src/sksl/SkSLAnalysis.h - skia - Git at Google

 /*
  * Copyright 2020 Google LLC
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */

 #ifndef SkSLAnalysis_DEFINED
 #define SkSLAnalysis_DEFINED

 #include "include/private/SkSLDefines.h"
 #include "include/private/SkSLSampleUsage.h"

 #include <memory>

 namespace SkSL {

 class ErrorReporter;
 class Expression;
 class ForStatement;
 class FunctionDeclaration;
 class FunctionDefinition;
 struct LoadedModule;
 struct Program;
 class ProgramElement;
 class ProgramUsage;
 class Statement;
 class Variable;
 class VariableReference;
 enum class VariableRefKind : int8_t;

 /**
  * Provides utilities for analyzing SkSL statically before it's composed into a full program.
  */
 struct Analysis {
     /**
      * Determines how `program` samples `fp`. By default, assumes that the sample coords
      * (SK_MAIN_COORDS_BUILTIN) might be modified, so `sample(fp, sampleCoords)` is treated as
      * Explicit. If writesToSampleCoords is false, treats that as PassThrough, instead.
      */
     static SampleUsage GetSampleUsage(const Program& program,
                                       const Variable& fp,
                                       bool writesToSampleCoords = true);

     static bool ReferencesBuiltin(const Program& program, int builtin);

     static bool ReferencesSampleCoords(const Program& program);
     static bool ReferencesFragCoords(const Program& program);

     static int NodeCountUpToLimit(const FunctionDefinition& function, int limit);

     /**
      * Finds unconditional exits from a switch-case. Returns true if this statement unconditionally
      * causes an exit from this switch (via continue, break or return).
      */
     static bool SwitchCaseContainsUnconditionalExit(Statement& stmt);

     /**
      * A switch-case "falls through" when it doesn't have an unconditional exit.
      */
     static bool SwitchCaseFallsThrough(Statement& stmt) {
         return !SwitchCaseContainsUnconditionalExit(stmt);
     }

     /**
      * Finds conditional exits from a switch-case. Returns true if this statement contains a
      * conditional that wraps a potential exit from the switch (via continue, break or return).
      */
     static bool SwitchCaseContainsConditionalExit(Statement& stmt);

     static std::unique_ptr<ProgramUsage> GetUsage(const Program& program);
     static std::unique_ptr<ProgramUsage> GetUsage(const LoadedModule& module);

     static bool StatementWritesToVariable(const Statement& stmt, const Variable& var);

     struct AssignmentInfo {
         VariableReference* fAssignedVar = nullptr;
     };
     static bool IsAssignable(Expression& expr, AssignmentInfo* info = nullptr,
                              ErrorReporter* errors = nullptr);

     // Updates the `refKind` field of exactly one VariableReference inside `expr`.
     // `expr` must be `IsAssignable`; returns an error otherwise.
     static bool MakeAssignmentExpr(Expression* expr, VariableRefKind kind, ErrorReporter* errors);

     // Updates the `refKind` field of every VariableReference found within `expr`.
     // `expr` is allowed to have zero, one, or multiple VariableReferences.
     static void UpdateRefKind(Expression* expr, VariableRefKind refKind);

     // A "trivial" expression is one where we'd feel comfortable cloning it multiple times in
     // the code, without worrying about incurring a performance penalty. Examples:
     // - true
     // - 3.14159265
     // - myIntVariable
     // - myColor.rgb
     // - myArray[123]
     // - myStruct.myField
     // - half4(0)
     //
     // Trivial-ness is stackable. Somewhat large expressions can occasionally make the cut:
     // - half4(myColor.a)
     // - myStruct.myArrayField[7].xyz
     static bool IsTrivialExpression(const Expression& expr);

     // Returns true if both expression trees are the same. Used by the optimizer to look for self-
     // assignment or self-comparison; won't necessarily catch complex cases. Rejects expressions
     // that may cause side effects.
     static bool IsSameExpressionTree(const Expression& left, const Expression& right);

     // Is 'expr' a constant-expression, as defined by GLSL 1.0, section 5.10? A constant expression
     // is one of:
     //
     // - A literal value
     // - A global or local variable qualified as 'const', excluding function parameters
     // - An expression formed by an operator on operands that are constant expressions, including
     //   getting an element of a constant vector or a constant matrix, or a field of a constant
     //   structure
     // - A constructor whose arguments are all constant expressions
     //
     // GLSL (but not SkSL, yet - skbug.com/10835) also provides:
     // - A built-in function call whose arguments are all constant expressions, with the exception
     //   of the texture lookup functions
     static bool IsConstantExpression(const Expression& expr);

     struct UnrollableLoopInfo {
         const Variable* fIndex;
         double fStart;
         double fDelta;
         int fCount;
     };

