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//
// Copyright (c) 2017 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.
//
// Applies the necessary AST transformations to support multiview rendering through instancing.
// Check the header file For more information.
//
#include "compiler/translator/DeclareAndInitBuiltinsForInstancedMultiview.h"
#include "compiler/translator/FindMain.h"
#include "compiler/translator/InitializeVariables.h"
#include "compiler/translator/IntermNode_util.h"
#include "compiler/translator/IntermTraverse.h"
#include "compiler/translator/SymbolTable.h"
#include "compiler/translator/util.h"
namespace sh
{
namespace
{
class ReplaceVariableTraverser : public TIntermTraverser
{
public:
ReplaceVariableTraverser(const TString &symbolName, TIntermSymbol *newSymbol)
: TIntermTraverser(true, false, false), mSymbolName(symbolName), mNewSymbol(newSymbol)
{
}
void visitSymbol(TIntermSymbol *node) override
{
TName &name = node->getName();
if (name.getString() == mSymbolName)
{
queueReplacement(mNewSymbol->deepCopy(), OriginalNode::IS_DROPPED);
}
}
private:
TString mSymbolName;
TIntermSymbol *mNewSymbol;
};
TIntermSymbol *CreateGLInstanceIDSymbol(const TSymbolTable &symbolTable)
{
return ReferenceBuiltInVariable("gl_InstanceID", symbolTable, 300);
}
// Adds the InstanceID and ViewID_OVR initializers to the end of the initializers' sequence.
void InitializeViewIDAndInstanceID(TIntermTyped *viewIDSymbol,
TIntermTyped *instanceIDSymbol,
unsigned numberOfViews,
const TSymbolTable &symbolTable,
TIntermSequence *initializers)
{
// Create an unsigned numberOfViews node.
TConstantUnion *numberOfViewsUnsignedConstant = new TConstantUnion();
numberOfViewsUnsignedConstant->setUConst(numberOfViews);
TIntermConstantUnion *numberOfViewsUint =
new TIntermConstantUnion(numberOfViewsUnsignedConstant, TType(EbtUInt, EbpHigh, EvqConst));
// Create a uint(gl_InstanceID) node.
TIntermSequence *glInstanceIDSymbolCastArguments = new TIntermSequence();
glInstanceIDSymbolCastArguments->push_back(CreateGLInstanceIDSymbol(symbolTable));
TIntermAggregate *glInstanceIDAsUint = TIntermAggregate::CreateConstructor(
TType(EbtUInt, EbpHigh, EvqTemporary), glInstanceIDSymbolCastArguments);
// Create a uint(gl_InstanceID) / numberOfViews node.
TIntermBinary *normalizedInstanceID =
new TIntermBinary(EOpDiv, glInstanceIDAsUint, numberOfViewsUint);
// Create an int(uint(gl_InstanceID) / numberOfViews) node.
TIntermSequence *normalizedInstanceIDCastArguments = new TIntermSequence();
normalizedInstanceIDCastArguments->push_back(normalizedInstanceID);
TIntermAggregate *normalizedInstanceIDAsInt = TIntermAggregate::CreateConstructor(
TType(EbtInt, EbpHigh, EvqTemporary), normalizedInstanceIDCastArguments);
// Create an InstanceID = int(uint(gl_InstanceID) / numberOfViews) node.
TIntermBinary *instanceIDInitializer =
new TIntermBinary(EOpAssign, instanceIDSymbol->deepCopy(), normalizedInstanceIDAsInt);
initializers->push_back(instanceIDInitializer);
// Create a uint(gl_InstanceID) % numberOfViews node.
TIntermBinary *normalizedViewID =
new TIntermBinary(EOpIMod, glInstanceIDAsUint->deepCopy(), numberOfViewsUint->deepCopy());
// Create a ViewID_OVR = uint(gl_InstanceID) % numberOfViews node.
TIntermBinary *viewIDInitializer =
new TIntermBinary(EOpAssign, viewIDSymbol->deepCopy(), normalizedViewID);
initializers->push_back(viewIDInitializer);
}
// Replaces every occurrence of a symbol with the name specified in symbolName with newSymbolNode.
void ReplaceSymbol(TIntermBlock *root, const TString &symbolName, TIntermSymbol *newSymbolNode)
{
ReplaceVariableTraverser traverser(symbolName, newSymbolNode);
root->traverse(&traverser);
traverser.updateTree();
}
void DeclareGlobalVariable(TIntermBlock *root, TIntermTyped *typedNode)
{
TIntermSequence *globalSequence = root->getSequence();
TIntermDeclaration *declaration = new TIntermDeclaration();
declaration->appendDeclarator(typedNode->deepCopy());
globalSequence->insert(globalSequence->begin(), declaration);
}
// Adds a branch to write int(ViewID_OVR) to either gl_ViewportIndex or gl_Layer. The branch is
// added to the end of the initializers' sequence.
void SelectViewIndexInVertexShader(TIntermTyped *viewIDSymbol,
TIntermTyped *multiviewBaseViewLayerIndexSymbol,
TIntermSequence *initializers,
const TSymbolTable &symbolTable)
{
// Create an int(ViewID_OVR) node.
