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//
// Copyright 2002 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.
//
// gl_FragColor needs to broadcast to all color buffers in ES2 if
// GL_EXT_draw_buffers is explicitly enabled in a fragment shader.
//
// We emulate this by replacing all gl_FragColor with gl_FragData[0], and in the end
// of main() function, assigning gl_FragData[1], ..., gl_FragData[maxDrawBuffers-1]
// with gl_FragData[0].
//
#include "compiler/translator/tree_ops/EmulateGLFragColorBroadcast.h"
#include "compiler/translator/Compiler.h"
#include "compiler/translator/Symbol.h"
#include "compiler/translator/tree_util/IntermNode_util.h"
#include "compiler/translator/tree_util/IntermTraverse.h"
#include "compiler/translator/tree_util/RunAtTheEndOfShader.h"
namespace sh
{
namespace
{
constexpr const ImmutableString kGlFragDataString("gl_FragData");
class GLFragColorBroadcastTraverser : public TIntermTraverser
{
public:
GLFragColorBroadcastTraverser(int maxDrawBuffers, TSymbolTable *symbolTable, int shaderVersion)
: TIntermTraverser(true, false, false, symbolTable),
mGLFragColorUsed(false),
mMaxDrawBuffers(maxDrawBuffers),
mShaderVersion(shaderVersion)
{}
[[nodiscard]] bool broadcastGLFragColor(TCompiler *compiler, TIntermBlock *root);
bool isGLFragColorUsed() const { return mGLFragColorUsed; }
protected:
void visitSymbol(TIntermSymbol *node) override;
TIntermBinary *constructGLFragDataNode(int index) const;
TIntermBinary *constructGLFragDataAssignNode(int index) const;
private:
bool mGLFragColorUsed;
int mMaxDrawBuffers;
const int mShaderVersion;
};
TIntermBinary *GLFragColorBroadcastTraverser::constructGLFragDataNode(int index) const
{
TIntermSymbol *symbol =
ReferenceBuiltInVariable(kGlFragDataString, *mSymbolTable, mShaderVersion);
TIntermTyped *indexNode = CreateIndexNode(index);
TIntermBinary *binary = new TIntermBinary(EOpIndexDirect, symbol, indexNode);
return binary;
}
TIntermBinary *GLFragColorBroadcastTraverser::constructGLFragDataAssignNode(int index) const
{
TIntermTyped *fragDataIndex = constructGLFragDataNode(index);
TIntermTyped *fragDataZero = constructGLFragDataNode(0);
return new TIntermBinary(EOpAssign, fragDataIndex, fragDataZero);
}
void GLFragColorBroadcastTraverser::visitSymbol(TIntermSymbol *node)
{
if (node->variable().symbolType() == SymbolType::BuiltIn && node->getName() == "gl_FragColor")
{
queueReplacement(constructGLFragDataNode(0), OriginalNode::IS_DROPPED);
mGLFragColorUsed = true;
}
}
bool GLFragColorBroadcastTraverser::broadcastGLFragColor(TCompiler *compiler, TIntermBlock *root)
{
ASSERT(mMaxDrawBuffers > 1);
if (!mGLFragColorUsed)
{
return true;
}
TIntermBlock *broadcastBlock = new TIntermBlock();
// Now insert statements
// gl_FragData[1] = gl_FragData[0];
// ...
// gl_FragData[maxDrawBuffers - 1] = gl_FragData[0];
for (int colorIndex = 1; colorIndex < mMaxDrawBuffers; ++colorIndex)
{
broadcastBlock->appendStatement(constructGLFragDataAssignNode(colorIndex));
}
return RunAtTheEndOfShader(compiler, root, broadcastBlock, mSymbolTable);
}
} // namespace
bool EmulateGLFragColorBroadcast(TCompiler *compiler,
TIntermBlock *root,
int maxDrawBuffers,
std::vector<sh::ShaderVariable> *outputVariables,
TSymbolTable *symbolTable,
int shaderVersion)
{
ASSERT(maxDrawBuffers > 1);
GLFragColorBroadcastTraverser traverser(maxDrawBuffers, symbolTable, shaderVersion);
root->traverse(&traverser);
if (traverser.isGLFragColorUsed())
{
if (!traverser.updateTree(compiler, root))
{
return false;
}
if (!traverser.broadcastGLFragColor(compiler, root))
{
return false;
}
for (auto &var : *outputVariables)
{
if (var.name == "gl_FragColor")
{
// TODO(zmo): Find a way to keep the original variable information.
var.name = "gl_FragData";
var.mappedName = "gl_FragData";
var.arraySizes.push_back(maxDrawBuffers);
ASSERT(var.arraySizes.size() == 1u);
}
}
}
return true;
}
} // namespace sh
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