraverser(builtInVar,
                                                       new TIntermSymbol(replacementVar),
                                                       /** exception */ redeclaredBuiltIn);
    root->traverse(&replaceTraverser);
    if (!replaceTraverser.updateTree(compiler, root))
    {
        return false;
    }

    // Read gl_ClipDistance to ANGLEClipDistance for getting a original data
    if (!replacementUtils.assignOriginalValueToANGLEVariable(shaderType))
    {
        return false;
    }

    // Reassign ANGLEClipDistance to gl_ClipDistance but ignore those that are disabled
    const bool isRedeclared = redeclaredBuiltIn != nullptr;
    if (!replacementUtils.assignANGLEValueToOriginalVariable(
            shaderType, isRedeclared, clipDistanceEnableFlags, &constIndices))
    {
        return false;
    }

    // If not redeclared, replace the built-in with one that is appropriately sized
    if (!isRedeclared)
    {
        TType *resizedType = new TType(builtInVar->getType());
        resizedType->setArraySize(0, enabledClipDistances);

        TVariable *resizedVar = new TVariable(symbolTable, name, resizedType, SymbolType::BuiltIn);

        return ReplaceVariable(compiler, root, builtInVar, resizedVar);
    }

    return true;
}

}  // anonymous namespace

ANGLE_NO_DISCARD bool ReplaceClipDistanceAssignments(TCompiler *compiler,
                                                     TIntermBlock *root,
                                                     TSymbolTable *symbolTable,
                                                     const GLenum shaderType,
                                                     const TIntermTyped *clipDistanceEnableFlags)
{
    return ReplaceClipCullDistanceAssignmentsImpl(compiler, root, symbolTable, shaderType,
                                                  clipDistanceEnableFlags, "gl_ClipDistance",
                                                  "ANGLEClipDistance", EvqClipDistance);
}

ANGLE_NO_DISCARD bool ReplaceCullDistanceAssignments(TCompiler *compiler,
                                                     TIntermBlock *root,
                                                     TSymbolTable *symbolTable,
                                                     const GLenum shaderType)
{
    return ReplaceClipCullDistanceAssignmentsImpl(compiler, root, symbolTable, shaderType, nullptr,
                                                  "gl_CullDistance", "ANGLECullDistance",
                                                  EvqCullDistance);
}

}  // namespace sh
kc3-lang/angle/src/compiler/translator/tree_util/ReplaceClipCullDistanceVariable.cpp

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kc3-lang/angle /src/compiler/translator/tree_util/ReplaceClipCullDistanceVariable.cpp