     // Ensures that a for-loop meets the strict requirements of The OpenGL ES Shading Language 1.00,
     // Appendix A, Section 4.
     // Information about the loop's structure are placed in outLoopInfo (if not nullptr).
     // If the function returns false, specific reasons are reported via errors (if not nullptr).
     static bool ForLoopIsValidForES2(int offset,
                                      const Statement* loopInitializer,
                                      const Expression* loopTest,
                                      const Expression* loopNext,
                                      const Statement* loopStatement,
                                      UnrollableLoopInfo* outLoopInfo,
                                      ErrorReporter* errors);

     static void ValidateIndexingForES2(const ProgramElement& pe, ErrorReporter& errors);

     // Detects functions that fail to return a value on at least one path.
     static bool CanExitWithoutReturningValue(const FunctionDeclaration& funcDecl,
                                              const Statement& body);
 };

 /**
  * Utility class to visit every element, statement, and expression in an SkSL program IR.
  * This is intended for simple analysis and accumulation, where custom visitation behavior is only
  * needed for a limited set of expression kinds.
  *
  * Subclasses should override visitExpression/visitStatement/visitProgramElement as needed and
  * intercept elements of interest. They can then invoke the base class's function to visit all
  * sub expressions. They can also choose not to call the base function to arrest recursion, or
  * implement custom recursion.
  *
  * The visit functions return a bool that determines how the default implementation recurses. Once
  * any visit call returns true, the default behavior stops recursing and propagates true up the
  * stack.
  */
 template <typename T>
 class TProgramVisitor {
 public:
     virtual ~TProgramVisitor() = default;

 protected:
     virtual bool visitExpression(typename T::Expression& expression);
     virtual bool visitStatement(typename T::Statement& statement);
     virtual bool visitProgramElement(typename T::ProgramElement& programElement);

     virtual bool visitExpressionPtr(typename T::UniquePtrExpression& expr) = 0;
     virtual bool visitStatementPtr(typename T::UniquePtrStatement& stmt) = 0;
 };

 // ProgramVisitors take const types; ProgramWriters do not.
 struct ProgramVisitorTypes {
     using Program = const SkSL::Program;
     using Expression = const SkSL::Expression;
     using Statement = const SkSL::Statement;
     using ProgramElement = const SkSL::ProgramElement;
     using UniquePtrExpression = const std::unique_ptr<SkSL::Expression>;
     using UniquePtrStatement = const std::unique_ptr<SkSL::Statement>;
 };

 struct ProgramWriterTypes {
     using Program = SkSL::Program;
     using Expression = SkSL::Expression;
     using Statement = SkSL::Statement;
     using ProgramElement = SkSL::ProgramElement;
     using UniquePtrExpression = std::unique_ptr<SkSL::Expression>;
     using UniquePtrStatement = std::unique_ptr<SkSL::Statement>;
 };

 // Squelch bogus Clang warning about template vtables: https://bugs.llvm.org/show_bug.cgi?id=18733
 #if defined(__clang__)
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wweak-template-vtables"
 #endif
 extern template class TProgramVisitor<ProgramVisitorTypes>;
 extern template class TProgramVisitor<ProgramWriterTypes>;
 #if defined(__clang__)
 #pragma clang diagnostic pop
 #endif

 class ProgramVisitor : public TProgramVisitor<ProgramVisitorTypes> {
 public:
     bool visit(const Program& program);

 private:
     // ProgramVisitors shouldn't need access to unique_ptrs, and marking these as final should help
     // these accessors inline away. Use ProgramWriter if you need the unique_ptrs.
     bool visitExpressionPtr(const std::unique_ptr<Expression>& e) final {
         return this->visitExpression(*e);
     }
     bool visitStatementPtr(const std::unique_ptr<Statement>& s) final {
         return this->visitStatement(*s);
     }
 };

 class ProgramWriter : public TProgramVisitor<ProgramWriterTypes> {
 public:
     // Subclass these methods if you want access to the unique_ptrs of IRNodes in a program.
     // This will allow statements or expressions to be replaced during a visit.
     bool visitExpressionPtr(std::unique_ptr<Expression>& e) override {
         return this->visitExpression(*e);
     }
     bool visitStatementPtr(std::unique_ptr<Statement>& s) override {
         return this->visitStatement(*s);
     }
 };