TIntermSequence *viewIDSymbolCastArguments = new TIntermSequence();
viewIDSymbolCastArguments->push_back(viewIDSymbol);
TIntermAggregate *viewIDAsInt = TIntermAggregate::CreateConstructor(
TType(EbtInt, EbpHigh, EvqTemporary), viewIDSymbolCastArguments);
// Create a gl_ViewportIndex node.
TIntermSymbol *viewportIndexSymbol =
ReferenceBuiltInVariable("gl_ViewportIndex", symbolTable, 0);
// Create a { gl_ViewportIndex = int(ViewID_OVR) } node.
TIntermBlock *viewportIndexInitializerInBlock = new TIntermBlock();
viewportIndexInitializerInBlock->appendStatement(
new TIntermBinary(EOpAssign, viewportIndexSymbol, viewIDAsInt));
// Create a gl_Layer node.
TIntermSymbol *layerSymbol = ReferenceBuiltInVariable("gl_Layer", symbolTable, 0);
// Create an int(ViewID_OVR) + multiviewBaseViewLayerIndex node
TIntermBinary *sumOfViewIDAndBaseViewIndex =
new TIntermBinary(EOpAdd, viewIDAsInt->deepCopy(), multiviewBaseViewLayerIndexSymbol);
// Create a { gl_Layer = int(ViewID_OVR) + multiviewBaseViewLayerIndex } node.
TIntermBlock *layerInitializerInBlock = new TIntermBlock();
layerInitializerInBlock->appendStatement(
new TIntermBinary(EOpAssign, layerSymbol, sumOfViewIDAndBaseViewIndex));
// Create a node to compare whether the base view index uniform is less than zero.
TIntermBinary *multiviewBaseViewLayerIndexZeroComparison =
new TIntermBinary(EOpLessThan, multiviewBaseViewLayerIndexSymbol->deepCopy(),
CreateZeroNode(TType(EbtInt, EbpHigh, EvqConst)));
// Create an if-else statement to select the code path.
TIntermIfElse *multiviewBranch =
new TIntermIfElse(multiviewBaseViewLayerIndexZeroComparison,
viewportIndexInitializerInBlock, layerInitializerInBlock);
initializers->push_back(multiviewBranch);
}
} // namespace
void DeclareAndInitBuiltinsForInstancedMultiview(TIntermBlock *root,
unsigned numberOfViews,
GLenum shaderType,
ShCompileOptions compileOptions,
ShShaderOutput shaderOutput,
TSymbolTable *symbolTable)
{
ASSERT(shaderType == GL_VERTEX_SHADER || shaderType == GL_FRAGMENT_SHADER);
TQualifier viewIDQualifier = (shaderType == GL_VERTEX_SHADER) ? EvqFlatOut : EvqFlatIn;
TIntermSymbol *viewIDSymbol = new TIntermSymbol(symbolTable->nextUniqueId(), "ViewID_OVR",
TType(EbtUInt, EbpHigh, viewIDQualifier));
viewIDSymbol->setInternal(true);
DeclareGlobalVariable(root, viewIDSymbol);
ReplaceSymbol(root, "gl_ViewID_OVR", viewIDSymbol);
if (shaderType == GL_VERTEX_SHADER)
{
// Replacing gl_InstanceID with InstanceID should happen before adding the initializers of
// InstanceID and ViewID.
TIntermSymbol *instanceIDSymbol = new TIntermSymbol(
symbolTable->nextUniqueId(), "InstanceID", TType(EbtInt, EbpHigh, EvqGlobal));
instanceIDSymbol->setInternal(true);
DeclareGlobalVariable(root, instanceIDSymbol);
ReplaceSymbol(root, "gl_InstanceID", instanceIDSymbol);
TIntermSequence *initializers = new TIntermSequence();
InitializeViewIDAndInstanceID(viewIDSymbol, instanceIDSymbol, numberOfViews, *symbolTable,
initializers);
// The AST transformation which adds the expression to select the viewport index should
// be done only for the GLSL and ESSL output.
const bool selectView = (compileOptions & SH_SELECT_VIEW_IN_NV_GLSL_VERTEX_SHADER) != 0u;
// Assert that if the view is selected in the vertex shader, then the output is
// either GLSL or ESSL.
ASSERT(!selectView || IsOutputGLSL(shaderOutput) || IsOutputESSL(shaderOutput));
if (selectView)
{
// Add a uniform to switch between side-by-side and layered rendering.
TIntermSymbol *multiviewBaseViewLayerIndexSymbol =
new TIntermSymbol(symbolTable->nextUniqueId(), "multiviewBaseViewLayerIndex",
TType(EbtInt, EbpHigh, EvqUniform));
multiviewBaseViewLayerIndexSymbol->setInternal(true);
DeclareGlobalVariable(root, multiviewBaseViewLayerIndexSymbol);
// Setting a value to gl_ViewportIndex or gl_Layer should happen after ViewID_OVR's
// initialization.
SelectViewIndexInVertexShader(viewIDSymbol->deepCopy(),
multiviewBaseViewLayerIndexSymbol->deepCopy(),
initializers, *symbolTable);
}
// Insert initializers at the beginning of main().
TIntermBlock *initializersBlock = new TIntermBlock();
initializersBlock->getSequence()->swap(*initializers);
TIntermBlock *mainBody = FindMainBody(root);
mainBody->getSequence()->insert(mainBody->getSequence()->begin(), initializersBlock);
}
}
} // namespace sh
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