blob: b65813874160c67b04beee5404ceaf2c3a609d5e [file] [log] [blame]
* Copyright 2022 Google Inc.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
#include "include/core/SkSpan.h"
#include "include/private/SkSLDefines.h"
#include "include/private/base/SkTArray.h"
#include "src/core/SkTHash.h"
#include "src/sksl/SkSLStringStream.h"
#include "src/sksl/codegen/SkSLCodeGenerator.h"
#include <cstdint>
#include <initializer_list>
#include <string>
#include <string_view>
#include <utility>
namespace sknonstd {
template <typename T> struct is_bitmask_enum;
} // namespace sknonstd
namespace SkSL {
class AnyConstructor;
class BinaryExpression;
class Block;
class Context;
class ConstructorCompound;
class ConstructorDiagonalMatrix;
class ConstructorMatrixResize;
class Expression;
class ExpressionStatement;
struct Field;
class FieldAccess;
class FunctionCall;
class FunctionDeclaration;
class FunctionDefinition;
class GlobalVarDeclaration;
class IfStatement;
class IndexExpression;
class Literal;
class MemoryLayout;
class OutputStream;
class Position;
class PrefixExpression;
class ProgramElement;
class ReturnStatement;
class Statement;
class StructDefinition;
class Swizzle;
class TernaryExpression;
class Type;
class VarDeclaration;
class Variable;
class VariableReference;
enum class OperatorPrecedence : uint8_t;
struct Modifiers;
struct Program;
* Convert a Program into WGSL code.
class WGSLCodeGenerator : public CodeGenerator {
// See
enum class Builtin {
// Vertex stage:
kVertexIndex, // input
kInstanceIndex, // input
kPosition, // output, fragment stage input
// Fragment stage:
kFrontFacing, // input
kSampleIndex, // input
kFragDepth, // output
kSampleMask, // input, output
// Compute stage:
kLocalInvocationId, // input
kLocalInvocationIndex, // input
kGlobalInvocationId, // input
kWorkgroupId, // input
kNumWorkgroups, // input
// Represents a function's dependencies that are not accessible in global scope. For instance,
// pipeline stage input and output parameters must be passed in as an argument.
// This is a bitmask enum.
enum class FunctionDependencies : uint8_t {
kNone = 0,
kPipelineInputs = 1,
kPipelineOutputs = 2,
// Variable declarations can be terminated by:
// - comma (","), e.g. in struct member declarations or function parameters
// - semicolon (";"), e.g. in function scope variables
// A "none" option is provided to skip the delimiter when not needed, e.g. at the end of a list
// of declarations.
enum class Delimiter {
struct ProgramRequirements {
using DepsMap = skia_private::THashMap<const FunctionDeclaration*, FunctionDependencies>;
ProgramRequirements() = default;
ProgramRequirements(DepsMap dependencies, bool mainNeedsCoordsArgument)
: dependencies(std::move(dependencies))
, mainNeedsCoordsArgument(mainNeedsCoordsArgument) {}
// Mappings used to synthesize function parameters according to dependencies on pipeline
// input/output variables.
DepsMap dependencies;
// True, if the main function takes a coordinate parameter. This is used to ensure that
// sk_FragCoord is declared as part of pipeline inputs.
bool mainNeedsCoordsArgument;
WGSLCodeGenerator(const Context* context, const Program* program, OutputStream* out)
: INHERITED(context, program, out)
, fReservedWords({"array",
"VSOut"}) {}
bool generateCode() override;
using INHERITED = CodeGenerator;
using Precedence = OperatorPrecedence;
// Called by generateCode() as the first step.
void preprocessProgram();
// Write output content while correctly handling indentation.
void write(std::string_view s);
void writeLine(std::string_view s = std::string_view());
void finishLine();
void writeVariableDecl(const Type& type, std::string_view name, Delimiter delimiter);
// Helpers to declare a pipeline stage IO parameter declaration.
void writePipelineIODeclaration(Modifiers modifiers,
const Type& type,
std::string_view name,
Delimiter delimiter);
void writeUserDefinedIODecl(const Type& type,
std::string_view name,
int location,
Delimiter delimiter);
void writeBuiltinIODecl(const Type& type,
std::string_view name,
Builtin builtin,
Delimiter delimiter);
// Write a function definition.
void writeFunction(const FunctionDefinition& f);
void writeFunctionDeclaration(const FunctionDeclaration& f);
// Write the program entry point.
void writeEntryPoint(const FunctionDefinition& f);
// Writers for supported statement types.
void writeStatement(const Statement& s);
void writeStatements(const StatementArray& statements);
void writeBlock(const Block& b);
void writeExpressionStatement(const ExpressionStatement& s);
void writeIfStatement(const IfStatement& s);
void writeReturnStatement(const ReturnStatement& s);
void writeVarDeclaration(const VarDeclaration& varDecl);
// Writers for expressions. These return the final expression text as a string, and emit any
// necessary setup code directly into the program as necessary.