 }  // namespace SkSL

 #endif
	/*
	* Copyright 2020 Google LLC
	*
	* Use of this source code is governed by a BSD-style license that can be
	* found in the LICENSE file.
	*/

	#ifndef SkSLAnalysis_DEFINED
	#define SkSLAnalysis_DEFINED

	#include "include/private/SkSLDefines.h"
	#include "include/private/SkSLSampleUsage.h"

	#include <memory>

	namespace SkSL {

	class ErrorReporter;
	class Expression;
	class ForStatement;
	class FunctionDeclaration;
	class FunctionDefinition;
	struct LoadedModule;
	struct Program;
	class ProgramElement;
	class ProgramUsage;
	class Statement;
	class Variable;
	class VariableReference;
	enum class VariableRefKind : int8_t;

	/**
	* Provides utilities for analyzing SkSL statically before it's composed into a full program.
	*/
	struct Analysis {
	/**
	* Determines how `program` samples `fp`. By default, assumes that the sample coords
	* (SK_MAIN_COORDS_BUILTIN) might be modified, so `sample(fp, sampleCoords)` is treated as
	* Explicit. If writesToSampleCoords is false, treats that as PassThrough, instead.
	*/
	static SampleUsage GetSampleUsage(const Program& program,
	const Variable& fp,
	bool writesToSampleCoords = true);

	static bool ReferencesBuiltin(const Program& program, int builtin);

	static bool ReferencesSampleCoords(const Program& program);
	static bool ReferencesFragCoords(const Program& program);

	static int NodeCountUpToLimit(const FunctionDefinition& function, int limit);

	/**
	* Finds unconditional exits from a switch-case. Returns true if this statement unconditionally
	* causes an exit from this switch (via continue, break or return).
	*/
	static bool SwitchCaseContainsUnconditionalExit(Statement& stmt);

	/**
	* A switch-case "falls through" when it doesn't have an unconditional exit.
	*/
	static bool SwitchCaseFallsThrough(Statement& stmt) {
	return !SwitchCaseContainsUnconditionalExit(stmt);
	}

	/**
	* Finds conditional exits from a switch-case. Returns true if this statement contains a
	* conditional that wraps a potential exit from the switch (via continue, break or return).
	*/
	static bool SwitchCaseContainsConditionalExit(Statement& stmt);

	static std::unique_ptr<ProgramUsage> GetUsage(const Program& program);
	static std::unique_ptr<ProgramUsage> GetUsage(const LoadedModule& module);

	static bool StatementWritesToVariable(const Statement& stmt, const Variable& var);

	struct AssignmentInfo {
	VariableReference* fAssignedVar = nullptr;
	};
	static bool IsAssignable(Expression& expr, AssignmentInfo* info = nullptr,
	ErrorReporter* errors = nullptr);

	// Updates the `refKind` field of exactly one VariableReference inside `expr`.
	// `expr` must be `IsAssignable`; returns an error otherwise.
	static bool MakeAssignmentExpr(Expression* expr, VariableRefKind kind, ErrorReporter* errors);

	// Updates the `refKind` field of every VariableReference found within `expr`.
	// `expr` is allowed to have zero, one, or multiple VariableReferences.
	static void UpdateRefKind(Expression* expr, VariableRefKind refKind);

	// A "trivial" expression is one where we'd feel comfortable cloning it multiple times in
	// the code, without worrying about incurring a performance penalty. Examples:
	// - true
	// - 3.14159265
	// - myIntVariable
	// - myColor.rgb
	// - myArray[123]
	// - myStruct.myField
	// - half4(0)
	//
	// Trivial-ness is stackable. Somewhat large expressions can occasionally make the cut:
	// - half4(myColor.a)
	// - myStruct.myArrayField[7].xyz
	static bool IsTrivialExpression(const Expression& expr);

	// Returns true if both expression trees are the same. Used by the optimizer to look for self-
	// assignment or self-comparison; won't necessarily catch complex cases. Rejects expressions
	// that may cause side effects.
	static bool IsSameExpressionTree(const Expression& left, const Expression& right);

	// Is 'expr' a constant-expression, as defined by GLSL 1.0, section 5.10? A constant expression
	// is one of:
	//
	// - A literal value
	// - A global or local variable qualified as 'const', excluding function parameters
	// - An expression formed by an operator on operands that are constant expressions, including
	// getting an element of a constant vector or a constant matrix, or a field of a constant
	// structure
	// - A constructor whose arguments are all constant expressions
	//
	// GLSL (but not SkSL, yet - skbug.com/10835) also provides:
	// - A built-in function call whose arguments are all constant expressions, with the exception
	// of the texture lookup functions
	static bool IsConstantExpression(const Expression& expr);

	struct UnrollableLoopInfo {
	const Variable* fIndex;
	double fStart;
	double fDelta;
	int fCount;
	};

