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//
// Copyright 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/tree_ops/DeclareAndInitBuiltinsForInstancedMultiview.h"
#include "compiler/translator/Compiler.h"
#include "compiler/translator/StaticType.h"
#include "compiler/translator/SymbolTable.h"
#include "compiler/translator/tree_ops/InitializeVariables.h"
#include "compiler/translator/tree_util/BuiltIn.h"
#include "compiler/translator/tree_util/FindMain.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/util.h"
namespace sh
{
namespace
{
constexpr const ImmutableString kViewIDVariableName("ViewID_OVR");
constexpr const ImmutableString kInstanceIDVariableName("InstanceID");
constexpr const ImmutableString kMultiviewBaseViewLayerIndexVariableName(
"multiviewBaseViewLayerIndex");
// Adds the InstanceID and ViewID_OVR initializers to the end of the initializers' sequence.
void InitializeViewIDAndInstanceID(const TVariable *viewID,
const TVariable *instanceID,
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, EbpLow, EvqConst));
// Create a uint(gl_InstanceID) node.
TIntermSequence glInstanceIDSymbolCastArguments;
glInstanceIDSymbolCastArguments.push_back(new TIntermSymbol(BuiltInVariable::gl_InstanceID()));
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;
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, new TIntermSymbol(instanceID), 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, new TIntermSymbol(viewID), normalizedViewID);
initializers->push_back(viewIDInitializer);
}
// 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(const TVariable *viewID,
const TVariable *multiviewBaseViewLayerIndex,
TIntermSequence *initializers,
const TSymbolTable &symbolTable)
{
// Create an int(ViewID_OVR) node.
TIntermSequence viewIDSymbolCastArguments;
viewIDSymbolCastArguments.push_back(new TIntermSymbol(viewID));
TIntermAggregate *viewIDAsInt = TIntermAggregate::CreateConstructor(
TType(EbtInt, EbpHigh, EvqTemporary), &viewIDSymbolCastArguments);
// Create a gl_ViewportIndex node.
TIntermSymbol *viewportIndexSymbol = new TIntermSymbol(BuiltInVariable::gl_ViewportIndex());
// 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 = new TIntermSymbol(BuiltInVariable::gl_LayerVS());
// Create an int(ViewID_OVR) + multiviewBaseViewLayerIndex node
TIntermBinary *sumOfViewIDAndBaseViewIndex = new TIntermBinary(
EOpAdd, viewIDAsInt->deepCopy(), new TIntermSymbol(multiviewBaseViewLayerIndex));
// 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, new TIntermSymbol(multiviewBaseViewLayerIndex),
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
bool DeclareAndInitBuiltinsForInstancedMultiview(TCompiler *compiler,
TIntermBlock *root,
unsigned numberOfViews,
GLenum shaderType,
const ShCompileOptions &compileOptions,
ShShaderOutput shaderOutput,
TSymbolTable *symbolTable)
{
ASSERT(shaderType == GL_VERTEX_SHADER || shaderType == GL_FRAGMENT_SHADER);
TQualifier viewIDQualifier = (shaderType == GL_VERTEX_SHADER) ? EvqFlatOut : EvqFlatIn;
const TVariable *viewID =
new TVariable(symbolTable, kViewIDVariableName,
new TType(EbtUInt, EbpHigh, viewIDQualifier), SymbolType::AngleInternal);
DeclareGlobalVariable(root, viewID);
if (!ReplaceVariable(compiler, root, BuiltInVariable::gl_ViewID_OVR(), viewID))
{
return false;
}
if (shaderType == GL_VERTEX_SHADER)
{
// Replacing gl_InstanceID with InstanceID should happen before adding the initializers of
// InstanceID and ViewID.
const TType *instanceIDVariableType = StaticType::Get<EbtInt, EbpHigh, EvqGlobal, 1, 1>();
const TVariable *instanceID =
new TVariable(symbolTable, kInstanceIDVariableName, instanceIDVariableType,
SymbolType::AngleInternal);
DeclareGlobalVariable(root, instanceID);
if (!ReplaceVariable(compiler, root, BuiltInVariable::gl_InstanceID(), instanceID))
{
return false;
}
TIntermSequence initializers;
InitializeViewIDAndInstanceID(viewID, instanceID, 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.selectViewInNvGLSLVertexShader;
// 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.
const TType *baseLayerIndexVariableType =
StaticType::Get<EbtInt, EbpHigh, EvqUniform, 1, 1>();
const TVariable *multiviewBaseViewLayerIndex =
new TVariable(symbolTable, kMultiviewBaseViewLayerIndexVariableName,
baseLayerIndexVariableType, SymbolType::AngleInternal);
DeclareGlobalVariable(root, multiviewBaseViewLayerIndex);
// Setting a value to gl_ViewportIndex or gl_Layer should happen after ViewID_OVR's
// initialization.
SelectViewIndexInVertexShader(viewID, multiviewBaseViewLayerIndex, &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);
}
return compiler->validateAST(root);
}
} // namespace sh
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