std::string assembleExpression(const Expression& e, Precedence parentPrecedence);
std::string assembleBinaryExpression(const BinaryExpression& b, Precedence parentPrecedence);
std::string assembleFieldAccess(const FieldAccess& f);
std::string assembleFunctionCall(const FunctionCall&);
std::string assembleIndexExpression(const IndexExpression& i);
std::string assembleLiteral(const Literal& l);
std::string assemblePrefixExpression(const PrefixExpression& p, Precedence parentPrecedence);
std::string assembleSwizzle(const Swizzle& swizzle);
std::string assembleTernaryExpression(const TernaryExpression& t, Precedence parentPrecedence);
std::string assembleVariableReference(const VariableReference& r);
std::string assembleName(std::string_view name);
// Constructor expressions
std::string assembleAnyConstructor(const AnyConstructor& c, Precedence parentPrecedence);
std::string assembleConstructorCompound(const ConstructorCompound& c,
Precedence parentPrecedence);
std::string assembleConstructorCompoundVector(const ConstructorCompound& c,
Precedence parentPrecedence);
std::string assembleConstructorCompoundMatrix(const ConstructorCompound& c,
Precedence parentPrecedence);
std::string assembleConstructorDiagonalMatrix(const ConstructorDiagonalMatrix& c,
Precedence parentPrecedence);
std::string assembleConstructorMatrixResize(const ConstructorMatrixResize& c,
Precedence parentPrecedence);
// Matrix constructor helpers.
bool isMatrixConstructorHelperNeeded(const ConstructorCompound& c);
std::string getMatrixConstructorHelper(const AnyConstructor& c);
void writeMatrixFromMatrixArgs(const Type& sourceMatrix, int columns, int rows);
void writeMatrixFromScalarAndVectorArgs(const AnyConstructor& ctor, int columns, int rows);
// Synthesized helper functions for comparison operators that are not supported by WGSL.
std::string assembleMatrixEqualityExpression(const Expression& left, const Expression& right);
// Writes a scratch variable into the program and returns its name (e.g. `_skTemp123`).
std::string writeScratchVar(const Type& type);
// Generic recursive ProgramElement visitor.
void writeProgramElement(const ProgramElement& e);
void writeGlobalVarDeclaration(const GlobalVarDeclaration& d);
void writeStructDefinition(const StructDefinition& s);
// Writes the WGSL struct fields for SkSL structs and interface blocks. Enforces WGSL address
// space layout constraints
// ( if a `layout` is
// provided. A struct that does not need to be host-shareable does not require a `layout`.
void writeFields(SkSpan<const Field> fields,
Position parentPos,
const MemoryLayout* layout = nullptr);
// We bundle all varying pipeline stage inputs and outputs in a struct.
void writeStageInputStruct();
void writeStageOutputStruct();
// Writes all top-level non-opaque global uniform declarations (i.e. not part of an interface
// block) into a single uniform block binding.
// In complete fragment/vertex/compute programs, uniforms will be declared only as interface
// blocks and global opaque types (like textures and samplers) which we expect to be declared
// with a unique binding and descriptor set index. However, test files that are declared as RTE
// programs may contain OpenGL-style global uniform declarations with no clear binding index to
// use for the containing synthesized block.
// Since we are handling these variables only to generate gold files from RTEs and never run
// them, we always declare them at the default bind group and binding index.
void writeNonBlockUniformsForTests();
// For a given function declaration, writes out any implicitly required pipeline stage arguments
// based on the function's pre-determined dependencies. These are expected to be written out as
// the first parameters for a function that requires them. Returns true if any arguments were
// written.
std::string functionDependencyArgs(const FunctionDeclaration&);
bool writeFunctionDependencyParams(const FunctionDeclaration&);
// Generate an out-parameter helper function for the given call and return its name.
std::string writeOutParamHelper(const FunctionCall&,
const ExpressionArray& args,
const skia_private::TArray<VariableReference*>& outVars);
// Stores the disallowed identifier names.
skia_private::THashSet<std::string_view> fReservedWords;
ProgramRequirements fRequirements;
int fPipelineInputCount = 0;
bool fDeclaredUniformsStruct = false;
// Out-parameters to functions are declared as pointers. While we process the arguments to a
// out-parameter helper function, we need to temporarily track that they are re-declared as
// pointer-parameters in the helper, so that expression-tree processing can know to correctly
// dereference them when the variable is referenced. The contents of this set are expected to
// be uniquely scoped for each out-param helper and will be cleared every time a new out-param
// helper function has been emitted.
skia_private::THashSet<const Variable*> fOutParamArgVars;
// Output processing state.
int fIndentation = 0;
bool fAtLineStart = false;
int fScratchCount = 0;
StringStream fExtraFunctions; // all internally synthesized helpers are written here
skia_private::THashSet<std::string> fHelpers; // all synthesized helper functions, by name
} // namespace SkSL
namespace sknonstd {
template <>
struct is_bitmask_enum<SkSL::WGSLCodeGenerator::FunctionDependencies> : std::true_type {};
} // namespace sknonstd