	// Ensures that a for-loop meets the strict requirements of The OpenGL ES Shading Language 1.00,
	// Appendix A, Section 4.
	// Information about the loop's structure are placed in outLoopInfo (if not nullptr).
	// If the function returns false, specific reasons are reported via errors (if not nullptr).
	static bool ForLoopIsValidForES2(int offset,
	const Statement* loopInitializer,
	const Expression* loopTest,
	const Expression* loopNext,
	const Statement* loopStatement,
	UnrollableLoopInfo* outLoopInfo,
	ErrorReporter* errors);

	static void ValidateIndexingForES2(const ProgramElement& pe, ErrorReporter& errors);

	// Detects functions that fail to return a value on at least one path.
	static bool CanExitWithoutReturningValue(const FunctionDeclaration& funcDecl,
	const Statement& body);
	};

	/**
	* Utility class to visit every element, statement, and expression in an SkSL program IR.
	* This is intended for simple analysis and accumulation, where custom visitation behavior is only
	* needed for a limited set of expression kinds.
	*
	* Subclasses should override visitExpression/visitStatement/visitProgramElement as needed and
	* intercept elements of interest. They can then invoke the base class's function to visit all
	* sub expressions. They can also choose not to call the base function to arrest recursion, or
	* implement custom recursion.
	*
	* The visit functions return a bool that determines how the default implementation recurses. Once
	* any visit call returns true, the default behavior stops recursing and propagates true up the
	* stack.
	*/
	template <typename T>
	class TProgramVisitor {
	public:
	virtual ~TProgramVisitor() = default;

	protected:
	virtual bool visitExpression(typename T::Expression& expression);
	virtual bool visitStatement(typename T::Statement& statement);
	virtual bool visitProgramElement(typename T::ProgramElement& programElement);

	virtual bool visitExpressionPtr(typename T::UniquePtrExpression& expr) = 0;
	virtual bool visitStatementPtr(typename T::UniquePtrStatement& stmt) = 0;
	};

	// ProgramVisitors take const types; ProgramWriters do not.
	struct ProgramVisitorTypes {
	using Program = const SkSL::Program;
	using Expression = const SkSL::Expression;
	using Statement = const SkSL::Statement;
	using ProgramElement = const SkSL::ProgramElement;
	using UniquePtrExpression = const std::unique_ptr<SkSL::Expression>;
	using UniquePtrStatement = const std::unique_ptr<SkSL::Statement>;
	};

	struct ProgramWriterTypes {
	using Program = SkSL::Program;
	using Expression = SkSL::Expression;
	using Statement = SkSL::Statement;
	using ProgramElement = SkSL::ProgramElement;
	using UniquePtrExpression = std::unique_ptr<SkSL::Expression>;
	using UniquePtrStatement = std::unique_ptr<SkSL::Statement>;
	};

	// Squelch bogus Clang warning about template vtables: https://bugs.llvm.org/show_bug.cgi?id=18733
	#if defined(__clang__)
	#pragma clang diagnostic push
	#pragma clang diagnostic ignored "-Wweak-template-vtables"
	#endif
	extern template class TProgramVisitor<ProgramVisitorTypes>;
	extern template class TProgramVisitor<ProgramWriterTypes>;
	#if defined(__clang__)
	#pragma clang diagnostic pop
	#endif

	class ProgramVisitor : public TProgramVisitor<ProgramVisitorTypes> {
	public:
	bool visit(const Program& program);

	private:
	// ProgramVisitors shouldn't need access to unique_ptrs, and marking these as final should help
	// these accessors inline away. Use ProgramWriter if you need the unique_ptrs.
	bool visitExpressionPtr(const std::unique_ptr<Expression>& e) final {
	return this->visitExpression(*e);
	}
	bool visitStatementPtr(const std::unique_ptr<Statement>& s) final {
	return this->visitStatement(*s);
	}
	};

	class ProgramWriter : public TProgramVisitor<ProgramWriterTypes> {
	public:
	// Subclass these methods if you want access to the unique_ptrs of IRNodes in a program.
	// This will allow statements or expressions to be replaced during a visit.
	bool visitExpressionPtr(std::unique_ptr<Expression>& e) override {
	return this->visitExpression(*e);
	}
	bool visitStatementPtr(std::unique_ptr<Statement>& s) override {
	return this->visitStatement(*s);
	}
	};

	} // namespace SkSL

	#endif